In elderly mice, a high consumption of vitamin B9 leads to a decrease in immune defenses, which makes them more vulnerable to infections.
Too much intake of vitamin B9, also known as folic acid, would cause a deficit in the immune system, warn researchers from Tufts University (Massachusetts, United States) in a study published in Journal of Nutritional Biochemistry.
This vitamin is strongly recommended for pregnant women to prevent the onset of spina bifida, an abnormality in the closure of the neural tube. In France, for women without risk, experts recommend one tablet of folic acid dosed at 0.4 mg per day. For women at risk, the dose is 10 times greater.
Apart from pregnancy, supplementation with folic acid is not necessary because this vitamin is naturally present in the diet (green vegetables, eggs, fish, etc.). In people over 50, many studies have shown an association between too much folic acid and a weakened immune system. These recent studies carried out in mice have now made it possible to establish a cause and effect link.
Immature and dysfunctional cells
American researchers studied two groups of old mice. One was fed very high intakes of vitamin B9, equivalent to 20 times the recommended daily dose for humans, while the other was fed normally.
Scientists report that supplemented mice have a high level of unmetabolized folic acid in their blood as well as a high concentration of this vitamin in the spleen, compared to the control group. In addition, these mice exhibited a greater proportion of NK cells, a type of immune cell, immature and less active, than the control animals.
These cells play a very important role in our immune system. Presented as formidable killers, they kill infected cells and tumor cells within hours. As a result, mice given large amounts of folic acid are no longer able to fight infections, and appear to be more susceptible to cancer.
This discovery is all the more important since the immune system of the elderly naturally declines. Supplementing with vitamin B9 could therefore worsen this consequence of aging.
.
