Because from the sexual taste, yam tastes sweet and flat, and long-term use of cold hurts the stomach, and dry heat hurts the yin; From the point of meridian tropism and efficacy, yam belongs to lung, spleen and kidney meridians, and has the functions of nourishing spleen and stomach, promoting fluid production and benefiting lung, tonifying kidney and astringent essence, and can be used for patients with diabetes with deficiency of lung, spleen and kidney and deficiency of both qi and yin. From the nutritional point of view, yam is rich in nutrition, containing a lot of starch, glycoprotein, free amino acids, vitamin C, amylase and so on. In addition, yam is easy to digest, which is a rare food therapy product. It can be eaten for a long time, especially for those who are weak and lose weight after a long illness or illness, need nutritional supplements and have poor spleen transport.