Fortification of the diet with folate has been used in the United States since 1997 to prevent neural tube defects in newborn babies. However, an increase in dietary folate intake could theoretically reduce the effectiveness of the anti-folate medication, methotrexate (MTX) in treating rheumatoid arthritis (RA) and other inflammatory diseases.
To investigate whether dietary fortification with folic acid interferes with MTX function in patients with RA.
We computed MTX dose per patient per year for the years 1988 to 1999 and plotted these against time, comparing the overall mean MTX dose before and after 1997, when dietary fortification with folic acid was instituted in the USA. Thirty-six subjects met eligibility criteria.
Mean annual MTX dose was stable between 1988 and 1996 (12.4 +/- 4.0mg), but then rose linearly from 1997 to 1999 (16.6 +/- 5.1 mg, p < 0.001).
This preliminary study suggests that folic acid supplementation may contribute to higher MTX dosing in patients with RA.