Is Sun Exposure Enough to Keep Vitamin D Levels Healthy?
August 16, 2007—Many physicians recommend brief periods of exposure to sunlight each day so that people’s bodies will produce the vitamin D needed to prevent disease and promote health. But a recent study suggests that sun alone may not be enough, as researchers found that a large proportion of Hawaiians exposed to high levels of daily sun have low levels of vitamin D.
To evaluate the effects of daily high sun exposure on vitamin D levels, the study authors performed a standard lab test for vitamin D in 93 white, Asian, Hawaiian/Pacific Island, and multiracial people living in Honolulu, Hawaii. Each person’s average sun exposure was nearly 30 hours per week, with an average of 11 hours unprotected by sunscreen.
Results, which were published in the Journal of Clinical Endocrinology & Metabolism, showed that 50% of the participants studied had vitamin D deficiency despite high levels of sun exposure. These findings raise a number of questions about vitamin D including:
- What should be considered a healthy level of vitamin D in the body?
- Is sun exposure alone enough to keep vitamin D levels normal?
- Are there genetic differences in how much vitamin D people manufacture?
- Can people get too much sun, interfering with the skin’s ability to properly manufacture and transport vitamin D into the body?
“We still have a great deal to learn about what constitutes optimal vitamin D status,” commented Alan Gaby, MD, Healthnotes chief science editor. “It is clear that supplementing with the standard 400 IU per day is not sufficient for some people, and that 800 to 1,000 IU per day is more appropriate for them. However, we do not know whether it is safe for the average person to take more than 2,000 IU per day for long periods of time.”
Vitamin D deficiency has been linked to a variety of chronic diseases such as osteoporosis, cancer, multiple sclerosis, and others.
(J Clin Endocrinol Metab 2007;92,6:2130–35)
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Jane Hart, MD, board-certified in internal medicine, serves in a variety of professional roles including consultant, journalist, and educator. Dr. Hart, a Clinical Instructor at Case Medical School in Cleveland, Ohio, writes extensively about health and wellness and a variety of other topics for nationally recognized organizations, Web sites, and print publications. Sought out for her expertise in the areas of integrative and preventive medicine, she is frequently quoted by national and local media. Dr. Hart is a professional lecturer for healthcare professionals, consumers, and youth and is a regular corporate speaker.
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