Sunlight and the vitamin D dilemma



Vitamin D deficiency, believed to be linked to a wide range of health problems, is becoming increasingly common in the United States, affecting as many as 30 to 40 percent of the population. While vitamin D can be found in some foods, such as salmon and vitamin-fortified milk and orange juice, the most readily available source of the nutrient is through exposure to the sun. Researchers now theorize that in seeking to avoid skin damage that can lead to cancer, many people no longer get the sunlight their bodies need to produce adequate levels of vitamin D.

Once thought primarily to affect bone health, insufficient vitamin D has begun to be associated with a growing list of problems, including heart and kidney disease, high blood pressure, rheumatoid arthritis and several types of cancer.

Because too much sun can lead to skin cancer, the challenge is how best to balance the pros and cons. Jean Tang, MD, PhD, assistant professor of dermatology at Stanford, said that balance largely depends on an individual's level of risk.

"If you've had skin cancer, take a vitamin D supplement and don't go out in the sun without sun protection," Tang said, including sunscreen, protective clothing and sunglasses at all times.  Staying in the shade and avoiding the peak hours of sunlight between 10 am and 4 pm, especially in the summertime, is advisable for anyone who wants to protect against the worst of the sun's rays.

Most fair-complexioned individuals get enough vitamin D production through 10 minutes of incidental sunlight, said Susan Swetter, MD, a professor of dermatology and director of the Pigmented Lesion and Melanoma Programs at Stanford and the Palo Alto Veterans Affairs Health Care System. That exposure does not need to be focused on the face, where skin cancer is more prone to appear, she said.

Swetter takes a vitamin D supplement daily. The daily recommended adult dose is 600 international units, and you don't want to exceed 4,000 international units per day, she advised.
Recent research by Tang and her colleagues has shown that Caucasians, who are at highest risk for skin cancer, are more likely to lack vitamin D if they wear long sleeves and stay in the shade. The researchers also found that people using sunscreen are still getting enough sun exposure to produce vitamin D. They theorize-and this is backed up by independent studies-that most people don't use enough sunscreen or reapply it often enough to significantly affect vitamin D levels.

For children, the dilemma is just as problematic. Children need vitamin D for their developing bones, but childhood burns caused by too much sun exposure have been linked to increased risk for skin cancer. Latanya Benjamin, MD, assistant professor of dermatology and pediatrics at Lucile Packard Children's Hospital, still sees young patients who come in with sunburns.  Though many parents are doing a good job in helping their kids apply sunscreen, "We are far, far from ideal," she said.

She recommends broad-spectrum sunscreen with SPF 30-50 and having parents involve kids in the choice of brand and application style. "If children are comfortable with it, they're more likely to use it," she said. She also advises using sunscreens that physically block the sun through ingredients such as titanium dioxide or zinc oxide, although those products do not filter out the full range of skin-damaging UVA light.

Tang and her colleagues are now doing focused research on how to balance prevention with risk. "Some dermatologists say no sun for anybody," said Tang. "On the other extreme are young people using any excuse to get a tan. It's not OK to say, 'I want to get a tan for vitamin D.'"

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2023 ISSUE 3

Exploring ways AI is applied to health care