From the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University, scientists found that excess folic acid intake leads to changes in the immune system that could affect its ability to fight off infections.
Folic acid is the synthetic form of folate, a B vitamin, found in dietary supplements (MedlinePlus). Folate is found naturally in many legumes like lentils, pinto beans, and garbonzo beans as well as vegetables like asparagus, spinach, and broccoli (Whole Foods).
In their study published in the Journal of Nutritional Biochemistry, researchers from the HNRCA looked at a mouse model of aging to see what specific changes occurred in the immune system when the mice were fed an excess amount of folic acid. This projected stemmed from a 2005 study, also from the HNRCA, which showed that a large majority of healthy postmenopausal women had significantly lower natural killer (NK) cell activity coinciding with an excess amount of folic acid in their blood plasma.
By measuring NK cell cytotoxicity, the ability of NK cells to destroy other cells, the researchers saw that experimental mice fed excess folic acid had many more “naïve and less effective NK cells” than mature, active cells when compared to control mice. They interpreted this ratio of effective to ineffective NK cells as a result of a dysfunction in the development process.
A loss of NK cell activity could severely impair the immune response, especially in elderly people whose immune systems are naturally weakened by age.
"If we want to optimize the efforts of NK cells to increase resistance to infections, the use of folic acid in some contexts may need to be reassessed. Among older adults, additional research might show that it is important to take supplements only if one has been documented to be folate-deficient," explained Ligi Paul, PhD, nutrition scientist at the HNRCA.
In future studies, scientists hope to continue making connections between excess folic acid intake and human health. Specifically, their next step is to identify a causal relationship between excess folic acid intake and vulnerability to disease.
Source: Tufts University