According to taste and color, rice can be divided into many kinds. There are glutinous rice, japonica rice and indica rice according to taste; According to the color, rice has many different colors, such as white, yellow, green, red, purple, brown and black. Whether glutinous rice, japonica rice or indica rice, there are purple, brown or even basically black varieties, which are often called black rice. The general law of nutritional value of food tells us that the darker the color, the higher the nutritional value of the same food raw material, and rice also conforms to this law. Therefore, the nutritional value of black rice is much higher than that of white rice. Melanin has anti-aging effect. The color of black rice is different from other rice mainly because its outer cortex contains anthocyanins, which has a strong anti-aging effect. Studies at home and abroad show that the darker the color of rice is, the stronger the anti-aging effect of epidermal pigment is, and the effect of black rice pigment is the strongest among all kinds of rice. In addition, this pigment is also rich in flavonoids active substances, which is five times that of white rice, and plays a great role in preventing arteriosclerosis. The content of B vitamins in black rice is about 4 times that of polished rice. The contents of trace elements such as potassium, magnesium, iron, zinc and manganese are 4.4 times, 6 times, 1.7 times, 3.8 times and 1.7 times respectively. The content of lysine is 2-2.5 times that of lysine. Since ancient times, black rice has been regarded as a nourishing health product. The "Yutian rouge rice" mentioned in A Dream of Red Mansions refers to purple-black blood glutinous rice. Traditional Chinese medicine believes that black rice has the functions of nourishing yin and tonifying kidney, strengthening spleen and warming liver, improving eyesight and promoting blood circulation, and can treat anemia, dizziness, premature gray hair and other diseases. Because black rice contains more dietary fiber, the digestion speed of starch is relatively slow, and the glycemic index is only 55 (87 for white rice). Therefore, eating black rice will not cause violent fluctuations in blood sugar like eating white rice. In addition, minerals such as potassium and magnesium in black rice are also beneficial to control blood pressure and reduce the risk of cardiovascular and cerebrovascular diseases. Therefore, diabetics and patients with cardiovascular diseases can eat black rice as part of their diet. The best effect of cooking porridge is to preserve more nutrition. Black rice is often not as refined as white rice, and it is mostly eaten directly in the form of "brown rice" after hulling. This thick black rice is best for porridge, not for rice. When cooking porridge, in order to make it soft quickly, it is best to soak it in advance so that it can fully absorb water. Soak in the water for one day and one night in summer and two days and one night in winter. Then cook it in a pressure cooker and you can eat it in about 20 minutes. In order to prevent the pigment contained in black rice from dissolving in water during soaking, it can be washed gently with cold water before soaking, and it is not suitable for rubbing; The water used for soaking rice should be boiled with rice and cannot be discarded to preserve its nutrients.