Vitamin D is often called the “sunshine vitamin” because it is naturally produced by the body when exposed to the Sun’s ultraviolet rays. A new study suggests, however, that even people who receive abundant Sun exposure (nearly 30 hours per week) may still suffer from low serum levels of vitamin D. The researchers measured a form of vitamin D known as 25-hydroxyvitamin, commonly written as 25(OH)D.
“Low vitamin D status is very common and can contribute to the development of osteoporosis and rickets,” said Dr. Neil Binkley of the University of Wisconsin Osteoporosis Clinical Research Program, Madison, and principal author of the study. “Low levels of vitamin D may also play a role in certain cancers, multiple sclerosis, hypertension, and diabetes.”
Researchers conducted a study of 93 adults in Hawaii with self-reported Sun exposure of 28.9 hours per week. Of the 93 participants (30 women and 63 men), 47 (51 percent) had low levels of vitamin D. No correlation was found between serum 25(OH)D and age, lightest or darkest skin color, hours per week of Sun exposure without sunscreen, sun index, total hours of Sun exposure per week, or body mass index (BMI).
The researchers suggest the common clinical recommendation to allow Sun exposure to the hands and face for 15 minutes a day may not assure vitamin D sufficiency.
This paper has been published online and will appear in the June 2007 issue of the Journal of Clinical Endocrinology & Metabolism, a publication of The Endocrine Society.