I came across a great article on the nutritional content of food on politco.com, check it out here. I learned about this three years ago, when I started growing open pollinated corn for myself and my sheep.
The farmer I bought the corn seed from was very passionate about maintaining open pollinated corn. He showed me studies and research that showed the reduction in nutrition in corn because of the continual need to maintain high yield with GMO corn.
This really opened my eyes to the reduction in nutrition in corn, and made growing open pollinated corn that much more important.
This article says this drop in nutrition is across the board. That sounds important.