Transitioning into the winter months equates to less sun exposure and significantly lower levels of Vitamin D systemically. Vitamin D deficiency was once thought to be fairly rare and usually associated with a condition known as rickets, but multiple research studies are now revealing that many of us are indeed Vitamin D deficient without knowing it and it can impact various aspects of our health.
Low vitamin D levels are serious business. Not only do you need vitamin D to keep your bones strong but it also plays an important role in your immune defenses against winter colds and flus, and can help prevent cancer, heart disease, multiple sclerosis, infertility and auto-immune diseases. According to the UV Foundation, low vitamin D levels can also lead to fatigue, depression, and aches and pains.
Fortunately, there are other ways to get your vitamin D. There aren't a whole lot of foods that are naturally rich in vitamin D. (Mackerel, sardines, and fish liver oil are among the top providers.) Because our diet does not contain a lot of vitamin D-rich foods, the government also mandates fortification of milk and baby formula with vitamin D. Other dairy products, like yogurt or cottage cheese may or may not contain additional vitamin D. The nutrient can also be taken as a dietary supplement.
However you choose to take your vitamin D, just be sure you're getting enough on a regular basis. The US Food and Nutrition Board recommends 200IU per day, but current research is indicating that that may not be enough. In the winter months I usually suggest a supplement of Vitamin D3 (the most absorbable and active form) of at least 2000IU per day (more if you have been tested and found to be deficient).
If you are concerned about your Vitamin D levels, a simple blood test can be performed by your physician to evaluate your levels.