Suntanning is healthy?

After reading an article on vitamin D that proclaimed High-Dose Vitamin D - One of the Best Nutritional Supplements on the Market, I was a little confused. I thought high dose vitamin D was toxic. But even more controversial, the author advises fullbody suntanning in real sunlight 20 minutes per day with no sunscreen. He does not even mention the issue of skin cancer once in his article. I was immediately reminded of an article I read many years ago in Mother Jones magazine about the apparent epidemiological correlation between sunscreen use and malignant melanoma (I abstracted two studies from medline that share this concern below). Thanks to the wonders of technology, you can see that Mother Jones article.

If melanoma is not prevented by sunscreen, then the only benefit is against the nonmalignant skin cancers, which are mainly cosmetic problems. There are several reasons why sunscreen would promote melanoma. One is that Caucasians spend much more time in the sun when they are not burning quickly. This ability to withstand the pain of the sun may be a major factor in melanoma. Since sunscreen blocks vitamin D formation and Vitamin D deficiency may predispose to cancer, the double whammy of increased sun with no vitamin D protection may be a key variable here. As the author of the MJ article notes, most Caucasians just do the sensible thing. They cover up. In fact, if you have ever traveled to hot places around the world, the locals always try to AVOID the sun, regardless of skin color. Only tourists lie about nude in the sand. Is it possible that if one tries to avoid the sun in general, but does get that 20 minutes per day fullbody exposure or the equivalent, then sunscreen is not only unnecessary, but actually unhealthy.

Caucasians who like to tan for hours may be defying evolution. But the same is probably true for those who get no directly absorbed UV. Humans evolved in subsaharan Africa on what was likely a vitamin D deficient diet. While they ate meat, early humans were scavengers, not hunters, and could not depend on steady supplies of foods like liver. Thus, they evolved powerful mechanisms for creating vitamin D from sunlight. Light skin absorbs more sunlight to create this vitamin due to this racial feature evolving in cold northern climates where sun was scarce. So while Caucasians need a good shot of sunlight, they really must be careful to get what they need and no more. Darker skin folks like Mediterranean, Jews, Arabs, Africans can tolerate much more. A nice tan is at least some reward after the centuries of oppression, no doubt. :-)

According to an article in Clin Exp Dermatol. 2000 Sep;25(6):459-63, entitled Epidemiology of melanoma (Marks R, University of Melbourne, Department of Medicine, St Vincent's Hospital Melbourne and Skin and Cancer Foundation of Victoria, Austrialia).

Melanoma incidence and morality rates are increasing in most countries throughout the world where they are being recorded. The annual incidence rates have increased in the order of 3-7% in fair-skinned populations in recent decades. The mortality rates have increased at a rate lower than for incidence. This has been attributed to educational programs designed to improve the early detection of melanoma, as the treatment of melanoma has not changed substantially in recent decades. There has been a decrease in the thickness of melanoma with an increasing proportion of thin melanomas at diagnosis. Causation of melanoma is a combination of constitutional risk factors of which skin colour is the major factor. The presence and number of common acquired and dysplastic melanocytic naevi is also a major constitutional risk factor in fair-skinned people. The only environmental risk factor that has been shown consistently is exposure to sunlight, particularly large doses of sunlight sufficient to cause sunburn in childhood that will be remembered many years later. However, recreational activity leading to sunburn in adulthood is also associated with risk. To date, no other environmental factors have been shown epidemiologically to be clearly associated with risk of melanoma. Recent epidemiological data from some studies suggesting that there is an increased risk of melanoma in sunscreen users requires further explanation.

Another in Br J Dermatol. 2002 Apr;146 Suppl 61:24-30, entitled Cutaneous malignant melanoma, sun exposure, and sunscreen use: epidemiological evidence (Bastuji-Garin S, Diepgen TL, Public Health Department, Paris XII University, Henri-Mondor Hospital, 51 avenue du Marechal de Lattre de Tassigny, 94000 Creteil, France), states,

Cutaneous malignant melanoma is the most serious form of skin cancer and accounts for about three-quarters of all skin cancer deaths. Over the last few decades the incidence and mortality rates of melanoma have been increasing worldwide. The risk of melanoma is higher in individuals with both phenotypic susceptibility and a history of sun exposure. Therefore, recommended sun protection behaviours include wearing long-sleeved clothing, seeking shade, avoiding the sun when it is strongest, and using sunscreen lotion with a sun protection factor of 15 or higher. It has been reported, however, that the use of sunscreens does not protect against melanoma and seems to increase the duration of recreational sun exposure. These results are controversial. Two case-control studies show a protective effect of sunscreen use, while three studies showed a significant risk associated with sunscreen use. However, the discordant results, the low relative risks, the lack of dose-effect relationship and the numerous biases, especially the uncertainty that exposure (sunscreen use) preceded melanoma do not suggest a causative association between sunscreen use and melanoma. Several hypotheses could partly explain these contradictory results.

According to Paul Bergner, a respected nutrition expert from medherb.com, in response to an interview question from me:

The safe upper limit is now considered to be 2000IU per day for adults, 1000 iu per day or infants. Vitamin D is big news this year, as it was discovered how many people in temperate latitudes are deficient, and how it contributes to depression, cancer, and other conditions. Vitamin D should probably be called a pro-hormone, and contributes to the endocrine and immune systems. 20 minutes of sunlight in a sunbathing-like situation gives you -a lot- more vitamin D than the upper limit above, but they say you can get toxicity only from taking too much orally. The chief risk in modern days is taking too much cod liver oil. I'd also like to point out that hunter gatherers eating animal fat got vast amount of vitamin D in their diet too. Anyway the big news is that a great majority of north Americans become deficient in vitamin D during the winter months, and that we are essentially in the midst of a mini-vitamin-D-deficiency-epidemic.

The situation has attracted the attention of the public health establishments, and the National Academy of Sciences recently upped the RDA for Vitamin D from 400 iu to 1000 iu per day. Raising the RDA that much is the equivalent of an earthquake at the NAS. I know a practitioner in Portland who runs serum vitamin D on all patients with depression, because of the possibility of winter depression being a major factor there. Then he supplements if deficient. He said he has seen the 2000iu a day dose improve but not completely cure winter depression in some patients. In one clinical trial, they compared vitamin D supplementation versus bright light for winter depression, and the vitamin D did better in the whole group, but did best in those who were D deficient in their blood work (see a similar study).

So that;'s just the depression. It would take a longer time for supplementation to affect cancer rates, but in light of our oil-and-D rich hunter-gatherer past, when we -also-walked around naked in the sun a lot, I think most modern people ought to be getting 1000-1500 oral vitamin D, and, more important, making an effort to get out in the sunlight. BTW one researcher some years ago calculated the benefits of avoiding sunlight to avoid relatively rare skin cancers, versus the number of serious internal cancers that would then be caused by vitamin D deficiency, and about 10 times as many people would diet from the serious cancers as would die from skin cancer if sunlight were avoided completely (see a supporting study). Here is a link to the best up to date and official info on vitamins.

If we are indeed experiencing a mini epidemic of vitamin D deficiency, studies such as these below may have significant ramifications, particularly for people with dark skin who live in cold northern climates:

From Am J Phys Anthropol. 1975 Nov;43(3):409-16, The evolutionary significance of vitamin D, skin pigment, and ultraviolet light (Neer RM),

Vitamin D is essential for normal growth, calcium absorption, and skeletal development. Vitamin D deficiency can cause death, immobilization, or pelvic deformities which prevent normal childbirth. In the past these problems were extremely common in North America and Europe, and were only eliminated by adding vitamin D to food. Prior to that, variations in available vitamin D affected health, survival and reproductive efficiency sufficiently to have evolutionary significance. Vitamin D is naturally present in few foods; most comes from the photo-conversion of 7-dehydrocholesterol in skin. The limiting factor in this conversion is the availability of ultraviolet light less than 310 nm. Seasonal and geographic variations in natural ultraviolet radiation cause parallel variations in blood vitamin D levels, intestinal calcium absorption, and clinical vitamin D deficiency. These physiological variations can be abolished by exposure to comparable artificial ultraviolet radiation, or by dietary vitamin D supplements. Ultraviolet radiation less than 310 nm is absorbed by skin pigment, but is also increases skin pigmentation. This has led to the hypothesis that skin pigment regulates skin vitamin D production. Little direct evidence exists to test this reasonable hypothesis, but necessary and sufficient conditions for establishing it can be outlined. Until this hypothesis is experimentally tested, it is impossible to evaluate the corollary hypothesis: that racial variations in the efficiency of cutaneous vitamin D production restricted the evolution of dark-skinned peoples to tropical latitudes and thereby caused the geographic distribution of the races.

And from Arch Dermatol. 1991 Apr;127(4):536-8, Racial pigmentation and the cutaneous synthesis of vitamin D (Matsuoka LY, Wortsman J, Haddad JG, Kolm P, Hollis BW. Department of Dermatology, Jefferson Medical College, Philadelphia, PA 19107)

The varying epidermal melanin content that produces racial pigmentation determines the number of photons that reach the lower (malpighian) cellular layers, where vitamin D3 synthesis takes place. We investigated the effect of racial pigmentation on vitamin D3 formation, stimulating the process with a fixed dose of UVB radiation. Following whole-body exposure to 27 mJ/cm2 of UVB, there was a significant racial group effect on serum vitamin D3 levels. Post-UVB levels were significantly higher in whites (31.4 +/- 4.4 nmol/L) than in Indians or blacks (12.8 +/- 2.9 and 9.1 +/- 2.1 nmol/L, respectively), while the levels in Orientals (27.8 +/- 4.4 nmol/L) differed significantly from those in blacks and Indians but not in whites. Race had only a marginal effect on serum 25-hydroxyvitamin D, with higher levels in whites than in blacks (69.9 +/- 12.7 vs 29.7 +/- 6.2 nmol/L). Serum 1,25-dihydroxyvitamin D and vitamin D binding protein levels were similar in all groups. We conclude that while racial pigmentation has a photoprotective effect, it does not prevent the generation of normal levels of active vitamin D metabolites.