The best way to help yourself and the environment is to buy all of your food, especially the fruit and vegetables from a local source. This means that you will get higher quality food that hasn't been shipped and flown all over the place (especially if it is organic) and that the environment will not suffer.
Eating locally is a great way to help yourself and the environment. Farmer's Markets are an easy way to do this because they do the work for you...everything for sale is likely to be local! Sometimes scouting out the local products in a grocery store can be quite a chore.