So what are top 20 healthiest foods? I thought this would be easy research, but like most anything, the answer is: it depends. What are you measuring for: antioxidants? Vitamins? Proteins? By season? By cultural acceptance? These and other variables/parameters will control the outcome of any list making efforts.
However, there are some that appear on more lists than others.
I dove in by doing a Google search on "Top 20 healthiest foods". I selected lists from the first two Google hit pages, choosing what appeared to be the top 4 lists, alphabetized them, and then looked to see which foods appeared on the most lists. I am sure I have a subjective lens, so please chew on this and let me know if there are some additions or changes you may suggest.
Dried Beans (lentils, kidney, pinto, red, soy)
Fatty (oily) fish
Low fat dairy
Nuts and Seeds
Whole grains, wheat (wheat germ, oat, whole wheat)
So what is the conclusion? A diet rich in simple, varied whole foods is the best thing for the body. This does not have to mean expensive. This searching came across a wonderful website called The Hillbilly Housewife shows with recipes and tips on convenient foods that are usually good buys.
Other sources for nutrition info for various foods: