Folic Acid Caveat
Megadoses may affect your immune system
Here’s another case of too much of a good thing: Researchers have found that excess folic acid can dampen the immune system, at least in mice.
In the study, scientists in the Vitamin Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts gave a group of older mice the equivalent of the Recommended Daily Allowance of folic acid, while another group got 20 times the RDA (very high even for a supplement, but it accounts for the mice’s ability to quickly metabolize the vitamin). The mice who took the high dose of folic acid later showed less effective natural killer cells, types of immune cells that are important for defending against viral infections and cancer.
The findings build on previous research by the same lab: In 2005, it found that 78 percent of healthy postmenopausal women had unmetabolized folic acid in their blood (a sign of excess intake) and that those women had significantly lower natural killer cell activity.
Additional research could determine whether excess folic acid actually increases susceptibility to infections and provide guidance on the use of supplements among older adults. The study appeared in the Journal of Nutritional Biochemistry.