Dr. Mercola being an absolute nut aside, what does "organic" have to do with the composition of the produce itself? I can perhaps understand wanting to avoid antibiotics in meat and animal products, but all organic fruit/vegetable production does is prohibit certain types of fertilizers and pesticides (while allowing others), which don't impact the composition of the final product anyway. It has an impact on the environment, land use, and the cost of food production, but the food is chemically the same. So how would it have any health benefit or produce a "purer" product?
