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Originally published March 20 2011

New research: "smart" vitamin A plays multiple roles in the immune system, depending on the body's needs

by S. L. Baker, features writer

(NaturalNews) It's been known for a long time that a lack of vitamin A can make you susceptible to infections. On the other hand, some research has shown vitamin A can suppress the immune system.

What gives? Now researchers think they know.

It turns out vitamin A is a remarkably 'smart' vitamin. It integrates both pro-inflammatory and anti-inflammatory immune responses in the gastrointestinal tract (GI), depending on what the body needs. So vitamin A pumps up the pro-inflammatory response when necessary to zap GI infections and it cools down the immune system to help prevent autoimmune responses.

That's the conclusion of a study recently published by Cell Press in the journal Immunity. Researchers from the National Institute of Allergy and Infectious Diseases found the vitamin A metabolite retinoic acid (RA)and one of its receptors (RAR) have specific anti-inflammatory properties which induce production of regulatory T cells. The result? A dampening of the immune response to self and foreign antigens, including the bacteria that are normally present in the gastrointestinal tract. However, the scientists also found evidence that RA helps stimulate a pro-inflammatory immune response, when needed, to overcome infection.

Dr Jason Hall, primary author of the study, and colleagues demonstrated through their new research that immune responses to infection and vaccination were compromised when there was a lack of vitamin A. They also documented that RA triggers the T cells driving these responses. Based on their findings, the research team thinks the vitamin A metabolite RA influences the immune response during the early stages of activation and can pump up the capacity of the host to develop regulatory or inflammatory responses.

This is especially important in the GI tract. After all, the gastrointestinal system needs to tolerate constant exposure to food and the beneficial microbes that colonize the GI tract while at the same time maintaining the capacity to rapidly respond to encounters with any disease-causing infectious agents.

'These conflicting pressures confront the immune system responsible for defending the gastrointestinal tract with a unique challenge. In our study, we identified RA/RAR signaling pathway as a fitting system to accomplish these identified RA/RAR tasks, promoting generation of regulatory T cells and likely tolerance during normal conditions and adaptive T cell responses when faced with pathogens,' senior study author Dr. Yasmine Belkaid explained in a statement to the media.

Simply put, the research team's studies reveal a fundamental role for vitamin A in the development of both regulatory and inflammatory arms of GI immune responses. These findings add to the growing body of evidence that nutritional status is a broad regulator of the immune system.

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