Myths and Facts About Vitamin D and Sun Exposure

Vitamin D

In recent weeks, many news reports have focused on the potential health benefits of vitamin D. This news coverage has led to the incorrect perception that you have to intentionally seek the sun or an artificial source of ultraviolet (UV) radiation in order to get the health benefits that vitamin D may provide.

"Any individual or organization advocating intentional sun exposure as the preferred means of obtaining vitamin D is doing a tremendous disservice to the public," said Barbara A. Gilchrest, M.D., professor and chair of the department of dermatology at Boston University School of Medicine. "Vitamin D is critical to healthy bones, and some research now suggests that maintaining higher levels than traditionally believed to be sufficient may offer additional health benefits. However, if you are concerned about getting enough vitamin D, the safe way to obtain it is through diet or oral supplements."

But many myths about vitamin D abound, leaving the average American confused over the contradictory messages. These myths can lead people to increase their risk of developing skin cancer, one of the most common cancers.

"While the potential benefits of vitamin D are still unknown and more scientific studies need to be done, we do know without a doubt that overexposure to UV radiation - from either natural or artificial sources (sun or tanning beds) - causes skin cancer," Dr. Gilchrest said. "It's important that people understand the facts about UV radiation and vitamin D so that they can make informed choices about their health."

Myth: People who use sunscreen are at risk of having a vitamin D deficiency.

Fact: Even when used correctly, sunscreen with a Sun Protection Factor (SPF) of 15, the minimum recommended by the American Academy of Dermatology (Academy), deflects or absorbs 93 percent of the sun's UVB rays and allows 7 percent to penetrate skin where the energy may produce vitamin D " or permanent damage. Indeed, because the same wavelengths of UV radiation produce both vitamin D, sunburn, DNA damage, and skin concerns, you cannot separate the wanted from unwanted effects.

Recent reports indicate that although the public may be using sunscreen, it is being incorrectly applied, used far too sparingly, and is therefore not as effective as it should be, usually well less than half as effective. "The average person requires one ounce of sunscreen, enough to fill a shot glass, to adequately cover the exposed areas of the body," advised Dr. Gilchrest. "However, the majority of people don't use enough sunscreen to receive the level of protection that is indicated on the package. Many people also fail to apply sunscreen at least 15-30 minutes before going outdoors in order to allow it to be completely absorbed into the skin, and they neglect to re-apply it every two hours or after swimming."

Many studies have measured "normal" vitamin D levels in regular sunscreen users, even among those also practicing extreme sun avoidance because of high skin cancer risk. Although some authorities now suggest that these "normal" levels should be higher to achieve optimal health in the general population, all authorities agree that even the highest recommended vitamin D levels can safely and readily be obtained exclusively from oral supplements of up to 1000 IU of vitamin D daily, depending on age and diet.

Myth: If spending a little time in the sun allows the skin to produce vitamin D, then the more time, the better.

Fact: Maximum production of vitamin D occurs after brief exposure to UV radiation. The exact amount of time depends on many factors including geographic location, time of day, time of year, and skin type. However, for a fair-skinned person in Boston or New York, at Noon in June, it is 2-5 minutes. After this, any additional vitamin D that your body produces will not be stored for future use, but instead will be converted into inactive compounds. In contrast, UV damage to DNA and other skin components continues at the same rate as long as the UV exposure continues, so additional exposure will only increase your risk of developing skin cancer and premature aging.

"Most people, especially fair-skinned Caucasians, get more than enough incidental sun exposure to manufacture the vitamin D they need, so there is no reason to intentionally seek the sun," Dr. Gilchrest said. "Without a sunscreen, a fair-skinned child or adult will maximize the skin's vitamin D production while running a brief errand or standing briefly in the yard. Even with a sunscreen, spending a total of 30 minutes outdoors over the course of the day will likely achieve this maximum. Even the most enthusiastic sun exposure advocates acknowledge that such exposure three times a week is quite enough."

Myth: The only way you can get vitamin D is through sun exposure.

Fact: If you are concerned that you are not getting enough vitamin D, there are safe and effective ways to obtain it without intentionally exposing yourself to the sun. Both milk and orange juice are fortified with vitamin D and oral supplements are available over-the-counter. Additionally, foods that are good sources of vitamin D include salmon, tuna, sardines, eggs, beef liver and Swiss cheese.

"Vitamin D does not need to be produced from UV radiation to be effective. Don't be misled into thinking that sunlight or tanning beds are better sources of vitamin D than foods or supplements. The only thing for which they are better is increasing your risk of developing skin cancer," Dr. Gilchrest said.

Myth: More people will be diagnosed with breast, colorectal and lung cancer due to vitamin D deficiency than will be diagnosed with skin cancer due to exposure to UV radiation.

Fact: In 2006, approximately 500,000 people will be diagnosed with breast, colorectal or lung cancer, according to the American Cancer Society. In contrast, this year more than one million people will be diagnosed with skin cancer. Among women ages 20 to 29, melanoma, the deadliest form of skin cancer, is the second most common form of cancer.

"The cause-and-effect link between UV exposure and the great majority of skin cancers is uncontested," said Dr. Gilchrest. "Whether more vitamin D would have reduced their cancer risk is far from proven. For example, a recent randomized, double-blind controlled study of more than 36,000 post-menopausal women performed by the Women's Health Initiative and published in The New England Journal of Medicine showed that daily vitamin D supplementation for at least seven years did not reduce their risk of developing colorectal cancer. This is telling because indirect evidence linking vitamin D levels and sun exposure to prevention of colorectal cancer was stated by vitamin D advocates to be stronger than for any other cancer."

"I would advise anyone who is confused by conflicting reports of the health benefits of sunlight, whether in conjunction with vitamin D production or otherwise, to remember that nearly 8,000 people will die from skin cancer this year and UV radiation is the most preventable risk factor," Dr. Gilchrest said.