December 20, 2010

The verdict on Vitamin D: Am I getting enough?

By Spencer Webb, CSCS, Dietetic Intern, Bay Pines VA Health Care System, Pinellas County Extension

With a nickname like “the sunshine vitamin” you would think most of us living in the sunshine state would have no problem getting enough vitamin D. Since 2000, the public has received conflicting information about the amount of vitamin D we should be getting to stay healthy. To help clarify this issue, the United States and Canadian governments asked the Institutes of Medicine (IOM) to examine the current information on health outcomes associated with vitamin D and calcium, as well as updating the recommendations for our daily intake.

Where do we get vitamin D?
We get vitamin D from the sun, food and supplements. The food sources of vitamin D are somewhat limited since it is only found naturally in mushrooms, egg yolks, and in some types of fish, like salmon and sardines. Beginning in the 1930’s, milk sold to consumers was fortified to combat a bone deformity called rickets. This disease resulted in a “bow-legged” appearance in individuals who consumed low amounts of vitamin D when they were children. Other foods like orange juice, breads and cereals have been added to the list of fortified foods.

The good news about vitamin D, and what makes it unique, is that we can make it in our bodies. When exposed to sun, the skin makes a compound that is converted to vitamin D in the liver and kidneys. We need 10–15 minutes of direct sun on our face and arms, without sunscreen, two to three times a week to make enough vitamin D.

Another source of vitamin D is supplements. Supplement companies have been cashing in on the controversy. According to the Nutrition Business Journal, sales for vitamin D supplements rose 83% in 2009, generating over $240 million.

Why do we need Vitamin D?
Vitamin D plays an important role with calcium and phosphorus in maintaining the health of teeth and bones. It also keeps the immune system functioning. Vitamin D has been studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, cancer, and autoimmune conditions such as multiple sclerosis. Based on the conflicting and mixed results of the studies, there is currently no evidence to confirm that vitamin D has any impact on these conditions.

How much do we need?
New intake recommendations (Recommended Dietary Allowances - RDA) for vitamin D have been recently released. Below is a table with those new recommendations.

Life StageVitamin D (IU/day)
Children and Teens600
Adults, up to age 70600
Adults, ages 71+800
IU = International Units

It is possible to get too much?
The IOM recently stated that while many Americans don’t get enough vitamin D from the foods they eat, most still have enough in their body, since they can make it from exposure to the sun. This means that the average American probably doesn't need to be taking large amounts of supplements as they have been shown to be toxic in large doses. The upper limit is 4000 IU and less for children younger that 9. Certain people like the elderly, dark-skinned individuals and people with liver and kidney disease may not get enough form the sun so they may benefit from fortified foods or a supplement.

To learn more about this vital nutrient, visit these websites:

National Institute of Health's Office of Dietary Supplements

The Institute of Food and Agricultural Sciences (IFAS)

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