Plant-based diets may increase the risk of vitamin B12 deficiency due to limited intake of animal-source foods, while dietary folate increases when adhering to plant-based diets.
In this cross-sectional study, we evaluated the B12 and folate status of Norwegian vegans and vegetarians using dietary B12 intake, B12- and folic acid supplement use, and biomarkers (serum B12 [B12], plasma total-homocysteine [tHcy], plasma-methylmalonic acid [MMA], and serum-folate). Vegans (n=115) and vegetarians (n=90) completed a 24-hour dietary recall and a food-frequency questionnaire and provided a non-fasting blood sample. cB12, a combined indicator for evaluation of B12 status, was calculated. B12 status were adequate in both vegans and vegetarians according to the cB12 indicator, however 4% had elevated B12. Serum B12, tHcy, MMA concentrations and the cB12 indicator (overall median: 357pmol/L, 9.0µmol/L, 0.18µmol/L, 1.30 (cB12)) did not differ between vegans and vegetarians, unlike for folate (vegans: 25.8nmol/L, vegetarians: 21.6nmol/L, p=0.027). Serum B12 concentration <221pmol/L, was found in 14% of all participants. Vegetarians revealed the highest proportion of participants below the RDI of 2 µg/day including supplements (40 vs. 18%, p<0.001). Predictors of higher serum B12 concentrations were average daily supplement use and older age. Folate deficiency (<10 nmol/L) was uncommon overall (<2.5%). The combined indicator cB12 suggested that none of the participants was B12 depleted, however low serum B12 concentration was found in 14% of the participants. Folate concentrations were adequate, indicating adequate folate intake in Norwegian vegans and vegetarians.