Chia as an omega-3 fatty acid source
for animal and human consumption
Ing. Ricardo Ayerza (h)
Office of Arid Lands Studies
The University of Arizona
<rayerza@ag.arizona.edu>
Introduction
Some of the information in this document is from a paper entitled “Chia as a new source of ω-3 fatty acids: advantage over other raw materials to produce ω-3 enriched eggs” which was presented by R. Ayerza (h) at the Symposium On Omega-3 Fatty Acids, Evolution and Human Health (Washington, D.C., September 23-24, 2002), organized by Belovo S.A. This was included since information on ω-3 enriched products is considered important for the reader to have a better understanding of the material contained in this document.
At present there are ω-3 enriched eggs on the market which are obtained by including flax seeds, chia seeds, fish oil/meal or marine algae in the hens' diet. Although all of these materials have high ω-3 fatty acid contents, there are remarkable differences among these four sources in terms of marketing factors such as availability, reliability of supply, uniformity, prices, etc. Other important factors are the chemical composition of these materials and their physiological and nutritional effects on human and animal health.
The purpose of this paper is to compare chia to other available raw materials, not only in terms of egg production, but when fed to other animals and eaten by humans as well.
Origin
Of all of the raw materials listed above, only flax (Linum usitatissimum L.) and chia (Salvia hispanica L.) are agricultural crops. These are the two vegetal species having the highest concentration of ω-3 α-linolenic fatty acid (Table 1) known to date (Ayerza, 1996, 1995; Coates and Ayerza, 1998,1996; Oomah and Kenasehuk, 1995). These omega-3 seed sources are often used as food and feed ingredients, or as a natural food supplement. Hence a complete nutritional comparison of these two crops is provided as Table 2. . Chia, along with maize and beans has been a core element in the diet of many pre-Columbian civilizations in America, including the Mayan and Aztec populations (Sahagun, 1579).
The other two sources, algae and fish oil/meal are of marine origin. Both sources contain long chain ω-3 fatty acids, DHA and DHA and EPA, respectively (Table 3). Comparing the oil composition of the four sources, it can be seen that the terrestrial sources have a much higher ω-3 content than the marine sources (Table 4).
Chia and flax are grown on agricultural lands and all operations are mechanized. Flax is grown in temperate and temperate-cold regions, whereas chia requires tropical and subtropical climates. Although both of crops have a long agricultural history, agricultural development of chia was interrupted in the XIV century, when the Spanish conquerors invaded America after its discovery by Christopher Columbus. Chia was persecuted and almost disappeared, because it was considered sacrilegious, as it was a main component used in the religious ceremonies that were dedicated to the Aztecs gods (Sahagun, 1579). Flax on the other hand, which was first used in Asia and Europe and later in America, went on an uninterrupted path of agricultural evolution. Today there are varieties rich in omega-6 fatty acids, modified through genetic engineering, which have been approved for cultivation and commercialization in the USA, Canada and other countries. In addition there are many traditional varieties which are rich in fatty acids omega-3 which are grown (Health Canada, 1999; United States Department of Agriculture, 1999a; Canadian Food Inspection Agency, 1998).
Fish oil depends almost exclusively on oceanic fishing. Algae, which was initially a wild sea plant, is today grown artificially in salt water ponds.
Nutrition
Fish and chia have a long history of use in human diet. Fish has constituted the staple food for populations settled along rivers and coasts for many years. Although the use of this resource is declining (Organization for Economic Cooperation and Development, 1998; Chipello, 1998), it is still the basic diet in some regions. However, the same does not apply to their oil, since only the oil produced from the species known as menhaden has been certified as being safe (GRAS-Generally Recognized as safe) by the United States Food and Drug Administration- FDA (Food and Drug Administration, 1999; Becker and Kyle, 1998).
For many people, a strong limitation for the use of fish as a food is that fish has been recognized as a potent allergen, both in food allergies and occupational allergies. Reactions to fish are among the most commonly encountered food allergies in children and adults (Hebling et al., 1996; James et al., 1997; Hansen et al., 1997; Madsen, 1997). Allergic disease is now a leading cause of illness and death, particularly in young children. An increase in the prevalence of allergic disorders has been documented in several countries (Chandra, 2002). The frequency of fish allergies varies according to geography and exposure. In Sweden, about 39 % of the pediatric population that has allergies is affected by fish allergies, and in Spain the figure ranges between 18-30 %. A general figure for the European pediatric population having food allergies is that fish allergies account for about 22 % (Pascual et al., 1992). In France the frequency of fish related allergies in adults is 15.4 % and 12.7 % for fish and shellfish, respectively (Moneret-Vautrin, 2001).
World fish stocks are in decline because of over fishing and pollution of water ways. Today, the high concentration of toxic substances found in marine fish are a cause of concern. A recent study monitored organic pollutants (∑14 PCB, DDT, oxychlordane, and others) in maternal blood of women from six circumpolar countries (Greenland, Canada, Iceland, Norway, Sweden, and Russia). Results showed persistent organic pollutants were found to be highest among Inuit (Eskimo) populations, and this follows in that marine products are their main source of food. The maternal blood concentration of PCBs in Greenlandic women was 3.7 times higher than the level considered to be safe for women of reproductive age according to the Canadian guidelines for PCBs in blood. As the Greenland Inuit population traditionally eats fish and other sea products such as seal and small whales (Helm et al., 2001; Hansen, 2000) this is considered to be the source of the PCBs. These findings are in agreement with a previous study conducted in Sweden, when populations consuming high amounts of fish (including salmon and herring) were shown to accumulate significantly higher levels of dioxin in their body fat than non fish consumers (Svenssson et al., 1991).
The Ireland Food Safety Authority (IFSA) conducted a survey to examine dioxin and PCB contamination in fish oils and fish liver oils sold for human consumption in the country. IFSA said that fish oil capsules, sold as a nutritional supplements, had dioxin levels that exceeded the allowable range for the European Union. Ten of the fifteen supplements tested had dioxin levels higher than the EU allows (Food Safety Authority of Ireland, 2002).
A survey conducted in Inuit adults of Nunavik, Arctic Québec, Canada, demonstrated that a significant proportion of reproductive-age women had lead and mercury concentrations that exceeded those that have been reported as being associated with subtle neuro-developmental deficits in other populations (Dewailly et al., 2001).
Recently, the Food and Drug Administration (FDA) announced that pregnant women and women of childbearing age who may become pregnant should avoid consumption of certain kinds of fish that may contain high levels of methyl mercury. The FDA is advising these women not to eat shark, swordfish, king mackerel, and tilefish. As a matter of prudent public health advice, the FDA is also recommending that nursing mothers and young children not to eat these fish as well (Food and Drug Administration, 2001). In addition, the 15-member panel that advises the FDA on food matters issued its recommendation July 25, 2002 to pregnant women to limit their consumption of tuna fish because it could expose an unborn babýs developing brain to possible harmful mercury levels (Neergaard, 2002).
A partial solution may be found in aquiculture. However, aquiculture can itself, because of the feeding methods used, significantly damage ecosystems with actual losses of fish stocks taking place. Also the nutritional value and safety of the fish produced depends on what they are fed, and ω-3 fatty acid levels may be extremely low (Alasalvar et al., 2002; Hunter and Roberts, 2000; Wahlqvist, 1999).
Flax and marine algae have never been considered important nutritional resources in the history of mankind. Moreover, flax has been strongly questioned on the grounds of a number of factors that interfere in the normal development of men and animals. Flax is used to manufacture industrial products such as coatings, floor coverings, paints and varnishes.
The restrictions on the use of flaxseed in humans is due mainly to the presence of toxic cianoglicosides (linamarin) and vitamin B6 antagonic factors (Vetter, 2000; Center for Alternative Plant and Animal Products, 1995; Stitt, 1989; Butler et al., 1965). Recent findings show that low blood levels of B vitamins are linked with an increased risk of fatal coronary heart disease and stroke (American Heart Association, 1999). Homocysteine, a non-protein forming sulfur amino acid, not a normal dietary constituent, is elevated when folic acid and B vitamins levels are inadequate (Herzlich et al., 1996; Selhub et al., 1996), and researchers believe that when body cells dump too much homocysteine into the blood, artery linings become irritated, encouraging the formation of plaque - fatty deposits that cling to artery walls (McBride, 1999). An elevated serum homocysteine concentration is now recognized as an important, independent risk factor for cardiovascular disease and stroke (Malinow, 1996; Boushey et al,1995).
All flax varieties have these anti-nutritional factors, even the new genetically modified varieties such as FP967, which has a concentration of total cyanogenic compounds (total linamarin, linustatin, and neolinustatin) very similar to the traditional varieties (Canadian Food Inspection Agency, 1998).
Human consumption of flaxseed is banned in France and used with limitations in Germany, Switzerland and Belgium (Le Conseil d'Etat, 1973). In the USA, although human consumption is not prohibited, it does not have FDA approval. This means that should a company decide to include flax in a food product, it shall be liable for the safety of that product (Vanderveen, 1986).
Recent research with animals has shown the negative action that flax has on pregnancy and reproductive development. These effects have been attributed to the action of the compound known as diclycoside ecoisolariciresinol (SDG), which through microbial action acts as estrogenic depressor or potentiator in mammals. Flax is known as the richest source of SDG and therefore special caution is recommended if consumed during pregnancy and lactation (Toug et al., 1998; Rickard and Thompson, 1998).
Terrestrial sources of ω-3 fatty acids show a very important advantage over algae and fish sources from the standpoint of CHD since they contain significantly lower quantities of saturated fatty acids (myristic, palmitic, and stearic). Chia oil has a 2.8 and 5.1-fold less saturated fatty acid content than does menhaden oil and algae oil, respectively (Table 4). Dietary saturated fatty acids are independent risk factors associated with CHD (Coronary Heart Disease); their negative effects on blood low-density lipoprotein cholesterol (LDL) are stronger than the effects of dietary cholesterol (American Hearth Association, 1988). In addition, as stearic fatty acid is considered much less hypercholesterolemic than palmitic and myristic (Katan et al., 1995; Nelson, 1992), or not hypercholesterolemic at all (Grundy, 1997; Bonanome and Grundy, 1988), comparing these two fatty acids shows chia has 3.3 and 7.1-fold less than menhaden and algae oil, respectively (Table 3).
Another important consideration in regards to fish oils is that as they are an animal product, they contain cholesterol. The amounts vary by species. For instance the cholesterol content per 100 grams of sardine oil is 710 mg, salmon oil is 485 mg, menhaden oil is 521 mg, herring oil is 766 mg, and cod liver oil is 570 mg, (Unites States Department of Agriculture, 1999). This is important considering that chia, flax and algae do not contain cholesterol because they are plant species.
Due to easy accessibly of fish oils/meals as an ω-3 source, use of various levels of these materials in poultry diets have been reported in recent years (Scheideler et.al, 1997; Nash et al., 1996; Nash et al., 1995; Van Elswyk et al., 1995; Marshall et.al, 1994; Van Elswyk et al., 1992 ). However, fish oils are generally by-products obtained during the preparation of fish meals and their composition is not uniform and changes according to the source of the marine oil and the degree of hydrogenation. Variations in fatty acid composition according to season, place, species, etc. are well known, and wide variations in commercial fish oils/meal have been reported. (Valenzuela and Uauy, 1999; Sebedio, 1995; Ackman, 1992). For example, menhaden fish oil and cod liver oil have approximately equivalent EPA levels (10%), whereas sardine fish oil has 20% EPA (Alexander et al., 1995).
Fish liver oils such as cod liver oil have higher vitamin A levels than do fish oils that are whole-body products. Increased dietary vitamin A has been shown to antagonize vitamin E status in poultry and other animals (MacGuire et al., 1997; Abawi and Sullivan, 1989; Tengerdy and Brown, 1977).
Reproductively active hens exhibited increased hepatic lipidosis following six months of feeding 3% menhaden fish oil. Van Elswyk et al. (1994) suggested that dietary menhaden oil enhances the lipogenic activity of the liver in laying hens.
The beneficial effects of fish have received much attention. However, EPA and DHA fatty acids are easily peroxidized to form hydroperoxides and their secondary degradation products which are thought to be deleterious to cells. There is strong evidence that lipid-derived aldehydes are really cytotoxic and the availability of a cellular GSH-depleting agent is a critical factor for the detoxication of the aldehydes (Sugihara et al., 1994). EPA and DHA are more readily oxidized and this results in more toxic oxidation products than with linoleic,
α-linolenic, and arachidonic acids (Cho et al., 1987). Scientific evidence shows that EPA and DHA are able to exert beneficial effects with regard to reducing the risk of suffering CHD, only if antioxidative protection against oxidative stress is sufficient to minimize the peroxidative damage of tissue lipids (Song et al., 2000).
Oxidation of food lipids is a major concern for both consumers and food manufacturers. If not controlled, oxidation can produce not only food off-flavors (typically known as fishy flavor), but also promote aging and the degenerative diseases of aging such as cancer, cardiovascular diseases, cataracts, immune system decline, and brain dysfunction, from which you want to be protected when eating ω-3 fatty acids (Okuyama et al., 1997).
Chia seed contains a number of compounds with potent antioxidant activity: myricetin, quercetin, kaemperol, and caffeic acid. These compounds are both primary and synergistic antioxidants and contribute in a major way to the strong antioxidant activity of chia (Castro-Martinez et al., 1986; Taga et al., 1984). Chia as an ω-3 source does not need the addition of artificial antioxidants such as vitamins. Antioxidant vitamins have been shown to nullify the protector effects of cardiovascular drugs. New research has found that a combination of antioxidant vitamins such as vitamin E, vitamin C, and β-carotene, blunt the rise in high density lipoprotein (HDL) cholesterol levels seen with the simvastatin drug (a cardiovascular protection compound) (Brown et al., 2001). Also, vitamin E has been demonstrated to promote the oxidation process when an upper level is reached. Low and high limits are very close to one another, making it very difficult to achieve the correct amount when ingredients are mixed for animal feeds (Leeson et al., 1998).
One advantage of the consumption of α-linolenic fatty acids over ω-3 fatty acids from fish/algae products is that the problem of having insufficient antioxidant intake does not exist with a higher intakes of α-linolenic from a plant source (Simopoulos, 1999).
Another concern with the recommendations being made to increase the intake of EPA as a source of ω-3 fatty acid is the potential for adverse immunological effects resulting from excessive intakes. A moderate to high amount of EPA, but not of α-linolenic fatty acid, can decrease a natural killer (NK) cell activity in healthy subjects (Thies et al., 2001). NK cells play an important role in host defense against virus infection and in inmunosurveillance against tumor cells (Lewis et al., 1992).
Traditionally, algae have not been part of human or animal diets (with the exception of fish). The need to use sodium chloride (NaCl) for the artificial production and the use of solvents for oil extraction (Nitsan et al., 1999; Becker and Kyle, 1998) are aspects that no doubt should at least be subjects to consider from an environmental standpoint.
Owing to the availability of flax (as industrial oil) and to its relatively low price, there have been many attempts to use it as an ω-3 fatty acid source in animal production, though not very successfully. Numerous scientific publications have shown the negative effects that the antinutritional factors of flax have on the development of layers, broilers, pigs, laboratory animals, etc. (Treviño et al., 2000; Toug et al., 1999; Novak and Scheideler, 1998; Bond et al., 1997; Ajuyah et al., 1993; Bell and Keith, 1993; Bhatty, 1993; Batterham et al., 1991; Lee et al., 1991; Bell, 1989; Homer and Schaible, 1980; Kung and Kummerow, 1950). Thus, in order to use flax in poultry diets, the seeds have to be detoxified. The most efficient processes require the use of solvents, and even then the seeds cannot be completely detoxified (Mazza and Oomah, 1995; Madhusudhan et al., 1986).
A recent review which compared chia to other sources of ω-3 fatty acids in the same experiment showed the advantage of chia over diets which included fish oil and flax for the production of ω-3 eggs. In addition, a research paper comparing flax and chia effects as an omega-3 source, reported the negative effects of flax on egg production when it is incorporated in a laying hen diet (Ayerza and Coates, 2001)
Considering the α-linolenic fatty acid content of flax and chia (Table 1) and the incorporation of ω-3 fatty acids they can produce in eggs when fed to chickens, chia has proven to have a higher efficiency, by almost 230%, compared to flax. This difference could be related to the different antioxidant compounds found in flax and chia and their influence on fatty acid incorporation. Ajuyah et al. (1993) found that including antioxidants in broiler diets caused a significant increase in ω-3 fatty acid incorporation into broiler white meat, but that adding antioxidants did not affect the decrease in body growth which took place when flax seeds were added to the diet.
The higher fatty acid deposition efficiency shown by chia, compared with flax, could also be related to the digestion process of the lipids. Numerous factors are capable of causing variations in intestinal absorption and tissue deposition of fat and fatty acids in non-ruminants. These factors include: saturated:unsaturated fatty acid ratio (Lessire et al., 1996); monounsaturated fatty acid plus polyunsaturated:saturated fatty acid ratio (Chang and Huang, 1998); and total ω-6:ω-3 fatty acid ratio (Wander et al., 1997) in the diet. Digestive utilization of fatty acids varies according to their position on the glycerol molecule, hence, differences between α-linolenic fatty acid positions in chia and flax could explain chia’s higher ω-3 fatty acid incorporation (Porsgaard, and Høy, 2000; Straarup and Høy, 2000; Innis and Dyer, 1997; Lessire et al., 1996).
None of the toxic factors found in flax have been found in either chia seeds or chia oil (Ayerza and Coates, 2002, 2001, 2000, 1999 and 1997; Lin et al., 1994; Weber et al., 1991; Ting et al., 1990, Bushway et al., 1984)
The metabolism of ω-3 fatty acids in humans and animals
The mechanism by which ω-3 fatty acid-rich diets reduce CHD mortality, remains controversial. Recent literature discusses the role of different ω-3 fatty acids in human and animal bodies, and ways of obtaining optimal levels for normal growth and development as well as for the prevention and treatment of CHD and other diseases. Alpha-linolenic fatty acid cannot be synthesized de novo, and that is why it is called “essential fatty acid”. EPA and DHA can, however, be formed from α-linolenic.
Humans of all ages, including pre-terms and very likely fetuses, convert α-linolenic to DHA (Brenna, 2002; Billeaud et al., 1997). This process has been reported for other species, as well (Ayerza and Coates, 2000). However the efficiency of this conversion within species (depends on age, diets, etc.) and between species is a controversial issue (Simopoulos, 2002) and is generating a lot of discussion to determine the most convenient way to provide ω-3 fatty acids to humans and animals. The main point of discussion came about because of the very poor scientific knowledge that was available describing the biochemistry and physiologic functions of ω-3 fatty acids in general, and of α-linolenic in particular. General acceptance that the function of α-linolenic fatty acids was just as a precursor of the long chain polyunsaturated fatty acids and because the first epidemiological studies were conducted in populations having high fish intake, were the main reasons for the low estimates for α-linolenic fatty acid requirements (Lauritzen et al., 2001).
However recent results from epidemiological and controlled studies regarding the role of α-linolenic fatty acid in humans and animals, are changing the way ω-3 sources are thought to work. Evidence that vegetarians do not suffer from diets containing no DHA, supported these changes (Kwok et al., 2000; Li et al., 1999). Williard et al. (2001) found that when increasing quantities of preformed DHA were added to the diet, DHA synthesis in astrocytes was reduced but not suppressed, even if the DHA was increased to a very high concentrations. This result is consistent with data from Ezaki et al. (1999) that found a serum increase in DHA after 10 months of feeding of α-linolenic to elderly volunteers (ages 67-91) in Japan. The authors were surprised, since the regular intake of long chain ω-3 from fish was already considerable in these volunteers. Williard et al. (2001) concluded that some DHA synthesis persists in the astrocytes, even when excess DHA is available. This suggests that DHA synthesis from α-linolenic fatty acid is a constitutive process that is required to fulfill an essential function in the brain.
Recently Fu and Sinclair (2000), based on a controlled experiment with guinea pigs, suggested that α-linolenic fatty acid may have a function in relation to fur, perhaps as a secreted lipid from sebaceous glands which protects the fur from damage by water, light, or other agents. The authors concluded that if there is a substantial removal of this fatty acid via sebaceous glands in humans, it might account for why α-linolenic fatty acid rarely accumulates in most tissues. Substantial quantities of α-linolenic fatty acid in the skin suggests that these could be potentially important reservoirs of ω-3 fatty acids in the body. In addition, Yli-Jama et al. (2001) determinated a highly significant correlation between percentage of α-linolenic in adipose tissue and in serum free fatty acid, and also, between intake and content in adipose tissue of humans.
As is the case with mammals and avians, fish do not form ω-3 fatty acids de novo, they need dietary sources to meet their nutritional requirements. Although, each species of fish has a specific fatty acid requirement, in general, and differentially from mammals and birds, most marine fish require highly polyunsaturated ω-3 fatty acids (EPA and/or DHA), while fresh water fish require ω-3 fatty acids from either α-linolenic or EPA/DHA, or a mixture of both types (Webster and Lim, 2002; Sargent et al., 1999). Some fish like Rainbow Trout (Oncorhynchus sp.), Milkfish (Chanos chanos) Chanel Catfish (Ictalurus punctatus) and Indian major Carps (Catla catla, Labeo rohita, and Cirrhinus mrigala) can elongate and desaturate ω-3 fatty acids obtained from lower down in the food chain (Hardy, 2002; Lim et al., 2002; Murthy, 2002; Robinson and Li, 2002); however, other fish like Yellowtail (Seriola quinqueradiata) are unable to use α-linolenic as an essential fatty acid, and require EPA and DHA (Masumoto, 2002), or they have a very limited ability to elongate and desaturate shorter-chain fatty acids, like the Red Drum (Sciaenops ocellatus) and Coregonids (Coregonus sp.) (Gatlin, 2002; Dabrowski et al., 2002).
Thus to produce the typical high EPA and DHA content in marine fish, a dietary source of ω-3 fatty acids must be supplied through the addition of marine fish oil/meal to their diet. The feeding requirement of 3 kg of fish or fish entrails to produce 2 kg of fish, adds another question mark to the sustainability of aquiculture as an ω-3 fatty acid source for humans and animals (Leaf, 2002).
The Commission of the European Communities has legislation in place to prohibit including certain animal by-products, including fish meal to ruminants, to prevent cases of bovine spongiform encephalopathy (BSE) from entering into the feed chain (Commission of the European Communities, 2000a). Later an amending decision, prohibiting feeding of fish meal to all farm animals which are kept, fattened or bred for the production of food, except for aquiculture (Commission of the European Communities, 2000b). In addition, since January 1, 2002, the EU prohibited importing fish meal from Chile and Peru, two of the world largest fish meal producers, in an effort to contro BSE (Agroenlinea, 2002).
The main goal in the commercialization of ω-3 enriched products is not that they are high in DHA, EPA or α-linolenic fatty acids, but rather that they act as a reliable source of fatty acids for human and animal consumption. In the case of chia and flax, the α-linolenic fatty acid that their seeds transmit to eggs, poultry meat, cows milk, pigs meat, etc., acts in the human body as a substratum for the transformation into DHA and EPA through the action of the enzymes desaturasa and elongasa. Even though the conversion of α-linolenic acid into DHA and EPA has been established for a significant period of time, the mathematical relationship of ω-6 and ω-3 18-carbon fatty acids in the concentration of their respective 20-carbon metabolites in tissues has only recently been reported (Muggli and Clough, 1994).
In 1995, research projects funded by the Australian National Health and Medical Research Council which were published in the USA showed that a higher content of α-linolenic acid in the diet increased the EPA content in the tissues in a predictable manner. A linear relationship was determined between the incorporation of vegetable origin α-linolenlc acid and the EPA concentrations in plasma and in cellular phospholipids (Mantzioris et al., 1995). Also, research work published in 1997 by the American Society for Clinical Nutrition (USA) which compared the effects of vegetable origin α-linolenic fatty acids with marine origin DHA and EPA acids in the hemostatic factors in human beings, could not prove statistically significant differences (Freese and Mutanen, 1997).
A pilot study conducted at the Beltsville Human Nutrition Research Center, Maryland, USA, demonstrated that dietary α-linolenic acid is an effective modulator of thromboxane and prostacyclin biosinthesis. Therefore, we can expect that the eicosanoid-mediated effects of
α-linolenic acid are similar to those elicited by marine lipids (Ferreti and Flanagan, 1996).
A number of epidemiologic and controlled studies support the theory that consumption of α-linolenic as an ω-3 fatty acids are associated with a reduced risk of suffering CHD and other cardiovascular diseases (Bemelmans et al., 2002; Hiroyasu et al., 2001; Mantzioris et al., 2000; Li et al., 1999; Hu et al., 1999; Loria and Padgett, 1997; Sing et al., 1997;Lorgeril et al., 1994; Indu and Ghafoorunissa, 1992; Renaud et al., 1986a, 1986b). A comparative trial in which people received α-linolenic fatty acid in the form of chia seeds and a placebo found HDL and triglyceride levels to be different between groups, with the difference favoring the consumption of chia (Coates and Ayerza, 2002). Composition of the chia supplement is contianed in the paper entitled "Chia seed nutrient composition and its relation with human daily nutrient requirements"
On the other hand, high amounts of DHA inhibit the action of Δ5 and Δ6 enzymes at the level of the essential fatty acids, linoleic (ω-6) and α-linolenic (ω-3). Although this action does not affect the total number of ω-3 long chain fatty acids, it will affect the ω-6 acids, thus causing a imbalance in the ω-6:ω-3 ratio which is considered vital for the good functioning of the human body (Simopoulos and Robinson, 1998; British Nutrition Foundation, 1992; Simopoulos, 1989).
Egg yolks from laying hens fed chia-enriched diets show a significant increase not only in α-linolenic fatty acid, but also in DHA. As in humans, poultry have shown the capacity to increase DHA by desaturation and elongation of α-linolenic fatty acid in their livers. Eggs from hens fed 7% and 14% chia diets had α-linolenic:DHA ratios of 1.8 and 3.1, respectively. Hens fed chia diets produced ω-3-enriched eggs with a relationship between α-linolenic essential fatty acid and its metabolite DHA, equal to that found in human milk.
Different organizations involved in human health care that have made recommendations on the necessary consumption level of ω-3 fatty acids either only include α-linolenic acid in their recommendations or, in cases when DHA and EPA are included, also set a lower limit only to the former, which is a precursor of the other two (Food and Agricultural Organization, 1994; British Nutrition Foundation, 1992; Canada [dept of] Health and Welfare, 1990).
Although there are variations between the recommendations made by nutritionists regarding the relationship among different ω-3 acids in the diet, especially between α-linolenic and DHA, they (nutritionists) agree that the α-linolenic content must be significantly higher than the DHA content, always being between the limits that both fatty acids have in human milk. Breast milk has a DHA:α-linolenic ratio of, 1:2.2; 1:2.2; 1:2.7; 1:3.3; 1:3.6; 1:4; and 1:8, in women from Germany, France, Cuba, Nigeria, Japon, China, and Nepal, respectively (Jensen and Lammi-Keefe, 1998; Yonekubo et al., 1998; Vander Jagt et al., 2000; Glew et al., 2001; Krasevec et al, 2002). In the USA, DHA:α-linolenic ratio in breast milk of women from Maryland, Connecticut, and Oklahoma was 1:4.4; 1:2.1 and 1:5, respectively (Bitman et al., 1981 and Henderson et al., 1992, cited by Nettleton, 1995; Jensen et al., 2000). In human milk, individual variation in fatty acid content has been reported; for example, in DHA a variation from 0.04 to 0.25% of total milk fatty acids was reported (Nettleton, 1994). Still, within the total ω-3 fatty acid content, the α-linolenic acid level was always significatively higher than the DHA content.
Eggs from hens fed chia have a relationship between α-linolenic fatty acid and its metabolite DHA, similar to that one found in human milk in Germany, France, Nigeria, Japan and China. Also the DHA:α-linolenic ratios of the eggs produced by hens fed 7% chia diets are similar to the eggs from hens fed under free range conditions, that is hens consuming green leafy vegetables, fresh and dried fruits, insects and occasional worms (Simopoulos and Salem, 1992).
The goal of not increasing the risk of suffering a CHD by including eggs in the diet, but rather reducing such a risk, was accomplished through the production of ω-3 enriched eggs produced by adding a source of α- linolenic acid to the hen’s diet. Comparing regular eggs and ω-3 enriched eggs produced by feeding α- linolenic acid to the hens and including such eggs in human diets have proven the capacity of the latter to reduce the risk of suffering cardiovascular disease by reducing the triglycerids and cholesterol content in plasma and decreasing blood pressure. Regular eggs, on the other hand, increased these parameters and thus the possibility of suffering CHD (Ferrier et al., 1995; Sim and Jiang, 1994; Ferrier et al., 1992; Oh et al., 1991). Recent results from a comparative trial showed that α-linolenic enriched eggs produce a significantly deeper reduction of platelet aggregation than do DHA enriched eggs, with the mechanism for dietary α-linolenic-induced reduction of platelet aggregation being different (Van Elswyk et al., 2000).
The large reduction in total saturated fatty acids in general, and especially in palmitic (up 30.6%) fatty acid found in eggs, and in broiler meat (up 20.6 %) from birds fed chia-enriched diets, indicates an additional health advantage for these omega-3-enriched products. Recent research suggests that the reduced saturated fatty acid content in poultry products is feed dependent, giving to chia a dramatic advantage compared with fish, algae and flax products (Ayerza et al., 2002; Ayerza and Coates, 2001 and 2000).
Organoleptic characteristics
The Health Focus Survey is a national survey of US shoppers conducted bi-annually since 1990. The 2000 survey showed that most shoppers believe foods can offer benefits that reach beyond basic nutrition to functional nutrition for disease prevention and health enhancement. However, the first obstacle for making healthy choices is taste. Todaýs shoppers are less willing than ever to compromise taste for health benefits (Gilbert, 2000).
Foods made by adding flax and marine lipids or products from animals fed one or more of these raw materials as ω-3 sources have a typical smell generally recognized as “fishy flavor”. A number of scientific studies conducted to evaluate products from broilers, hens, pigs, ruminants, etc., fed flax seed/oil or marine lipids have reported them smelling/tasting “fishy”(Ayerza, 2002b; Ayerza and Coates, 2001; Wood et al., 1999; Warnants et al., 1998; Romans et al., 1995).
Eggs laid by hens fed flax seeds have a characteristic (unpleasant) smell, similar to that of hens fed fish oil (Van Elswyk et al., 1995; Caston et al., 1994; Jiang et al., 1994; Van Elswyk et al., 1992; Adam et al., 1989; Koeheler and Bearse, 1975). Several trials have shown increasing off-flavor with increasing percentages of flaxseed and fish products in broiler diets. Off flavor/taste were found with dietary fish oil and flaxseed contents as low as 1.5% and 5%, respectively (Gonzalez-Esquerra and Leeson, 2000; Lopez-Ferrer et al., 1999; Hargis and Van Elswyk. 1993; Ratanayake et al., 1989; Miller and Robisch, 1969; Holdas and May, 1966; Fry et al., 1965; Hardin et al., 1964). Neither acceptance nor flavor of either type of meat (dark and white) was significantly different (P>0.05) between high content chia diets, and the control (Ayerza et al., 2002).
The difference in the organoleptic characteristics of eggs and meat produced with flax and chia can be attributed to the powerful action of chia antioxidants which are absent in flax (Shukla et al., 1996; Intemational FloraTechnologies, 1990; Castro-Martinez et al., 1986; Taga et al., 1984) and/or to the interaction between the other components of flax and the bird́s physiology. (Marshall et al., 1994) In the case of fish oil, the typical smell is due to the greater unstability of DHA and EPA compared to α-linolenic acid, along with the absence of antioxidants capable of preventing them from experiencing this degenerative process (Shukla and Perkins, 1998).
In a study conducted in the USA which took place in five cities, it was shown that consumers generally are reluctant to eat eggs smelling/tasting of fish (Marshall et al., 1994). The absence of atypical organoleptic characteristics in the eggs laid by hens fed chia, represents a significant comparative advantage for this grain, compared to flax and fishing by-products (Ayerza and Coates, 2002, 2001, and 1999).
In case of marine algae, available commercial information reports the absence of fish smell or taste in the eggs produced. However, it has not been possible to locate any scientific papers supporting this. An indirect reference about off-flavors in eggs from hens fed algae-enriched diets can be found in a non-scientific paper by Abril et al. (2000). They mention that including up to 1% algae in laying hens did not produce a significant decrease in overall egg acceptability in terms of aroma and/or flavor. Although there is no scientific information available for or against this, the high content of DHA combined with the strong instability of DHA in the presence of oxygen would indicate a strong ability to transmit undesirable organoleptic conditions to eggs produced with a high amounts of algae.
Not all, but some marine algae showed antioxidant activity related to the total polyphenol content. Therefore it has been suggested that polyphenol could prevent oxidative damage to important biological membranes. However, commercial algae shows very low antioxidant capacity. The explanations for this reduced antioxidant activity could be related to the effect of drying (50º C for 48h) the algae for commercialization. Jimenez-Escrig et al. (2001) recently reported that processing (drying) and storing decreases the antioxidant capacity of fresh algae. Thus, the explanation for the difference between chia and algae in terms of shelf life may be associated with the difference in the quantity and/or quality of the natural antioxidants in each raw material.
In summary, several studies provide solid evidence that including more than 5% flax seed, 1.5% fish oil or 1% algae in poultry diets will result in a significant decrease of overall product acceptability in terms of aroma and/or flavor. However it is possible to include up to 30 % chia in the birds diet, without encountering negative consumer preferences as compared to common products. For eggs this means a maximum ω-3 fatty acids enriching potential of 175 mg/egg for algae, 207 mg/egg for fish oil, 214 mg/egg for flaxseed and 986 mg/egg for chia seed, without affecting egg organoleptic characteristic (Ayamond and Van Elswyk, 1995; Van Elswyk et al., 1995; Abril et al., 2000; Ayerza and Coates, 2002, and 2000).
Conclusions
Available information suggests that none of the current levels of ω-3 fatty acids that can be produced by the incorporation of chia in animal diets can be reached using flax, fish oil or algae based diets without strongly affecting animal performance and/or one or more of the intrinsic characteristics of the final product. In all cases, the limiting factor for utilization of high percentages of available ω-3 sources, with the exception of chia, is flavor, smell and/or atypical textures transmitted by these sources to the products. Also, in the case of flax, animal production would be negatively affected.
In table5 the main characteristics of chia seeds discussed in this paper are synoptically compared with flaxseed, algae, and fish oil as raw material for food and feed industry.
The number of scientific papers reporting the nutritional advantage of chia over the other omega-3 sources, and the commercialization of products with chia as an ingredient to produce a number of products such as bread, energy bars, and as feed for horses, pigs, cats and dogs, in poultry diets for eggs and meat production, in the diet of milk cows for milk production, and as dietary supplement for humans, are rapidly increasing world-wide (samples of thes products are shown in Table 6).
Modern science can now explain why ancient mesoamerican civilizations considered chia a basic component of their diet, and after 500 years of being forced into obscurity, the Hidden Crop of the Aztecs offers to the world a new opportunity to go back to our origins and improve human nutrition by providing a natural source of ω-3 fatty acids and antioxidants.
References
Abawi, F.G., and W. Sullivan. 1989. Interactions of vitamins A, D3, E, and K in the diet of broiler chicks. Poultry Science, 68:1490-1498.
Abril. J.R., W.R. Barclay, and P.G. Abril. 2000. Safe use of microalgae (DHA GOLD) in laying hen feed for the production of DHA.enriched eggs. Pages 197-202 in Egg Nutrition and Technology edited by J.S. Sim, S. Nakai, and W. Guenter. CAB International 2000, Wallingford, Oxon, U.K.
Abril, R. and W. Barclay, 1998. Production of docosahexaenoic acid-enriched poultry eggs and meat using an algae-based feed ingredient. Pages 77-88 in A.P. Simopoulos ed. The return of ω3 fatty acids into the food supply. Karger AG., Basel, Switzerland.
Ackman, R.G. 1992. Fatty acids in fish and shelfish. Pages 169-184 in Fatty acids in food and their health implications, edited by C.K. Chow. Marcel Dekker, Inc., New York, USA.
Adam, R.L., D.E. Pratt, J.H. Lin and W.J. Stadelman, 1989. Introduction of omega-3 polyunsaturated fatty acid into eggs. Poultry Science, 68 (SPSS Abstracts.):166.
Agroenlinea. 2002. Mercado mundial de harina de pescado. Retrieved February 17, 2002 from the World Wide Web, http: //www.agroenlinea.com/agro/newsletter/150102.htm
Ajuyah, A.O., R.T. Hardin, and J.S. Sim. 1993. Effect of dietary full fat flax seed and without antioxidant on the fatty acid composition of major lipid classes of chicken meats. Poultry Science, 72:125-136.
Alasalvar, C., K.D.A. Taylor, E. Zubcov, F. Shahidi, and M.Alexis. 2002. Diferentiation of cultured and wild sea bass (Dicentrartchus labrax): total lipid content, fatty acids and trace mineral composition. Food Chemistry (In Press).
Alexander, D.W., S.O. McGuire, N.A. Cassity, and K.L. Fritsche. 1995. Fish oils lower rat plasma and hepatic, but not inmune cell α-tocopherol concentration. Journal of Nutrition, 125:2640-2649.
American Heart Association. 1999. Homocysteine, folic acid and cardiovascular disease. Retrieved November 11, 1999 from the World Wide Web, http: //www.americanheart.org/ Heart_ and_Stroke_A_Z_ Guide/ homocys. html
American Hearth Association. 1988. Dietary guidelines for healthy American Adults: A statement for physicians and health professionals. Arteriosclerosis, 8:221A.
Ayamond, W.M. and M.E. Van Elswyk. 1995. Yolk thiobarbituric acid reactive substances and n-3 fatty acids in response to whole and ground flaxseed. Poultry Science, 74:1388-1394.
Ayerza, R. (h). 2002a. Chia as a New Source of Omega-3 Fatty Acids: Advantage Over Other Raw Materials to Produce Omega-3 Enriched Eggs. Proceedings of the Symposium on Omega-3 Fatty Acids, Evolution and Human Health, Washington D.C., USA, September 23-24, 2002, (In press), Belovo S.A., Bastogne, Belgium.
Ayerza, R. (h). 2002b. Milk enriched in omega-3 fatty acids comercialized in Ar5gentina and Brazil. Southwest Center for Natural Products Research and Commercialization, Office of Arid Lands Studies, The University of Arizona, USA (Unpublished), 6p.
Ayerza, R. (h). 1996. Fatty acid composition, protein and oil content of chia (Salvia hispanica L.) grown in Columbia and Argentina. Third European Symposium on Industrial Crops and Products, Reims, France.
Ayerza, R. (h). 1995. Oil Content and Fatty Acid Composition of Chia (Salvia hispanica L.) from Five Northwestern Locations in Argentina. Journal of The American Oil Chemists' Society, 72:1079-1081.
Ayerza, R. (h) and W. Coates. 2002. Dietary levels of chia: influence on hen weight, egg production, and egg sensory quality. British Poultry Science, Basingstoke, Hants, U.K. (In Press).
Ayerza, R. (h).and W. Coates. 2001. The omega-3 enriched eggs: the influence of dietary linolenic fatty acid source combination on egg production and composition. Canadian Journal of Animal Science, 81:355-362.
Ayerza, R. (h) and W. Coates. 2000. Dietary levels of chia:influence on yolk cholesterol, lipid content and fatty acid composition, for two strains of hens. Poultry Science, 78:724-739.
Ayerza, R. (h), and W. Coates. 1999. An omega-3 fatty acid enriched chia diet: its influence on egg fatty acid composition, cholesterol and oil content. Canadian Journal of Animal Science,79:53-58..
Ayerza, R. (h), and W. Coates. 1997. An omega-3 fatty acid enriched chia diet: its influence on egg fatty acid composition, cholesterol and oil content. Page 51 in Abstracts of An International Conference of the Association for the Advancement of Industrial Crops, Saltillo, Mexico, September 14-18, 1997.
Batterham, E.S., L.M. Andersen, D.R. Baigent, and A.G. Green. 1991. Evaluation of meals from linola low-linolenic acid linseed and conventional linseed as protein sources for growing pigs. Animal Feed Science and Technology, 35.(3-4):181-190.
Becker, C.C. and D.J. Kyle. 1998. Developing functional foods containing algal docosahexaenoic acid. Food Technology, 52(7):68-71.
Bemelmans, W.J.E., J. Broer, E.J.M. Feskens, A.J. Smit, F.A.J. Muskiet, J.D. Lefrandt, V.J.J. Bom, J.F. May, and B. Meyboom-de Jong. 2002. Efgfect of an increased intake of α-linolenic acid and group nutritional education on cardiovascular risk factors: the Mediterranean alpha-linolenic enriched Groningen dietary intervention (MARGARIN) study. American Journal of Clinical Nutrition, 75:221-227.
Bell, J.M. 1989. Nutritional characteristics and protein uses of oilseed meals. Pages 192-207 in Oil crops of the world, edited by G. Robbelen, R.K. Downey, and A. Ashri. McGraw-Hill Publishing Co., New York, New York, USA .
Bell, J.M. and M.O. Keith. 1993. Nutritional evaluation of linseed meals from flax with yellow or brown hulls, using mice and pigs. Animal Feed Science and Technology, 43(1-2):1-18.
Bhatty, R.S. 1993. Further compositional analyses of flax: mucilage, trypsin inhibitors and hydrocyanic acid. Journal of American Oil Chemistś Society, 70(9):899-904.
Billeaud, C., D. Bouglé, P. Sarda, N. Combe, S. Mazette, F. Babin, B. Entressangles, B. Descomps, A. Nouvelot, and F. Mendy. 1997. Effects of preterm infant formula supplementation with alpha-linolenic acid with a linoleate/alpha-linolenate ratio of 6:1: a multicentric study. European Journal of Clinical Nutrition, 51:520-526.
Bond, J.M., R.J. Julian, and E.J. Squires. 1997. Effect of dietary flaxseed on broiler growth, erythrocyte deformability and fatty acid composition of erythrocyte membranes. Canadian
Journal of Animal Science, 77:279-286.
Brenna, J.T. 2002. Efficiency of conversion of α-linolenic acid to long chain n-3 fatty acids in man. Current Opinion in Clinical Nutrition and Mertabolic Care, 5:127-132.
British Nutrition Foundation. 1992. Unsaturated fatty acids: nutritional and physiological significance. British Nutrition Foundatiońs Task Force, London, England.
Brown, B.G., X.Q. Zhao, A. Chait, L.D. Fisher, M.C Cheung, J.S. Morse, A.A. Dowdy, E.K. Marino, E.L. Bolson, P. Alaupovic, J. Frohlich, and J.J. Albers. 2001. Simvastatin and niacion, antioxidant vitamins, or the combination for the prevention of coronary disease. The New England Journal of Medicine, 345(22):1583-1592.
Bonanome, A. and S.M. Grundy, 1988. Effect of dietary stearic acid on plasma cholesterol and lipoprotein levels. New England Journal of Medicine, 318:1244-1248.
Boushey, C.J., S.Beresford, G. Omenn, and A. Motulsky. 1995. A quantitative assessment of plasma homocysteine as a risk factor for vascular disease. Probable benefits of increasing folate intakes. Journal of American Medical Association, 274:1049-1057.
Bushway, A.A., A.M. Wilson, L. Houston, and R.J. Bushway. 1984. Selected properties of the lipid and protein fractions from chia seed. Journal of Food Science, 49:555-557.
Butler, G.W., R.W. Bailey, and L.D. Kennedy. 1965. Studies on the glucosidase linamarase. Phytochemistry, 4(3)369-381.
Canada [dept of] Health and Welfare. 1990. Nutrition recommendation. Canadian Government Publishing Center, Ottawa, Canada.
Canadian Food Inspection Agency. 1998. Decision document 98-24: determination of the safety of the Crop Development Centrés “CDC Triffied”, a flax (Linum usitatissimum L.) variety tolerant to soil residues of triasulfuron and metsulfuron-methyl. Plant Health and Production Division, Plant Biosafety Office. Download October 23, 2001 from http://www.inspection.gc.ca/english/plaveg/pbo/dd9824c.shtml
Caston, L.J., E.J. Squires and S. Leeson, 1994. Hen perfomance, egg quality, and the sensory evaluation of eggs from SCWL hens fed dietary flax. Canadian Journal of Animal Science, 74:347-353.
Castro-Martinez, R., D.E. Pratt, and E.E. Miller. 1986. Natural antioxidants of chia seeds. Pages 392-396 in Proccedings of The World Conference on Emerging Technologies in the Fats and Oils Industry, edited and published by American Oil ChemistśSociety, Champaign, Illinois, USA.
Chang, N.W. and P.C. Huang. 1998. Effects of the ratio of polyunsaturated and monounsaturated fatty acid to saturated fatty acid on rat plasma and liver lipid concentrations. Lipids, 33(5):481-487.
Chipello, C.J. 1998. Fishing industry fades as does a way of life in newfoundland ports. The Wall Street Journal, 131(97):1.
Cho, S.Y., K. Mayashita, T. Miyazawa, K. Fujimoto, T. Kaneda. 1987. Autoxidation of ethyl eicosapentaenoate and docosahexaenoate. Journal of American Oil Chemists’ Society, 64:876:879.
Coates, W. and R. Ayerza (h). 1998. Commercial production of chia in Northwestern Argentina. Journal of American Chemists’ Society, 75(10):1417-1420.
Coates, W. and R. Ayerza (h). 1996. Production potential of chia in Northwestern Argentina. Industrial Crops and Products, 5:229-233.
Commission of the European Communities. 2000a. Council decision of 4 December concerning certain protection measures with regard to trasmissible spongiform encephalophaties and the feeding of animal protein. Official Journal of the European Communities, L 306, 07/12/2000, p.0032.
Commission of the European Communities. 2000b. Proposal for a Council Decision concerning certain protection measures with regard to trasmissible spongiform encephalophaties and the feeding of animal protein. Document 500PC0820, Brussels, Belgium..
Dabrowski, K., S. Czesny, and M. Matusiewicz. 2002. Coregonids. Pages 230-244 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Dewailly, E., S. Bruneau, G. Lebel, P. Levallois, and J.P. Weber. 2001. Exposure of the Inuits population of Nunavik (Arctic, Québec) to lead and mercury. Archives of Environmental Health, 56(4):350-357.
Ezaki, O., M. Takahashi, and T. Shigematsu. 1999. Long-term effects of dietary alpha-linolenic acid from perilla oil on serum fatty acids composition and on the risk factors of coronary heart disease in Japanese elderly subjects.. Journal of Nutritional Science and Vitaminology, 45(6):759-772.
Ferretti, A., and V.P. Flanagan. 1996. Anthitromboxane activity of dietary alpha-linolenic acid: a pilot study. Prostaglandins, Leukotrienes and Essential Fatty Acids, 54(6), 451-455.
Ferrier, L.K., L. Caston, S. Leeson, J. Squires, B.J. Weaver, and B.J. Holub. 1995. α-linolenic acid and
docosahexaenoic acid-enriched eggs from hens fed flaxseed: influence on blood lipids and platelet phospholipid fatty acids in humans. American Journal of Clinical Nutrition, 62:81-86.
Ferrier, L.K., L. Caston, S. Leeson, E.J. Squires, B. Celi, L. Thomas, and B.J. Holub. 1992. Changes in serum lipids and platelet fatty acid composition following consumption of eggs enriched in alpha-linolenic acid (LnA). Food Research International, 25:263-268.
Food and Agricultural Organization. 1994. Fats and oils in human nutrition: report of a joint expert consultation. Food and Nutrition Paper N:57. FAO, Rome, Italy.
Food and Drug Administration. 2001. FDA announces advisory on methyl mercury in fish. Food and Drug Administration Talk Paper TO1-04.
Food and Drug Administration. 1999. Fish-derived oils proposed as margarine ingredients. Electronic page (www.fda.gov), Washington, D.C., USA..
Food Safety Authority of Ireland. 2002. Summary of investigation of dioxins, furans and PCBs in farmed salmon, wild salmon, farmed trout and fish oil capsules. Retrieved March 21, 2002 from the World Wide Web, http://www.fsai.ie/pressreleases_index.htm
Fry, J.L., P. Van Walleghem, P.W. Waldroup, and R.H. Harms. 1965. Fish meal studies: effects of levels and sources of fishy flavor in broiler meat. Poultry Science, 44:1016-1019.
Freese, R., and M. Mutanen. 1997. α-Linolenic acid and marine long-chain n-3 fatty acids differ only slighty in their effects on hemostatic factors in healthy subjects. American Journal of Clinical Nutrition, 66:591-598.
Fu, Z. and A.J. Sinclair. 2000. Novel pathway of metabolism of α-linolenic acid in the guinea pig. Pediatric Research, 47(3): 414-417.
Gatlin, D.M. 2002. Red drum, Sciaenops ocellatus. Pages 147-158 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Gilbert, L.C. 2000. The functional food trend: What́s next and what Americans think about eggs. Journal of the American College of Nutrition, (19)5: 507S-512S.
Glew, R.H., Y.S. Huang, T.A. Vander Jagt, L.T. Chuang, S.K. Bhatti, M.A. Magnussen, and D.J. Vander Jagt. 2001. Fatty acid composition of the milk lipids of Nepalese women: correlation between fatty acid composition of serum phospholipids and melting point. Prostaglandins, Leukotrienes and Essential Fatty Acids, 65(3):147-156.
Gonzalez-Esquerra, R. and S. Leeson. 2000. Effects of menhaden oil and flaxseed in broiler diets on sensory quality and lipid composition of poultry meat. British Poultry Science, 41(4):481-488.
Groundy, S.M. 1997. What is the desirable ratio of saturated, polyunsaturated, and monounsaturated fatty acids in the diet?. Pages 988-990 in R.S. Rivlin ed. Fats and oil consumption in health and disease. Proceedings of a Symposium held at The Rockefeller University, New York, April 24-25, 1995. The American Journal of Clinical Nutrition, 66(4s).
Hansen, J.C. 2000. Environmental contaminants and human health in the Arctic. Toxicology Letters, 112/113:119-125.
Hansen, T.K., C. Bindsley-Jensen, P.S. Skov, and L.K. Poulsen. 1997. Codfish allergy in adults: IgE cross-reactivity among fish species. Annals of Allergy, Ashma and Inmunology, 78:187-194.
Hardin, J.O., J.L. Milligan, and V.D. Sidwell. 1964. The influence of solvent extracted fish meal and stabilized fish oil in broiler rations on performance and on the flavor of broiler meat. Poultry Science, 43:858:860.
Hardy, R.W. 2002. Rainbow trout, Oncorhynchus mykiss. Pages 184-202 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Hargis, P.S., and M.E. Van Elswyk. 1993. Manipulating the fatty acid composition of poultry meat and eggs for the health conscious consumer. World́s Poultry Science Journal, 70:874- 883.
Hebling A., M.L. McCants, J.J. Musmand, H.J. Schwartz, and S.B. Lehrer. 1996. Inmunopathogenesis of fish allergy: identification of fish-allergic adults by skin test and radioallergsorbent test. Annals of Allergy, Ashma and Inmunology, 77:48-54.
Helm, P.A., T.F. Bidleman, G.A. Stern, and K. Koczanski. 2002. Plychlorinated naphthalenes and coplanar polychrorinated biphenyls in beluga whale (Delphinapterus leucas) and ringed seal (Phoca hispida) from the eastern Canadian Arctic. Environmental Pollution, 119:60-78.
Health Canada. 1999. Novel food information - Food biotechnology: sulfonylurea tolerant flax, CDC Triffied - Health Protection Branch, FP 967. FD/OFB-098-047-A, Ottawa, Canada, 7p.
Hernandez Gomez, J.A. 1994. Chia (Salvia hispanica): antecedentes y perspectivas en Mexico. Pages 173-180 in J.A. Cuevas Sanchez, E. Estrada Lugo, and E. Cedillo Portugal eds. I Simposio Internacional sobre Etnobotanica en Mesoamerica, Chapingo, Mexico.
Herzlich, B.C., E. Lichstein, N. Schulhoff, M. Weinstock, M. Pagala, K. Ravindran, T. Namba, F. Nieto, S. Stabler, R. Allen, and M. Malinow. 1996. Relationship among homocyst(e)ine, vitamin B-12 and cardiac disease in the elderly: association between vitamin B-12 defficiency and decreased left ventricular ejection fraction. Journal of Nutrition, 126:1249S-1253S.
Holdas, A. and K.N. May, 1966. Fish oil and fishy flavor of eggs and carcasses of hens. Poultry Science, 45:1405-1407.
Homer, P. and P.J. Schaible. 1980. Poultry: feeds and nutrition. AVI Publishing Co., Inc., Westport, USA.
Hu, F.B., M.J. Stampfer, J.E. Manson, E.B. Rimm, A. Wolk, G.A. Colditz, C.H. Hennekens, and W.C. Willet. 1999. Dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease among women. American Journal of Clinical Nutrition, 69:890-897.
Hunter, B.J. and D.C.K. Roberts. 2000. Potential impact of the fat composition of farmed fish on hu,man health. Nutrition Research, 20(/):1047-1058.
Indu, M. and M. Ghafoorunissa, 1992. N-3 fatty acids in Indian diets - comparison of the effects of precursor (Alpha-linolenic acid) vs. long chain n-3 polyunsaturated fatty acids. Nutrition Research, 12:569-582.
Innis, S.M., and R. Dyer. 1997. Dietary triacygycerols with palmitic acid (16:0) in the 2-position increase 16:0 in the 2-position of plasma and chylomicron triacyglycerols, but reduce phospholipid arachidonic and docosahexaenoic acids, and alter cholesteryl ester metabolism in formula-fed piglets. Journal of Nutrition, 127:1311-1319.
International Flora Technologies, Inc. 1990. Oil of Chia. Apache Junction, USA.
James, J.M., R.M. Helm, A.W. Burks, and S.B. Leherer. 1997. Comparison of pediatric and adult IgE antibody binding to fish proteins. Annals of Allergy, Asthma and Immunology, 79:131-137.
Jensen, R.G. and C.L. Lammi-Keefe. 1998. Current status of research on the composition of bovine and human milk lipids. Pages 168-191 in Lipids in Infant Nutrition. edited by Y.S. Huang and A.J. Sinclair. American Oil ChemistśSociety Press, Champaign, Illinois, USA..
Jiang, Z., D.U. Ahn, L. Lander and J.S. Sim, 1992. Influence of feeding full-flax and sunflower seeds on internal and sensory qualities of eggs. Poultry Science, 71:378-382.
Jimenez-Escrig, A., I. Jimenez-Jimenez, R. Pulido, and F. Saura-Calixto. 2001. Antioxidant activity of fresh and processed edible seaweeds. Journal of the Science of Food and Agriculture, 81:530-534.
Katan, M., P. Zock and R. Mensink, 1995. Dietary oils, serum lipoproteins, and coronary heart disease. American Journal of Clinical Nutrition, 61 (suppl):1368-1373.
Koeheler, H.H., and G.E. Bearse. 1975. Egg flavor quality as affected by fish meals or fish oils in laying rations. Poultry Science, 54:881-889.
Krasevec, J.M., P.J. Jones, A. Cabrera-Hernandez, D.L. Mayer, and W.E. Connor. 2002. Maternal and infant essential fatty acids status in Havana, Cuba. American Journal Of Clinical Nutrition, 76:834-844.
Kung, T.K. and F.A. Kummerow. 1950. The deposition of linolenic acid in chickens fed linseed oil. Poultry Science, 29:846-851.
Kwok, T., J. Woo, S. Ho, and A. Sham. 2000. Vegetarianism and ischemic heart disease in older Chinese women. Journal of the American College of Nutrition, 19(5):622-627.
Leaf, A. 2002. On the reanalysis of the GISS-prevenzione. Circulation, 105(16):1874-1875.
Lauritzen, L., H.S. Hansen, M.H. Jorgensen, and K.F. Michaelson. 2001. The essentiality of long chain n-3 fatty acids in relation to development and function of the braind and retina. Progress in Lipid Research, 40:1-94.
Le Conseil d'Etat. 1973. Interdiction de l'huile de lin. Journal Officiel, 1523-1526.
Lee, K.H., J.M. Olomu, and J.S. Sim. 1991. Live perfomance, carcass yield, protein, and energy retention of broiler chikens fed canola and flax full-fat seeds and the restored mixtures of meal and oil. Canadian Journal of Animal Science, 71:897-903.
Lewis, C.E. and J.O. McGee. 1992. Natural killer cells in tumor biology. Pages 175-203, in The natural killer cells edited by Lewis, C.E. and J.O. McGee. Oxford University Press, Oxford, United Kingdom.
Lessire, M., Doreau, M., and Aumaitre, A. 1996. Digestive and metabolic utilization of fats in domestic animals. Pages 703-713 in Oils and fats manual, edited by A. Karleskind. Lavoisier Publishing, Paris, France.
Leeson, S., L. Caston and T. MacLaurin. 1998. Organoleptic evaluation of eggs produced by laying hens fed diets containing graded levels of flaxseed and vitamin E. Poultry Science, 77:1436-1440.
Li, D., A. Sinclair, A. Wilson, S. Nakkote, F. Kelly, L. Abedin, N. Mann, and A. Turner. 1999. Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men. American Journal of Clinical Nutrition, 69:872-882.
Lim, Ch., I.G. Borlongan, and F.P. Pascual. 2002. Pages 172-183 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Lin, K.Y., and J.R. Daniel. 1994. Structure of chia seed polysaccharide exudate.Carbohydrate Polymers (23):13-18.
Lopez-Ferrer, M.D. Baucells, A.C. Barroeta, and M.A. Grashorn. 1999. N-3 enrichment of chicken meat using fish oil: alternative substitution with rapeseed and linseed oils. Poultry Science.,.78:356-365.
Lorgeril, M. de, S. Renaud, N. Mamelle, P. Salen, J.L. Martin, I., Monjaud, J. Guidollet, P. Touboul, and J. Delaye. 1994. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. The Lancet, 343:1454-1459.
Loria, R.M., and D.A. Padgett.1997. Alpha-linolenic acid prevents the hypercholesteremic effects of cholesterol addition to a corn oil diet. Nutritional Biochemistry, 8:140-146.
McBride, J. 1999. A snapshot of blood homocysteine levels. Retrieved October 6, 1999 from the World Wide Web, http: //www.ars.usda.gov/is/AR/archive/mar99/snap0399.htm.
Madhusudhan, K.T., H.P. Ramesh, T. Ogawa, K.Sasaoka, and N. Singh. 1986. Detoxification of commercial linseed meal for use in broiler rations. Poultry Science, 65:164:171.
Madsen, C. 1997. Prevalence of food allergyIintolerance in Europe. Environmental Toxicology and Pharmacology, 4:163-167.
Malinow, M.R. 1996. Plasma homocyst(e)ine: a risk factor for arterial occlusive diseases. Journal of Nutrition, 126:1238S-1243S.
Marshall, A.C., A.R. Sams, and M.E. Van Elswyk. 1994. Oxidative stability and sensory quality of stored eggs from hens fed 1.5% menhaden oil. Journal of Food Science, 59(3):561-563.
Mantzioris, E., M.J. James, R.A. Gibson, y L.G. Cleland. 1995. Differences exist in the relationships between dietary linoleic and ά-linolenic acids and their respective long-chain metabolites. American Journal of Clinical Nutrition, (61):320-324.
Masumoto; T. 200 . Yellowtail, Seriola quinqueradiata.2002. Pages 131-146 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Mazza, G. and B.D. Oomah. 1995. Flaxseed, dietary fiber, and cyanogens. Pages 56-81 in Flaxseed in Human Nutrition, edited by S.C. Cunnane and L.U. Thompson. American Oil Chemists' Society Press, Champaign, USA.
McGuire, S.O., D.W. Alexander, and K.L. Fritsche. 1997. Fish oil source differentially affects rat inmune cell α-tocopherol concentration. Journal of Nutrition, 127:1388-1394.
Miller, D. and P. Robisch. 1969. Comparative effect of herring, menhaden, and safflolwer oils on broiler tissues fatty acid composition and flavor. Poultry Science, 48:2146-2157.
Moneret-Vautrin D.A., G. Kanny, and L. Parisot. 2001. Accidents graves par allergie alimentaire en France: fréquence, caractéristiques cliniques, et idéologiques. Première enquête du Réseau d́allergovigilance, avril-mai
2001. Revis Français de Allergologie et Immunologie Clinique, 451:696-700.
Muggli, R. y P. Clough. 1994. The Fats of Life. Roche Magazine, 49:11.
Murthy, H.S. 2002.Indian major carps. Pages 262-272 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Nash, D.M., R.M.G. Hamilton, K.A. Sanford, and H.W. Hulan. 1996. The effect of dietary menhaden meal and storage on the omega-3 fatty acids and sensory attributes of egg yolk in laying hens. Canadian Journal of Animal Sciences, 76:377-383.
Nash, D.M., R.M.G. Hamilton, and H.W. Hulan. 1995. The effect of dietary herring meal on the omega-3 fatty acid content of plasma and egg yolk lipids of laying hens. Canadian Journal of Animal Science, 75:247-253.
Neely, E. 1999. Dietary modification of egg yolk lipids. Thesis. School of Agriculture and Food Science, The Queeńs University of Belfast, Northern Ireland, UK.
Neergaard, L. 2002. Scientific advisers urged government to tell pregnant women to limit how much tuna they eat. Associated Press. Retrieved July 27, 2002 from the World Wide Web, http://sfgate.com.
Nelson, G.J. 1992. Dietary Fatty Acids and Lipid Metabolism. Pages 437-471 In: Fatty acids in foods and their health implications, edited by C.K. Chow. Marcel Dekker, Inc.
Nettleton, J.A. 1995. ω-3 fatty acids and helth. Chapman & Hall, New York, New York, USA.
Nettleton, J.A. 1994. Fats and oils in human nutrition: report of a joint expert consultation. Food and Agricultural Organization, Food and Nutrition Paper, Rome, Italy, (57):2-6.
Nitsan; Z, S. Mokady, and A. Sukenik. 1999. Enrichment of poultry products with ω-3 fatty acids by dietary supplementation with the alga Nannochloropsis and Mantur oil. Journal of Agricultural Food and Chemistry, 47:5127-5132.
Novak, C. and S. Scheideler. 1998. The effect of calcium and/or vitamin D, supplementation of flax based diets on production parameters and egg composition. University of Nebraska Cooperative Extension MP 70, Lincoln, USA..
Oh, S.Y., J. Ryue, C.H. Hsieh, and D.E. Bell. Eggs enriched in ω-3 fatty acids and alterations in lipid concentrations in plasma and lipoproteins in lipid concentrations in plasma and lipoproteins and in blood pressure. American Journal of Clinical Nutrition, 54:689-695.
Okuyama, H., T. Kobayashi, and S. Watanabe. 1997. Dietary fatty acids - the n-6/n-3 balance and chronic elderly diseases excess linoleic acid and relative n-3 deficiency syndrome seen in Japan. Progress in Lipid Research, 35(4):409--457.
Oomah, B.D. and E.O. Kenaschuk. 1995. Cultivars and agronomic aspects. Pages 43-45 in Flaxseed in Human Nutrition, edited by S.C. Cunnane and L.U. Thompson. American Oil Chemists' Society Press, Champaign, USA.
Organisation for Economic Co-Operation and Development. 1998. Towards sustainable development, Environmental Indicators: Fish Resources.OECD, Paris, France.
Pascual, C., M.M. Esteban, and J.F. Crespo. 1992. Fish allergy: evaluation of the importance of crossreactivity. Journal of Pediatry, 121:S29-34.
Porsgaard, T., and C.E. Høy. 2000. Lymphatic transport in rats of several dietary fats differing in fatty acid profile and triacyglycerol structure. Journal of Nutrition, 130:1619-1624.
Ratanayake, W.M.N., R.G. Ackman, and H.W. Hulan. 1989. Effect of redfish meal enriched diets on the taste and n-3 PUFA of 42-day-old broiler chickens. Journal of Science and Food Agricultural, 49:59-74.
Renaud, S., R. Morazain, F. Godsey, E. Dumont, C. Thevenson, J.L. Martin, and F. Mendy. 1986a. Nutrients, platelet function and composition in nine groups of French and British farmers. Atherosclerosis, 60:37-48.
.Renaud, S., F. Godsey, E. Dumont, C. Thevenson, E. Ortchanian, and J.L. Martin. 1986b Influence of long-term diet modification on platelet function and composition in Moselle farmers. American Journal of Clinical Nutrition, 43:136-150.
Rickard, S.E. and L.U. Thompson. 1988. Chronic exposure to secoisolariciresinol diglycosede alters lignan disposition in rats. The Journal of Nutrition, 128(3):615-623.
Robinson, E.H. and M.H. Li. 2002. Channel Catfish, Ictalurus punctatus. Pages 293-318 in Nutrient Requirements and Feeding of Finfish for Aquaculture, edited by C.D. Webster and C. Lim.. CAB International Publishing, Wallingford, Oxfordshire, UK.
Romans, J.R., D.M. Wulf, R.C. Johsdon, G.W. Libal, and W.J. Costello. 1995. Effect of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork: II. Duration of 15% dietary flaxseed. Journal of Animal Science, 73(7):1987-1999.
Sahagun, B. de. 1579. Historia general de las cosas de Nueva España. 1982. Reprinted by School of American
Research, Santa Fe, USA.
Sargent, J. G. Bell, L. McEvoy, D. Tocher, and A. Estevez. 1999. Recent developments in the essential fatty acids nutrition of fish. Aquaculture, 77:191-199.
Sebedio, J.L. 1995. Marine oils. Pages 266-299 in Oils & Fats Manual, edited by A. Karleskind Lavoisier Publishing, Paris, France.
Selhub, J., P. Jaques, A. Bostom, R. D́Agostino, P. Wilson, A. Belanger, D. Oleary, P. Wolf, D. Rush, E. Schefer, and I. Rosenberg. 1996. Relationship between plasma homocysteine, vitamin status and extracranial carotid-artery stenosis in the Framingham Study Population. Journal of Nutrition, 126:1258S-1265S.
Scheideler, S.E., G. Froning, and S. Cuppett. 1997. Studies of consumer acceptance of high omega-3 fatty acid-enriched eggs. Journal of Applied Poultry Research, 6:137-146.
Shukla, V.K.S. and E.G. Perkins. 1998. Rancidity in encapsulated health-food oils. INFORM, 9(10):955-961.
Shukla, V.K.S., P.K.J.P.D. Wanasundra, and F. Shahidi. 1996. Natural antioxidants from oilseeds. Pages 97-132 in Natural Antioxidants, edited by F. Shahidi. American Oil Chemistś Press, Champaign, USA.
Sim, J.S. and Z. Jiang. 1994. Consumption of ω-3 PUFA enriched eggs and changes of plasma lipids in human subjects. Pages 414-420 in Egg uses and Processing technologies edited by J.S. Sim and S. Nakai eds. CAB International, Wallingford, England.
Simopoulos, A.P. 2002. Omega-3 fatty acids in wild plants, nuts and seeds. Asia Pacific Journal of Clinical Nutrition, 11(56):S163-S173.
Simopoulos, A.P. 1999. Essential fatty acids in health and chronic disease. American Journal of Clinical Nutrition, 70(3):560S-569S.
Simopoulos, A.P. 1989. General recommendations on dietary fats for human consumption. Pages 403-404 in Dietary ω3 and ω6 fatty acids: biological effects and nutritional essentiality, edited by C. Galli and A.P. Simopoulos. NATO Scientific Affairs Division and Plenum Press, New York, USA.
Simopoulos, A.P. and Robinson, J. 1998. The omega plan. Harper Collins Publishers, New York, USA.
Simopoulos, A.P. and N. Salem Jr. 1992. Egg yolk as a source of long-chain polyunsaturated fatty acids in infant feeding. American Journal of Clinical Nutrition, 55:411-414.
Singh M.A., R.B. Niaz, J.P. Sharma, R. Kumar, V. Rastogi, and M. Moshiri. 1997. Randomozed, double-blind, placebo-controlled trial of fish oil and mustard oil in patients with suspected acute myocardial infarction: fhe Indian experiment of infarct survival - 4. Cardiovascular Drugs and Therapy, 11:485-491
Stitt, P.A. 1989. Flax as a source of alpha-linolenic acid. Pages 389-390 in Dietary ω3 and ω6 fatty acids: biological effects and nutritional essentiality, edited by C. Galli and A.P. Simopoulos. NATO Scientific Affairs Division and Plenum Press, New York, USA.
Song, J.H., K. Fujimoto, and T. Miyazawa. 2000. Polyunsaturated (n-3) fatty acids suceptible to peroxidation are increased in plasma and tissue lipids of rats fed docosahexaenoic acid-containing oils. Journal of Nutrition, 130:3028:3033.
Straarup, E.M., and C.E. Høy. 2000. Structured lipids improve fat absorption in normal and malabsorbing rats. Journal of Nutrition, 130:2802-2808.
Sugihara, N., Y. Tsuruta, Y. Date, K. Furuno, and K. Kohashi. 1994. High peroxidative susceptibility of fish oil polyunsaturated fatty acid in cultured rat hepatocytes. Toxicology and Applied Pharmacology, 126:124-128.
Svensson, B.G., A. Nilsson, M. Hansson, C. Rappe, B. Akesson, and S. Skerfving. 1991. Exposure to dioxins and dibenzofurans through the consumption of fish. The New England Journal of Medicine, 32(1):8-12.
Taga, M.S., E.E. Miller, and D.E. Pratt, 1984. Chia seeds as a source of natural lipid antioxidants. Journal of American Oil Chemists' Society, 61:928-931.
Tengerdy, R.P., and J.C. Brown. 1977. Effect of vitamin E and A on humoral inmunity and phagocytosis in E. coli infected chicken. Poultry Science, 56:957-963.
Ting, I.P., J.H. Brown, H.H. Naqvi, J. Kumamoto, and M. Matsumura. 1990. Chia: a potential oil crop for arid zones. Pages 197-202 in H.H. Naqvi, A. Estilai, and I.P. Ting eds. New Industrial Crops and Products. Proceedings of The First International Conference on New Industrial Crops and Products, Riverside, California, USA, October 8-12, 1990.
Toug, J.C., J. Chen, and L.U. Thompson. 1999. Dose, timing, and duration of flaxseed expopsure affect reproductive indices and sex hormone levels in rats. Journal of Toxicology and Environmental Health, Part A, 56(8):555-570.
Toug, J.C., J. Chen, and L.U. Thompson. 1998. Flaxseed and its lignan precursor secoisolariciresinol diglycoside, affect pregnancy outcome and reproductive development in rats. The Journal of Nutrition, 128(11):1861-1868.
Treviño, J., M.L. Rodriguez, L.T. Ortiz, A. Rebole, and C. Alzueta. 2000. Protein quality of linseed for growing broiler chicks. Animal Food Science and Technology, 84:155-166.
United States Department of Agriculture. 1999a. University of Saskatchewan; availability of determination of non regulated status for flax genetically engineered for tolerance to soil residues of sulfonylurea herbicides. Animal and Plant Health Inspection, Washington D.C., Docket No. 99-002-2, Federal Register 64(102):28794-28795.
United States Department of Agriculture. 1999b. USDA Nutrient database for standard reference, release 13. Agricultural Research Service, Nutrient Data Laboratory Home Page, Download 26/3/01, http://www.nal.usda.gov/fnic/foodcomp
Valenzuela, A. and R. Uauy. 1999. Consumption pattern of dietary fats in Chile: n-6 and n-3 fatty acids. International Journal of Food Sciences and Nutrition, 50:127-133.
Vander Jag D.J., C.D. Arndt, S. N. Okolo, Y.S. Huang, L.T. Chuang, and R.H. Glew. 2000. Fatty acid composition of the milk lipid of Fulani women and the serum phospholipids of their exclusivity breast-fed infants. Early Human Development, 60:73-87.
Van Elswyk, M.E., P.L. Dawson, and A.R. Sams. 1995. Dietary menhaden oil influences sensory characteristics and headspace volatiles of shell eggs. Journal of Food Science, 60:85-89.
Van Elswyk, M.E., B.M. Hargis, J.D. Williams, and P.S. Hargis. 1994. Dietary menhaden oil contributes to hepatic lipidosis in laying hens. Poultry Science, 73:653-662.
Van Elswyk, M.E., A.R. Sams, and P.S. Hargis. 1992. Composition, functionality, and sensory evaluation of
eggs from hens fed dietary menhaden oil. Journal of Food Science, 57:342-349.
Vetter, J. 2000. Plant cyanogenetic glycosides. Toxicon, 38:11-36.