Vitamin D Deficiency and Immunity

Vitamin D deficiency is becoming an increasingly recognized problem. The link between vitamin D and metabolizing calcium has long been known. More recent work has shown links between vitamin D level and heart health -- even back pain.

In fact, by some estimates, around half of the world's population is vitamin D deficient. For the body to make vitamin D, the skin needs to be exposed to light. As more and more people spend time indoors, their daily sunlight exposure is less and less, leading to low vitamin D levels.

We've talked on this site about some of the other consequences of vitamin D deficiency before, but researchers have more recently taken a leap forward in understanding a vital role of vitamin D in the immune system.

Vitamin D Deficiency and Immunity

Your immune system's primary weapon against disease is a cell called a T cell. These are the cells that seek out invaders in the body and destroy them. It turns out that T cells rely on vitamin D being present in the body to become active and do their work. Without vitamin D, the immune response to invaders is dulled.

Researchers are excited about this finding not only because it points to an inexpensive way to address the burden of disease worldwide, but it suggests new ways to interact with the immune system to create new vaccines or even help transplant patients.

I personally think that this finding is interesting because it reminds us of how limited our knowledge about the body really is.

We've known about vitamin D for many years, but we (clearly) have not fully understood its role and importance. It begs the question: What else don't we fully understand?

Get More Vitamin D

If you spend a lot of time indoors, or live in an area where sun in scarce, you may need more vitamin D. Ask your doctor about whether you should get the simple blood test that can check your levels.
Optimal vitamin D levels are debated, but the general range is 25-50 ng/ml.

At most latitudes, you can get enough vitamin D simply by spending 15 or so minutes in the sunshine everyday without wearing sunscreen; at extreme latitudes, the atmosphere filters more of the UV out and you need longer exposure. Vitamin D supplements are also available.


Edward Giovannucci, MD, ScD; Yan Liu, MS; Bruce W. Hollis, MD, PhD; Eric B. Rimm, ScD. 25-Hydroxyvitamin D and Risk of Myocardial Infarction in Men: A Prospective Study. Arch Intern Med. 2008;168(11):1174-1180.

Hicks, E Gregory, Shardell, Michelle, Miller, R Ram, Bandinelli, Stefania, Guralnik, Jack, Cherubini, Antonio, Lauretani, Fulvio, Ferrucci, Luigi. Associations Between Vitamin D Status and Pain in Older Adults: The Invecchiare in Chianti Study. Journal of the American Geriatrics Society, Vol. 56, No. 5. (May 2008), pp. 785-791.

Marina Rode von Essen, Martin Kongsbak, Peter Schjerling, Klaus Olgaard, Niels Ødum, & Carsten Geisler. Vitamin D controls T cell antigen receptor signaling and activation of human T cells. Nature Immunology. Published online: 7 March 2010 | doi:10.1038/ni.1851

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