The American Academy of Dermatology recommends slathering on sunscreen whenever anyone is outdoors, in any weather. Since this will cause a vitamin D deficiency, they also suggest vitamin D supplementation be discussed with a doctor.

The purpose of this is to prevent skin cancer. There three principal types: basal and squamous cell are indeed caused by excessive sun exposure, but easily treated and, if treated, rarely fatal. The risk of these hardly justifies the use of sunscreen, since, as we will dive into below, we need sun.

The other major type of skin cancer is melanoma. However, melanoma may not be caused by normal sun exposure, but rather by excess intense sun exposure—frequent severe sunburn. In fact, the sun may otherwise be protective of this cancer.

Two factors appear to point in this direction.

First, melanomas often show up in places never exposed to the sun. Dr. Mike found one between a patient’s toes! Now skin that is frequently irritated, by sunburn for instance, will be prone to greater incidences of all skin cancers, including melanoma. This is always the case with damaged or weakened cells.

But suppose one is frequently in the sun, gets a tan, and seldom burns? This is the second puzzling factor. People that get frequent sun exposure, farm workers for instance, have lower rates of melanoma that those that seldom see any sun. More here.

Is it possible that complete avoidance of the sun, or, equivalently, putting on sunscreen whenever outdoors might increase the incidence of melanoma? It may well be. Malignant melanoma rates have risen—tripled over the last 35 years—and of course, so has sunscreen use. (This increase may be largely due to an increase in diagnosis of relatively harmless skin anomalies as melanoma, see here.)

However, the idea that sunscreen prevents melanoma seems to be on quite shaky ground. There is a fair amount of data supporting a lack of association between sun exposure and melanoma here and here. It may well turn out that the advice to slather on the sunscreen, advice given under the sincerest of intentions to be sure, will backfire. The practice gets on our radar screen because it is meddling with Mother Nature, and rare indeed are instances where this has been done without harmful consequences.

Why do we need the sun?

We need vitamin D, of course, and low levels are associated with increased risk of several cancers. And we could take pills. We probably should. We get a lot less sun than our hunter-gatherer ancestors. But vitamins D isn’t enough: here is a benefit list:

1. We start with vitamin D. What all does it do? It supports the immune system, probably because of this, it reduces cancer risk. It encourages bone growth. It encourages fat loss. And much more.
2. Sunshine up-regulates white cells count. A direct immune system boost.
3. Sunlight is important to the circadian rhythm—the sleep cycle. Night workers have a much higher rate of cancer.
4. Sunlight enhances mood and energy through the release of endorphins
5. The UV in sunlight is sterilizing. This reduces unhealthy skin bacteria and related rashes.
6. The UV in sunlight triggers nitric oxide production, which, in turn, lowers blood pressure, improves erectile dysfunction and helps protect against cardiovascular disease in general.
7. Many sunscreen products contain toxic chemicals—some of them actually carcinogenic.
8. And last, and FAR from least, regular sunshine exposure may well decrease melanoma risk.
9. Increased sun exposure time is associated with fewer environmental allergies; this may be related to outdoor activities rather than the sun itself but it is a nice ‘side effect.’

What to do?

Simple. Get plenty of sun. Avoid burns. Save the sunscreen for the mountains or prolonged time at the beach.

Oh, and by the way…

Not all sunscreens are created equal. In many studies, it was found that the majority of them do not actually block UV as claimed. Many contain chemicals that may be undesirable, particularly oxybenzone and vitamin A (retinyl palmitate), both known carcinogens.