Vitamin D is an important hormone that has a number of different functions in human physiology. One of the most important roles for vitamin D is the maintenance of the immune system. Evidence suggests that vitamin D deficiency significantly increases the risk of infection, and this is likely the reason that upper respiratory tract infections are more prominent in the winter. During the winter months, sunlight induced vitamin D production drops, and this increases the risk of infection due to poorer immune status. Studies have investigated the effects of vitamin D supplementation on the infection rates in vitamin D deficient humans. In one study, 300 IU of vitamin D, a modest to small dose, caused a significant reduction acute respiratory infections over a 3 month period, when compared to a placebo group. The vitamin D supplements cause significant increases in the 25-hydroxyvitamin D concentrations in the blood of the vitamin D group, suggesting vitamin D status had been improved.
Eat Well, Stay Healthy, Protect Yourself