Many years ago, I read an article describing a medical research study, the results of which suggested a connection between regular consumption of coffee and the development of lung cancer. I was immediately concerned by this report, because I used to drink several cups of strong coffee each day. I was also immediately puzzled, because I could not see any plausible causal connection between the consumption of coffee and the health of the lungs. I could more easily have understood that coffee might have harmful effects on the mouth or the throat or the stomach, but I had always considered it a wonderful feature of the human anatomy that while both air and liquids come into the body through the same entrance, somehow we were able to direct the former to the lungs to be processed in the aerobic system and the later to the stomach to be processed in the digestive system. I have no expertise in medicine or anatomy, but the article’s result seemed suspect to me.
I was right. A short time later, I read an article that rebutted the conclusions of the first research paper, pointing out that the reason why there was a connection between coffee drinking and lung cancer was simply because many people who smoked numerous cigarettes also liked to drink plenty of coffee. Nicotine not caffeine was the cause of the lung cancer, but smoking was highly correlated to coffee drinking, and thus coffee drinking is indirectly related to the prevalence of lung cancer, but in a non-causal way. It is not hard to imagine other examples of this sort of relationship. Eating fish – high in protein but low in fat – is generally regarded as a healthier choice to eating meat, especially processed meat. However, if my habitual piscine meal is English style “fish ‘n’ chips”, which I eat most days of the week, then any health benefits from the fish are likely to be overwhelmed by the excess calories and saturated fats that I absorb via my consumption of chips.
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