Kale: This nutrition powerhouse "of

Kale: This nutrition powerhouse "offers everything you want in a leafy green," says Nussinow, who gave it her first-place ranking. It's an excellent source of vitamins A C, and K, has a good amount of calcium for a vegetable, and also supplies folate and potassium. Kale's ruffle-edged leaves may range in color from cream to purple to black depending on the variety.

Before cooking with kale, collards, turnips, and chard, Nussinow recommends swishing the greens in a water-filled sink, draining the sink, then repeating this rinse until the leaves are dirt-free. Her favorite cooking method for these four greens is to rub the leaves in olive oil or tahini (sesame paste) and cook them for five minutes with garlic, olive oil, and broth.