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DRI Dietary Reference Intakes: For Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
Total in Dietary Folate Equivalents
Results
300 plus diet
Serum folate low in 40%
Diet
1,000 plus diet
Increase 40–60% abnormal erythrocyte folate normal level compared with 10–20% in supplemented group
≤ 100
200 plus diet
600 plus diet
900 plus diet
Prevented deficiency in 72%, 84%, and 94%, respectively, comparable with nonpregnancy control
100 plus diet
200 plus diet
400 plus diet
1,000 plus diet
Decrease in serum folate in 15%; normal level serum folate
660 plus diet
Prevented deficiency in supplemented groups
Diet
200 plus diet
Maintained normal levels erythrocyte folate
Diet
510 plus diet
850 plus diet
1,700 plus diet
Folate depletion
No apparent folate depletion
Three of the four studies provided data that 100 to 150 µg/day of supplemental folate plus a low-folate diet was inadequate to maintain normal serum and hematological indices, which were the only outcomes measured in all of the subjects. The accuracy of the dietary estimates could not be ascertained, but they were lower than the one analyzed intake estimate (676 µg/day) reported by Chanarin and coworkers (1968).
Other Evidence Considered. McPartlin and colleagues (1993) quantitated the urinary excretion of the major folate catabolites in six pregnant women and six nonpregnant control subjects. These in-
