Effects of folate and zinc supplementation on patients undergoing chronic hemodialysis

Twelve men and nine women undergoing chronic hemodialysis were studied to evaluate folate intake and status in relation to use of folate supplements. Because of possible folate-zinc interactions, zinc status was also evaluated. The patients were classified into four groups based on daily supplementation: no folate or zinc, 22.5 mg zinc, 5 mg folate, and 5 mg folate and 22.5 mg zinc. A food frequency questionnaire was developed to estimate average daily intakes of folate and zinc. Patients' mean dietary folate intake was 30% or more above the Recommended Dietary Allowance (RDA), whereas their mean dietary zinc intake was close to the RDA. No significant differences in dietary folate or zinc intakes existed among groups. Red blood cell (RBC) folate levels of folate-supplemented patients were approximately 10 times higher than those of patients who did not receive folate and who had normal RBC folate levels. Serum zinc levels in all four groups of patients were close to the lower limit of the normal range and were unaffected by supplementation; however, hair zinc levels of six zinc-supplemented patients were significantly higher than those of healthy unsupplemented control patients. Generalization of this study's findings are limited by its descriptive nature; nevertheless, for these patients and presumably for similar patients who also have adequate dietary folate intakes, high-dose folate supplementation does not appear to be necessary to maintain normal folate status. No evidence of a folate-zinc interaction was obtained; however, serum zinc may not be a valid index of zinc status in these patients.