Vitamin D: Emerging Role in Health
Vitamin D is well known for its role in developing and maintaining strong bones, but new research suggests that it may also play an expanded role in promoting health and preventing disease. At the same time, many people do not get enough.
Article By: The Weight Watchers Research Department
Vitamin D is a fat-soluble vitamin needed for healthy bone development, cell growth and immune function. The vitamin is unique because, given adequate exposure to sunlight, the body can make all it needs. There are only a few foods that are a naturally rich source, such as oily fish (e.g., mackerel). So foods such as milk, other dairy foods (e.g., some yogurts, cheese), and some breakfast cereals are often fortified with vitamin D.
Many people do not get enough vitamin D
According to a study published in the Journal of the American College of Cardiology, up to half of all adults and 30 percent of children and teenagers have insufficient levels of vitamin D in their blood. 1 Some groups, including infants, African Americans and older adults, have increased odds of developing a vitamin D deficiency. Also, being overweight is linked to lower concentrations of the nutrient. 2
Role in health
The pool of evidence continues to grow to show that vitamin D’s importance extends far beyond strong bones. Several studies have found that low levels of vitamin D may increase the risk for a number of conditions, including some types of cancer, hypertension, cardiovascular disease, type 1 diabetes, rheumatoid arthritis and multiple sclerosis. Furthermore, amounts of vitamin D higher than the current dietary recommendation are linked to increased calcium absorption and a reduced risk of these diseases.
While the results are promising, the evidence does not definitively prove cause and effect because the research comes mostly from epidemiological, lab and animal studies. Clinical trials are needed to make firm conclusions.
How much is enough?
The current dietary recommendation for vitamin D is 600 IU per day (e.g., 1 cup of milk provides 100 IU) in the United States and Canada. 3 The recommendation in the European Union, Australia, and New Zealand is 200 to 400 IU, depending on age.
To optimize intake, include foods rich in vitamin D, fortified foods and adequate sunlight (i.e., 5 to 15 minutes a few times per week). Avoid large doses of dietary supplements that exceed the Upper Limit of 4,000 IU, which can be toxic.
This content is reviewed regularly. Last updated August 18, 2011.
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1 Lee JH, O’Keefe JH, Bell D, Hensrud DD, Holick MF. Vitamin D deficiency an important, common and easily treatable cardiovascular risk factor?J Am Coll Cardiol. 2008 Dec 9;52(24):1949-56.
2Yetley EA. Assessing the vitamin D status of the US population.. Am J Clin Nutr. 2008 Aug;88(2):558S-564S.
3Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D.. 2010.