Omega-3 polyunsaturated fatty acids in vegetarians (lacto-ovo-vegetarians and vegans): Metabolism, status, and clinical aspects

Polyunsaturated fatty acids (PUFAs) are essential nutrients. In the omega-3 (n-3) class, the long-chain PUFAs (LCPUFAs) eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are involved in many metabolic functions in humans. α-Linolenic acid (ALA) can serve as a precursor to them or be used as an energy substrate. EPA and DHA are involved in the regulation of gene expression and can be substrates for the synthesis of eicosanoids and docosanoids, which modulate immune processes and blood clotting. Vegetarians do not consume fish and marine invertebrates, the main sources of EPA and DHA: in the diet of lacto-ovo-vegetarians and vegans, flaxseed oil, chia seeds, walnuts, and flaxseeds are the main sources of n-3 acids in the form of ALA, which should be further endogenously converted to EPA and DHA. Consequently, all vegetarians can have lower n-3 blood levels and a higher n-6:n-3 ratio in comparison to omnivores: therefore, both lacto-ovo-vegetarians and vegans should be recommended to emphasize the intake of n-3-rich foods and pay special attention to enhance their endogenous conversion by limiting factors negatively affecting it. The intake of DHA/EPA-containing supplements, available now from microalgae, can be recommended in specific life stages, such as infancy, pregnancy, lactation, and early childhood. Recent studies show that stearidonic acid, found in several plant oils, could represent a promising source of EPA and DHA as well.