As every mild chocolate-addict, I am always keen to read studies arguing that chocolate is somehow beneficial to one's health. The most recent exemplar in this long line of studies is one recently published in the New England Journal of Medicine, which indicated that the number of Nobel laureates of a country, controlling for population size, correlates positively with annual chocolate consumption per capita. As always in this sort of correlational studies involving chocolate, the results are probably spurious. They crumble on closer scrutiny, and at present seem to invoke mainly snickering in the scientific community. The bitter lesson is that we should raise the bar in our research, in particular in controlling for lurking variables, or just freaky results (in a large sample, so a statistical dictum goes, outrageous results are bound to happen; moreover, the author "reports regular daily chocolate consumption, mostly but not exclusively in the form of Lindt's dark varieties.")
Even if we do not take this pessimistic outlook, a lot of data reported in the medical (and it looks more and more, in the social sciences too) are false positives. So given the high probability of false positives, why is news about the adverse or beneficial effects of food, even if published in relatively obscure journals, headline material?
What is the proper attitude of an individual? Obviously, a persistent link between diet/habits and health warrants scrutiny (e.g., drinking alcohol during pregnancy is harmful, increasing vegetables in the diet is conducive to health), but it would hard to maintain that we are under an obligation, epistemic or otherwise, to heed the more occasional and quixotic results like chocolate and broccoli. But what about grey zone health advice, like the health risks of red meat or the benefits of a "Mediterranean diet" (whereby it's often not specified sufficiently what this would look like on a weekly, let alone daily basis)? Do we just use common sense, try to follow up on those studies, or be conservative and only stick to government-based health advice (e.g., the five-a-day campaign)?
Even if founded on relatively solid evidence, there are various practical dimensions that complicate the desirability of issuing such advice through the government. For instance, the five-a-day program does not take into account that calorie-rich food happens to be cheap, which may explain why people from poorer backgrounds indulge in crisps, candy bars, and fatty meat, rather than in blueberries, wild salmon and lettuce. As sociobiologist Daniel Nettle puts it "It's much more expensive to get 2000 calories a day from fresh fruit and vegetables compared with eating junk food".
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