Can eating too much fish cause mercury poisoning?

In daily life, many people think that eating more fish can not only help reduce blood lipids and cholesterol, but also replenish the brain; However, many people say that eating too much fish may cause mercury poisoning
.
So, which statement is correct, can eating too much fish really cause mercury poisoning?

Ruan Guangfeng, director of the Science and Technology Communication Department and deputy research librarian of the Kexin Food and Health Information Exchange Center, said in an interview with China Consumer Daily that replacing some animal fat with fish in the daily diet does help reduce blood lipids and cholesterol; Eating too much fish can lead to mercury poisoning, mainly because of regular or excessive consumption of certain deep-sea fish
.

Ruan Quang Feng analyzed that fish meat is relatively low in fat and contains more unsaturated fatty acids, and their cholesterol and saturated fat content are lower
than red meat.
At present, most residents in China consume relatively much animal meat, poultry meat and fish relatively little, and this eating habit has a greater relationship with the occurrence of many chronic diseases, so it is recommended to replace some animal fat meat with fish meat in the daily diet (fatty meat, that is, meat with a fat content of more than 30%, such as pork belly).

The statement of eating fish to supplement the brain is not entirely reliable
.
Nguyen Quang Feng explained that fish meat is rich in essential fatty acids - n-3 fatty acids, and the two amino acids EPA and DHA in this fatty acid are important
for nervous system and brain development.
However, they only work on fetuses or infants, and have little effect
on the adult brain.
That is, adults do not become smarter
even if they eat a lot of fish every day.

As for people's concern that eating too much fish will cause mercury poisoning, it is because some fish, especially deep-sea fish, contain more
mercury.
Mercury, commonly known as mercury, is the only metal
in liquid form at room temperature and pressure.
There are two kinds of mercury in food, inorganic mercury and organic mercury, which are harmful to the human body, and organic mercury is more toxic
.
Mercury ingested by humans through food, mainly from fish
.

The mercury in fish is a highly toxic organic mercury - methylmercury
.
It is a fat-soluble substance, and the gastrointestinal absorption rate is very high, after being absorbed, it can cross the blood-brain barrier, accumulate in brain tissue with high fat content, and gradually cause brain function impairment
.

However, methylmercury levels vary widely
from fish to fish.
Mercury in fish is accumulated through the food chain, so larger pelagic fish at the top of the food chain often contain more methylmercury, such as sharks, swordfish, mackerel, tilefish, tuna, sailfish, etc.
; Some small fish or freshwater fish have relatively low mercury content, such as catfish, cod, tilapia, flounder, sardines, salmon, barracuda, etc
.

In the past, people ate less marine fish, and most of the marine fish they often ate were relatively small offshore fish, such as mullet and flounder; Now that far more people like fish and can eat deep-sea fish, the risk of mercury poisoning is indeed greater
than ever.

Studies have found that the developing brain is more sensitive to the toxic effects of methylmercury, so pregnant women and children are at higher risk of poisoning when they eat fish containing methylmercury
.
In addition to avoiding fish with high mercury content, pregnant women, infants and young children are advised to choose small fish that are basically no more than the size of a plate from beginning to tail and limit the amount of
food.

At present, there is no clear and uniform assessment of the risks and benefits of fish consumption, but it is certain that more fish is not better
.
The "Dietary Guidelines for Chinese Residents (2022)" recommends that the average daily intake of fish for adults is 120-200g, which is equivalent to eating fish twice a week or 300-500g
.
If you want to eat deep-sea big fish, in general, a person weighing 50kg can only eat "half a palm size", that is, about 80g of fish a week
.

At the same time, it is recommended to eat only fish meat as much as possible and avoid parts such as fish heads, skins, internal organs and fats that may be enriched with harmful substances such as mercury to reduce the chance
of ingesting toxic chemicals.