Data from metabolic folate status assessment and epidemiological studies support an EAR for adults ages 51 years and older of 320 µg/day of DFEs. The EAR for this age group is expected to be the same as that for younger age groups because the aging process does not appear to impair folate absorption or utilization nor do studies separate those over age 70 from those 51 to 70 years.

The RDA for folate is set by assuming a coefficient of variation (CV) of 10 percent (see Chapter 1) because information is not available on the standard deviation of the requirement for folate; the RDA is defined as equal to the EAR plus twice the CV to cover the needs of 97 to 98 percent of the individuals in the group (therefore, for folate the RDA is 120 percent of the EAR).

Folate requirements increase substantially during pregnancy because of the marked acceleration in single-carbon transfer reactions, including those required for nucleotide synthesis and thus cell division. During pregnancy, cells multiply in association with uterine enlargement, placental development, expansion of maternal erythrocyte number, and fetal growth (Cunningham et al., 1989). Additionally, folate is actively transferred to the fetus as indicated by elevated folate concentrations in cord blood relative to that of maternal blood. When folate intake is inadequate, maternal serum and erythrocyte folate concentrations decrease and megaloblastic marrow changes may occur (Picciano, 1996). If inadequate intake continues, megaloblastic anemia may develop. This section does not address the reduction of risk of neural tube defects because the neural tube is formed before most women know that they are pregnant (see “Neural Tube Defects”).