Cow milk and food folate bioavailability in women

Nutrition Research Newsletter, Jan, 2005

The importance of adequate folate nutrition for the maintenance of health and the prevention of various diseases, such as neural tube defects and occlusive vascular disease, has been well recognized in recent years. However, it is difficult to accurately assess the dietary folate intake of the general population because of the inadequate values of food folate. Furthermore, information on food folate bioavailability and the factors affecting it in our diets is extremely limited.

Several groups of researchers using various animal models have evaluated the influence of the components of milk on the bioavailability of folate. It appears that there is only one human study performed to evaluate the effect of milk on folate bioavailability. Since more research is needed in this area, a group of researchers evaluated whether cow milk enhances the bioavailability on food folate in humans.

Thirty-one women participated in the study. The subjects were randomly assigned to one of two dietary groups. One group received diets with skim milk and the other received diets containing no milk, which was replaced with apple juice and egg substitutes for 8 weeks. Fasting blood samples were taken at baseline and then at the end of each week. Plasma and erythrocyte folate concentrations--the most commonly used means to assess folate nutritional adequacy and plasma tHcy concentrations--were used.

Plasma folate concentrations steadily declined in both the milk and the nonmilk groups; however, the declines were not significantly different between groups. In contrast, erythrocyte folate concentrations declined only in the non-milk group and remained unchanged in the milk group. The difference between the two groups was significant. Plasma tHcy concentrations significantly increased in the nonmilk group and remained unchanged in the milk group. This difference was significant as well.

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 such action by the components of cow milk remain to be explored and further studies are needed to address how much milk is needed to affect dietary folate bioavailability.

Mary Frances Picciano, Sheila G West, Amanda L Ruch et al. Effect of cow milk on food folate bioavailability in young women, Am J Clin Nutr 80:1565-1569 (December 2004) [Address reprint requests to MF Picciano, Office of Dietary Supplements, 6100 Executive Boulevard, Bethesda, MD 20892-7517. E-mail: piccianm@od.nih.gov]