Ever wonder why so many of us feel exhausted and run down— and get sick more often—during the winter? One major cause is a deficiency in a critical vitamin that our body needs and we usually don't get enough of... As crazy as it sounds, the vast majority of the population is deficient in Vitamin D, and this has major consequences for our health. Vitamin D plays a critical role in many of our body's functions and especially in supporting our immune system to help us feel our best. In this quick v