My understanding is that He first made us to be fruitarians. After the fall, God incorporated the greens into our diet, since we were then susceptible to sickness, etc. Then after the flood, he allowed us to eat meat.
Hallelujah Acres - hacres.com - is where I first started learning about the different diets that God gave us. Many folks have reportedly been healed of many, many "incurable" illnesses by returning to the Genesis 1:29 diet. I personally have had to add organic eggs and occasional cheeses (on pizza) and some kefir back to my diet.