Background/aims: Folic acid mediates transfer of one-carbon units into methionine and DNA-thymine biosynthesis. Discretionary and mandatory use of synthetic folic acid (SFA) to reduce spina bifida is on the increase. We show that historically, the seasonal cycle of abundance of folate-rich foods may have regulated embryo viability by acting as a selection factor for a significant polymorphism within a gene encoding 5,10-methylenetetrahydrofolate reductase (677C-->T-MTHFR).
Methods: Blood was collected from 150 UK and 118 Australian subjects born prior to discretionary or mandatory use of SFA. 677C-->T-MTHFR genotype was determined using PCR.
Results: The highest prevalence for 677T-MTHFR occurred 9 months post-harvest in UK subjects and was significantly higher at this time of year (July-Sept.) compared with Jan.-Mar. (OR = 2.0, 95% CI 1.03-3.87, p = 0.039) and Oct.-Dec. (OR = 2.2, 95% CI 1.12-4.31, p = 0.021). This effect was not detected in an Australian population subject to more moderate seasonality.
Conclusions: Dietary folate may confer significant genetic buffering within populations dependent upon seasonal food sources that modify an individual's vitamin status at the time of conception.
Copyright 2007 S. Karger AG, Basel.