Sunscreens are big business. Americans spend well over $8 billion a year slathering on creams, lotions and gels to protect themselves from sunburns.
People have gotten the message that exposure to the sun’s ultraviolet radiation equals aging, wrinkling and skin cancer as well as sunburn. But they have also been told that vitamin D, made in the skin from sun exposure, is vital for good health.
These messages are somewhat contradictory. This reader is understandably confused:
Q. I use sunscreen religiously. I think you have written that this may interfere with my skin’s ability to make vitamin D. If that is true, how much should I take?
A. The old understanding was that sunscreen prevented the skin from manufacturing the precursor to vitamin D. Some experts told us that properly applied sunscreens prevent the formation of vitamin D3 as well as sunburn and skin damage (Advances in Experimental Medicine and Biology, 2014, vol. 810).
More recent research suggests that is not necessarily true (British Journal of Dermatology, Nov. 2019). Many factors affect how well people make vitamin D. Skin coloration, time in the sun, protective clothing and body surface exposure all impact vitamin D levels. A recent review concludes that you can reach optimal vitamin D levels without burning your skin (JBMR Plus, Jan. 19, 2021).
The best way to determine how much vitamin D you should be taking is to have blood levels of 25-hydroxyvitamin D measured periodically. Between 30 and 50 ng/mL is considered desirable.
What If You Want to Get Vitamin D from the Sun?
How do you get enough sun to make vitamin D but not so much that you damage your skin? The answer is complicated, because the amount of sun exposure required varies depending on the time of year, the geographical location, the color of the skin and the time of day.
Obviously, the sun is strongest in summertime in the middle of the day. In a sunny place like Phoenix, Arizona, or Tampa, Florida, just about six minutes of sun exposure midday offers enough ultraviolet (UV) for fair skin to make 1,000 IU of vitamin D. Dark brown skin requires more exposure, up to 15 minutes, to make the same amount of vitamin D.
Further north, in Madison, Wisconsin, or Boston, Massachusetts, someone with fair skin might need an hour of sunshine on bare skin, even midday in the summer, to make that much vitamin D. Dark-skinned folks would need twice that much time. In the winter, even if someone were brave or foolish enough to go outside in shorts and short sleeves, the sun is not strong enough for anyone to make much vitamin D.
Take Advantage of Summer Sun
Ideally, then, a person would take advantage of summer sunshine to get 15 or 20 minutes of sun without sunscreen several times a week. After that, slather on the sunscreen and pull on the long sleeves and the hat.
Finding the Best Sunscreen
How do you make an informed decision about your sunscreen? It is important to select a product that protects against UVA as well as UVB radiation. Look for a product that declares “Broad Spectrum” right on the front label. It should have an SPF (Sun Protection Factor) of at least 15.
Scoping Out SPF
Higher SPF sunscreens provide better protection, up to a point. FDA will be limiting companies from claiming SPF values above 50, since there doesn’t appear to be data showing a reliable difference between an SPF of 50 and one of 75 or 100.
Skip the spray: consumer groups such as the Environmental Working Group (EWG) and Consumer Reports say it is difficult to apply an aerosol sunscreen thickly enough and to keep it out of eyes and lungs while applying it.
Put On Enough
Applying enough sunscreen is an important consideration. Many people skimp on the amount they smear over their skin. That significantly reduces the protection a sunscreen can offer. It is also important to re-apply it after getting out of the water or sweating.
Some of the ingredients in sunscreens, particularly oxybenzone and octinoxate, can act like hormones in human tissues. It would be smart to avoid such endocrine disruptors. EWG lists sunscreens that don’t contain hormone-disrupting chemicals on its website: ewg.org.
And for more information about vitamin D, check out our eGuide to Vitamin D and Optimal Health.