Effects Of Vitamin D And Skin’s Physiology Examined

The benefits of moderately increased exposure to sunlight – namely the production of vitamin D, which protects against the lethal effects of many forms of cancer and other diseases – may outweigh the risk of developing skin cancer in populations deficient in vitamin D. (Credit: iStockphoto/Wolfgang Amri)

ScienceDaily (Feb. 24, 2008) — Researchers from Boston University School of Medicine (BUSM) have found that previtamin D3 production varies depending on several factors including skin type and weather conditions. Excessive exposure to sunlight does not result in Vitamin D intoxification because previtamin D3 and vitamin D3 are photolyzed to several photoproducts. During the winter at latitudes above ~35 degrees, there is minimal if any previtamin D3 production in the skin.

Increased skin pigmentation, application of a sunscreen, aging and clothing have a dramatic effect on previtamin D3 production in the skin. It has been speculated that people living at higher latitudes may be able to more efficiently produce vitamin D3 in their skin because there is less ozone to absorb the UVB photons. Forty-five nursing home residents who were taking a multivitamin that contained 400 IU of vitamin D2 showed a dramatic decline in their 25(OH)D levels from the end of summer to the beginning of the following summer. Forty-nine percent, 67 percent, 74 percent, and 78 percent of the nursing home residents were vitamin D deficient in August, November, February, and May respectively

Fifteen healthy adults aged 20-53 received exposure three times per week from a commercial tanning bed that emitted five percent of its UV energy in the UVB range 290-320 nm to most of their body while in a bathing suit. 25(OH)D levels were determined weekly for a total of seven weeks.

Exposure of 7-dehydrocholesterol to tanning bed irradiation revealed -1 percent production of previtamin D after one minute and a linear increase to -10 percent at 10 minutes. After one week, there was a 50 percent increase in 25 (OH)D levels that continued to increase over a period of five weeks to -150 percent above baseline levels. The blood levels of 25 (OH)D plateaued after five weeks and were sustained out to seven weeks.

“Vitamin D deficiency is common in both children and adults worldwide,” said Michael Holick, PhD, MD, director of the General Clinical Research Center and professor of medicine, physiology and biophysics at BUSM and senior author of this study. “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.”

It has been observed that living at higher latitudes and being more prone to vitamin D deficiency markedly increases risk of many deadly cancers including cancer of the colon, prostate, breast, and esophagus, according to Holick, who is also director of the Bone Healthcare Clinic and the vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center. Living at higher latitudes also increase the risk of having hypertension, type I diabetes, multiple sclerosis and other autoimmune diseases, and infectious diseases including tuberculosis and influenza.

According to researchers, most experts now agree that a minimum of 1000 IU of vitamin D3 per day is necessary to maintain circulating concentrations of 25(OH)D.

The study will appear in the March 2008 issue of the Journal of Bone and Mineral Research.

This study was funded in part by the National Institutes of Health and the Ultraviolet Light Foundation.

Adapted from materials provided by Boston University.

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Tanning is associated with optimal vitamin D status

 Conclusion: The regular use of a tanning bed that emits vitamin D–producing ultraviolet radiation is associated with higher 25(OH)D concentrations and thus may have a benefit for the skeleton. Am J Clin Nutr 2004;80:1645–9.

The use of tanning beds has been promoted to the public for the cosmetic purpose of tanning, but this study shows that a moderate use of tanning beds may also provide some medical benefit.

Higher concentrations of 25(OH)D throughout the year may have a significant effect in enhancing intestinal calcium absorption and improving bone health (7, 8, 42). Blood concentrations of 25(OH)D in tanners are  75 nmol/L, which is considered to be necessary for maximum intestinal calcium transport (23, 42).

This may explain why higher serum 25(OH)D concentrations are associated with higher bone density. There is mounting evidence that a healthy concentration of 25(OH)D (ie, 75 nmol/L) may reduce the risk of colon, breast, and prostate cancers, hypertension,
and autoimmune diseases (2, 3, 39–42).

In conclusion, the regular use of a tanning bed results in higher 25(OH)D concentrations and prevents increased seasonal prevalence of vitamin D deficiency during the winter.

The subjects who had used tanning beds for a mean of5 y had higher BMD
at the hip than did the nontanners (control subjects). Larger studies should be conducted to investigate the potential positive effect of chronic use of tanning beds on vitamin D status and bone health.

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Shedding light on skin color

APRIL SAUL / Inquirer Staff Photographer

Nina Jablonski, speaking in Philadelphia, says the key to skin color lies in the need for two kinds of vitamins – and in the sun.

By Faye Flam

Inquirer Staff Writer

 

At the beginning of anthropologist Nina Jablonski’s lecture yesterday at the Wagner Free Institute of Science, it appeared her audience of about 100 was composed of several different races. By the end of the free lecture, titled “The Evolution of Human Skin Color,” the Pennsylvania State University professor had made a case that we are all just people with varying levels of melanin.

As author of the book Skin: A Natural History, Jablonski has studied all aspects of skin, perhaps none more important than why it appears in such a puzzling array of hues. It all comes down to the planet’s uneven distribution of sunlight and the universal human need for two vitamins, she explained.

This knowledge was very recently acquired. “Only in the last decade or so has our data allowed us to crack open the mystery,” Jablonski said as she began her lecture at the 152-year-old science museum near Temple University.

Nature has painted human skin using one major brown pigment, melanin, which evolved in many species. “It’s a natural sunscreen,” she said, which is important because humans have a troubled relationship with the sun.

Since we are relatively hairless creatures, our skin gets bombarded by ultraviolet light, which can burn us, destroy the DNA in skin cells, and lead to cancer. Hence an advantage of dark skin.

But there is more to melanin than protection from skin cancer and sunburn. Scientists recently realized that ultraviolet rays penetrating skin destroy the B-vitamin folate. With too little folate, or folic acid, men cannot make adequate sperm and women cannot start healthy pregnancies. So in very sunny places, any genetic mutations that created light skin would likely die out with their owners.

But with melanin offering so many advantages, the question was why anyone would evolve light skin.

Lighter shades came about because humans need some sunlight to penetrate skin and trigger a chemical reaction that produces vitamin D.

To illustrate the devastating effects of vitamin D deficiency, Jablonski showed slides of children with badly bowed legs and softened bones. In women, a lesser deficiency can lead to a narrowed pelvis, making childbirth impossible.

The original skin color was almost certainly very dark, since scientific evidence points to sunny Africa as the cradle of humanity. But once some branches of the human family starting moving north to Asia and Europe, the need for vitamin D gave those with lighter skin an advantage in absorbing the meager sunlight in winter.

Because vitamins lie at the heart of our color differences, locally consumed foods also play a role. Whales and fatty fish can give people some vitamin D, Jablonski said, so diet may explain why the Inuit, who live in Alaska and Greenland, are much darker than people from Northern Europe.

Recent findings from genetics labs show that there are many roads to what we think of as white and black skin – both of which, or course, are really shades of brown. In 2005, for example, scientists found that Europeans became light-skinned through a different combination of mutations than did Northern Asians.

Last year, scientists scraped enough DNA from the bones of a Neanderthal man to show that this extinct branch of humanity carried genes associated with fair skin and red hair.

Currently, Jablonski said, researchers are seeking genetic variants that led to dark skin in far-flung peoples – those from Australia, New Guinea and southern India as well as Africa.

While Jablonski hopes that examining skin through science can help defuse racism and racial tension, she said, she is also concerned with what she calls colorism. Colorism has more to do with perception of beauty, she said. Its primary victims are women.

With a slide of people frying on the beach and an advertisement for bronzer, she explained that colorism has white women thinking they look sickly without a tan. More dangerous still, dark-complexioned women in some countries are driven to use dangerous skin-lightening products, many containing arsenic, mercury and other poisons.

“Why are we always trying to change the way we appear?” Jablonski asked. “Skin color is a beautiful product of evolution. . . . We should revel in it.”