Until the end of the Middle Ages, kale was one of the most common green vegetables in all of Europe. Curly leafed varieties of cabbage already existed along with flat leafed varieties in Greece in the fourth century BC. These forms, which were referred to by the Romans as Sabellian kale, are considered to be the ancestors of modern kales. Today one may differentiate between varieties according to the low, intermediate, or high length of the stem, with varying leaf types. The leaf colours range from light green through green, dark green and violet-green to violet-brown. Russian kale was introduced into Canada (and then into the U.S.) by Russian traders in the 19th century.
During World War II, the cultivation of kale in the U.K. was encouraged by the Dig for Victory campaign. The vegetable was easy to grow and provided important nutrients to supplement those missing from a normal diet because of rationing. Kai-lan, a separate cultivar of Brassica oleracea much used in Chinese cuisine, is somewhat similar to kale in appearance and is occasionally called "kale" in English. - Kale, History, Wikipedia
Kale can provide you with some special cholesterol-lowering benefits if you will cook it by steaming. The fiber-related components in kale do a better job of binding together with bile acids in your digestive tract when they've been steamed. When this binding process takes place, it's easier for bile acids to be excreted, and the result is a lowering of your cholesterol levels. Raw kale still has cholesterol-lowering ability--just not as much. - Worlds Healthiest Foods
One cup of kale has only 36 calories and zero grams of fat, which makes it a great diet aid. Furthermore, one cup contains nearly 20% of the RDA of dietary fiber, which promotes regular digestion, prevents constipation, lowers blood sugar and curbs overeating. Finally, kale contains the glucosinolate isothiocyanate (ITC) that fights the formation of H. pylori (Helicobacter pylori), a bacterial growth in the stomach lining that can lead to gastric cancer. - Health Diaries
Kale is high in iron. Per calorie, kale has more iron than beef. Iron is essential for good health, such as the formation of hemoglobin and enzymes, transporting oxygen to various parts of the body, cell growth, proper liver function and more. - Alison Lewis
One cup of kale contains 36 calories, 5 grams of fiber, and 15% of the daily requirement of calcium and vitamin B6 (pyridoxine), 40% of magnesium, 180% of vitamin A, 200% of vitamin C, and 1,020% of vitamin K. It is also a good source of minerals copper, potassium, iron, manganese, and phosphorus. - WebMD
Eating a diet rich in the powerful antioxidant vitamin K can reduce the overall risk of developing or dying from cancer, according to a study in the American Journal of Clinical Nutrition. Vitamin K is abundant in kale. - WebMD
100 g of fresh kale contain 120 mg or 200% of daily-recommended levels of vitamin C. Scottish curly leaf variety yet has more of this vitamin, 130 mg/100g. Vitamin C is a powerful antioxidant, which helps body develop resistance against infectious agents and scavenge harmful oxygen free radicals - Nutrition & You