Antioxidants are plentiful in plant foods, particularly those that have bright colours. As of May, 2005, the most comprehensive study of the antioxidant content of common foods that I know of was published in the June 2004 edition of the Journal of Agricultural and Food Chemistry.
The highest ranked foods in four major categories are as follows:
Fruits: blueberries, cranberries, and blackberries.
Vegetables: beans, artichoke hearts, and surprisingly, russet potatoes.
Nuts: pecans, walnuts, and hazelnuts.
Spices: cinnamon, oregano, and ground cloves.
Here are a few points to keep in mind when choosing antioxidant-rich foods:
Because there are many different types of antioxidants that can protect your tissues from different types of damage, it is best to eat a wide range of antioxidant-rich foods. How much you benefit from the antioxidants found in the foods you eat depends on how well you breakdown and absorb these foods. One of the best ways of making sure that you are getting plenty of antioxidants in your diet is to strive to eat lots of fresh vegetables. If you just don't have the time to eat a large green salad every day, consider buying a good juicer and drinking a fresh vegetable juice on a daily basis. Another more convenient option is to use a high quality super green food product. When washing and preparing vegetables and fruits, be sure to wash non-organic varieties with extra care to help remove pesticide residues. This is especially important for vegetables and fruits that are known to be heavily contaminated with pesticides. Raw chocolate and goji berries are two foods that are extremely rich in antioxidants but were not evaluated for the study cited above."