SDonald Davis, a biochemist at the University of Texas, said that 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.
Fruits, vegetables not as nutritious as 50 years ago