Some time ago, Zhejiang Industrial and Commercial Department randomly sampled 30,000 blood swallows and found that all the nitrite contents exceeded the standard, which seriously endangered consumers' health. The exposure of the "blood swallow incident" has focused the public's attention on high-end health care products and tonics such as bird's nest and shark's fin. What are the nutritional values of bird's nest and shark's fin? How do consumers treat rationally and choose scientifically? Bird's nest is almost as nutritious as eggs. It is a nest built by mucus and feathers secreted by the digestive gland of the stomach after Jin Siyan, a swift animal, and other swallows ate small fish and seaweed in the sea. Bird's nest is considered as "resolving phlegm and relieving cough, eliminating fatigue". So, what are its nutrition and ingredients? Ma Guansheng, deputy director of the Institute of Nutrition and Food Safety of China Center for Disease Control and Prevention, said that according to the determination, bird's nest contains about 50% protein, 20% carbohydrates, 5% iron, 3% other minerals and little vitamins. Judging from these data, there is not much difference in nutritional components between bird's nest and eggs, but the content of individual nutritional components is different, but the price is very different. Bird's nest, which is praised as a high-quality nourishing product by Chinese people, has very limited nutritional value. Therefore, it is not the more expensive food that provides more nutrition. In addition to nourishing health, eating bird's nest has become a way for people to show their identity and show off. Vanity and showing off wealth psychology provide a part of market demand for bird's nest. Shark fin has no special nutrition. Fan Zhihong, an associate professor in the Department of Nutrition and Food Safety, College of Food Science, China Agricultural University, said that from a nutritional point of view, the main components of shark fin are collagen and a small amount of minerals. Macromolecule protein will not be absorbed directly in human body, but collagen will be converted into amino acids in human body. There is nothing special about shark fin from the point of view of supplying nutrition. If you want to get collagen, you don't have to eat shark's fin, you can eat pig's trotters. There are too many similar foods that can provide collagen. Fan Zhihong said that shark fin is not a medicinal material and has no special nutritional value. People who can afford shark fin are generally not short of protein; People who can't afford shark fin can ensure the supply of protein by eating eggs and drinking milk. From the perspective of environmental protection, sharks are already endangered animals. In order to obtain shark's fin, the shark who cut off the shark's fin will die, thus affecting the biological chain of the whole ocean. In addition, in the marine environment, sharks are at the top of the food chain, and pollutants such as metallic mercury will accumulate hundreds of times in sharks after accumulating and precipitating in the primary food chain of small fish and big fish. Mercury has a half-life of more than 200 days and is not easy to discharge. It doesn't mean that more nutrition is better for your health. Behind the small bird's nest and shark's fin, people's misunderstanding of nutrition knowledge is reflected: the more expensive food is, the more nutritious it is, and the more beneficial it is to eat. Nutrition is the material basis of health. There are more than 40 kinds of nutrients necessary to maintain human life and health. They all perform their duties and are indispensable in the body. The lack or deficiency of any nutrient will affect the function and health of the body and even lead to diseases. Ma Guansheng suggested that when buying food, we should first have the awareness of food diversification. "From a nutritional point of view, food is generally divided into five categories. The first category is cereals and potatoes; The second category is animal food; The third category is beans and nuts; The fourth category is vegetables, fruits and bacteria and algae; The fifth category is pure energy food, including animal and vegetable oil, starch, edible sugar, alcohol and so on. When choosing to buy, we should pay attention to these five foods, and similar foods should be diverse and constantly changing. Special attention should be paid to the intake of dark vegetables, which accounts for half of the total intake of vegetables, and attention should also be paid to increasing the intake of cruciferous vegetables and bacteria. " Nutrition is indispensable, but by no means the more the better. Ma Guansheng said: "protein is very important for health, but it doesn't mean that the more, the better. Too much will also affect health. Excessive intake of protein will increase the decomposition of protein in the body and increase the nitrogen-containing substances excreted by urine, thereby increasing the load on the kidneys, accelerating the loss of calcium in bones and increasing the risk of osteoporosis. "