For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU vitamin D into the circulation within 24 hours of exposure, for tanned individuals the same amount of exposure yields 20,000-30,000 IU and for those with dark skin 8,000-10,000 IU.
At least 1,000 different genes governing virtually every tissue in the body are now thought to be regulated by 1,25-dihydroxyvitamin D, the active form of the vitamin, including several involved in calcium metabolism and neuromuscular and immune system functioning. According to Michael Holick, medical professor and director of the Bone Health Care Clinic at the Boston University Medical Center, the primary physiologic function of vitamin D is to maintain serum calcium and phosphorous levels within the normal physiologic range to support most metabolic functions, neuromuscular transmission, and bone mineralization.
In a study reported in the Journal of Investigative Dermatology, June 2003, Holick pointed out that most melanomas occur on the least sun-exposed areas of the body and occupational exposure to sunlight actually reduced melanoma risk.
Rolfdieter Krause and his colleagues of the Free University of Berlin Department of Natural Medicine studied to determine the potential link between sun exposure and the protective effect in preventing hypertension by exposing a group of hypertensive adults to a tanning bed that emitted full-spectrum UVR, which is similar to the summer sunlight and another group of hypertensive adults to a tanning bed that only emitted UVA radiation, which is similar to the winter sunlight. After 3 months, those who used the full-spectrum UVR tanning beds had an average 180% increase in their 25(OH)D levels and an average 6 mm Hg decrease in their systolic and diastolic blood pressures, which brought them into normal ranges. The group that used the UVA-only tanning beds showed no change in either 25(OH)D or blood pressure.
A research, published in the Archives of Internal Medicine, showed that those with the lowest vitamin D levels have more than double the risk of dying from heart disease and other causes over an eight-year period compared with those with the highest vitamin D levels.
In the International Journal of Epidemiology, a study led by Robyn Lucas, an epidemiologist at Australian National University, concluded that, far more lives are lost to diseases caused by a lack of sunlight than to those caused by too much.
As reported in Arthritis & Rheumatism, January 2004, the greater intake of vitamin D has been linked with lower rheumatoid arthritis risk.
Source: www.ncbi.nlm.nih.gov/pmc/articles/PMC2290997
For your information:
The United States UV Index Forecast - Everyday the National Weather Service calculates the predicted UV Index for the next day in the U.S.
The United States Naval Observatory - Gives data on when the sun is at 50 degrees or more in any given area, which is the best range to get vitamin D exposure on sunny days.
Shared with: the healthy home economist
