Li Shizhen's Compendium of Materia Medica said that sharks "have wings under their bellies, taste delicious and are treasured by southerners", so it can be seen that only southerners valued shark fins at that time. By the Qing Dynasty, shark's fin had become the most precious dish in grand banquets in the north and the south, and it was called "no banquet without wings". This luxurious banquet was simply called "shark's fin banquet". In the late Qing Dynasty, the reputation of shark fin in China spread abroad. According to unofficial history's records, Li Zhanghan, Li Hongzhang's eldest brother, hosted a banquet for foreigners when he was the governor of Guangdong and Guangxi. As usual, he held a western-style banquet, but it caused dissatisfaction among a foreign guest. He said on the spot, "I wanted to try the delicious barbecue and shark's fin in your country." It can also be seen that it was difficult to eat shark fin if you didn't go to the banquet of the giants. The reason why shark's fin is respected is also related to China's health culture, and it is regarded as a superior tonic. Traditional Chinese medicine believes that shark's fin can "replenish qi, tonify deficiency and stimulate appetite", while modern gourmets say that shark's fin is rich in nutrition and collagen, which has the effects of preventing bone aging, preventing cancer, caring skin and prolonging life. In fact, from a nutritional point of view, shark fin has no special nutritional value. The main component of shark fin is collagen, which is a kind of protein. Even if protein has some magical effect, it will not directly enter the human body after being eaten, but will be digested into amino acids in the gastrointestinal tract and then absorbed by the human body. So no matter what protein you eat, the outcome is the same, and it is digested into amino acids that make up protein. There are 20 kinds of amino acids that make up protein. Some protein (such as protein of eggs, milk and meat) contains all 20 kinds of amino acids, which is called complete protein and has high nutritional value. However, some protein (such as plant proteins) are incomplete protein, lacking some amino acids and having poor nutritional value. Collagen lacks tryptophan and cysteine and belongs to incomplete protein, so the nutritional value of shark fin is not high, which is not as good as that of complete fish in protein. No matter from the point of view of nutrition or health care, eating shark fin is useless. On the contrary, eating shark fin is harmful to health. The content of heavy metals such as mercury in shark fin is much higher than other fish. This is because industrial wastewater is continuously discharged into the ocean, which makes the content of heavy metals in seawater higher and enters marine organisms, and sharks are at the top of the marine food chain. After swallowing other fish, heavy metals in food will also enter the shark and accumulate, so the heavy metal content in the shark will increase. ?