High homocysteine in vegetarians and vegans is mainly related to a deficiency in B12.
Therefore, methylation in these people can be under-active, but not specifically due to a mutation in an MTHFR gene. This was reflected in a study completed on a vegan and vegetarian population that w
However, a mutation in the MTHFR C677T gene may also contribute to this condition. Therefore, blood status of homocysteine, B12, folate, B6 and MTHFR C677T was studied in vegans and vegetarians. Results founds vegans to exhibit significantly higher levels of homocysteine, with a C677T mutation not related to this. Serum folate levels did however decrease in the severity of the MTHFR C677T mutation, with those individuals showing the 677TT mutation found to have much lower levels of folate that those with a CC genotype.