The general requirement of dietary selection is reasonable and balanced, i.e., the energy and nutrients supplied by the diet are balanced with the energy and nutrients required by the human body in terms of total quantity and structure. An imbalance between nutritional supply and demand is the root cause of disease and other negative consequences.

Food selection should follow the following principles:

Except for breast milk, no single natural food can provide all the nutrients needed by the body. Therefore, it is advocated that people should consume a wide variety of foods, preferably more than 20 kinds of food every day. These foods are usually divided into the following five categories:

1, cereals, potatoes: cereals, including rice, noodles, grains, etc., potatoes, including potatoes, sweet potatoes, cassava, etc., mainly to provide sugar, protein, dietary fiber and B vitamins.

Each person (refers to healthy adults, the same below) to provide at least 3 varieties of food grains per day, the intake of 300-500 grams, and pay attention to the supply of coarse grains.

2, animal food: including meat, poultry, fish, milk, eggs, etc., mainly to provide protein, fat, minerals, vitamin A and B vitamins.

The proportion of animal food can not be too low, it is appropriate to consume 50-100 grams of meat per person per day, 50 grams of fish and shrimp, 25-50 grams of eggs, milk and its products 100 grams. Each person per week the best intake of about 50 grams of animal offal, especially liver.

3, beans and their products: including soybeans and other dry legumes, mainly providing protein, fat, dietary fiber, minerals and B vitamins.

Beans are the only plant-based food comparable to animal food sources of high-quality protein. It is advisable to consume 50 grams of beans and their products per person per day.

4, vegetables and fruits: including fresh beans, roots and stems, leafy vegetables, eggplant, etc., mainly to provide dietary fiber, minerals, vitamin C and carotene.

Each person should consume 400-500 grams of vegetables and 100-200 grams of fruit per day, and should consume more than 50 grams of fungi and algae and more than 200 grams of hard fruits per week.

5, pure caloric food: including animal and vegetable oils, starch, edible sugar and alcohol, mainly to provide energy, vegetable oil is also a source of vitamin E and essential fatty acids.

Each person should consume 25 grams of fats and oils per day, mainly vegetable oils, vector intake of animal fats but should be strictly controlled.

In addition to infants and young children suitable for small meals, the general adult three meals a day is more reasonable. In general, mixed food stays in the stomach for 4-5 hours, so the interval between two meals should be 4-6 hours.

The calorie distribution of each meal, generally breakfast accounts for 25%-30% of the total calories of the day, lunch accounts for 40%, dinner accounts for 30%-35%.

Breakfast should consume food with high nutrient density, focusing on improving quality. In addition to grain foods, it should be accompanied by protein-rich foods, such as eggs, peanut rice, dried tofu, milk, soy milk and so on.

Lunch should be nutritionally balanced and slightly more specific gravity. Protein, fat food can be slightly more, and then with fresh vegetables.

Dinner should be a nutritionally balanced and light meal. Calories should not be too high, meat and greasy food should be eaten less. There should be a moderate amount of cereals, soy products, a small amount of animal food and an abundance of fresh vegetables.

Temperature changes in different seasons also have an impact on people's appetite and nutrient needs. For example, spring is prone to "spring fever" phenomenon, should pay special attention to the intake of vitamins; summer sweating, easy to lose more vitamins and inorganic salts, should pay attention to make up for the lack of; fall climate is pleasant, people's appetites greatly enhanced, should avoid excessive food intake; winter weather is cold, heat consumption, should be supplied with some rich in calories, animal foods, while paying attention to vitamin C and vitamin A, and the use of animal foods. The first thing that you need to do is to get your hands on some animal food and pay attention to the vitamin C ration.

Dietary habits and products vary from place to place, and people should make full use of local food resources. For example, pastoral areas are rich in milk resources, can be appropriate to increase the amount of milk intake, fishing areas can be appropriate to increase the amount of fish and other aquatic products intake, rural mountainous areas can be utilized goat's milk, as well as peanuts, melon seeds, walnuts, hazelnuts and other resources. Under certain constraints, beans can be used temporarily to replace dairy and meat, or eggs can be used to replace fish and meat, and dried nuts can be used as a last resort to replace animal foods such as meat, fish and milk.

The differences in age, gender, occupation, labor intensity, and physiological state of the body determine different nutrient requirements and food choices. For example, obese people have opposite needs for food quantity and fats to those who are thin. Adults, pregnant women, infants, young children and the elderly, as well as people with special occupations and those suffering from certain diseases have different food requirements. In addition, the dietary habits of the diner, taste preferences, cultural interests, dietary taboos, etc., is also an important factor affecting the dietary options.