Eat, drink, and be merry

Almost every bit of health advice I’ve heard has been contradicted. Should you eat more carbs or fewer carbs? More fat or less fat? Take vitamin supplements or not? It reminds me of this clip from Sleeper in which Woody Allen wakes up after 200 years of suspended animation.

Offhand I can only think of a couple things on which there seems to be near unanimous agreement: smoking is bad for you, and moderate exercise is good for you.

Here are a couple suggestions for evaluating health studies.

Be suspicious of linear extrapolation. It does not follow that because moderate exercise is good for you, extreme exercise is extremely good for you. Nor does it follow that because extreme alcohol consumption is harmful, moderate alcohol consumption is moderately harmful.

Start from a default assumption that something natural or traditional is probably OK. This should not be dogmatic, only a starting point. In statistical terms, it’s a prior distribution informed by historical experience. The more a claim is at odds with nature and tradition, the more evidence it requires. If someone says fresh fruit is bad for you, for example, they need to present more evidence than someone who says an newly synthesized chemical compound is harmful. Extraordinary claims require extraordinary evidence.

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12 thoughts on “Eat, drink, and be merry

  1. William Sullivan

    John S. – That herbal remedy issue seems very much in line with the final paragraph. The crucial sentence in that final paragraph began “Start from a default assumption” not “Conclude with an unshakable certainty.” The traditional remedy was examined and we now have significant evidence that it’s harmful. More studies will be done and the issue will be, more or less, settled. They have moved on from any default assumptions, which is exactly what we have science for.

  2. No doubt some traditional remedies cause more harm than good, but the same can be said for scientifically designed compounds. For example, antiarrythmic drugs.

    I didn’t have in mind herbal remedies, but things like breast feeding. For a generation, many people thought (because they were told my manufacturers) that baby formula was superior to breast milk. Now we’ve gone back to believing there may be some advantages to the way the human race has fed babies since time out of mind.

    I’d also add that “tradition” requires context. Something be healthy, or at least harmless, in its cultural context but harmful in a different context. A Japanese herbal remedy, for example, may be harmless for people of Japanese origin, living in Japan, eating a Japanese diet, and living a traditional Japanese lifestyle. That doesn’t mean it’s necessarily harmless elsewhere.

    But the same objection could be raised for clinical trials: just because a drug is safe when given to starving college students who make some cash by participating in a trial, that doesn’t necessarily mean the drug is safe for a different demographic.

  3. And ’round it goes. I think Gary Taubes has some very interesting things to say on diet. I use this heuristic: everyone is right. Seems to work out as well as picking sides ;)

    Even within reasonable boundaries, diet advice swings wildly due to the many factors: health, weight, exercise, calories, carbs, fat, cholesterol, heart health, diabetes, biases etc. Everyones’ bio signature is different. Complexity and unknown unknowns always muck up our desire for (illusion of?) deterministic certainty.

  4. Dimitriy Masterov

    I like this heuristic very much, but let me play devil’s advocate using one of your examples. If a prior distribution is informed by historical experience, how heavily should it weight the brief time when humans had access to sweet fruit year round?

  5. Dan: Gary Taubes is interesting. If he’s right, the majority of medical community has been flat wrong about some basic assumptions for a long time. It’s sobering to think that might be the case. Even if Taubes is wrong, it’s unsettling that he’s not obviously wrong, that he can make a plausible argument that some widely held scientific beliefs are upside-down.

    Dimitriy: People living in the tropics have always had year-round access to fruit.

  6. Dimitry, the heuristic serves to leaves everything open to consideration and is just a philosophical starting point. It works best in politics when they call each other names ;-)

    John, also sobering is that the practice of Science needs a serious housecleaning.

    Negative results must be published, not swept under the rug. A point well made by Stuart Firestein:

    The first 88 pages of this small, easy to read book are gold.

  7. John,

    Have you undertaken any sort of assessment of the science around caloric restriction and healthy longevity? If so, what are you thoughts?

    Thanks in advance.

  8. From a sample set of 1 (me) I have found that there is no silver bullet, at least in term of weight loss. I have lost weight an kept it off while on weight watchers, but also by exercising only with no change to my eating habits
    (both of these could have different long term health effects obviously).

    Interesting was also the the “Twinkie diet helps nutrition professor lose 27 pounds” (

    Regarding “caloric restriction and healthy longevity” , I’ve hear a couple of times this it is possible but once on the diet it is very hard (on place is the podcast below).

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