Just "D" Facts about Vitamin D

Benefits of Moderate UV Sunshine Exposure

Tanning Beds Help Vitamin D Deficiency

Posted by D3forU on February 23, 2008

By David Liu, Ph. D.
Feb 22, 2008 – 2:27:23 PM

(Foodconsumer.org) — Researchers at the University of Boston found that vitamin D deficiency was common among the elderly people during non-summer days and exposure to UV rays from a commercial tanning bed could effectively stimulate production of this essential vitamin that now is believed to provide a potent anti-cancer activity among others.

The study of 45 nursing home residents by Michael Holick, a heavy weight vitamin D researcher and senior author of the study, and colleagues showed the rate of 25(OH)D deficiency among the subjects raised to 49, 67, 74 and 78 percent in August, November, February and May, respectively. The participants took a vitamin D supplement containing 400 IU vitamin D2 during the study.

Vitamin D is naturally synthesized in the body while exposure to sunlight. Full exposure of both hands and the face for 15 to 20 minutes to the sun would render production of enough vitamin D3 in a person. Overexposure would not lead to overproduction of this vitamin.

In regions where exposure to the sunshine is not intense, people are more likely to develop a range of cancers including the colon, prostate, breast, and esophagus, according to Holick. Vitamin D deficiency has been linked to increased risk of having hypertension, type 1 diabetes, multiple sclerosis, and other autoimmune disease and infectious disease including tuberculosis and influenza in addition to cancers.

For the study, Holick and colleagues exposed 15 healthy adults aged 20 to 53 in a bathing suit three times per week from a commercial tanning bed that emitted five percent of its UV energy in the UVB ranging 290 to 320 nm. The 25(OH)D level in the blood was determined weekly for seven weeks.

Exposure to tanning bed irradiation increased pre-vitamin D at a linear rate of 1 percent per minute. One week of exposure led to an increase in 25(OH)D by 50 percent and five weeks of exposure increased the level by 150 percent compared to baseline. After five weeks, 25(OH)D leveled off in the next two weeks.“Vitamin D deficiency is common in both children and adults worldwide,” said Michael Holick. “Exposure to lamps that emit UVB radiation is an excellent source for producing vitamin D3 in the skin and is especially efficacious in patients with fat malabsortion syndromes.”

The recommended daily allowance (RDA) for vitamin D is 400 IU for adults, which most experts now believe is too low. According to the researchers, experts would recommend 1000 IU per day as the minimal daily intake to maintain circulating concentrations of 25(OH)D.

Sunshine is the most abundant source of vitamin D although there are a limited number of foods that supply vitamin D. Some people may fear that exposure to sunshine would increase risk of skin cancers. But experts have warned that deficiency of vitamin D could be more serious than most cases of skin cancers, which are not as deadly in most cases. Although vitamin D can be toxic at high doses, it’s believed that up to 10,000 IU per day can be tolerated.

Studies have suggested that high intake of vitamin D would drastically reduce risk of cancer. For breast cancer, the reduction is 70 percent. In addition to vitamin D supplements, fatty fish such as salmon and mackerel and cod liver oil are excellent sources of this vitamin.

This current study was funded in part by the National Institutes of Health and the Ultraviolet Light Foundation and will be published in the March 2008 issue of the Journal of Bone and Mineral Research.



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