Lots more. According to a new biochemical analysis, the nutritional value of US vegetables has declined over the last 50 years. That’s because new varieties of fast-growing crops designed to maximize output cannot take up or synthesize nutrients as quickly as more slow-growing plants. The result:

…of 13 major nutrients in fruits and vegetables tracked by the Agriculture Department from 1950 to 1999, six showed noticeable declines—protein, calcium, phosphorus, iron, riboflavin and vitamin C. The declines ranged from 6 percent for protein, 15 percent for iron, 20 percent for vitamin C, and 38 percent for riboflavin.

Yikes. Just when the slow food movement is taking off, it turns out we need a slow-growing food movement too.