More on vitamin D

A few highlights from the articles about vitamin D that I mentioned this morning:

• Besides helping the body absorb calcium, vitamin D is an important immune system regulator with anti-inflammatory and anticancer actions. It plays a role in the activation of around 1000 different genes. New research is finding a link between increased risks of heart disease and diabetes in people who are deficient in the vitamin.
• There are few food sources, and the limited number of foods, like milk, that are fortified with vitamin D have fairly low levels of it.
• Vitamin D is produced by the body when the skin is exposed to UV light. Properly applied sunscreens, however, can reduce the body's ability to manufacture the vitamin by up to 98%. People living at higher latitudes are also hindered in their ability to make vitamin D by the lack of strong sunshine, especially in the winter.
• While the daily recommended allowance is 400 IUs, spending 15-20 minutes in midday summertime sun will naturally produce between 10,000 and 20,000 IUs. Spending more time does not produce higher levels of the vitamin as UV rays also degrade it.

Scientific American reports:

Accumulating evidence suggests that the subtle and longer-term effects of even slight vitamin D deficiency may be multifold and manifested later in life, in the form of increased frequency of bone fractures and enhanced susceptibility to infection and autoimmune diseases, as well as elevated frequencies of certain cancers. The research strongly implies that at the very least the general public would benefit substantially from greater awareness of the broad physiological benefits of vitamin D, a sound medical consensus on sensible sun exposure and a clear indication of optimal recommended daily intakes of vitamin D from dietary sources.

And from the LA Times:

Current guidelines call for blood levels of about 30 nanograms per milliliter. By that definition, perhaps 10% to 15% of white people in the U.S. and 50% of the black population is deficient in summer, with the percentages rising in winter when there is less sunlight.

Many researchers say that people should be striving for average blood levels of 50 to 60 nanograms per milliliter, at which level the bulk of the U.S. population would be considered deficient.

Most researchers in the field now take supplements of at least 1,500 IUs per day. Most recommend taking no more than 4,000 IUs because of potential toxicity.

Since reading the Scientific American article in January, I've started taking a 400 IU supplement (once daily in the summer, twice daily in the winter). Here in Vegas it's pretty easy to get 15 minutes of sun while I'm walking around campus.

UPDATE: Also see this post on a link between low vitamin D levels and an elevated risk of cardiovascular disease.