Since the 1970's, our country has witnessed a 30-fold increase in the sales of sunscreen products, alongside a 30% increase in deaths from melanoma. You might think that this is just due to cases in the elderly that were caused by bad practices many years ago. However, the incidence of melanoma has been consistently rising in children by about 3% per year since the 1970's  (Melanoma in Children) . Isn't it time to admit that sunscreen is not useful? Even the sunscreen executives will admit that they have never been able to find evidence that sunscreen prevents melanoma. However, it's unfortunately easy to sell the simplistic idea that, because the sun's UV rays can cause cancer, and because sunscreen blocks these rays, then sunscreen must, quite logically, prevent cancer.
The reason this formula is incorrect is very simple: sunscreen also blocks a mechanism that biology put in place many millions of years ago, also for the purpose of protecting us from the sun's rays. Biology's own mechanism, however, is far more effective than sunscreen, because it produces products that linger on our skin (melanin) and in our blood stream (vitamin D) long after the particular outing to the beach has passed. In the spring, if we go outside without sunscreen, we will slowly pick up a protective tan, while also generating a good supply of vitamin D. By the time the summer comes around, the tan affords protection from the sun's harsher rays, and we continue to accumulate vitamin D, which will be able to carry us through the lean winter months, when sunlight is in short supply.
Melanin in the tanned skin prevents the sunburn in the summer. Vitamin D in the blood stream protects us not just from skin cancer, but from just about any cancer you can name. If you type "vitamin D" into a search engine along with "prostate cancer," "breast cancer," "ovarian cancer," "pancreatic cancer," etc., you will find that the entire first page of the result is filled with pointers to studies that show vitamin D affords significant protection from that cancer. For instance, a controlled study conducted at the Creighton University in Nevada showed that people who were given supplements of Vitamin D and calcium experienced a 77% reduction in cancer incidence over those given a placebo  (Vitamin D Prevents Cancer) .
You might think that you could get the best of both worlds by liberally applying sunscreen and taking lots of Vitamin D orally. But this is a tricky game to play. Sunscreen may give you false security by preventing the sunburn that provides a warning signal to get out of the sun. And oral vitamin D may not be properly absorbed if it's not accompanied by ingested fats to dissolve the vitamin D. If you just take excessive amounts to compensate for this problem, you can run into toxic reactions and a suppression of the immune system, the opposite of the effect of sunlight  (Issues with Vitamin D Supplements) . Better to trust biological mechanisms which have had millions of years to perfect the natural process that exploits the sun's rays to beneficial effect.
In my view, a large part of the reason that we are losing the war against cancer is that we are increasing the base rate significantly through the excessive use of sunscreen products.
1. Daniel Redwood, "We Fought Cancer ... and Cancer Won," Newsweek, September 10, 2008.
2. Lange, J.R. et al., "Melanoma in children and teenagers: An analysis of patients from the National Cancer Data Base." J. Clinical Oncology, 2007 Apr 10; 25:1363-8.
3. Joan M Lappe, Dianne Travers-Gustafson, K Michael Davies, Robert R Recker and Robert P Heaney, "Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial," American Journal of Clinical Nutrition, Vol. 85, No. 6, 1586-1591, June 2007.
4. Marshall T. G., "Vitamin D discovery outpaces FDA decision making." Bioessays, 30(2), pp. 173-182, Jan 15, 2008.