A reader writes:

My kid was diagnosed with fructose malabsorption early in 2012. Essentially, any fructose that he eats, in excess of approximately the same amount of glucose, makes him sick. Most fruits are relatively balanced 1:1 with fructose to glucose, so they're okay: pineapples, berries, a lot of citrus fruits. But popular fruits like apples, mangoes and watermelons are screamingly high in fructose relative to glucose. Oh, and wheat. And honey. And agave syrup. Fruit juice is just as bad as Honey Boo Boo's Mountain Dew habit from a metabolic standpoint, but at least it doesn't have the other crap in it.

You'd think such a disorder is rare? It's really common. Estimates are 30-50% of the U.S. population. And they tend to have metabolic syndrome.