Effect of cow milk on food folate bioavailability in young women.

BACKGROUND: The findings of animal and human studies suggest that a certain component in milk enhances food folate bioavailability. OBJECTIVE: The objective was to evaluate whether cow milk enhances the bioavailability of food folate in humans. DESIGN: Thirty-one young women were fed low-folate diets on a 4-d rotation with (n=17) or without (n=14) cow milk for 8 wk. Plasma and erythrocyte folate and plasma total homocysteine (tHcy) concentrations were monitored. RESULTS: Plasma folate concentrations steadily declined in both the milk and the nonmilk groups; however, the declines were not significantly different between groups (P=0.09). In contrast, erythrocyte folate concentrations declined only in the nonmilk group and remained unchanged in the milk group; the difference between the 2 groups was significant (P=0.01). Plasma tHcy concentrations significantly increased in the nonmilk group and remained unchanged in the milk group; the difference between the 2 groups was significant (P=0.02). CONCLUSION: The inclusion of cow milk in the diet enhanced the bioavailability of food folate as assessed by the changes in erythrocyte folate and plasma tHcy concentrations but not in plasma folate concentrations. The mechanisms of action by the components of cow milk remain to be investigated.