It may not be the cold air or Old Man Winter’s roar that keeps even seasoned athletes indoors during the winter. According to the scientific literature, vitamin D may improve athletic performance, but only in athletes who are deficient in vitamin D.
So who is most likely to be deficient in vitamin D? Since vitamin D is produced in the body when the skin is exposed to sunlight, it shouldn’t worry people who get at least some sun exposure throughout most of the year, unless they live north of 37 degrees latitude during the winter. The sun’s rays are too weak north of 37 degrees, and it’s even worse if your skin is dark, since melanin can block sunlight.
The elderly also have problems making vitamin D, even if they get sufficient sunlight. Vitamin D(a misnomer, it is actually a hormone) is necessary for calcium absorption, which helps build strong bones, and may also boost the immune system, among other things. Scientists have found links between vitamin D deficiency and certain forms of cancer, but a lot more research needs to be done.
Eating a healthy, varied diet can provide just about all the nutrients the average person needs, but hardly any foods contain sufficient quantities of vitamin D to meet new nutritional guidelines. Even multivitamins fall short of the new guidelines. So it looks like eating food fortified with vitamin D(like milk) or vitamin D supplements may be the answer, for those who live north of 37 degrees latitude from autumn to spring.
A rather interesting possible solution which doesn’t involve supplements is to get some mushrooms(button mushrooms, shiitake, and many other mushroom species, but do not pick any wild mushrooms unless you know what you are doing) and place them in the sun for a few hours. When exposed to sunlight, they will manufacture vitamin D, just like humans, in quantities that are as good as or even better than supplements. This is certainly a wild solution!
I take a 5,000 I.U vitamin D supplement about twice a week during the winter since I am in the north-east U.S. I don’t take them at all during the summer, since I get enough sunlight during that time of year. I take it twice a week since vitamin D is fat-soluble, which means it can be stored in the liver and fatty tissue, unlike water soluble nutrients like vitamin C, which are quickly removed from the body which is why you need to get it every day.
So if you’re an athlete or even if you’re not an athlete, and you feel sluggish and you live in the northern U.S, see if you can get your vitamin D levels checked by your doctor. Or, you can just eat more mushrooms that have been sun-bathed as suggested above if you suspect you’re deficient. Like many nutrients, Vitamin D can be toxic in large quantities, so be careful.
For my fellow vegetarians and vegans – vitamin D-3, also called “cholecalciferol” is not vegan since it is derived from animal sources. However, vitamin D-2, also called “ergocalciferol” is vegan since it comes from plant sources. The type of vitamin D that is in mushrooms is D-2/ergocalciferol.