Total Homocysteine, Vitamin B12, and Total Antioxidant Status in Vegetarians

Abstract

AbstractBackground: Decreasing or eliminating animal products from the diet decreases the intake of some essential nutrients, such as vitamin B12, which may lead to hyperhomocysteinemia. We investigated vitamin B12-dependent metabolism and oxidative stress in groups with various or no intake of meat or animal products.Methods: We investigated 44 high meat eaters, 19 low meat eaters, 34 lacto-ovo/lacto vegetarians, and 7 vegan vegetarians. Homocysteine (HCY) was assayed by HPLC, methylmalonic acid (MMA) by capillary gas chromatography–mass spectrometry, serum folate and vitamin B12 with a chemiluminescence immunoassay, and total antioxidant status (TAS) by a Randox method.Results: The mean serum HCY concentration of vegetarians was significantly increased, and in vegans the median concentration exceeded 15 μmol/L. Vegetarians had a higher serum concentration of MMA but a lower TAS. Vitamin B12 and folate did not differ significantly between vegetarian and omnivorous subjects. Overall, HCY and MMA were significantly correlated. Vitamin B12 correlated negatively with MMA, HCY, and folate, whereas the correlation with TAS was positive. Backward regression analysis revealed an independent influence of MMA on HCY, of HCY and vitamin B12 on MMA, and of vitamin B12 on TAS. The increased MMA concentration suggested a 25% frequency of functional vitamin B12 deficiency in all vegetarians. Serum vitamin B12 was below the lower reference limit in only five subjects.Conclusions: Functional vitamin B12 deficiency in vegetarians may contribute to hyperhomocysteinemia and decreased TAS, which may partly counteract the beneficial lifestyle of vegetarians. However, increased serum HCY is most likely not responsible for the lower TAS values in vegetarians. We recommend assaying of MMA and HCY to investigate functional vitamin B12 status.