Does Too Much Vitamin A Reduce Immunity to Infection?

A new study proves that too much of a good thing can cause serious harm — even if it is a vitamin.

The Centers for Disease Control and Prevention (CDC) has linked vitamin A with maintaining healthy eyesight and immune system function. In addition, it has been noted that a vitamin A deficiency can increase a child’s risk of dying from infections. However, what happens when an individual consumes too much vitamin A? A collaborative team from Radboud University Medical Center, Statens Serum Institut, and University of Southern Denmark/Odense University Hospital documented its findings in the Journal of Leukocyte Biology.

“The interface of nutrition and immunity is an area of considerable importance, especially in an age when dietary supplements and vitamins are quite common,” John Wherry, PhD, deputy editor of the journal, said in a news release.

The researchers stimulated immune cells with vitamin A and predicted that this would inhibit the body’s trained immunity against infections. The hypothesis was proven true when the team observed that the cells were producing fewer of the immune cell signaling proteins known as cytokines.

“This study helps to explain the mechanisms of anti-inflammatory effects of vitamin A and by doing so opens the door to identifying novel ways to modulate the immune response and restore its function in situations in which it is dysregulated,” said one of the authors, Mihai G. Netea, MD, PhD, of Radboud University Medical Center in The Netherlands.

The results also indicated that low vitamin A levels are not always a bad thing and may actually be considered “normal” depending on the circumstances. These outcomes show how the immune system is trained to react to different infections in certain ways, which verifies the need to understand vitamins’ impact on the body.

“These new findings shed light on an important balance in vitamin levels for optimal immunity,” Wherry said.