Are we going overboard by avoiding it all the time?
It’s a gorgeous summer morning, so you step outside to enjoy a touch of sun while sipping your morning coffee. But wait…what about sunscreen?
According to some medical organizations, any sun exposure is a serious risk factor for melanoma and other skin cancers. For this reason, Americans often are advised to get vitamin D only from foods and/or supplements. But not all medical experts agree with that advice.
To get a different perspective, Bottom Line Health spoke with Michael F. Holick, PhD, MD, a leading expert on vitamin D and a firm believer that avoiding all sunshine can pose health risks that may be worse than those from sensible sun exposure.
His advice on finding the sweet spot for just the right amount of sun exposure…
A COMMON DEFICIENCY
Vitamin D is one of the most common nutrition deficiencies in the US. More than half of older adults are deficient—in part because the body’s ability to synthesize vitamin D from sunlight declines with age. Those with dark skin fare worst: Research has found that 40% of Hispanics and a staggering 84% of African-Americans over age 50 were vitamin D deficient.
Only a few foods (such as salmon, sun-dried mushrooms, cod-liver oil and, to a much lesser extent, egg yolks) contain vitamin D, so most Americans rely on fortified foods (such as milk and some breakfast cereals). Taking a vitamin D supplement helps, but it isn’t the same as sunshine. The vitamin D produced by sunshine enters the bloodstream slowly and maintains its health-promoting biological activity for at least twice as long as supplemental D.
DANGERS OF LOW VITAMIN D
Humans have evolved to depend on sunshine. So what happens when you never go outside without wearing sunscreen—or rarely go outside at all? When used properly, a sunscreen with an SPF of 30 reduces vitamin D production by 97%. Important health risks now being linked to low vitamin D levels…
- Multiple sclerosis. You’re five times more likely to get this disease if you live in North America or Europe than in the tropics. In the US, prevalence of this disease in northern states such as Maine, Minnesota and Washington is nearly double that found in sunnier areas.
- Cancer. There isn’t conclusive proof that people with low vitamin D have an increased risk for cancer. But there’s persuasive evidence from population and observational studies that people with sufficient vitamin D are 30% to 50% less likely to develop breast, colorectal or other cancers than those with vitamin D deficiencies.
- Heart disease. Vitamin D deficiency is associated with increased heart attack risk. People who live in sunny climates are also less likely to have high blood pressure.
Other health problems linked to vitamin D deficiency include osteoporosis, diabetes and depression.
THE REAL CANCER RISK
Dermatologists have long used the “C” word to warn people about the sun. It’s true that chronic sun exposure increases one’s risk for basal and squamous cell carcinomas.
While these “nonmelanoma” skin cancers are a significant health problem, they’re fortunately among the easiest to cure and are rarely fatal. Meanwhile, the noncancer health risks from low vitamin D, such as those described earlier, generally outweigh the risks from these cancers.
Melanoma is another story. A frequently fatal cancer that results in some 10,000 deaths in the US each year, melanoma is strongly linked to sunburns. People who get only short-term and occasional sun exposure don’t face the same risk. In addition, melanoma often develops on parts of the body with little (or no) sun exposure, such as the buttocks.
A SENSIBLE COMPROMISE
Let me be clear: I do not recommend sunbathing or tanning. I advise most adults to get just enough sun (without sunscreen) to help produce a vitamin D blood level of at least 30 ng/mL, as measured by a 25-hydroxy vitamin D blood test. The rest of the time, you should use sunscreen and wear a hat and other protective clothing. My approach…
Follow the “no sunburn” rule. The amount of vitamin D produced by your body depends on such factors as the season, time of day, your geographic location and your pigmentation. I advise my patients to spend about one-half the time in the sun that it would ordinarily take them to get a mild sunburn. This should be done between 10 am and 3 pm (when the angle of the sun’s rays maximizes vitamin D production).
During this time, expose your arms and legs to the sun (without sunscreen). Together, your limbs account for about half of your body’s surface area. Exposing them to sun (with the rest of your body covered) should gradually increase your vitamin D level over four to eight weeks and then stabilize it.
Keep close track of the time. While one’s sun “dose” is highly individual, people with dark skin will usually be able to expose their skin to sunshine for up to 30 minutes, three times a week. If you’re fair, five to 10 minutes is likely enough.
Use sunscreen the rest of the time. I recommend using sunscreen with an SPF 30 rating whenever you’re not getting your controlled sun dose.
Important: Be sure to use sunscreen on your face anytime you’re outdoors. Very little vitamin D is produced via sun exposure to your face…and too much sun on your face, which gets sun whenever you’re outdoors, will cause wrinkles and increase your risk for skin cancer.
Take a supplement. Even if you enjoy regular “sun sessions,” there will be times (particularly in the winter) when your body won’t produce enough vitamin D. To ensure consistent adequate levels of vitamin D, a supplement (typically 2,000 IU daily for adults) will make up the difference. To determine your optimal dose of a vitamin D supplement, ask your doctor for advice. He/she may recommend a 25-hydroxy vitamin D blood test to check your body’s vitamin D level.
Important: If you have had skin cancer or are at increased risk (due, for example, to family history)…or have a medical condition or take medication that increases your sun sensitivity, ask your doctor about appropriate sun exposure and the best ways to maintain adequate vitamin D levels.