The following account includes my own personal views and also some conventional perspectives. Some of these are likely incompatible. I'm not a scientist, so I am not in a position to determine the scientifically preferable perspective; at this stage, I just don't know, but I give you here the information I have.
A suntan became attractive to Westerners in the 1950s. Before then, it was seen as a sign simply that the tanned person had worked a lot out of doors or, possibly, as a European, had been employed in tropical countries.  By the 1970s evidence that the sun's rays caused skin cancers began to emerge - specifically, that ultra violet radiation damages DNA in skin cells, leading to three sorts of cancers, including the deadliest form, malignant melanoma (1).
More recent epidemiological research indicates that avoiding sunlight actually increases our risk of colon, prostate, breast, lung and even skin cancers (1). William Grant concluded that every year at least 23,600 Americans die of cancer through lack of sunshine while about 9,800 die from skin cancer (2). Grant has more recently revised the number of people dying from inadequate sunlight to 40,000 (1).
In 2000 Rob Faigin reviewed the available medical, physiological and epidemiological research and came to similar conclusions. He was also able to draw out the practical implications for human health beyond cancer (3).
The physiology of sunlight and health
They key link between sunlight and human health is through vitamin D. The body has two sources of this important chemical: foods such as oily fish and dairy products, and skin cells, which use those same cancer-causing UV rays to convert a precursor chemical into vitamin D3. Further processing in the liver and kidneys results in 'active vitamin D'. Active vitamin D's best-known function is enabling calcium to be absorbed from the gut. Calcium plays a key role in nerve, muscle and metabolic signaling, as well as cementing bone cells together. (That is why the most obvious sign of vitamin D deficiency is rickets, the weak bone disease.) Research since the 1980s has pointed to active vitamin D being an important brake on cell proliferation - so a lack of it could dispose people to cancer, the result of cells multiplying out of control (1).
Rickets appears to be making a comeback in the US (1, 3). The problem is seen with breast-fed infants, as formula milk is fortified with vitamins. US doctors advise that all breastfed infants should be given vitamin D drops. However, there may even be benefits from sunshine that are not available from vitamin D pills. This complements the Palaeo idea that people who use vitamin supplements instead of eating healthily miss out on hundreds of bio-available beneficial compounds in fruit and vegetables (1).
The physiology of skin damage
In 1981, dermatologist Dr Peter Berger in Save your Skin, warned of the special dangers of tanning in solariums that used treatments that "penetrate deeper and can cause damage to the supportive layers of the skin which house the collagen and elastic fibres. Celtic skin is unable to adequately repair this damage due, it is thought, to certain blood vessel changes, as well as cellular mutations. As a result, abnormal cells are formed which may lead to skin cancer. The elastic tissue also becomes abnormal and loses its elasticity, and the collagen tissue becomes thin, 'liver spots' appear, dryness occurs, and wrinkles develop - all features of premature ageing - and in time skin cancer will appear". (4)
How much sun exposure?
The 'RDA' for sunlight varies greatly, depending on:
• your latitude (and altitude)
• the time of year
• your skin colour
• the time of day
This works out at one-quarter of the exposure that would cause redness, two or three times a week. These variables have been included in Michael Holick's book The UV Advantage, published early in 2004 (1). But tanning without burning can still cause skin damage and skin cancer. A natural tan offers very limited sunburn protection, usually similar to an SP3 sunscreen, depending on skin type. It offers no protection against DNA damage, which can occur without burning. (4)
Public health research in Denmark in 2001 has led there to restrictions being placed on sunscreens, particularly when used for children, where they contain hormone disruptors - and they usually do.
My personal experience
The story: In December 2003 my annual medical checkup revealed a cholesterol level up into the range that indicated a statin prescription. I was referred to a consultant physician who reached the same conclusion. He asked me to return a month later, after the Christmas/New Year break, for a statin prescription. In the intervening period I worked outside every day paving a driveway and part of my yard. I wore shorts and a short-sleeve shirt and a broad-brim sun hat in the full sun - it's summer here in Australia. I did not apply any sunscree. The work was heavy and active. I was moving all the time, sweating all the time. I developed a deep suntan, without any sunburn along the way. When I returned to the consultant in mid-January, my cholesterol reading had halved - to the amazement of the physician who declared he had never seen anything like it. He agreed willingly there were no grounds for prescribing statins.
My interpretation: It's my belief that the cholesterol was drawn out of my system for use in skin protection. The vigorous work meant that my skin was always shifting relative to the angle of the sun. The heavy nature of the work meant my healthy metabolism was active and well able to mobilize the cholesterol for its natural role in skin protection. I should add that I tan relatively easily, although as a child (1950s and early 1960s) I burnt once early each summer; there is nothing at all 'olive' about my complexion. I believe that a healthy person with normal Celtic skin like mine should be able to avoid sun damage providing they are active in the sun and undertaking vigorous physical activity. In the process, they will draw heavily on their serum cholesterol. Since 2003 I have remained active, worked out in the sun every summer, developed a deep tan, had no basal cell carcinomas - and been happy to keep my cholesterol levels relatively high. From the above, you can see how my sun exposure is different from the exposure of solarium users, or of "sun bathers". Reports of research linking skin damage to sun exposure need to take into account all the variables I cited, rather than assuming a simple direct link between hours of exposure and skin damage.
1. Visiting Singapore in 1972 I was amused to find creams for sale to lighten naturally darker skins. In Australia, even then, pharmacies stocked many lotions (like 'Coppertone') that purported to speed or darken a sun tan.
1 New Scientist, 9 August 2003, pages 30-33
2 Cancer, 2002, vol 94, p 1867
3 Rob Faigin, Natural Hormonal Enhancement, 2000
4 Beth Wilson, Victorian Health Commissioner, The Age, 27 December 2009
Last updated 27 December 2009
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