What to think if you are a “well informed” person when the information changes so often and quickly? Melinda Wenner Moyer’s article in Aeon, Against Grain, is a good place to start. She observes:
In the midst of all the claims and counterclaims, there is a single clear piece of common ground. Experts of every stripe ask dieters to avoid refined sugars and grains. ‘Losing body weight on a plant-based diet is much less likely to occur if the diet includes too many refined carbohydrates,’ writes Cornell’s T. Colin Campbell in his book, The China Study, based in part on his Cornell-Oxford-China study research. Esselstyn instructs his dieters to consume only whole-grain products and avoid fruit juice. And McDougall urges his readers to eat complex carbohydrates instead of refined sugars and flours.
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So where does all this leave us, other than confused and wondering if we should stop eating cupcakes? On the health side, the science does collectively suggest, but not prove, that a calorie is not always just a calorie, and that carbohydrates – particularly refined ones – might have unique metabolic effects that increase risk for chronic disease. Indeed, the notion that sugar and refined carbs are dangerous seems to be the one point on which nutrition scientists at either end of the carb-fat spectrum agree. I suspect that my weight-loss success a decade ago had something to do with the fact that, by cutting out wheat, I was replacing some refined carbohydrates with other macronutrients.
The problem here is what Jim Manzi in Uncontrolled terms “high causal density.” The most famous researchers, such as Dean Ornish and Robert Atkins, tend to present you with one-size-fits-all strident solutions. But the fact is that there are people who remain thin, who do not exercise, and consume processed carb and sugar.* I know them, and you probably know them. There are many factors which go into the end product of a person’s physical appearance and overall morbidity risk. On an aggregate scale of societies a few significant variables changing can result in enormous differences in outcomes, but people need to see efficacy on the individual level, and the causal signals can be confusing (in particular if efficacy varies from person to person for the same regime!).
A bigger issue has been institutional health’s monomaniacal focus on fat and a few biomarkers has left many not trusting scientific recommendations. That focus is shifting, as science does update. Unfortunately the generation of new robust inferences is noisy and prone to dead ends in domains of high causal density. This is not always the case in public health. It turns out that the model of germ theory is not too subtle; it describes the world in pretty uncomplicated terms. Similarly, why and how vaccines work is tractable because the etiology of how you get polio is much easier to tackle than how you get type 2 diabetes. In all likelihood there are many ways to get type 2 diabetes, and multiple factors impact different people at different weights (e.g., there are people with a greater genetic disposition to type 2 diabetes given the same exercise and nutritional regimes, though one might be able to explain this with something like the nature of fat deposition).
This reality of science as a messy and iterative process is obvious to anyone who practices science. A year ago I had a conversation with a friend who happens to be a professor of biology at a university, and we were talking about the problems with convincing the public about the efficacy of vaccination. He admitted that he had a bit of guilt in this area because when it came to his own health he took a very critically-rational perspective as to what his physicians told him. As someone who was aware of the protean nature of scientific literature he had no great confidence that the recommendations from on high were definitive or the “final answer.” Another friend who is a medical doctor did admit to me that for him patients who had a good science background were a pleasure to work with because for them healthcare was a collaborative process in which they were active participants, instead of being recipients of his commands ex cathedra. This reality is why I am somewhat uncomfortable with the “Because Science” meme. It attributes to science almost Solomonic powers of judgment, and in actuality is wielded to reinforce the prior conceptions of interlocutors.
Where does that leave us? Describing a problem is not a solution, and due to the nature of the reality here there isn’t an easy answer. But it does imply to me that we should be cautious about engineering aspects of human life when the scientific basis for that engineering is less than certain. The war on fat and salt over the past few generations have been due to putting science forward as the basis of policy which turned out to not be robust. In the case of salt the establishment has even done an about face, “the government says there is no good reason based on health outcomes for many Americans to drive their sodium consumption down to the very low levels recommended in national dietary guidelines.” Salt tastes good, so one can imagine just how much utility was left on the table because people changed their diet to become more insipid. Policies have consequences.
Increasingly new way of thinking about diet has been to focus less on the latest science, and fall back on cultural culinary history. “Eat like your grandmother cooked” is trendy advice proffered by influential writers such as Mark Bittman and Michael Pollan. But by removing heavily processed foods it might be a major upgrade from modern diets, which are designed to sustain the profits of the food industry, not our own health (that’s a negative externality, the cost of which they don’t have to eat). Whether you go mostly plant-based or carnivorous, you’re probably going to be fitter in either direction, even if one is superior to the other at the end of the day.** Instead of deduction from what we know, anengineering an appropriate nutritional outcome, in the best course of action in the near future is probably “hipster nutrition.” Artisan hand-crafted diets which look back to the past, though in a non-ironic fashion, might be the best way to go because they’re the outcome of hundreds of years of innovation and experimentation. If you don’t have randomized control trials, go with the next best thing. History.
* Whether they are healthy is a different question obviously.
** One issue is that the different options might be superior for different people.
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