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Skin Cancers and Diet
Part 4: Cancer prevention: For Vitamin D, It has to be midday sunshine
UVB is the only band of light capable of producing vitamin D. It is significantly present only around midday during the summer months in most of the Britain. That's the time we are told to stay out of the sun! It's no wonder we have an international disaster in progress due to a misunderstanding of the nature of and need for UVB and vitamin D. A study some years ago looked at the position in Edmonton, Alberta, Canada, at latitude 52°N.[i] It found that vitamin D could only be made from April to September and, even then, only if people went out in the sun for the two hours each side of noon. For the rest of the day and during the rest of the year, the angle of the sun was too low in the sky to allow adequate UVB to reach the earth.
A study in 2003 during the first 10 days of April,[ii] showed that one in three children in Alberta between 3 and 17 years of age had levels of circulating vitamin D was less than half the amount that is now considered to be the lower limit of normal. It is impossible to make sufficient D during Alberta's winter even though the days are far sunnier than in the UK.
The amount of sunlight is roughly the same in the UK as it is in Alberta, as the UK mainland lies between 50° and 59°N. For this reason, no vitamin D is made in the skin in London (latitude 52°N) from about October to March. And, of course, there is even less the further north you live. Yet, we in the UK are told to stay out of the sun at the only times that do us any good. One has to wonder at the reasoning behind such advice.
It's clear that two weeks holiday a year on the Spanish costas just doesn't cut it. In the UK, you really need regular sun exposure, in the middle of the day when the sun is high enough to allow UVB to penetrate to ground level, all through the summer — and then take your holidays in the winter months in sunnier climes to top up.
Some need more sunshine than others
In all populations across the world, females are lighter skinned than males. Women's skin is lighter because their need for vitamin D3 is particularly important when pregnant or lactating. Nature arranged for this higher need to be met by lightening women's skin to permit synthesis of the relatively higher amounts of the necessary vitamin D.[iii]
Darker skinned people in Britain require 10 to 20 times the length of sun exposure compared to lighter skinned people to build up the same amount of vitamin D.
Vitamin D supplements are not the answer
It is obvious from the literature that Vitamin D is one of the essential nutrients most lacking in the average Westerner's body. This is due to a combination of high latitude with weak sunshine, a predominantly indoor-based lifestyle, and current 'healthy' advice to stay out of the sun take or cover up while in it. But, you might ask, couldn't we merely eat more vitamin D-rich foods or take supplements?
It is very important to realise that the recommended daily allowance (RDA) of vitamin D of 400 IUs is totally inadequate for most people who do not have exposure to regular sunshine. Many people may need up to 10,000 IUs per day for a short time to build their vitamin D levels up to healthy levels. And there are very few foods that contain significant amounts of vitamin D naturally. A supplement of cod liver oil does, but you would need to drink quite a lot to get sufficient D. And there is a danger of overdosing as D is a fat-soluble vitamin. If you take too much it can cause calcium to build up in soft tissues and kidneys.
There is also another problem which relates to the type of chemical used for supplementation, whether in supplemented foods or in pills. The 'vitamin D' used for this purpose is ergocalciferol, a synthetic vitamin known as vitamin D2. D2 is not nearly as good as cholecalciferol, the vitamin D3 which our bodies make with sunlight or obtain from natural food sources like fish oils. There is no doubt that the best — and healthiest — way to get vitamin D is the natural way: from sunlight.
There is another benefit with this method: there is no risk of overdosing: The skin does an amazing thing with cholecalciferol. Once you make about 20,000 IU, the same ultraviolet light that created cholecalciferol, begins to degrade it. The more you make, the more is destroyed. So a steady state is reached that prevents the skin from making too much cholecalciferol. No-one has ever been reported to develop vitamin D toxicity from sunbathing — but they can when taking it by mouth.
Conclusion
To reduce the risk of skin cancer — and all other cancers — a high level of vitamin D is essential. Current advice to stay out of the sun and to wear a sunscreen or cover up when in it, has proven to be disastrous to our health. For your health's sake, you should get out in the sun, in the middle of the day, without a sunscreen, as often as possible. It doesn't need to be for long — 10 - 15 minutes a day will suffice. Do that and we could see cancer death rates take a steep nose-dive.
References
[i]. Webb AR, et al. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 1988; 67: 373-378.
[ii]. Daniel E. Roth DE, et al. Vitamin D insufficiency is common in Canadian children and adolescents: national guidelines provide insufficient vitamin D to maintain adequate blood levels. Can J Public Health 2005 In press
[iii]. Jablonski NG, Chaplin G. The evolution of human skin coloration. J Hum Evol 2000; 39: 57-106.
Last updated 1 August 2008
