With the continuous development of chemical reagents, more and more chemistry has been applied to every aspect of our life. Among them, chemical food additives are of great concern. For example, Sudan in salted duck eggs has caused an uproar, while another food additive has also attracted widespread attention, that is, a chemical called "canthaxanthin". The incident started with a column published by Cailan, a Hong Kong Gourmet: "a lot of raw fish slices change color after a long time. Only salmon is still so orange red. Because the fish farms add a chemical called canthaxanthin to the feed they eat, the meat remains bright red and yellow when it is bad." he said, "the recent research of the EU food safety organization is that if you inhale a high amount of canthaxanthin, this substance will accumulate in the retina and affect your eyesight."

　　But will eating salmon sashimi fed with canthaxanthin really cause blindness? But in fact, canthaxanthin exists naturally in many foods. Canthaxanthin is an orange red carotenoid pigment and an antioxidant. It naturally exists in many foods, such as mushrooms, green algae, crustaceans, fish and eggs. "Generally, canthaxanthin is not used for food coloring. It is only used for the addition of feed. It can be extracted naturally or synthesized artificially. Because of its small molecule, it can be synthesized exactly like nature. It is generally emphasized that natural farms will use natural extraction. Its role is to make the egg yolk more bright, and the color of poultry and salmon more ruddy."

    However, generally speaking, it is unscientific to talk about toxicity without avoiding the dose. The study found that the amount of canthaxanthin basically consumed through food did not reach the toxic level. EFSA (European Food Safety Agency) discussed the dose of canthaxanthin in the assessment conducted in 2010, and concluded that the amount of canthaxanthin that can be consumed through food (directly added food pigments and from salmon, etc.) will not exceed the current ADI (acceptable  daily  intake), so the currently approved usage is safe. According to the assessment of the European Union, the use of canthaxanthin in common salmon is unlikely to make the human intake reach an "excessive" level. Generally used in feed is synthetic. However, for substances with small molecules such as canthaxanthin, synthetic substances are highly similar to natural substances. It is easy to determine whether they are completely consistent. Moreover, keratin can be excreted without toxic accumulation. Although canthaxanthin is a natural pigment, it does not naturally mean safety. But what kind of impact it has on health must be examined through rigorous scientific experiments. Through experiments, it is found that only a small part of the canthaxanthin in food can be absorbed, and most of it is directly discharged from the body. The proportion of absorption is related to the fat content in food. In animals, the absorption rate is only 3% ~ 8%. In human body, the absorption rate is between 9% and 34%. The absorbed parts may be liver, spleen, adipose tissue and adrenal gland. After stopping eating, the keratin in other tissues will disappear quickly, while that in fat will decline slowly. In general, it can only be reduced by half in 5 days. In various toxicity tests, canthaxanthin showed good performance in lethality, genotoxicity, reproduction, carcinogenesis, organic diseases, sensitization and so on. The safety audit focuses more on the deposition on the retina. Although the "retina deposition experience" of tanning enthusiasts has not caused irreparable consequences, it is still a very awkward thing to deposit a pile of things that should not be on the retina. Scientists are concerned about the relationship between intake and deposition. In the monkey and human experiments, when the daily intake per kilogram of body weight was no more than 300 micrograms, the deposition on the retina could not be observed. In its recent assessment in 2000, the Committee concluded that the long-term intake of food using canthaxanthin as a feed additive would not exceed the current daily allowance for canthaxanthin. But making suntan pills may have side effects. Because the dose that can cause skin color changes is associated with some side effects, including liver damage, aplastic anemia and keratoflavin retinopathy. The doctor's recommendation is that the safe range for daily administration of canthaxanthin is between 60 and 90 mg.

    TakeCanthaxanthinOverdose can produce unpleasant negative reactions, including diarrhea, nausea, stomach cramps and red and orange body secretions. It can also cause side effects such as pruritus, rubella or allergic urticaria. In addition, taking this drug may also cause aplastic anemia. Only when a large amount of canthaxanthin is ingested can it lead to pigment accumulation in the retina and affect vision.   The amount of "dyed fish" such as salmon eaten by the Chinese probably cannot be compared with that of the Irish. Therefore, we need not worry about the blindness caused by the intake of canthaxanthin. However, from a safety point of view, it is not recommended to eat sashimi. After all, parasites on fresh fish still need attention.