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Skin Cancers and Diet
Introduction
There are many conditions in Western industrialised societies today that were unheard of, or at least very rare, just a century ago. The same conditions are still unheard of in primitive peoples who do not have the 'benefits' of our knowledge. There is a very good reason for this: They eat what Nature intended; we don't. The diseases caused by our incorrect and unnatural diets are those featured on these pages.
Part 1: Skin cancers — An Introduction
Dietary Causes of skin cancers:
Insufficient sunbathing (lack of Vitamin D); polyunsaturated vegetable oils and margarines; sunscreens.Introduction
For the past few decades the numbers of skin cancers have risen dramatically among pale-skinned, Caucasian populations throughout the world. Melanoma is the seventh most commonly diagnosed cancer in the USA with a rate of 14.2 cases per 100,000 population;[i] Queensland, Australia, had the world's highest rate at 55.8 cases per 100,000 in 1987.[ii] The incidence of skin cancers in the general British population has been increasing at an annual rate of 2% to 8% over the past two decades.[iii] The contributory factors seem to be a light-skinned, northern European population living in areas of high ambient sunlight, and the incidence of the disease is seasonal, with more cases reported in summer than winter.
Not surprisingly perhaps, clinicians, physicians, national media and health gurus have warned us to stay out of the sun to prevent the most serious form of skin cancer: melanoma. Yet in spite of the ever-increasing use of sunscreens and intentional reduction of sun exposure, the number of cases of this cancer continues to rise.
This may be because several aspects of melanoma are anomalous compared with other sunlight-associated skin cancers. For example, people with the greatest risk of melanoma are not those with the greatest cumulative exposure to the sun; the areas of the body that receive the most exposure to the sun are not the most affected; and not all light-skinned people suffer the same: albino Africans who have no pigmentation, for example, are likely to get sunburn and other skin complaints as a result of exposure to the sun, but they don't get melanomas.[iv]
In the 1960s I lived in Singapore, which was almost on the Equator. I have blond hair, fair skin and blue eyes. It is a combination not believed to be suited to the harsh sun of the tropics. Nevertheless, I regularly went on the beach, to the swimming pool, or sailing on the South China Sea, with little or nothing on, in the heat of the midday sun. I don't tan easily. I remember, in an effort to deepen my tan, I would lie out for hours with the sun to one side of me and its reflection in a mirror of cooking foil on the other to increase my exposure. Like everyone else in the ex-patriot Singapore community, I didn't give skin cancer a thought; in those days the phrase ?malignant melanoma' was unheard of.
Nobody used a sunscreen. If we used anything at all ? which most of the time we did not ? it was a well-shaken mixture of coconut oil and vinegar, a concoction used at the time by naturists. We smelled like a fried fish shop, but my skin never burnt while I lived there.
Today, it seems, all that has changed. Why? What has changed in the last 40 years?
Skin cancers
There are three major forms of skin cancer:
- Basal cell carcinoma (BCC) is the most common form of skin cancer. It occurs most frequently in men who spend a great deal of time outdoors and is usually found on the head and neck.[v] BCC is not dangerous as it rarely spreads, although it can extend below the skin to the bone.
- Squamous cell carcinoma (SCC) is the second most common skin cancer. It usually affects people who sunburn easily, tan poorly, and have blue eyes and red or blond hair. SCC often develops from actinic keratoses, which are rather like warts, and can metastasise (spread) if left untreated.[vi]
- Malignant melanoma (MM) is the rarest form of skin cancer but the most deadly. It originates in the melanocytes ? the cells that produce the skin colouring or pigment known as melanin ? and can be recognised by its black or grey colour. It often grows from an existing mole, which may enlarge, become lumpy, bleed, change colour, develop a spreading black edge, turn into a scab, or begin to itch.
Malignant melanoma is more prevalent among city and office workers than among people who work out-of-doors and is thought to be linked to brief, intense periods of sun exposure such as one might get on annual holidays on sunny beaches and a history of severe sunburn in childhood or adolescence. MM metastasises readily and is almost always fatal if not caught in time[vii] as it responds poorly to conventional therapy.[viii] Malignant melanoma is growing at a rate of 7% per year in the United States. In 1991 cancer experts estimated that there would be about 32,000 cases during the year of which 6,500 would be fatal.[ix] In Canada, melanoma incidence rose by 6% per year for men and by 4.6% per year for women during the period 1970 to 1986.[x] In Australia the rate for men doubled between 1980 and 1987 and for women it increased by more than 50%.[xi] It is now estimated that, by the age of 75, two out of three Australians will have been treated for some form of skin cancer.[xii]
References
[i]. American Cancer Society. Cancer facts and figures 1998. The Society, Atlanta, 1998.
[ii]. MacLennan R, et al. Increasing incidence of cutaneous melanoma in Queensland, Australia. J Natl Cancer Inst 1992; 84: 1427-32.
[iii]. Potten CS, et al. DNA damage in UV-irradiated human skin in vivo: automated direct measurement by image analysis (thymine dimers) compared with indirect measurement (unscheduled DNA synthesis) and protection by 5-methoxypsoralen. Int J Radiat Biol 1993; 63: 313-24.
[iv]. Diffey BL, et al. Melanin, melanocytes and melanoma. Lancet 1995; 346: 1713.
[v]. Harmful effects of ultraviolet radiation. JAMA 1989; 262: 380-84.
[vi]. Hacker SM, Flowers FP. Squamous cell carcinoma of the skin. Postgrad Med 1993; 93: 115-26.
[vii]. Lee JAH. The relationship between malignant melanoma of skin and exposure to sunlight. Photochem Photobiol 1989; 50: 493-96.
[viii]. Malignant melanoma ? Report of a meeting of physicians and scientists, University College, London Medical School. Lancet 1992; 340: 948-51.
[ix]. Skolnick AA. Revised regulations for sunscreen labelling expected soon from FDA. JAMA 1991; 265: 3217-20.
[x]. Statistics Canada. Canadian Cancer Statistics, 1991.
[xi]. Reynolds T. Sun plays havoc with light skin down under. J Natl Cancer Inst 1992; 84: 1392- 94.
[xii]. Ozone depletion and health. Lancet 1988; ii: 1377.
