Vitamin D, the vitamin we get from exposure to the sun, is a pretty unique vitamin. Most vitamins we need come directly from the food we eat. We can get *some* vitamin D from food, but in order to meet our bodies needs for vitamin D, we need exposure to the sun!
How does this work?
There is a provitamin in our skin, a substance that can get converted into a vitamin, that can be converted into vitamin D3. This is where the sun comes in! When sunlight reaches our skin, the UVB rays it omits aid in a reaction that converts this provitamin to vitamin D.
There are a lot of factors that can affect how much vitamin D you get, such as skin tone, time of the year, geographic location, pollution, clothing, time of day, etc. For example, people living in the majority of the United States are prone to vitamin D deficiency, simply because of the weakened UVB wavelengths that reach this part of the earth. On the East Coast, this is anyone living from Virginia to Maine.
How do I know if I am deficient in vitamin D?
At most doctors offices, your annual bloodwork includes a check on your vitamin D. This is the best way to know when you are at! If it's not included, you can always ask if they can add it! Since there are so many factors that contribute to vitamin D status, it is hard to confirm that any one thing (like living in a certain state) automatically grants you as deficient.
There's actually some disagreement in the sports medicine world in regards to what is sufficient for athletes. Labs from you PCP will likely show that anything above 20 ng/mL is sufficient. However, recent literature shows athletes likely need closer to 50 ng/mL for adequate bone health and muscle function. This is something to discuss with your PCP, sports medicine physician, or dietitian if you are unsure if you are meeting your needs.
How do I get more vitamin D?
As I mentioned, vitamin D is not widely found in food sources. Some fish and mushrooms contain significant amounts of vitamin D, as well as some fortified foods, but for the most part, we need exposure to the sun to meet our needs.
If your bloodwork indicates you are low in vitamin D, you may benefit from a supplement. Look for a supplement containing 600-2000IU of vitamin D3 (vitamin D2 is less bioavailable, meaning your body will get less from it). Keep in mind, most multivitamins contain vitamin D; double check before starting a vitamin D supplement if you already take a multivitamin. Always be sure to check with your doctor or a dietitian before starting a new supplement. Vitamin D can become toxic if taken in excess.
Pro tip! Take your vitamin D with your meals to maximize absorption! It's a vitamin that is absorbed with the help of fats.