We all know that too much sun can lead to sunburns and skin cancer, but avoiding it completely can cause other problems, such as bone loss and cancer. These, and other conditions, have been linked to low levels of vitamin D, which we mainly get from spending time in the sun. Vitamin D plays key roles in the body, such as helping your intestines absorb calcium and phosphorus from food, both of which are needed for healthy bones. Low levels of vitamin D have also been associated with muscle weakness and severe asthma in children. While vitamin D can be found in oily fish and certain fortified foods, it is also created in the body when sunlight falls on the skin. If you spend too much time indoors or live in a place with long, dark winters—think Seattle or London—you might be at risk of vitamin D deficiency. Fortunately, the treatment may be as easy as going outside on sunny days. Fifteen minutes of sunlight on your face and arms can provide you with all the vitamin D that you need. If you have darker skin, it may take longer because skin pigmentation can interfere with vitamin D synthesis. During the winter months, you can eat more oily fish—such as salmon, tuna, or trout—or foods fortified with vitamin D. You can also consider taking a vitamin D supplement. Now that the days are sunnier, though, put away the vitamin bottles and head outside. Just don’t undo the health benefits of sun by getting burned.