In my last post, I talked about the importance of maintaining humility when promoting or dismissing lifestyle interventions for better health. Today I’m going to flesh that out a bit further.
There’s an old joke among epidemiologists that goes like this:
The Japanese eat very little fat and suffer fewer heart attacks than the British or Americans. The French eat a lot of fat and also suffer fewer heart attacks than the British or Americans. The Japanese drink very little red wine and suffer fewer heart attacks than the British or Americans. The Italians drink excessive amounts of red wine and also suffer fewer heart attacks than the British or Americans. The Germans drink a lot of beer and eat lots of sausages and fats and suffer fewer heart attacks than the British or Americans.
Conclusion: Eat and drink what you like. Speaking English is what kills you.
Like all good humor this joke captures an essential truth: we are in fact not all that great at figuring out why some groups of people seem to live longer and healthier lives than others.
The reason for this is that humans (fortunately) do not live in petri dishes. Doing perfectly controlled experiments on living human beings is almost impossible, and doing perfectly controlled experiments on the questions we really want to answer (such as: what is the best diet for human health and longevity) is totally impossible. Ideally we would separate many thousands of babies at birth, randomly assign each to a different prison, and feed each prison a tightly controlled diet. One prison would get a standard American diet as a control group, another the keto diet, another the vegan diet, another the “mediterranean diet,” and so forth.
After 80 or so years, we’d then compile statistics on rates of cancer, heart disease, diabetes, and any other outcome of interest, and be able to draw some conclusions. But even then, there would be lots of questions that only invited another round of studies: if the vegans live longer, is it due to the absence of meat, or the higher consumption of plants? Since different diets tend to lead to slightly different caloric intakes, is it simply a calorie effect if one diet turns out better than another? And so forth.
Then we’d have to set up another study, and wait another 80 years to answer some of these questions. More questions would inevitably follow. Perhaps in 500 years or so, we’d finally be able to make some definitive conclusions.
Point being: we’ll never do these studies, for ethical and other reasons, and even if we did, our great-great-grandchildren would be long since dead by the time we got the answers we were looking for.
In the meanwhile, I’d suggest sticking to the basics: don’t smoke. Get a good night of sleep as often as possible. Don’t abuse drugs or alcohol. Get some movement every day of your life. A few times per week get some moderate to intense exercise that raises your heart rate and/or challenges your muscles to grow stronger. Eat a diet of mostly unprocessed foods. Adopt any strategies you can that help you to maintain a normal body weight. Get a regular checkup with a doctor and undergo recommended screenings for things like colon cancer, breast cancer, and high blood pressure. And yes, consider taking medication for chronic conditions when appropriate, especially if vigorous application of all of the above is not successful in eliminating the problem.
And: be humble and kind about it all. You don’t know the answers with 100% certainty. Not because you are uniquely ignorant, but because we are all ignorant.
