In Brief: The whole package—calcium, fiber, and protein, plus antioxidants like vitamin C and beta-carotene
The Lowdown: There's a reason this humble leaf ranks first among powerhouse vegetables. Sure, it's got the usual suspects, including vitamins A and C, but here's the kicker: Watercress also packs a healthy dose of calcium—plus the vitamin K you need to absorb it—as well as fiber and protein, earning it a perfect score on the nutrient-density scale. (Kale, by contrast, has just under 50/100.) Still not convinced? Research published in the American Journal of Clinical Nutrition indicates that adults who consumed watercress saw less DNA damage and higher levels of antioxidants in the body.
How to Eat It: Like arugula, watercress makes a peppery, flavorful salad—but it's just as delicious in a hot or chilled soup.