To the Editor.
—Several analyses presented in the article by Dr Boushey and colleagues1 require comment because the recommendations reached by the authors are at variance with those proposed by the Food and Drug Administration (FDA).2My first concern pertains to the authors' estimate of the mean decrease in plasma homocysteine (4 μmol/L occurring from an increase in folic acid intake of 200 μg/d. Regrettably, there are no clinical trial data from which to assess the impact of small increases in dietary folate on homocysteine; the paucity of data is particularly marked at the lowest end of usual folate intake. In the absence of such data, the authors construct a dose-response curve, compiling data across four disparate studies. Unfortunately, there are several problems with these data. For instance, six of the 13 data points in their analyses (Figure 3) are repeated measurements obtained from one metabolic study3
Appel LJ. Folic Acid Fortification of Food. JAMA. 1996;275(9):681-682. doi:10.1001/jama.1996.03530330025013