Vitamin A has been shown to help direct a key set of immune cells that protect the body from infection.

Researchers from Purdue University found retinoic acid, a byproduct of digested vitamin A, is necessary for the function of two of the three types of immune cells that reside in the intestines.

"It is known that vitamin A deficiencies lead to increased susceptibility to disease and low concentrations of immune cells in the mucosal barrier that lines the intestines," said Chang Kim, a professor of microbiology and immunology in Purdue's College of Veterinary Medicine who led the research.

"We wanted to find the specific role the vitamin plays in the immune system and how it influences the cells and biological processes. The more we understand the details of how the immune system works, the better we will be able to design treatments for infection, and autoimmune and inflammatory diseases."

The findings, based on studies of laboratory cell cultures and mice, were published online in the journal Immunity.

Foods rich in vitamin A include sweet potatoes, carrots, pumpkin, spinach, mango, cantaloupe, and apricots.

The study was funded by the National Institutes of Health.