With the nights getting cooler and the days getting shorter, it is a good time to think about vitamin D again and consider why supplementation is essential for all of us from now until late spring.
While vitamin D is best known for its role in bone health and the prevention of osteoporosis, there are multiple other reasons why vitamin D is essential for optimal health. Low levels of Vitamin D are known to be associated with increased risk for colon cancer, breast cancer, prostate cancer and ovarian cancer. There are also links with reduced muscle strength, muscle stiffness, higher LDL cholesterol and triglyceride levels, and macular degeneration. Vitamin D also affects cell growth in the body and has roles in neuromuscular and immune system function as well as helping to decrease inflammation. Low levels are linked to multiple sclerosis and Crohn,s disease.
During the long Canadian winters we are steadily losing our vitamin D stores, making it easier to fall victim to colds and flu. This is because vitamin D is essential for activating the quick response part of our immune system which helps us deal with exposure to new infectious agents. There are studies that have shown that people with higher levels of vitamin D get fewer wintertime respiratory infections.
Vitamin D3 (or cholecalciferol) is the naturally occurring form that is present in most supplements and is identical to the vitamin D3 made in your skin after being exposed to direct sunlight (UVB radiation). Food sources include fatty fish, beef liver and egg yolks but it is not possible to obtain sufficient vitamin D through diet alone.
Vitamin D2 (ergocalciferol) is a synthetic form made from irradiated mushrooms. This is often preferred by vegans as vitamin D3 is obtained from the lanolin from sheep wool. The problem with vitamin D2 is that it is less effective in raising blood levels and is not effective for as long as vitamin D3.
Whether you get vitamin D from sun exposure or ingesting it, the gut sends the vitamin D to the liver where it is changed to a substance called 25(OH)D. When your vitamin D levels are tested, it is actually the amount of 25(OH)D in the bloodstream that is measured. This chemical is sent all over the body where different tissues, including the kidney turn it into activated vitamin D. Activated vitamin D is now ready to perform its duties of managing calcium in the blood, bones and gut, and helping cells all over the body to communicate properly.
In summer, we are able to make between 10 000 and 25 000 IU (international units) in half the time it takes for the skin to turn pink. This might be 15 minutes for a fair skinned person, and up to two hours for someone with dark skin and dark eyes. You do not need to tan or burn to get this benefit. However, during winter in the Okanagan (and indeed, all of Canada) - the angle of the sun is too great for most of the day, so UVB rays are blocked and it is not possible to make vitamin D in the skin. So, basically, if your shadow is longer than you are tall, you cannot make vitamin D!