Kagawa Y, Nishijima C, Nakayama K, Iwamoto S, Tanaka A, Kamachi K and Kawabata T
This review investigates how the genotype of vegetarians controls lipid metabolism responses to the dietary intake of n-3 fatty acids. While health indices of Japanese vegetarians are superior to those of omnivores, the effects of genetics have not been studied. The lipid intake of Japanese omnivores and vegans is less than that of Western vegans. Mongolian carnivores and Inuit piscivores have shorter lifespans compared to other Asians who consume a rice diet or taro-fish diet. Our genetic studies on Mongoloids in Asia Pacific regions revealed similar allele frequencies of genes related to diabetes and cardiovascular diseases, which are increasing with recent Westernization because of genetic differences between Mongoloids and Caucasoids. Long-chain n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), play a role in preventing these diseases, yet vegetarians consume nearly 0 g per day. Conversion of plant-derived α-linolenic acid (ALA) to EPA and DHA, and linoleic acid to arachidonic acid (AA) requires the Δ5 desaturase. Thus, plasma concentrations of EPA, DHA and AA in vegetarians are lower than those in omnivores, especially vegans with the C allele of the Δ5 desaturase polymorphism rs174547. The following hypotheses have been proposed to explain the health of C homozygote vegans: 1. They are unable to survive, 2. They cease the vegan diet, 3. They preferentially preserve EPA/DHA by lowered catabolism, 4. Their Δ5 desaturase is activated by specific factors, and 5. Their EPA/AA ratio is elevated and harmful LDL-C and inflammation etc. is reduced. This review does not support hypotheses 1 and 2, but partially accepts 3 and 4 and completely confirms 5. In future, genotype-specific personalized dietary recommendations for optimal health span based on telomere length will be developed. Currently, the pesco-vegetarian diet, which is similar to the traditional Japanese (Washoku) diet, is the healthiest for the majority of subjects.