Chinese yam, a medicinal herb recorded in the "Chinese Pharmacopoeia," is derived from the dried roots and rhizomes of Dioscorea polystachya Turcz., a plant in the Dioscoreaceae family. It has the following effects: 

1. Tonifying the spleen and nourishing the stomach: Chinese yam contains substances such as amylase and polyphenol oxidase, which enhance the digestive and absorptive functions of the spleen and stomach. It serves as a dual-purpose medicinal and food item for tonifying the spleen and stomach. It can be consumed by patients with spleen yang deficiency or stomach yin deficiency.

2. Tonifying the kidneys and nourishing essence: Chinese yam contains various nutrients that strengthen the body and tonify the kidneys, benefiting those with kidney deficiency leading to spermatorrhea, excessive leukorrhea in women, or frequent urination.

3. Benefitting the lungs and relieving cough: Chinese yam contains saponins and mucilage, which have lubricating and moisturizing effects. Therefore, it can benefit lung qi, nourish lung yin, and alleviate chronic cough due to lung deficiency and phlegm.

4. Lowering blood sugar: Chinese yam contains mucoproteins, which can lower blood sugar levels. It is an excellent dietary therapy for diabetic patients.