An annual plant with convolvulaceae. Creeping herbs, more than 2 meters long, lying on the ground. With underground tuberous roots, the tuberous roots are spindle-shaped with yellowish or purplish red skin. Leaves alternate, broadly ovate, 3-5 palmately lobed. Cymes axillary, bracts small, subulate, sepals oblong, unequal in length, corolla bell-shaped, funnel-shaped, white to purplish red. Capsule ovoid or oblate, seed 1-4. Tuber root is starch raw material, which can be eaten, brewed or used as feed. Widely planted all over the country. According to ancient documents such as Compendium of Materia Medica and Addendum to Compendium of Materia Medica, sweet potato has the effects of "tonifying deficiency and benefiting qi, strengthening spleen and stomach, and strengthening kidney yin", which makes people "live longer and have fewer diseases". It can also tonify the middle energizer, promote blood circulation, warm the stomach and nourish the five internal organs. Contemporary Chinese Materia Medica says: "Sweet in taste and flat in nature. Meridian of spleen and kidney. " "Tonifying the middle and blood, benefiting qi and being holy, widening the stomach and relaxing the bowels. Indications: Spleen edema, sores and swelling, intestinal dryness and constipation. " Sweet potato is rich in starch, dietary fiber, carotene, vitamins A, B, C and E, as well as potassium, iron, copper, selenium, calcium and other trace elements 10 and linoleic acid. With high nutritional value, it is called the most balanced healthy food by nutritionists. These substances can maintain the elasticity of blood vessels and are very effective in preventing and treating habitual constipation in the elderly. Unfortunately, most people think that eating sweet potatoes will make people fat and dare not eat them. In fact, on the contrary, eating sweet potatoes will not only make you fat, but also help you lose weight, keep fit, prevent sub-health, and relieve constipation and detoxify. Every100g of fresh sweet potato contains only 0.2g of fat, which generates 99 kilocalories of heat energy, which is about 1/3 of that of rice. It is a good food with low fat and low heat energy, and it can effectively prevent sugar from transforming into fat, which is conducive to weight loss and bodybuilding. Sweet potato contains a lot of dietary fiber, which cannot be digested and absorbed in the intestine. It can stimulate intestinal tract, enhance peristalsis, relieve constipation and detoxify, especially for senile constipation. Pay attention to steaming and cooking sweet potatoes. Eating sweet potato should not be excessive, and it should be used with caution for those diagnosed as dampness blocking the spleen and stomach and qi stagnation in traditional Chinese medicine.