Vitamin D helps your body use calcium for building strong bones, has benefits for heart health, helps keep your immune system in top form, and helps keep you in good spirits. The good news is that your body can actually manufacture Vitamin D if you get enough exposure to natural sunlight.

But there are a number of risk factors that could be keeping you from getting enough Vitamin D in your diet.

Vitamin D only occurs naturally in a certain foods like fish, fish oil, eggs, and some fortified foods. That means that if you are following a strict vegetarian diet you might not be getting enough from food alone.

Vitamin D is naturally produced by your body through exposure to sunlight, but during the long winter months and short days, it’s unlikely you are getting enough sun to manufacture the D you need. This is especially true if you live in the northern latitudes or work all day indoors.

Fat cells absorb Vitamin D out of the blood stream and studies show that having a Body Mass Index of over 30 increases your risk of having low levels of Vitamin D in the blood.

The pigment melanin reduces the bodies ability to convert natural sunlight to Vitamin D. The darker your skin the more melanin you have, and therefor the longer you need to be exposed to sunlight to produce enough Vitamin D.

On top of all these risk factors, is the fact that the USDA guidelines appear to woefully underestimate the quantity of Vitamin D that we actually do need in our diets. So make sure you are getting enough D in your diet, and try to get some regular exposure to the sun, and consider adding supplements to your diet. 

Here are a couple videos on the subject, if you are interested in deeper research on the topic.