U.S. Vitamin D Deficiency and Sunlight Avoidance
September 30, 2004—Many people in the US get less than the recommended amount of vitamin D each day, reports the Journal of the American Dietetic Association (2004;104:980–3).
Vitamin D is a fat-soluble vitamin produced from cholesterol in the skin in a process triggered by exposure to the sun’s ultraviolet light. Vitamin D plays an important role in calcium metabolism: by increasing calcium absorption and decreasing calcium loss in the urine, it ensures that calcium is available to keep bones and teeth healthy. Vitamin D deficiency in children, known as rickets, is characterized by bone deformities. In adults, deficiency can contribute a number of health problems, including osteoporosis, a condition marked by decreased mineral content of bone and high risk of fracture.
Getting sufficient sunlight is critical to having enough vitamin D in the body. Taking supplements and eating foods rich in vitamin D, such as fish, eggs, and fortified dairy products, can help prevent vitamin D deficiency. The recommended amount of dietary and supplemental vitamin D is 200 IU per day for people under 50 years old, 400 IU per day for people from 51 to 70, and 600 IU per day for people over 70.
The current study analyzed the data from two previous survey studies. The reported diets of more than 27,000 people who participated in the Third National Health and Nutrition Examination Survey (NHANES III) and almost 19,000 people who participated in the Continuing Survey of Food Intakes by Individuals (CSFII) were used to estimate vitamin D intake. Less than 10% of adults 50 to 70 years old, and only about 2% of people over 70, were found to be getting the recommended amounts of vitamin D from food. When supplements were added into consideration, still only about 30% of people aged 50 to 70 and 10% of those over 70 were reaching the recommended vitamin D intake. Among people 14 to 50 years old, significantly fewer females (about 50%) than males (about 65%) were getting recommended amounts of vitamin D from food and supplements. Recommended vitamin D intake was achieved by about 53 to 63% of all children.
The results of the current study suggest that the dietary and supplemental vitamin D intake of many people in the US is less than recommended. Disturbing results have also come from a previous study in which 42% of a group of hospitalized patients under age 65 were found to have vitamin D deficiency, and 37% of people eating recommended amounts of vitamin D were still found to be deficient. It would be sensible, in light of these findings, for nutritionists and other healthcare providers to recommend vitamin D supplements, particularly for females and the elderly.
In addition, some researchers have challenged the modern notion that people should stay out of the sun as much as possible. While excessive sun exposure can increase the risk of skin damage and skin cancer, these scientists argue that modest amounts of sun exposure are safe. Exposing the hands, face, and arms, or arms and legs, daily to sunlight for one-quarter of the time it would take to cause a light pinkness of the skin would be enough to satisfy the body’s vitamin D requirement, and to manufacture enough vitamin D to store for times when sunlight exposure is inadequate.
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Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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