Her doctor was helpless and went to consult a rheumatologist. The expert had no clue, but found another similar case. By the middle of 10, the third case appeared. The eosinophils in all three patients increased sharply, and the same symptoms were myalgia, fatigue, oral ulcer, abdominal pain, shortness of breath, rash and so on.
All three patients were tryptophan users. Tryptophan is an essential amino acid for human body. Ordinary people take a few grams through protein every day. Pure tryptophan is sold in the market as a dietary supplement to help sleep. Because it is ubiquitous in daily diet, no one doubts its safety.
Three patients are taking tryptophan, so is it the culprit? Or is it just a coincidence?
Doctors don't know, and neither do scientists. From the point of view of scientific logic, we can't draw any conclusions from the fact that all three patients took tryptophan. However, it is a matter of life, and people must make public health decisions based on this extremely limited evidence. 165438+1October 7th, a magazine reported these strange cases. On June 1 1, the FDA issued an announcement against the use of tryptophan. Immediately, the CDC named these symptoms "eosinophilia-myalgia syndrome", referred to as EMS, and began a nationwide investigation. On June 7th, 65438, FDA ordered the recall of tryptophan products with daily dosage exceeding 100 mg. By the end of March of the following year, the daily dose was less than 100 mg. The FDA subsequently extended the recall to all products containing tryptophan, except for specially approved uses. The CDC received more than 65,438+0,500 case reports and 38 people died. It is speculated that the actual number of victims is much higher than this.
Obviously, there is not enough evidence to support the FDA's ban on tryptophan. If this decision is "correct", no one will protest against "unfair procedures"-in public decision-making in the field of health, it has always been "I would rather kill one thousand by mistake than let one go". But if tryptophan is innocent, pulling tryptophan as a scapegoat will not protect the public at all. Banning tryptophan is only a stopgap measure, and it is urgent to find out who is behind it. The etiological study of EMS once became a hot topic.
Two "case control" studies were published soon. This study collected some EMS "cases" and found some "controls" similar to the cases in other aspects, but without EMS. Comparing their lifestyles, it was found that most patients took tryptophan, while the control group rarely took tryptophan. So tryptophan was involved in the EMS event.
However, tryptophan is, after all, an amino acid that the human body needs and ingests in large quantities from food. These two investigations and studies are still "insufficient evidence" to convict it. More interestingly, the tryptophan taken by EMS patients was produced by the same company, and there were six companies that produced this product at that time. It is easy to think that it is not tryptophan itself, but impurities in it.
Before the outbreak of EMS, the company changed a strain to produce tryptophan. Because this strain has been genetically engineered, there are still "anti-transgenic people" who use it to "prove" the harm of transgenic. In fact, before that, the strain used by that company was also genetically modified. With the renewal of this strain, there are subsequent separation and purification steps. In other words, taking this example to "illustrate" the harm of transgenic technology is completely out of context.
Therefore, many researchers have compared the similarities and differences between tryptophan products that lead to EMS and other "normal" tryptophan products. With the help of modern separation and analysis technology, it is indeed found that pathogenic tryptophan contains some impurities that are not found in "normal" tryptophan products. In the journal Science from 65438 to 0990, another paper reported this discovery.
To confirm which impurities are at work, it is also necessary to prove that those impurities themselves can cause EMS symptoms. For ethical reasons, it is obviously impossible to do experiments on people. Later, some papers appeared, claiming that some symptoms of EMS were reproduced in animals with these impurities.
Everything seems clear and can be finalized. Indeed, many people have accepted the "impurity pathogenic theory" of EMS. The European Union for Biotechnology held this view in its communiqué issued in 2000. There is also evidence to support this conclusion and decision: 1989 After the outbreak of EMS, there were no EMS patients. After the production process of tryptophan was modified, tryptophan was also lifted.
However, some scientists disagree with this conclusion. In some documents in the 1990s, some scholars pointed out that the original two "case-control" studies were not rigorous and had many defects, so they could not draw the conclusion that tryptophan supplementation caused EMS. On the other hand, the study of impurities is the idea of "conviction first, then handling the case". Later, the study of EMS induced by impurities in animals also had design defects. What is the cause of EMS? It's still vague.
Another study found that excessive intake of tryptophan will increase a variety of metabolites, and some of these metabolites will inhibit the decomposition of histamine, which will eventually lead to EMS symptoms. In addition, some studies have found that there are also differences in internal factors between EMS patients and non-patients.