Pascal’s Wager and the Mediterranean Diet

Wanna bet?

I like to think of Blaise Pascal (1623 — 1662), the French mathematician, as the western world’s first practitioner of Twitter. His collected Pensées were brief, enigmatic thoughts about mathematics, religion, and philosophy. Collected after his death, they read like the tweets of the 17th century (though they were intended to be a much more comprehensive defense of religion).

In the Pensées, Pascal made his famous wager. We all bet with our lives on whether God exists or not. We can live as if God exists and practice the traditional forms and virtues of religion. Or we can do the opposite and ignore our religious duties, assuming that God does not exist. If we live as if God exists and we’re right then the rewards are infinite. If we’re wrong, the loss is finite — indeed it’s quite small. Thus, Pascal argues, it’s only rational to live a pious life. The wager is heavily stacked to that side.

In today’s world, we don’t spend much time wagering on God’s existence (perhaps we should) but we make lots of bets that are much like Pascal’s. The cumulative effects are enormous.

For instance, consider the Mediterranean diet. The diet — which features olive oil, nuts, vegetables, and fish but not much red meat — has been on our radar for a number of years now. Epidemiologists observed that people who live near the Mediterranean have a much lower rate of heart disease than would be expected. Maybe it’s the diet. Or maybe it’s something else, like religion, culture, family structure, heredity, etc.

So the evidence for the positive health effects of the diet was an observed correlation. We could see that the diet was correlated (inversely) to heart disease but we couldn’t be sure that it caused the lower rates. Maybe a hidden, third factor was in play. Still, we could make a version of Pascal’s wager: eat as if the Mediterranean diet does reduce the risk of heart disease. If we’re right, we live longer. If we’re wrong … well, we’ve missed out on a few tasty bacon cheeseburgers. Would you take the bet?

Last week, the level of evidence changed dramatically. A five-year, randomized Spanish study of nearly 7,5000 people was published. People who followed the Mediterranean diet had 30% fewer heart attacks, strokes, and deaths from heart disease than the control group. Since the study used the experimental method, we can now talk about cause and effect, not just correlation. Now will you take the bet?

Of course, there’s still some doubt about the results. It’s only one study; it hasn’t been replicated yet. It was conducted in Spain. Maybe we wouldn’t get the same results in America. Maybe there were methodological or measurement errors. Still, the evidence seems pretty strong and it points toward a version of Pascal’s classic wager.

We all make versions of Pascal’s wager every day but we rarely think about them. Perhaps it’s time that we pay more attention. Perhaps it’s time to think about what levels of evidence we need before we take the bet. Is correlation enough or do we need to prove cause and effect? Life is uncertain but perhaps we can make it more comfortable by thinking — and betting — logically. While you’re pondering that, I’m going to drizzle some olive oil over a bowl of walnuts. Drop by if you’re hungry.