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Recently, it has been found that the number and frequency of drinking milk at home are getting higher and higher. I asked my parents, and they said that drinking milk is good, nutritious and can supplement calcium. Not long ago, I saw on TV that in June, 2000, 1 1, the state passed a "milk drinking plan for students", which was mainly distributed by special departments, so that primary and secondary school students could drink milk every day during recess. Objective To improve the physical quality of teenagers. Why does ordinary milk become a "magic weapon" to improve physical fitness? What are the nutrients in milk? What benefits does it have for human body? In view of these problems, the teacher suggested that we take this as the subject, conduct some investigations and find out the information so as to have a comprehensive understanding of this.
I. Chemical Composition and Nutritional Value of Milk
The chemical composition of milk is very complicated, with at least 100 species. The main ingredients are water, fat, phospholipids, protein, lactose and inorganic salts. The main chemical components of ordinary milk are:
Humidity: 87.5%
Fat: 3.5%
Protein: 3.4%
Lactose: 4.6%
Inorganic salt: 0.7%
There are 20 kinds of amino acids that make up human protein, 8 of which are not synthesized by human body. These amino acids are called essential amino acids. If the protein we eat contains all the essential amino acids, this protein is called total protein. Protein in milk is whole protein.
Inorganic salts in milk are also called minerals. Milk contains cations such as Ca2+, Mg2+, K+ and Fe3+ and anions such as PO43-, SO42- and Cl-. In addition, there are trace elements I, Cu, Zn, Mn and so on. Most of these elements play an important role in human development, growth and metabolic regulation. Calcium is the most abundant inorganic salt in human body and the main component of bones and teeth. 90% of calcium in human body is concentrated in teeth and bones. Children and adolescents need adequate calcium for their growth and development, as do pregnant women, adults and middle-aged and elderly people. Calcium deficiency will affect the normal development of teeth and bones, leading to rickets. Calcium in nature exists in a bound state. Only when it is passively absorbed by plants to form bioactive calcium can it be better absorbed and utilized by human body. Milk is rich in active calcium, which is one of the best sources of calcium in human body. 1 l fresh milk contains about1250mg of active calcium, ranking first among many foods, which is about 10 1 times of rice, 75 times of lean beef and10/0 times of lean pork. Good absorption is especially critical for calcium supplementation. Therefore, the saying that "milk can supplement calcium" has its scientific reason.
For middle-aged and elderly people, milk also has a great advantage, that is, compared with the high cholesterol of many animal proteins, the cholesterol content in milk is lower (milk:13mg/100g; Lean meat: 77 mg/100 g). It is worth mentioning that some ingredients in milk can also inhibit the amount of cholesterol produced by the liver, so milk can also lower cholesterol.
Second, the consumption of dairy products in countries around the world and China
In fact, before China put forward the "Student Drinking Milk Plan", many countries and nations regarded milk as a magic weapon to improve their physical fitness. At present, a global "school milk plan" is being launched around the world. When talking about the reconstruction of Europe after World War II, former British Prime Minister Winston Churchill once said: "Nothing is more important than providing milk to children!" . After World War II, the Japanese even put forward the slogan "A glass of milk makes a nation strong", which greatly improved the physical quality of the post-war generation. Historically, American residents have also solved the problem of calcium nutrition through the "three cups of milk" campaign. Dairy products have become the main food for westerners.
At present, the average annual consumption of dairy products in the world is 100kg, while that in China is only 6 kg, which is less than one tenth of the world average. This is related to China people's eating habits and understanding of milk. To this end, we launched a survey. The subjects of the survey are mainly the parents of classmates around them and some of their neighbors and relatives (attached: questionnaire), which can not represent all of them, but it can also explain the problem to some extent. The survey results show that in the past 80% families did not drink milk often, and 20% families never even drank milk. Only 20% families have the habit of drinking milk. Many families said that they only used milk as their children's staple food in infancy, and then they stopped emphasizing drinking milk when they were a little older. Regarding the question "How do you supplement your children's nutrition?", 60% of parents choose to buy expensive nutrition and health care products, and 75% choose to buy some advanced foods. Only less than 10% of parents choose to give their children a glass of milk every day. These are mainly due to ignorance of milk nutrition. Do you know the nutritional value of milk? In the answer, 30% "do not know"; 60% "know a thing or two"; Only 10% "knows".
The lack of knowledge makes people generally think that milk is only a dispensable food, and the consumption of dairy products is seriously insufficient, which directly leads to the serious shortage of daily dietary calcium intake of Chinese residents. The results of many nutritional surveys show that the average daily dietary calcium intake of Chinese residents is only about 400 mg, while the average daily dietary calcium intake recommended by the World Health Organization is 800- 1200 mg, which is two to three times that of China. At the same time, the survey shows that the calcium intake of infants, children, teenagers, middle-aged and elderly people, pregnant women and other people who need calcium most is also less than 60% of the standard. This shows that residents in China are generally short of calcium. Calcium deficiency will not only lead to rickets, osteomalacia, senile osteoporosis and other common diseases, but also affect the full development of bones.
Teenagers are an important period for the healthy growth of life. During this period, a reasonable diet and adequate nutrition will surely lay a good foundation for future physical and intellectual growth. Give your child 250 ml of fresh milk or 30-40 g of milk powder every day. 300 mg of calcium, 7-8 g of high-quality protein and quite a few trace elements can be obtained. If we persist in this way, the child's physique, physical quality and intellectual development will be fundamentally changed in 5 to 10 years or longer.
Fortunately, our survey results also show that in recent years, with the improvement of people's living standards and the deepening of health awareness, people have gradually realized the nutritional value of milk under the propaganda of various media, and more and more families have begun to consciously incorporate milk into their daily recipes like my family. For the sake of health, the habit of a glass of milk every day for the whole family is taking shape. We also specially visited several supermarkets and asked about the sales of dairy products. They all said that the sales of dairy products, especially fresh milk, have been rising in the past two years. Fresh milk that just arrived in the afternoon is usually sold out at noon the next day. According to the prediction of experts from China Dairy Industry Association, the consumption of dairy products in China will increase substantially in the next five years, and the annual growth rate is expected to reach more than 15%.
Third, how to buy dairy products?
Since dairy products are a kind of food that can accompany human life, how to choose and drink them correctly is also worthy of attention. At present, dairy products in the domestic market can be roughly divided into two categories. One is liquid milk, including sterilized milk, ultra-high temperature sterilized milk, yogurt and lactic acid beverage. The other is milk powder.
Liquid milk is mainly fresh milk, and it is also one of the most popular dairy products for consumers. According to the survey, 60% people like to drink fresh milk. Since it is fresh milk, it is expensive in a fresh word. Its freshness and quality inspection are particularly important. The survey also found that many people don't know how to identify and choose. Here are some simple ways to identify the freshness of fresh milk:
Methods 1 Sensory identification: fresh milk (sterilized milk) is milky white or yellowish, with the inherent fragrance of fresh milk, no peculiar smell, uniform liquid, no precipitation, no coagulation, no impurities, no foreign bodies and no stickiness.
Method 2: Drop milk into clear water, and it will be fresh milk if it does not melt; If it melts, it is not fresh milk. If it is bottled milk, it is not new milk as long as thinning phenomenon is observed on the upper part of the milk or precipitation is observed at the bottom of the bottle.
Method 3: Boiling test: Take about 10ml milk sample in a test tube (or a transparent glass) and put it in boiling water for 5 minutes to observe. If there is coagulation or floc, it means that the milk is not fresh or has gone bad.
In addition, we should pay attention to the difference between pure milk and milk-containing drinks: pure milk is also called fresh milk, pure fresh milk. As can be seen from the ingredient list of the product, there is only one ingredient in this product, namely fresh milk. There are two main indexes to distinguish the quality of pure milk: total dry matter (also called whole milk solids) and protein. The contents of these two indicators are generally stated on the packaging bag of the product. The higher their content, the higher the nutritional value of milk, and generally speaking, the higher the price. In addition, yogurt popular with consumers is fermented from pure milk, so yogurt is also pure milk.
Milk-containing drinks are allowed to be mixed with water. As can be seen from the ingredient list, in addition to fresh milk, the ingredients of this milk beverage generally include water, sweeteners, fruity agents and so on. And water is often ranked first (the state requires the ingredients in the ingredient list to be listed from high to low). According to the national standard, the milk content of milk-containing beverages should not be lower than 30%, that is to say, the water content should not be higher than 70%. Because milk-containing beverage is not made of pure milk, its nutritional value cannot be compared with pure milk.
It is worth noting that there are some vague names such as "active milk" and "fresh milk" written in big letters on the packaging bags of milk-containing drinks in the market. If you look closely, you will find that there is a line of small print "milk-containing drinks" next to it, but there is not even this line of small print for individual products. Only one "water" is added to the ingredient list, which needs to be read carefully to distinguish clearly.
Fourth, drink milk scientifically.
Everyone knows that drinking milk is good, but there are many stresses about drinking milk. If you don't drink it properly, milk will not only help your health, but also cause some harm:
1, don't drink raw milk, drink fresh milk and heat it at high temperature to prevent the disease from entering the mouth;
Some people are used to drinking milk on an empty stomach, which is unscientific. Because eating on an empty stomach will make the intestines move quickly. And the protein in milk will be quickly converted into energy and consumed. Nutrients in milk can't be digested and absorbed, so they are discharged into the large intestine, which virtually causes waste. It's best to eat something before drinking milk or drink it while eating.
3. 80% protein in milk is casein. When the pH value of milk is lower than 4.6, a large amount of casein will agglutinate and precipitate, which is difficult to digest and absorb, and even lead to indigestion or diarrhea in severe cases. Therefore, it is not advisable to add acidic drinks such as fruit juice to milk.
Some people like to take medicine with milk instead of boiled water. In fact, milk obviously affects the human body's absorption of drugs. Milk is easy to form a covering film on the surface of drugs, which makes calcium, magnesium and other minerals in milk react with drugs to form water-insoluble substances, thus affecting the release and absorption of drug effects. Do not drink milk before and after taking the medicine 1 hour.
5, it is not appropriate to drink more cold milk, because cold milk will affect gastrointestinal peristalsis, causing mild diarrhea, so that most of the nutrients in milk can not be absorbed and utilized by the human body.
6. It is not advisable to cook at high temperature for a long time. Protein in milk will change from sol state to gel state under the action of high temperature, which will lead to precipitation and reduce its nutritional value.
It can be seen that milk is really nutritious, and it is a convenient, affordable, economical and nutritious food, which is worth popularizing. Unexpectedly, ordinary milk also has so much knowledge! Actually, it's not just milk. Everything in the world contains a lot of knowledge, waiting for us to discover and explore!
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1. How to drink milk reasonably?
People often like to drink a glass of milk at breakfast, which is good. Because the quantity and quality of breakfast directly affect the efficiency of work and study throughout the day. The ideal breakfast should not only have a certain amount of carbohydrates, but also a proper amount of protein food, vitamins and minerals. In addition to providing high-quality protein, milk is also rich in calcium and vitamin B2, but it should also be accompanied by starchy foods, such as steamed bread, bread, rolls, cakes and porridge. Provide carbohydrates to make a balanced diet. Other time
Occasionally, if possible, you can drink some milk as a drink around 4 pm and 0-2 hours before dinner, or you can drink some milk before going to bed at night to help you sleep, and you can also drink some biscuits.
2. How to drink milk is beneficial to the absorption of calcium?
The content of calcium in milk is very rich, which can reach 100 ~110 mg per100 g of milk, and this kind of calcium is natural milk calcium, which is easily digested and absorbed by human body. Milk is easy to drink, but to achieve the real purpose of calcium supplementation, we need to pay attention to the following issues:
1. Do not drink milk on an empty stomach. Because milk stays in the stomach for a short time on an empty stomach, it will affect the digestion and absorption of milk, so it is best to drink while eating.
Drinking a small amount of milk many times a day is better than drinking a large amount at one time, which can make the body absorb more calcium.
3. Avoid eating with some vegetables containing more oxalic acid, because oxalic acid will combine with calcium to form insoluble calcium oxalate, which will affect the absorption of calcium.
3. Can milk be drunk with soybean milk?
Soybean milk is a product obtained by crushing soybeans, extracting water-soluble components and removing insoluble substances by centrifugal filtration. Soybean milk is rich in protein and fat, and is known as "vegetable meat". It also contains a large number of lysine and tryptophan necessary for human body. The composition and content of many amino acids are basically consistent with the essential amino acid model of protein proposed by FAO/ WHO.
Soymilk is high in iron, low in calcium, rich in water-soluble vitamins and less in fat-soluble vitamins. After mixing soybean milk with milk, it can not only produce a flavor that is easily accepted by people, but also supplement sulfur-containing amino acids, calcium and fat-soluble vitamins in milk, and enrich and balance various nutrients needed by human body. The most common soybean milk product on the market is that soybean milk contains 5% milk powder or 30% fresh milk, so we can mix soybean milk and milk in a certain proportion to get a more nutritious and balanced diet.
4. What are the five advantages of a glass of milk in the morning and evening?
1. Milk contains potassium, which can keep arterial blood stable when blood pressure is high and reduce the risk of stroke;
2. Iodine, zinc and lecithin in milk can improve the working efficiency of the brain.
3. Magnesium in milk can increase the anti-fatigue ability of heart and nervous system, and zinc in milk can promote wound healing;
4. Calcium in milk can enhance bone density and prevent osteoporosis;
5. Milk contains L- tryptophan and other substances. Drinking it before going to bed can promote sleep.
5. Seven principles of breastfeeding babies
1. No need to add water.
Infants under 3 months have imperfect renal function and excessive water in the body, which is easy to cause water poisoning. Practice has proved that as long as children can't vomit and diarrhea after eating, they should be fed pure milk, so that the weight of newborns fed will increase rapidly.
Preserve milk skin
During the heating process of milk, a film is often produced on the surface, which is called milk skin. Many people like to throw away this layer of milk skin. In fact, milk skin is rich in vitamin A, which is good for eye health. Babies who eat milk will have eye diseases if they drink milk with the skin removed for a long time.
Don't overdo it
Babies who take milk as their staple food should not drink more than 1 kg every day, otherwise there will be hidden hematochezia and anemia will easily occur over time.
4. Milk is "afraid of acid"
Children who drink milk tend to have dry stools and have difficulty defecating. In fact, as long as the amount of milk is appropriately reduced and some sugar is added, the problem will be solved. If children are allowed to drink juice regularly, it will not only have a bad influence, but also affect their health. Because some protein in milk will form a gelatinous substance when encountering these acidic drinks, it becomes difficult to digest and absorb. The time to drink juice should be separated from the time to feed, and it is generally appropriate to feed for one hour.
Don't mix rice soup
Some parents like to mix some rice soup and rice porridge with milk and feed them to their children, which is also a wrong way to eat. Some people have done experiments: after milk and rice soup are mixed at different temperatures, vitamin A loses a lot. If the child's intake of vitamin A is insufficient for a long time, it will be stunted and sickly, so it is best to feed the child milk, milk powder and rice soup respectively.
6. Scientific insulation
Some parents put the boiled milk in a thermos cup for convenience. Once the baby cries and wants to eat milk, he can pour the milk into the bottle to feed it. This is really convenient, but unscientific. In milk, bacteria can reproduce every 20 minutes, and milk will go bad after 3-4 hours. In addition, the constant temperature in the thermos cup will destroy the vitamins in milk and directly affect the health of children.
7. Don't drink too much frozen milk.
Many parents often buy many bags of fresh milk at a time for convenience or can't buy milk, and then put them in the refrigerator and take them while eating. However, the quality of milk will be seriously affected after freezing. The fat and protein in milk were separated, and casein was dispersed in milk in the form of granules. Even if it is reheated and melted, the taste of milk will obviously become thinner and its nutritional value will be greatly reduced. So, don't drink more frozen milk. In addition, frozen milk will increase gastrointestinal peristalsis and cause mild diarrhea. Children with colds and colds will get worse if they drink frozen milk.
6.9 people can't drink milk?
1. Patients after abdominal surgery: Patients often have flatulence after abdominal surgery, which is caused by gastrointestinal exposure and surgical trauma. Milk contains fat and casein, which is difficult to digest in gastrointestinal tract. In addition, lactic acid bacteria in milk will produce gas after fermentation, which will aggravate flatulence and is not conducive to the recovery of intestinal peristalsis.
2. People with liquid esophagitis and hiatal hernia: Liquid esophagitis is inflammation caused by the decrease of lower esophageal sphincter pressure and the inflow of gastric and duodenal fluids into the esophagus. Studies have shown that milk containing fat can shrink the lower esophageal sphincter, increase the reflux of gastric juice or intestinal juice and aggravate esophagitis.
3. Patients in kidney calculi: After sleeping, urine volume decreases, and various tangible substances in urine increase, which can thicken urine. Because milk contains more calcium, kidney calculi mostly contains calcium. The most dangerous factor of stone formation is the sudden increase of calcium concentration in urine for a short time, and the peak of calcium elimination through the kidney is 2-3 hours after drinking milk. At this time, it is in a sleep state, and the urine is concentrated, so that more calcium passes through the kidney, which is easy to form stones. Therefore, kidney calculi patients should not drink milk before going to bed.
4. Patients with ulcerative colitis: Low-priced volatile fatty acids in milk can stimulate the intestines, so drinking milk when suffering from ulcerative colitis will aggravate the symptoms.
5. Patients with iron deficiency anemia: Although milk is rich in nutrition, its iron content is low, and the iron in food must be converted into ferrous iron in the digestive tract before it can be absorbed and utilized. However, this transformation is easily influenced by high phosphorus and calcium in milk, which will combine iron in the body with calcium and phosphorus salts in milk to form insoluble iron-containing compounds, making iron in the body even more insufficient.
6. Milk will aggravate cholecystitis and pancreatitis: the digestion of fat in milk requires bile and pancreatic lipase, and drinking milk will increase the burden on gallbladder and pancreas, thus aggravating the condition.
7. Patients with stomach disease and duodenal ulcer: Milk can cause a large amount of gastric acid secretion. When the milk just flows in
When you are in the stomach, you can dilute the concentration of gastric acid, reduce the stimulation of gastric acid on duodenal ulcer, and make the upper abdomen slightly relieved. After a period of time, milk will also stimulate the gastric mucosa, so that gastric acid will be secreted in large quantities, which will aggravate the condition.
8. People who are allergic to milk: Milk allergy is an allergic reaction of infants and some people to protein in milk. Symptoms include abdominal pain, abdominal distension, vomiting and eczema. In severe cases, symptoms such as cataract, ascites, convulsion and systemic edema may occur.
9. Lactose intolerance: If lactase is lacking in the body, lactose cannot be digested and absorbed in the small intestine, and directly enters the large intestine for fermentation, causing symptoms such as abdominal distension, abdominal sound, exhaust or diarrhea.
7. Will drinking milk get angry?
Milk is sweet and flat, and has the effects of tonifying deficiency, benefiting lung and stomach, promoting fluid production and moistening dryness, and quenching thirst. Protein and fat in milk are easily digested and absorbed by human body. Milk contains a variety of immune proteins, such as antibodies against salmonella, so drinking milk has a strong physical resistance to diseases. There is no scientific basis for saying that drinking milk "gets angry".
8. Why not advocate drinking milk on an empty stomach?
Some people get up in the morning, drink a large glass of milk on an empty stomach, thinking it is the most nourishing, and then rush to work. This is not good. Because it is empty, milk stays in the stomach for a short time and cannot be fully hydrolyzed and quickly enters the intestine, which affects the digestion and absorption of milk. In addition, some people may have stomachache and diarrhea after drinking milk on an empty stomach for 2-3 hours. 1-2 After diarrhea, everything will return to normal. This is because this kind of human body produces little or very little lactase. After drinking a lot of milk on an empty stomach, the lactose contained in milk can not be digested in time, but is decomposed by bacteria in the intestine to produce a lot of gas and acid, which stimulates intestinal contraction and strengthens intestinal peristalsis, thus causing abdominal pain and diarrhea. This phenomenon is called lactose intolerance.
The solution is to avoid drinking a lot of milk on an empty stomach, but to eat a certain amount of other foods or eat milk with other foods in advance, so as to reduce the relative concentration of lactose in the intestine, so that bacteria slowly decompose and the decomposition products are gradually absorbed. A better method is to use yogurt instead of fresh milk, because yogurt uses lactic acid bacteria to ferment milk to produce lactic acid, which can reduce lactose content and avoid lactose intolerance.
9. What should I pay attention to when eating ice products in summer?
1. Please don't eat cold food two hours before eating or before going to bed.
Don't drink cold water or eat immediately after strenuous exercise and sweating.
Cold food.
People with asthma, coronary heart disease, hypertension, gastritis, gastric ulcer or dyspepsia should avoid eating cold food.
People with hyperacidity and gastric ulcer should avoid sour cold drinks.
Many cold drinks or ice products are foods with high sugar content and high calories, and people with diabetes or obesity should avoid eating them.
6. Drink cold drinks and eat ice products, pay attention to cleanliness and avoid eating bad stomachs.
7. When enjoying cold drinks and ice products, you should chew slowly to avoid gorging.
8. Children, the elderly or women should try to avoid eating cold food during menstruation.
9. Don't chew ice cubes to cool off when you are thirsty, so as not to hurt your teeth.