Scary rumors
Many people may have seen such a "strange news" on the Internet: "A girl suddenly died of bleeding in her seven orifices. After a preliminary autopsy, she was diagnosed as dead due to arsenic poisoning. A professor from a medical school came to help solve the case at invitation. After carefully examining the extract from the deceased's stomach, he thought that arsenic was produced in the deceased's abdomen. Because the deceased took vitamin C every day before his death and ate a lot of shrimp for dinner, arsenic was produced." Is that true? Can't vitamin C and seafood be eaten together?
This is a rumor with a certain "technical content", because it fabricated a "research result": the so-called "University of Chicago researchers" found through experiments that shrimp and other seafood "contain a large number of pentavalent arsenic compounds with high concentration". This substance itself has no toxic and harmful effect on human body. However, after taking vitamin C, "due to chemical action, the originally non-toxic pentavalent arsenic will be transformed into toxic trivalent arsenic", also known as arsenic trioxide, which is commonly known as arsenic! The victim of poisoning is often "bleeding from the seven orifices". Therefore, for the sake of caution, seafood should be avoided during the period of taking vitamin C.
Arsenic is indeed trivalent arsenic, and vitamin C is indeed a reducing agent. Reducing pentavalent to trivalent is also a reasonable reaction. For most non chemical professionals, such an expression is really lethal. Therefore, since the prototype of this rumor first appeared in May 2001, it has spread rapidly and is still circulating in all corners of the Internet. In 2008, according to the rumor, some film companies produced a film "double food", in which the protagonist was poisoned by arsenic because he ate seafood and vitamin C at the same time.
Rumor dissection
In fact, arsenic in seafood is mainly organic arsenic, most of which exists in the form of arsenic betaine. After ingestion, they are basically excreted intact, so they will not be toxic to the human body. The content of inorganic arsenic in seafood does not exceed 4% of the total arsenic content at most, most of which is pentavalent arsenic and a small amount is trivalent arsenic. In fact, inorganic arsenic in seafood is not the main factor in food. If we want to be serious about this issue, we should worry about cereal products, including rice and flour, which provide most of the inorganic arsenic in our daily diet. It can be seen that if vitamin C can easily reduce arsenic pentoxide and make people poisoned, you should consider not only the problem of "whether to eat shrimp", but the problem of "whether to eat".
Fortunately, we don't seem to have heard of anyone dying from eating "vitamin C + a lot of rice". Apart from the vague case in the rumor, we have never heard of poisoning due to eating "vitamin C + a lot of shrimp". In fact, so far, no case of arsenic poisoning considered to be related to fish and shrimp has been seen.
There are some discussions about whether pentavalent arsenic can be reduced to trivalent arsenic by vitamin C in the body. However, even without considering this issue, it is not difficult to find the ridicule of this rumor. Assuming that the human body is the perfect place for this reduction reaction, the pentavalent arsenic eaten into the stomach is completely reduced without waste to obtain trivalent arsenic. So how much shrimp does a person have to eat to be poisoned?
According to China's national standard (GB 2762-2005), the upper limit of inorganic arsenic in shrimp and crab is 0.5 mg / kg (fresh weight). That is, the inorganic arsenic content in each kilogram of fresh shrimp should not exceed 0.5 mg. For healthy adults, the oral lethal dose of arsenic is 100 ~ 300 mg. According to 100 mg of arsenic, it contains 75 mg of arsenic. Assuming that the rumored victim eats all the heavily polluted shrimps that reach the upper limit of inorganic arsenic, she also needs to eat a full 150 kg of shrimps to be poisoned by arsenic. For a little girl, she was broken before arsenic poisoning occurred in this way.
So rumor cracking, this rumor is a masterpiece of scaring people with low-level chemical knowledge. The inorganic arsenic content in shrimp is very low. Even if it can be reduced by vitamin C to arsenic, such a small amount will not even cause poisoning reaction, let alone "sudden death".