Vitamin D May Activate Immune Function

There has been a seemingly endless supply of new research demonstrating benefits related to having enough vitamin D in the body. Vitamin D has been linked to a surprising number of health benefits, including heart and bone health, cognitive function, cancer risk, diabetes risk and even risk of death.

Now, researchers from the University of Copenhagen have found that vitamin D is critical to the function of the immune system. Over the last few years numerous studies have tied improved immune function and lower risk of certain cancers. But until this study, no one understood why.

In short, through a fascinating process, vitamin D is an essential chemical trigger that triggers specialized immune cells to do their job; without adequate vitamin D, the immune cells remain dormant. These specialized cells are "T-cells." T-cells are a type of white blood cell that that seek out and kill pathogens in the body. For a T-cell to properly perform it's job, it must first encounter traces of the pathogen. Another type of immune cell, a macrophage, performs this task by presenting cell fragments to the T-cell. The T-cells bind to these cell fragments and divide, multiplying to produce hundreds of identical T-cells. These identical T-cells then extend a vitamin D receptor which searches for vitamin D. If the T-cells cannot find enough vitamin D in the blood, the T-cells will not be activated to fight the infection. The T-cells that do find enough vitamin D become either natural killer cells that search for and destroy any cells carrying any traces of the pathogen, or they become helper cells. Helper cells aid the immune system in acquiring a biological memory, passing information about the pathogen to the immune system. The immune system retains that information about the pathogen and how to fight it, in case the pathogen is encountered again in the future.

The researchers stated that "scientists have known for a long time that vitamin D is important for calcium absorption and the vitamin has also been implicated in diseases such as cancer and multiple sclerosis, but what we didn't realize is how crucial vitamin D is for actually activating the immune system -- which we know now."

This discovery may have implications that reach well beyond helping the immune system fight colds and everyday pathogens. It may also be useful in controlling autoimmune diseases and controlling tissue rejection in transplant surgeries.

Vitamin D comes in several forms. The two forms of vitamin D that come from diet and supplements, cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2), are converted within the body into 25-hydroxyvitamin D, the "storage form" of vitamin D, and 1,25-hydroxyvitamin D, the "active form."

1. von Essen, M. R., M. Kongsbak, et al. "Vitamin D controls T cell antigen receptor signaling and activation of human T cells." Nat Immunol.