David L. Katz, MD
Photo: Mackenzie Stroh
Q: Do I lose or gain anything nutritionally by eating a banana before it's ripe?
— Maria Cetrola, Barnegat, New Jersey

A: Nutrient content does change slightly as fruit ripens. As a banana turns yellow, its levels of antioxidants—substances that seem to protect against cancer and heart disease—increase somewhat, so you may be missing a small nutritional benefit. On the other hand, you may be gaining something. The reason bananas get sweeter as they ripen is that their starch is broken down into sugar. When your body has to break down the starch itself (as it does when you eat a green banana), your blood sugar rises more slowly.

All of this may not matter much—after all, both green and yellow bananas are rich sources of potassium, vitamin B6, fiber, and vitamin C, and particularly low in sugar when compared with, say, a doughnut. The real issue is that so few of us eat enough fruit, ripe or not. In January scientists at the Centers for Disease Control and Prevention reported that fewer than 1 percent of adolescents, roughly 2 percent of adult men, and only 3.5 percent of adult women meet the guidelines of three and a half to five cups of produce a day. This despite the fact that the researchers counted jam, jelly, and orange juice as fruit, and both French fries and the ketchup poured over them as vegetables! If you are fretting over which fruit to eat—rather than glibly strolling past the produce aisle—you're ahead of the game.

David L. Katz, MD, is director of the Yale-Griffin Prevention Research Center and president of the nonprofit Turn the Tide Foundation.