"The Potential of Seal Oil as Omega-3 Polyunsaturated Fatty Acid (Omega 3 PUFA) Supplements"
Dr. Anthony Nahkla and Dr. Comas Ho
September 1997
Since the original reports in the early 1970's that Greenland Eskimos exhibited low incidences of cardiovascular diseases and cancer in comparison to populations of the Western world, several health benefits have been associated with Omega 3 polyunsaturated fatty acids (Omega 3 PUFA). In particular, beneficial effects have been described in relation to coronary heart disease, artherosclerosis, arthritis, hypertension, thrombosis, and the development of visual acuity and motor skills in infants.Many studies have examined the health benefits associated with Omega 3 PUFA described above, although the most extensively studied source of these essential fatty acids has been fish oils. It is noteworthy, however, that two decades of large scale human and animal feeding trials have failed to show conclusively that fish oil supplements can achieve the low levels of coronary artery disease (CAD) observed among the Eskimo population of northern Greenland. This may not be surprising, since the major source of dietary Omega 3 PUFA for the Greenland Eskimos is not fish, but rather is derived from the fat of marine mammals, such as seal and whale.Several laboratories, including our own, have shown that the Omega 3 PUFA compositions of seal oil lipids, as well as the distribution of these fatty acids within the lipids (an important factor in the absorption of dietary fatty acids), are significantly different from those of fish oils. It is, therefore, possible that seal oils may be more effective in preventing CAD than fish oils.Further, it is believed that certain Omega 3 PUFA are essential for early development, including visual acuity and mental development. Human breast milk contains long-chain Omega 3 PUFA, among which docsahexaenoic acid (DHA) is the most abundant, in addition to eicosapentaenoic acid (EPA) and considerable amounts of docosapentaenoic acid (DPA), that are required by term infants in order to synthesize long-chain PUFA shortly after birth. Most currently available commercial infant formulas however, have only trace amounts of these essential fatty acids.In recent years, several studies have attempted to provide Omega 3 PUFA to infants by supplementing formula with fish oil, because of their naturally elevated Omega 3 PUFA concentrations. However, the relative proportions of the Omega 3 PUFA in most fish oil preparations do not correspond with that of human breast milk very well. We believe that it may be possible to establish a closer match to the Omega 3 PUFA composition of human breast milk by supplementing infant formula with low levels of purified seal oil. Researchers and industry representatives agree that supplementing infant formula with Omega 3 PUFA is beneficial. The source of the Omega 3 PUFA supplement however, is a point of contention. Although breast milk naturally contains EPA, there is an apprehension of EPA among the infant formula manufacturers that is based on the theory that EPA can inhibit arachdonic acid (ARA) levels.Compositional analyses of TNF seal oils have consistently indicated that seal oils are a suitable source of Omega 3 PUFA that can be utilized as either an infant formula supplement or as an adult nutritional supplement. In terms of the fatty acid profiles, the ratio of EOA to DHA in "MaxEPA" fish oil is roughly 1.5:1, while the ratio in TNF seal oils was consistently 1:1, which appears to be favourable for teh infant formula industry. In addition, seal oils exhibit lower levels of linolenic acid (LLA), a fatty acid which is postulated to reduce ARA levels in humans than does "MaxEPA" fish oil. Other particular advantages that seal oil may have over fish oil include slightly lower levels of saturated fatty acids and considerably higher levels of DPA, a fatty acid which has been associated with stimulating endothelial cell migration, and inversely associated with coronary artery disease in women. Therefore, the elevated DPA levels present in TNF seal oils is possibly a benefit with respect to an adult nutritional supplement.Tissue incorporation trials conducted in our laboratories indicate that, although there were no statistically significant differences in the fatty acid compositions of the erythrocyte, brain and retinal tissue lipids of neonatal rabbits that were fed formula or formula supplemented with "TNF seal oil," "MaxEPA" fish oil or "Formulaid." The levels of EPA, DPA, and DHA in the lipids of teh oil-supplemented groups however, were elevated, compared to the groups given non-supplemented formula. These results are comparable to recent studies that reported elevated levels of DHA in erythrocyte membrane lipids of pre-term infants following marine oil supplementation and suggest that, with respect to the tissue incorporation of Omega 3 PUFA, seal oil is at least as efficient as fish oil and Formulaid as a viable Omega 3 PUFA supplement for infant formula.It is particularly noteworthy that the levels of ARA were comparable in the erythrocyte, brain and retinal tissue lipids of all groups, regardless of diet or source of supplement, which indicates that the levels of LLA and EPA introduced into teh infant formula did not inhibit ARA levels. This observation contradicts the postulate that Omega 3 PUFA supplementation, and in particular EPA levels, can be detrimental to infant development, and would appear to be advantageous for the infant formula industry.There are concerns among the edible oil industry regarding Omega 3 PUFA supplementation, since these fatty acids are highly susceptible to natural oxidation processes. The major products of autooxidation are lipid hydroperoxides, which function as chemically toxic substances that are believed to lead to a variety of deteriorative processes in humans. In agreement with previous reports, in vitro experiments conducted in our laboratories indicate that there are lower amounts of primary and secondary oxidation products in seal oils than in fish oils, a property which could have major implications for the nutrition industry.Evidence strongly suggests that oxidative modifications of low-density lipoprotein (LDL) is involved in the pathogenesis of atherosclerosis. It has also been reported that because of the susceptibility of Omega 3 PUFA to oxidative processes, fish oil enriched diets may result in LDL particles that can be more readily oxidized and that plasma enrichment with Omega 3 PUFA from fish oil enriched diets may weaken plasma antioxidant potential. Animal trials conducted in our laboratories aimed at determining the potential of seal oil as an adult nutritional supplement examined the levels of oxidized LDL in response to different diets. Since it is believed that seal oils are less susceptible to oxidative processes than are fish oils, these experiments were designed to determine the degree of oxidation of LDL in rabbits that were fed seal oil, or fish oil supplemented diets, as compared to those fed control diets (canola-oil supplemented).We observed no statistically significant differences between the levels of oxidized LDL isolated from the oil-supplemented groups and the canola oil-supplemented group, suggesting that the LDL isolated from the rabbits fed canola oil-supplemented diets had undergone the same degree of oxidation as the LDL isolated from the marine oil-supplemented groups. It should be noted that these effects are notable, since the canola oil used in these trials had antioxidant added, which would render the oil stable to oxidative processes.Examination of rabbit aorta for lesion development following eight weeks of feeding oil-supplemented diets indicated that there were no statistically significant differences in lesion development of the aorta of rabbits fed oil-supplemented diets.There appear to be considerable beneficial biological effects associated with the appropriate dietary intake of Omega 3 PUFA. Both fish and seal are known to be good sources of oils enriched in Omega 3 PUFA, although seal oils appear to have advantages over fish oils as Omega 3 PUFA supplements, which include a favourable Omega 3 PUFA composition (including DPA), a significant squalene concentration (roughly 1.5% to 2%), an enhanced resistance to oxidation and a distribution which may allow for augmented digestion and absorption of fatty acids.Together, the results of tissue incorporation trials and the in vitro and in vivo oxidation trials suggest that TNF seal oils are viable Omega 3 PUFA supplements for infant formula and are also valuable as adult nutritional supplements. TNF seal oils are considerably less expensive than fortified fish oil and single cell oils, both of which are currently on the market as Omega 3 PUFA supplements.
