Summer is here and the sun is shining, which is one of the best ways to get your vitamin D. But what if we do not get enough sunlight throughout the year? Is a vitamin D supplement necessary? What the studies say: Vitamin D may help to prevent a number of diseases such as heart disease and diabetes. It also has a range of potential anti-cancer actions. But much of the information on vitamin D comes from studies that cannot be reproduced for the general public. Currently, a handful of trials are happening, in and outside of the U.S., which will likely tell us if supplementation is protective for our health. What we already know: Vitamin D helps to keep our bones and teeth healthy, and is associated with other aspects of health. According to the new Dietary Guidelines, we should get most of our vitamin D from foods. Fortified foods and dietary supplements may be helpful when we fall short of recommendations. Vitamin D is also called the sunshine vitamin because our bodies can make it whe