Kale and collards come from the cabbage family. Both vegetables originated at least 2,000 years ago. Most kale varieties have curly leaves and colors ranging from gray to dark bluish-green. Collards have flat, broad, thick, dark green leaves that require long cooking duration. Many nutrients are susceptible to damage during cooking. Kale is often steamed or lightly sauteed, whereas collards are often submerged in water and cooked for long periods, reducing some of their nutritional content.
A 1-cup serving of kale provides 80 mg of vitamin C, 19 mcg of folic acid and 10,302 IU of vitamin A. One cup of collard greens offers 12.7 mg of vitamin C, 60 mcg of folic acid and 2,400 IU of vitamin A. The overall vitamin content in kale is greater than in collards, particularly after the lengthy cooking time required for the preparation of collards that reduces their nutrient value.
Kale provides 90 mg of calcium and 299 mg of potassium per cup. Collards provide 52 mg of calcium and 61 mg of potassium. The mineral content in kale is higher. Potassium and calcium are important for muscle contractions in the body. Athletes and those at risk for cardiovascular disease may benefit from including kale in the diet.
Per cup, kale provides 2.2 g of protein and collards contain .88 g. Both contain 1.3 g of fiber per cup. The protein content in kale is higher. The value of kale's macronutrients is higher because of the energy-sustaining quality of a combination of protein and fiber.
Lutein is a carotenoid related to beta carotene, precursor to vitamin A, that supports ocular health. The lutein content in collards is 3.2 mg. The lutein content in kale is 10.3 mg. The standard daily dose for vision loss treatment and prevention is approximately 10 mg, according to the University of Pittsburgh Medical Center. Including kale in the diet is particularly beneficial for those vulnerable to vision disorders.