MELANOMA: It’s down to omega-6, not the sun

The sun has got his hat on, and many of you are packing your buckets and spades for the annual summer holiday. So it’s a good time to draw your attention to two reports that are about holidays and sun worship.

The first questions the link between sunbathing and melanoma, the skin cancer. It’s passed into medical lore that exposure to the ultraviolet rays of the sun can cause melanoma, and it’s been observed that people who live in parts of the world that are invariably sunny are more inclined to develop melanoma than those living in cloudier northern climes.

But one recent report suggests that the story is more complicated. Some studies have shown a link while others have failed to do so, for instance, while a recent Australian study that was conducted over 10 years found that there was a 40 per cent reduction in melanoma among sun worshippers who regularly ate fish. Fish are rich in omega-3 oils, and so a diet that includes the oils may play a key role in determining who gets melanoma. Interestingly, the National Academy of Sciences came to a similar conclusion back in 2001 after they reviewed all the available studies, but they saw it as a balance or ratio between the omega-3s and the omega-6 fats. The ideal ratio is 2:1 (twice as much omega-3 for each portion of omega-6), but that’s been changed in recent years to 10:20. In short, we’re consuming too much omega-6 fats, which are extracted from plants or found in cooking oils derived from vegetables, such as corn oil, safflower oil, peanut oil, and so on. The omega-3s are found not just in seafood but also in whole grains, beans and other seeds.

The second study looks at mosquito repellents that contain DEET. DEET (or N,N-diethyl-3-methylbenzamide, if you want to be formal) is a powerful pesticide that certainly works if you’re off to the Far East or other tropical regions where the mosquitoes mean business.

Trouble is it could affect the health of your children. One study has found that it can cause brain cell death and behavioural changes, and the risk is greater among children aged below six. The American Academy of Pediatrics has advised parents not to use any repellent that contains more than 10 per cent DEET on young children.

The effects of DEET seem to get magnified when it’s mixed with oxybenzone, a common ingredient in sunscreens. When the two are combined, absorption of the DEET increases to 30 per cent compared with the usual 9 per cent. Together, there could be an increased risk of stroke, headache and high blood pressure, say researchers.

(Sources: Melanoma – New York Times, July 20, 2004; DEET – Duke University Medical Center press release, June 2004).

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Written by What Doctors Don't Tell You

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