2. Milk: Milk and its products are one of the important sources of protein, calcium, phosphorus, vitamin A, vitamin D and vitamin B2 in the diet. Fresh milk is a complex emulsion, which is mainly composed of water, fat, protein, lactose, minerals and vitamins. The moisture content accounts for 86%~90%, so its nutrient content is relatively low compared with other foods. The average specific gravity of milk is 1.032, which is related to the solid content in milk. The composition of milk is basically stable except fat content, so the specific gravity can be used as a simple index to evaluate the quality of fresh milk.
3. Oats: (1) Reduce cholesterol and blood fat. The results of clinical trials show that oat can obviously reduce serum total cholesterol, low-density cholesterol, triglyceride and β-lipoprotein, and can also increase serum high-density cholesterol to a certain extent, and the effect of reducing blood lipid is very obvious. The main reason is that oats contain many substances that can lower cholesterol, such as monounsaturated fatty acids and soluble dietary fiber. β -glucan in oat soluble dietary fiber can form colloid when digested in small intestine, thus wrapping cholic acid rich in cholesterol and preventing cholesterol from being absorbed into blood. At the same time, oats contain more linoleic acid, which can combine with cholesterol to form esters, and then degrade into cholic acid for excretion. In particular, a large amount of linoleic acid can soften capillaries and prevent arteriosclerosis. (2) Regulating blood sugar: Compared with other major cereals (such as wheat, corn and rice), oats can inhibit the rise of postprandial blood sugar concentration and regulate insulin. Therefore, oat is suitable as a therapeutic food for diabetic patients. After the carbohydrates in rice and flour are ingested, they will all be hydrolyzed out of control into glucose and enter the blood, which will suddenly increase the glucose concentration in the blood, while the carbohydrates in oats will be slowly hydrolyzed into glucose, which will not lead to a rapid increase in blood glucose concentration. At the same time, dietary fiber in oats can delay the absorption of carbohydrates, improve the sensitivity of nerve endings to insulin and reduce insulin secretion, which is beneficial to diabetic patients. (3) Improve constipation: Dietary fiber has the abilities of water retention, oil retention, strong water absorption, expansion and strong adsorption, therefore, it can improve digestive function, promote gastrointestinal peristalsis, moisten intestines and relieve constipation. Oat fiber can shorten the retention time of feces in the large intestine and avoid the absorption of residual toxins in the intestine, thus reducing the probability of intestinal diseases and intestinal cancer caused by toxic waste accumulation. This function of relaxing bowels is especially beneficial to patients with hypertension and heart disease, because many patients with hypertension and heart disease often have cerebral hemorrhage and heart attack due to dry stool and excessive defecation.