I was flipping through one of Michael Pollan's books at the airport bookstore last weekend. It may have been In Defense of Food, but I can't remember. Anyway, I came across this puzzling piece of advice:
Be the kind of person who takes supplements.That is, you don't really have to take the supplements, as long as you are the kind of person who might. Pollan explains that studies have shown people who take multivitamins are generally healthier, but in controlled studies, multivitamins haven't been shown to actually make anyone healthier. This is reasonable, as it could be that supplement-takers are more health-conscious to begin with, and taking the supplements simply indicates their health-conscious status.
The puzzling part is this: how can someone follow Pollan's advice, other than by taking supplements?
This is related to a few philosophical paradoxes. Here's Kavka's toxin puzzle (from Wikipedia):
An eccentric billionaire places before you a vial of toxin that, if you drink it, will make you painfully ill for a day, but will not threaten your life or have any lasting effects. The billionaire will pay you one million dollars tomorrow morning if, at midnight tonight, you intend to drink the toxin tomorrow afternoon. He emphasizes that you need not drink the toxin to receive the money; in fact, the money will already be in your bank account hours before the time for drinking it arrives, if you succeed. All you have to do is. . . intend at midnight tonight to drink the stuff tomorrow afternoon. You are perfectly free to change your mind after receiving the money and not drink the toxin.The question being, is it possible to intend to drink the toxin tonight if you know you won't actually have to tomorrow?
