• Weak nutrition science and public health: hard to mix

    For the Washington Post, Peter Whoriskey reports:

    The nation’s top nutrition advisory panel has decided to drop its caution about eating cholesterol-laden food, a move that could undo almost 40 years of government warnings about its consumption. […]

    The finding follows an evolution of thinking among many nutritionists who now believe that, for healthy adults, eating foods high in cholesterol may not significantly affect the level of cholesterol in the blood or increase the risk of heart disease.

    According to my reading of Gary Taubes’ Good Calories, Bad Calories, this is, at long last, consistent with the available evidence. However, the Post article makes no mention of any consideration of the role of carbohydrates, which probably is causing Taubes’ head to explode. (If you don’t know, his read of the evidence is that it is far more consistent with the idea that first world diseases — diabetes and obesity among them — are due to overconsumption of carbs. Though he’s also quick to admit that the evidence about anything in nutrition is not as strong as it could or should be.)

    By the way, Good Calories, Bad Calories (GCBC), though a seemingly thorough tour of the history of nutrition and its (abysmal) evidence base, is not an easy read. It’s very long, repetitive, and doesn’t do a good job of helping the lay reader comprehend the physiological mechanisms, to the extent they’re known (or hypothesized). Your mileage may vary.

    I see that Taubes has written a more recent book, which my be better in these regards. Or, perhaps, one of his articles or those of others offers a more accessible treatment of the carbohydrate hypothesis, but I don’t know. You can email or tweet at me if you’ve seen something particularly good and relatively brief in this area.

    One of the most interesting bits of meta from GCBC is the idea that maximal promotion for public health purposes must gloss over scientific uncertainty. Articulate just a little bit of daylight between the science as known and the science as we’d like to believe and getting people to “do the right thing” becomes substantially harder. (Imagine, in today’s environment, articulating a single shred of uncertainty about vaccination, for instance. It’d be a disaster, as we’ve already seen from fraudulent claims of harm from vaccines.)

    This tension comes through in Whoriskey’s reporting: “the problem in nutrition stems from the arrogance that sometimes accompanies dietary advice.” That arrogance exists, in part, because expressing uncertainty can water down impact. When one believes that one is likely on the right side of science, even with the uncertainty (and even when one is wrong about it), if one wants people to change, one cannot be the least bit wishy-washy. “We kinda think perhaps cholesterol is [or carbs are] not so good, maybe” will get you nowhere, as accurate a reflection of the science as that may or may not be.

    Science is hard enough. Evidence-based public health with uncertain science is often even harder. If there’s a good way out, short of just keeping mum until the science is “sufficiently certain” (whatever that means), I’m not sure what it is.


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