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Fish are an excellent source of health-promoting nutrients, such as omega-3 fatty acids, calcium, iron and vitamin D. However, some fish may also contain mercury, an element harmful to the human body. Which fish have the most mercury and which are the least?
- Fish are very healthy – probably everyone knows that. But some fish, especially in heavily polluted seas, contain mercury that is harmful to health
- The greatest amount of methylmercury, or its organic form, is found in the largest species of fish
- The symptoms of mercury poisoning include numbness and tingling in the mouth and fingers, hands and feet, problems with coordination and memory, speech impairment
- Fortunately, fish and other food products available in Poland contain safe amounts of mercury
- More information can be found on the Onet homepage
Why is it worth eating fish?
“Fish is rich in omega-3 fatty acids, which is good for the brain and heart,” notes Felicia Wu, professor of nutrition, food safety and toxicology at Michigan State University.
Fish that contain large amounts of omega-3 fatty acids include salmon, mackerel, anchovies, sardine and herring.
Fish is also a good source of protein, calcium, iron, vitamin D, and other nutrients. This is one reason the American Heart Association recommends eating fish at least twice a week.
But some species of fish can also contain mercury, a neurotoxin that can cause a lot of damage to our body.
Mercury poisoning – when is it threatening us?
Mercury is an element found in soil, water and air. Small amounts contained in food are not dangerous to our health, but their higher dose is toxic.
You can poison yourself with mercury not only by eating mercury-containing foods. “People can be exposed to mercury released from containers or damaged mercury-containing items such as thermometers and dental seals,” says Malina Malkani, nutritionist and author of mercury dangers.
There are two main types of mercury – methylmercury and metallic mercury. The former can be found in fish and fruits. The latter is located, among others in thermometers (no longer produced in the European Union), it may also occur – although less and less frequently – in pesticides, fungicides and preservatives.
Both are harmful to our body.
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Symptoms of mercury poisoning
This element is especially dangerous for pregnant women and young children. In the past, children under 3 years of age were most often exposed to mercury poisoning through contact with a damaged mercury thermometer. However, in 2009, their production was stopped in the European Union.
Mercury poisoning causes a number of ailments, most often neurological, and very often the kidneys are damaged.
According to the World Health Organization, the most common symptoms of mercury poisoning are:
- problems with memory
- seizures
- bow
- irritability
- depression
- insomnia
- headaches
- vision loss
- impaired speech
- muscle weakness
- uraemia
In addition, there may be:
- violent vomiting with more or less blood,
- burning sensation in the mouth and esophagus,
- salivation,
- stomach pain,
- profuse bloody diarrhea,
- dehydration, shock and heart failure
- excitability
- swallowing problems
- trouble coordinating movements
“Poisoning with a high dose of mercury during pregnancy can cause fetal death, craniofacial malformations, neural tube defects, brain damage and cerebral palsy,” says Malina Malkani.
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Fish with a high mercury content
As Felicia Wu points out, the most mercury is found in fish, which are at the end of the food chain in seas and oceans. These are:
- larger species of tuna
- shark
- swordfish
- Marlin
- king mackerel
“These species contain the most mercury because it bioaccumulates in the food chain of marine species. Starting with plankton, which takes mercury from the marine environment, it is eaten by smaller fish, which in turn are eaten by larger species, ”explains Wu.
When it comes to fish consumed in Poland, butterfish, perch, eel and roach contain the most mercury.
Low mercury fish
“Safe” fish, i.e. those with little mercury in them are:
- salmon
- trout
- sardine
- sardines
- Herring
- cod
- pollock
- crustaceans such as prawns or scallops
“The mercury levels in fish and crustaceans depend on the species’ food sources, their lifespan and how high they are in the food chain,” says Malkani.
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High-mercury fish can have 10 to 20 times more mercury than low-level fish.
Mercury in fish – should this worry us?
Mercury is a naturally occurring element on Earth, so it is also found in the ocean and marine environments. “But you also have to add to that the infiltration of human-induced mercury into the water, such as coal burning, gold mining and various productive activities,” says Wu.
It is rare for mercury poisoning from fish or seafood to be so severe that it could cause serious injury or death. But exposure to even low doses of mercury is undesirable. This can affect the heart, brain, and other parts of the body.
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“Fortunately, the benefits of eating fish outweigh the potential risks of mercury,” says Malkani.
«If you eat seafood or fish once or twice a week, you shouldn’t worry too much about mercury. But you should be careful if you eat large amounts of these largest marine and ocean fish »he adds and emphasizes that the more such fish we eat, the more mercury accumulates in our body.
How to avoid mercury poisoning from fish?
As Malkani points out, we should choose small fish from sustainable sources. This will provide us with the right amount of omega-3 fatty acids and less mercury.
«The best options are salmon, trout, sardine, herring, mackerel and mackerel“- says the dietitian.
Malkani reminds that infants, pregnant and breastfeeding women should avoid eating fish that are high in mercury, such as shark, swordfish, tilefish, king mackerel and large-eyed tuna.
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