The Doctor’s Surgery
The best diet? It’s a fishy question Fish is good for you – but not in great amounts theodore dalrymple
Flesh is, in the last analysis, grass. But increasingly enlightened medical opinion believes that more of it ought to be, at least in the intermediate phases, fish. Fish is said to be good for you, even if it is a myth that it does for your mind what we were once told that carrots did for our eyesight. Fish is often thought to stave off heart attack and stroke. I first realised that diet was more than a matter of taste when a (much older) cousin of mine tried to impress upon me that we inevitably took on the psychological characteristics of the animals whose flesh we ate. He had recently converted from gangsterism to vegetarianism, and being a disrespectful, sly little boy, I asked him what we became (mentally) if we ate cabbage. Many years later, by the way, quite a number of my patients complained to me, ‘My ’ead’s cabbaged, doctor.’ Fortunately, I always liked fish. My brother, brought up on the same diet as I and sharing half my genes, detested it.
Perhaps one day the vagaries of personal taste will be fully explicable, though I certainly hope not. Explanation would lead inevitably to abuse and manipulation. It is not easy conclusively to demonstrate the benefits of a diet of fish. Populations rarely differ only by their consumption of this commodity. It would be difficult to perform prospective trials in which the participants were unaware of whether they were in the experimental or the control arm of the study. Still, an attempt at answering the question must be made. A paper published by the Journal of the American Medical Association (JAMA) tried to compare the rate of heart attack and stroke in
Those who ate at least 175g of fish a week had a lower rate of heart attack or stroke
‘...and here’s one of us sitting in our mother’s garden...’
191,558 people in 58 countries (pooled from four separate studies) who ate less than 50 grams, up to 175 grams and more than 175 grams of fish a week. After what must have been immensely complex calculations, an answer resulted that might at first sight please some and disappoint others. Those who ate at least 175 grams of fish a week had a roughly 10 per cent lower rate of heart attack or stroke than those who ate hardly any. Still, eating more than 175 grams conferred no additional protective effect among those who had cardiovascular disease in the first place. Oily fish was more protective than white fish, which conferred little or no benefit. No protective effect was found among those who had no disease at the outset of the studies. The deficiencies of this research are obvious. Fish is expensive in most countries, and so those who eat it tend to be better off than those who do not, and we know that people who are better off are less susceptible to disease. The paper gives an average body mass index (BMI: weight in kilos divided by height in metres squared) for the various subgroups of the 191,558 people, but it is not credible that this could be known for more than a small proportion of them. Since a high BMI is a known risk factor for cardiovascular disease, this means that the results are simply not trustworthy. Uncertain data cannot lead to certain conclusions. Fish is not medicine. If it were eaten as such, the effect of its consumption would have to be compared with that of its consumption for pleasure, for the difference between the two types of consumer might affect the results. Incidentally, I notice that JAMA considers 175 grams of fish to be two portions. Not for me, it isn’t – but then I’m slightly overweight, so I’m told. There is a lot to worry about in this world. The Oldie August 2021 39
