Monday, November 19, 2007

Alcohol, health, and tunnel view

tunnel view
Beware of getting drunk by distilled, isolated findings from medical studies, you may miss important points.

In the food and cancer report, well-known to my regular readers, not each and every finding is likely to be nonsense. I have concentrated on the weakest points and tried to debunk false claims but, given the huge numbers of studies cited in the report, some hard evidence should be around. Where? Let's try to find some.

Alcohol in moderate amounts has no cancer effect in men. In higher amounts, the risks of cancers in the digestive tract begins to rise.

I women, the report says there is no safe threshold. Even moderate amounts of alcohol increase the breast cancer risk, only very little, but measurable in studies with hundreds of thousands of women. But it seems that the style of consumption also must be taken into account. See my earlier post: How many drinks, how many breast cancers?

First, let's do the math job. For breast cancers, a relative risk increase of 5 percent has been calculated out of 13 studies for a consumption of five drinks a week. The lifetime breast cancer risk for a woman in the United States is 12.5 percent or one in eight women. Without alcohol, 87.5 percent of women will stay free of breast cancer until they die from other causes. With one drink a day, this amount diminishes by 0.6 percent to 86.9 percent. I leave it up to you if you like to see a difference here. Yet the food and cancer report concludes:

"There is ample, generally consistent evidence from case-control and cohort studies. A dose-response relationship is apparent. There is robust evidence for mechanisms operating in humans. The evidence that alcoholic drinks are a cause of premenopausal and postmenopausal breast cancer is convincing. No threshold was identified."
You may wonder if they have looked at the same numbers.

Beware of tunnel view

At least, the experts don't fall into the tunnel view trap. They also have looked at the fact that alcohol is protective against heart attacks, and therefore, they recommend:
"If alcoholic drinks are consumed, limit consumption to no more than two drinks a day for men and one drink a day for women."
Alcohol and breast cancer is one, but certainly not the only example. Cholesterol, high blood pressure, body weight and other factors may all be linked with some adverse outcomes on the one hand and beneficial outcomes on the other hand, depending on age, constitution, genetic heritage, and other personal factors. Whenever you come across a study finding some special evidence in a special field, take a broad scope and be aware that the findings may be different in other fields.

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