The Benefits of Kale. At just 33 calories, one cup of raw kale has: 1  Nearly 3 grams of protein. 2  2.5 grams of fiber (which helps manage blood sugar and makes you feel full). 3  Vitamins A, C, and K. 4  Folate, a B vitamin thatâs key for brain development. 5  Alpha-linolenic acid, an omega-3 fatty acid.t just 33 calories, one cup of raw kale has: 1  Nearly 3 grams of protein. 2  2.5 grams of fiber (which helps manage blood sugar and makes you feel full). 3  Vitamins A, C, and K.