Folate catabolism in normal subjects.

All official recommendations for folate tend to be far in excess of current estimated intakes. Several recent studies have highlighted this, showing satisfactory folate status in healthy populations consuming considerably less than official RDAs. This study takes a critical look at current RDAs for folate. We have recently developed an assay to quantify the end product of folate catabolism in human urine, thus affording the possibility of a more rational and scientific approach to setting the RDA for folate. Results of this study (now confirmed by further work) suggest that, under normal dietary conditions, the body appears to catabolize only about 100 micrograms total folate per day. Furthermore, this rate of catabolism remained relatively unchanged in response to saturating doses of a 5 mg folic acid supplement over several days. It is therefore most unlikely that our diet is as seriously deficient in folate as current official RDAs seem to imply.