Eat food. Not too much. Mostly plants.

From Unhappy Meals, by Michael Pollan:

"The problem with nutrient-by-nutrient nutrition science,” points out Marion Nestle, the New York University nutritionist, “is that it takes the nutrient out of the context of food, the food out of the context of diet and the diet out of the context of lifestyle.” If nutritional scientists know this, why do they do it anyway? Because a nutrient bias is built into the way science is done: scientists need individual variables they can isolate. Yet even the simplest food is a hopelessly complex thing to study, a virtual wilderness of chemical compounds, many of which exist in complex and dynamic relation to one another, and all of which together are in the process of changing from one state to another. So if you’re a nutritional scientist, you do the only thing you can do, given the tools at your disposal: break the thing down into its component parts and study those one by one, even if that means ignoring complex interactions and contexts, as well as the fact that the whole may be more than, or just different from, the sum of its parts. This is what we mean by reductionist science. ‘New York Times’, 28 January

Applying the same reductionism to policymaking can be just as problematic. The linkages between cause and effect in our increasingly complex world are ever more obscure. The number of variables, the interactions between them, and the time lags combine in such a way that successful policymaking is about as hit-and-miss as nutritional science. Mr Pollan ends his article with a list of ten recommendations for healthy eating. He begins it by simplifying those to just three: Eat food. Not too much. Mostly plants. Are there equivalent short but pithy maxims for policymakers? I believe so: Target outcomes. Make sure the outcomes are transparent, and meaningful to real people. Don’t be frightened of using markets.