Bioavailability of folates in selected foods incorporated into amino acid-based diets fed to rats.

Two experiments were conducted to determine the feasibility of using a folate depletion/repletion protocol with rats fed an amino acid-based diet to measure the bioavailability of food folate. Growth, liver folate and serum folate of depleted rats that were fed test foods incorporated into a folate-free, amino acid-based diet were standardized against similar responses of rats fed known amounts of folic acid incorporated into the same diet. Bioavailability of folate of cooked broccoli, refried beans and orange juice concentrate in experiment 1 was 80-89, 113 and 62%, respectively, based on growth response; in experiment 2, values for cooked and raw broccoli, cooked cabbage and cantaloupe were 95, 103, 74 and 81%, respectively. The results demonstrate that in addition to serum and liver folate concentrations, growth may be a useful response criterion to evaluate the bioavailability of folates in foods. Further research is needed to determine the relevance of these bioavailability estimates to human nutrition.