Vitamin D and Immune Function

Over 3,200 studies concerning vitamin D have been published over the last 10 years alone. The interesting thing is that vitamin D is not even a vitamin but rather a hormone with many important functions. Ty Vincent, M.D., discussing vitamin D and immune function, was one of many excellent lecturers at the recent annual American Academy of Environmental Medicine Conference. Some important points are summarized here.

It is well accepted among medical experts that being deficient in vitamin D increases our risk of certain cancers, hypertension, allergies, asthma, osteoporosis and many autoimmune conditions. Deficiency is usually defined as a serum level below 30 ng/mL. Unfortunately, vitamin D deficiency is not at all uncommon.

Vitamin D is known to be very important for proper tissue integrity and an important regulator of barrier function. It also increases the production and regulation of T regulatory white blood cells, which play a critical role in directing the immune response away from certain antigens. Thereby, vitamin D regulates "tolerance" within the immune system function and is critical for protection against allergy and autoimmune conditions. Vitamin D also regulates the production of cathelicidin and defensin—two proteins that play an important role in the immune system response against bacteria, fungi and viruses.

Vitamin D is critical to keeping the immune system on the right track. So how much vitamin D do we need to take? The answer depends on a few things and points out one of the principles of environmental medicine—the concept of biochemical individuality. In other words, we are all genetically unique.

DIET

An important source of vitamin D is through certain foods, especially fish and dairy. One website (WHFoods.org) lists the following important sources of vitamin D: salmon, sardines, tuna, cow milk, eggs, and even shiitake mushrooms. Clinical experience has shown that most people do not meet their vitamin D requirement with diet. However, diet should be taken into consideration when trying to estimate an appropriate vitamin D supplementation dose.

SUN

Ideally, we would each get just the right amount of sun exposure to generate vitamin D while not too much to increase the risk of skin cancer. In perfect conditions, it is estimated that between 10 to 15 minutes of direct sun exposure on unprotected skin over 35 percent of body surface produces around 20,000 IU of vitamin D. Even more fascinating is the fact that there is a mechanism that prevents our body from making too much vitamin D with sun exposure. We make the amount needed, then it "shuts off." This mechanism depends on genetics, location on the globe, the time of year and amount of exposure.

SUPPLEMENTS

Many of us may need to resort to supplementation. The recommended dosage is the amount required to get our serum D3 level between 50 to 80 ng/mL. In some cases, it is recommended shooting for a higher number of around 100 ng/mL, but for general health benefits most studies suggest levels around 50 to 70 ng/mL are optimal. The only way to know how much is required is through a standard vitamin D level blood test.

The general recommendation for everyone living in the U.S. is to supplement with an amount of vitamin D3 to maintain serum levels between 50 to 80 ng/mL through fall, winter and spring. Most adults do best with a 5,000 IU daily dose. However, there are patients that only need 2,000 IU daily to achieve optimal levels and other patients that need more than 15,000 IU daily just to stay in normal serum range. That is why it is always recommended that adults supplement with a dose they are comfortable with for a month or two, then have their level checked. It only takes a few measurements to figure out an individual’s required dose.

William J. Weirs, M.D., FAAEM, is a physician at the Center for Occupational and Environmental Medicine. For more information on vitamin D testing and immune function, visit online at COEM.com or call 843-572-1600.