Does the MTHFR 677C-->T variant affect the Recommended Dietary Allowance for folate in the US population?
BACKGROUND
The MTHFR 677C-->T variant is associated with reduced enzyme activity, abnormalities of folate metabolism, and potential increase in folate requirement. The effect of this variant on the Recommended Dietary Allowance (RDA) for folate is unclear.


OBJECTIVE
The aim of this study was to assess the effect of the MTHFR 677C-->T polymorphism on the current folate RDA for US adults aged > or =19 y (400 microg/d) by race and ethnicity.


METHODS
We calculated the projected RDA for folate for each racial and ethnic group according to the methods of the Institute of Medicine. We modeled the projected RDA with different hypothetical effect sizes ranging from 5% to 50%. The RDA value was then weighted according to the US prevalence of the TT (or the combined CT/TT) genotype in each racial and ethnic group.


RESULTS
The projected RDA ranges were based on TT genotype frequencies and on different effect sizes (5-50%) that ranged from 400 to 421 microg/d for non-Hispanic whites, 401-436 microg/d for Mexican Americans, and 400-402 microg/d for non-Hispanic blacks.


CONCLUSIONS
Our findings suggest that the current RDA for folate differs little for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans irrespective of the MTHFR TT genotype, and, from a population perspective, the MTHFR 677C-->T variant does not warrant modifications to the current RDA for dietary folate at this time.
Robitaille
Julie
J
National Center on Birth Defects and Developmental Disabilities, Centers for Diseases Control and Prevention, Atlanta, GA, USA. julie.robitaille@fsaa.ulaval.ca
Hamner
Heather C
HC
Cogswell
Mary E
ME
Yang
Quanhe
Q
D000328:Adult; D001741:Black or African American / Q000235:genetics; D005006:Ethnicity / Q000235:genetics*; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood*; D005494:Folic Acid Deficiency / Q000097:blood / Q000517:prevention & control; D005838:Genotype; D006801:Humans; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D017058:Mexican Americans / Q000235:genetics; D018673:Nutrition Policy; D014481:United States; D044465:White People / Q000235:genetics; D055815:Young Adult
D005492:Folic Acid; D042965:Methylenetetrahydrofolate Reductase (NADPH2)