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Ditch your iceberg lettuce for a darker green with a loose arrangement of leaves. "Tightly wrapped leaves like iceberg don't get as much sun or nutrients," says Jo Robinson. "Go with loose leaf plants like arugula or spinach." Arugula is particularly rich in glucosinolate, which has anticancer properties, according to a number of studies, and is also high in calcium, magnesium, folate, and vitamin E. Always toss your lettuce in olive oil, which helps you get the most out of your nutrients, and tear your lettuce before eating it, a simple method that can double its antioxidant value.