To maintain immunity, attention should be paid to maintaining a healthy lifestyle, such as a reasonable diet, moderate exercise and sedentary lifestyle, smoking and alcohol restriction, psychological balance, and regular sleep habits. In terms of diet, no single food has such a great ability to maintain immunity. To maintain a good immune system, it is essential to ensure a diverse range of foods. Diversification of food can maintain immunity. Here are two numbers for everyone: eat more than 12 types of food every day, and more than 25 types of food per week, including grains, potatoes, beans, nuts, vegetables, fruits, poultry, livestock, seafood, eggs, dairy, etc. Seasonings are not included. Within a certain range, the wider the range and variety of food, the stronger the ability to resist external invasion. This is like an army, where the deployment of troops is reasonable and each position has sufficient troops. On the basis of diversified and comprehensive food, it is necessary to ensure food balance, and one essential food is staple food. Staple food is the main source of energy. To maintain immunity, the first step is to have sufficient energy intake. Staple food is the main source of energy. If a normal person does not have staple food for energy supply, on the one hand, the efficiency of brain operation will greatly decrease; On the other hand, if the supply of staple food is insufficient, the human body will burn muscles to provide energy, causing muscle loss. Over time, people will become weak, weak, and immune system will decline. The staple food should not be too refined, and attention should be paid to the combination of thickness, including whole grains, mixed beans, and potatoes. The dietary guidelines suggest that adults can consume 250-400 grams of grains and potatoes per day (raw weight). The daily intake of potatoes can account for more than 30% of the total staple food, and can be consumed up to 50-100 grams (raw weight). For example, a medium-sized egg weighs approximately 50-60 grams. Potatoes include yam, taro, sweet potato, etc. They all have a common characteristic of containing mucin that promotes immune activity and helps maintain immunity. Sweet potato is recommended as the staple food due to its relatively high protein quality, which can compensate for the nutritional deficiencies in rice and white flour. Regular consumption can improve the utilization rate of nutrients in the human body's staple food. Therefore, sweet potato is an ideal substitute for staple food. In addition, sweet potatoes have lower calories, with the same weight of sweet potatoes only having 1/4 of the calories of rice. They are also rich in dietary fiber and have an anti constipation effect. Moreover, sweet potatoes are rich in potassium β- Ingredients such as carotene, folic acid, vitamin C, vitamin B6, dehydroepiandrosterone, etc., have various effects such as protecting blood vessels and assisting in cancer prevention. For people with weak digestive function, it is best to eat sweet potatoes for breakfast or lunch, and try to eat less or avoid dinner. Otherwise, the probability of acid reflux will be higher when lying flat and sleeping at night. When eating sweet potatoes, the skin should be removed, especially in areas with brown or dark brown spots or black lumps, which must be removed thoroughly. (Le Xin She) Wen/Yu Kang (Professor of Clinical Nutrition at Peking Union Medical College Hospital)