Excess Folic Acid Intake Linked With Immune System’s Inability To Ward Off Infections

Excess intake of folic acid might impact negatively on the body’s ability to combat infections by bringing changes in the immune system, according to a new study published in the Journal of Nutritional Biochemistry.

Folic acid spilling from green pill bottle

Folic acid is needed by everyone for the making of healthy cells and is also specifically taken by pregnant women because a deficiency thereof might lead to neural tube defects in the baby. However, as the golden rule governing life on Earth goes, even good things can be harmful if taken in excess. This is what has been found in a study conducted by researchers from Tufts University, Medford.

While folic acid is found naturally in certain foods (like green vegetables and grains), many are those who take it in the form of dietary supplements, and some even go overboard, consuming an excessive amount of the nutrient. Past studies have linked high folic acid consumption with weakened immune systems. Now, the team of scientists behind the new research, led by Hathairat Sawaengsri, wanted to establish whether excess folic acid can affect the immune system negatively.

The researchers used old mice to study a specific type of immune system cell called the natural killer (NK) cells. NKs defend the body by killing cells infected by viruses or affected by cancer. If NKs are impaired, the person has a greater risk of developing diseases, specially old people since ageing tends to be associated with a weakened immune system.

A group of mice were fed with folic acid of a quantity equivalent to the human Recommended Daily Allowance (RDA) while another group was given an amount 20 times greater than the human RDA (the amount was much higher than what most adults would take because of the greater efficiency of mice at metabolising the nutrient).

The results showed that mice from the second group had a higher level of unmetabolised folic acid in their blood together with greater concentrations of folate in their spleens as opposed to those of the first group. Furthermore, the former also had lower NK cell activity. The researchers interpreted these results as implying that excess folic acid intake might be linked with a decreased NK cell activity in aged mice.

The authors, therefore, advise for the use of folic acid to be reviewed in certain situations where the NK activity has to be optimised. Furthermore, the elderly might have to take supplements only in cases where they have a deficiency of folic acid.

The next step for the scientists now is to find whether excess folic acid can actually cause greater vulnerability to infections.

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