Alpha linolenic acid (ALA, C18:3 (n-3)) is an essential fatty acid (EFA) required to form a number of important short-lived anti-inflammatory compounds in humans. Theoretically, ALA can be elongated and desaturated to eicosapentanoic acid (EPA, C20:5 (n-3)) and docosahexanoic acid (DHA, C22:6 (n-3)), which can subsequently form anti-inflammatory eicosanoid and docosanoid hormones, respectively. However, most humans possess a genetic deficiency of the necessary delta 5-desaturase enzyme and as a result ALA is only slowly converted to EPA and DHA. Omnivores can circumvent this problem by consuming fish oils, which are a good source of both EPA and DHA. However, vegetarians are unable to consume fish oil and as a result it is more difficult for them to obtain adequate n-3 fatty acids in their diets. However, research suggests that eggs can be a good source of DHA, if the chickens are fed a diet high in flaxseeds.
For example, when Leghorn chickens are fed increasing quantities of flaxseeds from 0 to 10 to 20 % by weight, a significant increase in the content of ALA (28, 261 and 527 mg/egg) and DHA (51, 81 and 87 mg/egg) in the eggs is reported1. These eggs have been fed to healthy male volunteers in a study that was designed to investigate the effects of the eggs on plasma phospholipid levels of EFAs. Subject were divided into groups and for two weeks consumed eggs from chickens fed 0, 10 or 20 % flaxseeds. Consumption of the eggs caused a significant increase in platelet phospholipid DHA concentrations from 1.0 to 1.8 % and total n-3 fatty acids from 1.5 to 2.0 % by weight. This resulted in a significant reduction in the n-6 to n-3 ratio. However, there was no significant difference in the ALA or DHA plasma phospholipid concentrations between the different EFA enriched eggs.
Therefore, consumption of ALA and DHA enriched eggs may be a useful method of increasing n-3 fatty acid intake that could be beneficial to vegetarians. Interestingly, the cholesterol in the EFA enriched eggs did not differ with control eggs. The subjects consumed 4 of these eggs per day, providing 715 mg/d cholesterol, and yet no increase in total cholesterol, high density lipoprotein (HDL) cholesterol or triglycerides were reported, in either the EFA enriched or normal eggs. This adds further evidence to the already substantial number of studies showing that dietary cholesterol does not influence plasma cholesterol. The n-6 to n-3 fatty acid ratios in platelets fell from 9.3 to 2.2 to 1.4 with 0, 10 and 20 % flax fed chicken, suggesting that the inflammatory risk had been reduced. This may make DHA and ALA enriched eggs beneficial in inflammatory conditions such as cardiovascular disease.
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