It is not recommended to talk about the acidity or alkalinity of food, and no authoritative literature on the acidity or alkalinity of food can be found. Some of the elaboration of food acidity and alkalinity refers to food ash, which is the oxides of some elements left over from the combustion of food, which is quite different in nature from the metabolites of food after digestion, absorption and utilization in the body. Purple kale is rich in nutritional value, containing certain proteins, various vitamins and more water. According to the Chinese nutrition science book, every 100 grams of purple kale contains 1.4 grams of protein, 0.1 grams of fat, 57 mg of calcium. The anthocyanin contained in purple kale is purple kale water, which can be consumed in moderation on a daily basis, but does not have any special efficacy or effect.