Nutritional genetics: the case of alcohol and the MTHFR C677T polymorphism in relation to homocysteine in a black South African population.

Background/aims: It is unknown whether the effect of alcohol consumption on homocysteine (Hcy) is modulated by the methylenetetrahydrofolate reductase (MTHFR) C677T. We explored this hypothesized effect by analyzing cross-sectional data of 1,827 black South Africans.

Methods: Total Hcy concentrations were determined by fluorescence polarization immunoassay and the genotype through polymerase chain reaction-based RFLP analysis.

Results: Subjects harboring the 677 TT genotype had the highest Hcy. Among subjects harboring the 677 CC genotype, men had higher Hcy (p = 0.04). Age and gamma-glutamyltransferase (GGT) correlated best (r = 0.26 and r = 0.27; p < 0.05), while the percentage carbohydrate-deficient transferrin and the B vitamins correlated weakly (r < 0.1; p < 0.05) with Hcy. Hcy was positively associated with the reported alcohol intake (p ≤ 0.01). There was no interaction between alcohol consumption and the MTHFR 677 CC or CT genotypes (p > 0.05) for Hcy concentrations; however, an interaction was determined for GGT and the MTHFR genotype (p = 0.02). Age, GGT, gender, MTHFR and vitamin B6 explained 16.8% of the variation in Hcy (p < 0.01).

Conclusion: The determined interactions might result in differences in the risk conveyed through Hcy with regard to disease development in those with unfavorable GGT concentrations.