This fish is the best for hot pot, because it is "sick"! But there is a type of people who should never eat it...

In Guangdong, there is a very special delicacy. It is obviously fish meat, but unlike ordinary fish, it is not soft and loose in texture. It will fall apart after being boiled in water for a while. Instead, it is very chewy and has no earthy smell. This is the crispy grass carp.

What is Crispy Meat Wan?

Crisp-fleshed grass carp is a type of grass carp, which is one of my country's four major carps, with an annual output of more than 5 million tons.

Crispy grass carp is an invention of people in Zhongshan, Guangdong. It is not a new species, but a grass carp that is fed with broad beans and grows up. The meat becomes crispy and is very suitable for hot pot. It is also suitable for pan-frying or stir-frying.

Crispy grass carp. Image source: Dianping.com

The emergence of the crispy-fleshed grass carp has doubled or tripled the price of grass carp. Due to the longer breeding time, the crispy-fleshed grass carp sold on the market are larger in size, generally weighing 10 to 15 kilograms, while ordinary grass carp generally only weighs 3 to 6 kilograms.

A little-known fact:

The word "鲩" is pronounced huàn, you can’t type it as wǎ, but I usually also eat crispy meat wǎn.

Why did the grass carp eat broad beans?

Will the meat become crispy?

There is a special substance in broad beans called L-3,4-dihydroxyphenylalanine, which destroys the stability of red blood cells in the body. It is also the causative factor of "favism". In fact, the crispy grass carp is essentially a patient with favism.

The standard name of favism is G6PD deficiency. Patients lack G6PD (glucose-6-phosphate dehydrogenase) in their bodies. When they come into contact with specific food ingredients (such as broad beans) or drugs, they will have an acute hemolytic reaction. The severity of the reaction depends on the type and dose of the substance contacted.

Why didn't the grass carp die of acute hemolytic disease after eating broad beans? Because grass carp is different from humans in that it has a strong antioxidant enzyme in its body that can quickly repair hemolytic damage. So after eating broad beans, the grass carp's body will continue to cycle from hemolysis to hemolysis repair. Over time, the grass carp's muscle fiber hardness and density will increase, and the hardness and crispness of the meat will increase. (The proteomics research results were published by the Pearl River Fisheries Research Institute in Scientific Reports, a journal under Nature, in 2017, DOI: 10.1038/srep45950(2017))

Can people with favism eat crispy grass carp?

This issue is controversial. Because the L-3,4-dihydroxyphenylalanine in broad beans is an amino acid, it has passed through the digestive system of grass carp and then been cooked at high temperature in the hot pot, so it is unclear how much is left. However, for safety reasons, it is not recommended for patients with favism to eat it. Another point is that the allergenicity of grass carp itself is relatively high, whether it is ordinary grass carp or crispy meat grass carp. Grass carp contains a small albumin Cteni1, which is the main fish allergen in Hong Kong, China. It has high IgE reactivity and its allergenicity is higher than the small albumin in carp, salmon and cod. It should be noted that studies have shown that Chinese fish allergy patients generally have tolerance to some fish, and some patients who are allergic to grass carp can still eat other species of fish.

Broad beans make the grass carp crispy. Image source: pexels

Favism is prevalent in southern China, with an incidence rate of about 6% to 10% in Guangdong Province. Some friends may be curious, why is favism prevalent in southern provinces? In fact, although favism can cause mild or severe impacts on the daily life of patients, it can play a protective role in some aspects, such as malaria.

In ancient times, malaria was prevalent in southern provinces, but patients with favism have a stronger resistance to malaria because the pathogen of malaria is Plasmodium, which grows, develops, and reproduces inside red blood cells. The red blood cells of patients with favism are of relatively poor quality for Plasmodium. For example, they are easy to rupture and have a short survival time, making them less suitable for the growth of Plasmodium. As a result, these patients are relatively less susceptible to malaria.

Therefore, in southern provinces, there are more people carrying the favism gene, which is the result of natural selection over thousands of years. However, in the 21st century, malaria has been very well controlled in China (China was certified as a malaria-free country by the WHO in 2021), so these pathogenic genes are almost no longer needed to protect against malaria.

Finally, for patients with favism, in addition to broad beans, some other drugs also have certain risks. For example, acetaminophen should be used with caution when you have a headache or fever. You need to read the drug instructions carefully before taking the medicine.

Author: Zhuang Shili and medical science blogger

Reviewer: Tang Qin, Director and Researcher of the Medical Science Department of the Chinese Medical Association