Why do I need Vitamin D? Vitamin D has gained more attention by the research community and public than a reality TV star in the past few years. Traditionally, vitamin D was known to play a key role in calcium absorption – without it you cannot, I repeat cannot, absorb calcium from your diet. Most recently, it has been found that vitamin D may play a critical role in numerous cellular processes; some researchers have even developed a modified mechanism for cancer with vitamin sitting center stage. A total of 35 tissues in humans have receptors for the active form of vitamin D.
Where can I get Vitamin D? Vitamin D is a fat soluble vitamin that is stored in its inactive form. While it is fat soluble, doses of 50,000IU are needed to see side effects. A dose lower than 10,000 IU should not show any problems. Food sources of vitamin D are few and far between – fatty fish is really the only place to find it.
Luckily, our bodies are able to make vitamin D. When our skin is exposed to UVB rays at a high enough intensity, cholesterol in our skin is converted to an inactive form of vitamin D. Depending where you live, you may only be exposed to rays at a high enough intensity for a few months out of the year. Below is a picture showing the latitude line. Anyone in the gray region is not able to make vitamin D during the winter months The further north you go the longer you are out of the range to receive high intensity UVB rays. It is important to note that sunscreen is still important – you only need to have your skin exposed to the sun for 5-15 minutes without sunscreen to make adequate levels of vitamin D. Your body will only synthesize as much as it needs, so you do not need to worry about overdosing on vitamin D through sunlight.
How much do I need? Vitamin D requirements are being reviewed to see if they should be increased and if so, how much. Presently, the RDA is only 200IU for a healthy adult and 400IU for older adults and those with dark skin (because decreased ability to make vitamin D in the skin). Many organizations are recommending all adults to get 1000-2000IU per day. Most Americans have insufficient levels of vitamin D.
Where can I learn more? For more information on vitamin D, visit the vitamin D council’s website, the Linus Pauling Institutes’s website, or read one of these articles I wrote: Vit D FAQ Dec 2009 JADA and MLO Vitamin D Article.
Weekly Challenge: Ask your doctor if you can get a vitamin D test done this winter to see how low your levels drop when the UVB intensity falls. Also, talk with doctor to see if it is safe for you to take a vitamin D supplement.