|VITAMIN D AND SUN EXPOSURE|
New research in the June 2007 Journal of Clinical Endocrinology & Metabolism appears to indicate that vitamin D levels can be low for many people, even when they have a lot of exposure to sunlight. This goes against the prevailing thought that not enough sun exposure is the reason why so many have low vitamin D levels. This theory has been supported by the correlation of low vitamin D levels with the medical recommendation that people stay out of the sun.
Dr. Neil Binkley and colleagues, working in the University of Wisconsin Osteoporosis Clinical Research Program, investigated the vitamin D status of people living in sun-drenched Hawaii. The 93 participants in the study spent an average 22.4 hours per week outside without sunscreen and 28.9 hours per week outside with and without sunscreen. The authors calculated that this translated to an average of 11.1 hours per week of total body skin exposure with no sunscreen used. Despite this abundant sun exposure, 51 percent of these individuals were found to have low vitamin D levels, the researchers found.
"This implies that the common clinical recommendation to allow sun exposure to the hands and face for 15 minutes may not ensure vitamin D sufficiency," Binkley and colleagues report. Their conclusion was that it should not be assumed that individuals with abundant sun exposure have adequate vitamin D status.
The mechanism by which vitamin D levels could be low, even with more than adequate sunlight exposure was not proposed in this study. However, there are some known issues. Prednisone or other steroids can interfere with vitamin D. The same is true for Dilantin, a drug used for seizures. Sufficient bile production is necessary for the absorption of vitamin D from the small intestine so those with liver/gallbladder disease, or those who takes drugs that affect these organs-like the millions who take drugs for cholesterol-may have difficulty producing enough vitamin D.
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