A: The difference between low-fat milk, skim milk and ordinary milk lies in the different fat content in their milk. After scientific disinfection and sterilization, ordinary milk retains the original nutrients and fat of fresh milk. Fresh milk contains about 3.8% fat. For healthy people, especially adults, the standard of healthy eating is to reduce fat intake in addition to not creating excess calories. Therefore, among the varieties of milk, low-fat milk and skim milk are added. The fat content of low-fat milk is about half that of ordinary fresh milk. It is suitable for diabetic patients who need to control their diet. Infants with weak digestive ability or diarrhea can also take it. Because of the low fat content, it is not suitable for feeding babies for a long time, otherwise it may cause malnutrition due to insufficient energy supply. In industrial production, the fat in milk is often taken out by centrifugation and made into cream. Low-fat milk can also be made at home. Because the milk fat contained in milk has a light specific gravity, it will float on the surface of milk. Let the fresh milk stand overnight, and then remove the floating milk fat with a straw or spoon to become low-fat milk. You can also boil the fresh milk and let it stand. After a little cooling, a layer of milk skin, that is, fat skin, is formed on the surface of milk, and after removal, it is low-fat milk. The fat content of skim milk is below 65438 0%. Homemade, you need to let the fresh milk stand overnight or boil for 3 times to minimize the fat. Skim milk is more suitable for adults to drink, especially those who need to limit and reduce saturated fat intake, because they do not rely on milk for energy supply. Drinking milk is to supplement the high-quality protein and calcium in milk. Skim milk with calcium is more suitable for middle-aged and elderly people. Yogurt is a product made of fermented milk, which not only has the nutritional value of milk, but also contains beneficial microorganisms such as lactic acid bacteria, which can inhibit spoilage bacteria in human intestines and promote the digestion and absorption of nutrients. It is a nutritious food suitable for all ages. It is not suitable for drinking yogurt on an empty stomach, and the pH value suitable for the growth of lactic acid bacteria is below 5.4. On an empty stomach, people's stomach acid is high, and the pH value is below 2. After meals, the gastric juice is diluted and the pH value rises to 3.5. Therefore, drinking yogurt on an empty stomach is easy to kill lactic acid bacteria, and the health care effect is weakened, but drinking yogurt two hours after meals is better. The active lactic acid bacteria in yogurt should not be heated, which is beneficial and harmless to human body. It can decompose lactose in fresh milk to produce lactic acid, increase intestinal acidity, inhibit the growth of spoilage bacteria and weaken toxins produced by spoilage bacteria in the intestine. In addition, active lactic acid bacteria also have the function of enhancing gastrointestinal digestion. After heating and boiling, not only the unique flavor of yogurt disappears, but also the beneficial bacteria in it are killed, and the nutritional value is greatly reduced. Babies shouldn't feed yogurt. In modern families, it is often seen that parents feed their babies with yogurt. In fact, this practice is unscientific. Although yogurt can inhibit and eliminate the growth of pathogenic bacteria, it also destroys the growth conditions of beneficial bacteria for infants and affects the normal digestive function. People who drink milk and have bloating can drink yogurt. Some people will produce gas in their stomachs after drinking milk, feeling bloating and even diarrhea. This is because these people lack lactobionic acid, and lactose in milk cannot be decomposed by glycosidase in the small intestine, that is, it enters the large intestine and is fermented by other bacteria in the large intestine to produce gas. However, these people will not have the above phenomenon when drinking yogurt, because lactic acid bacteria in yogurt have decomposed lactose in milk during fermentation and converted it into sugars that are easily absorbed by the human body. So people who drink milk and have bloating can drink yogurt.