Aquaculture experts recommend eating less of these 6 types of fish, as they may contain excessive levels of heavy metals.

(SOURCE: China Women’s News)

Reprinted from: China Women’s News

From a nutrition perspective, most fish are rich in high-quality protein and polyunsaturated fatty acids. However, in terms of food safety and taste, there are some differences among different types of fish.

Fishery experts rarely eat 6 kinds of fish

Professor Chen Shunsheng of the College of Food Science at Shanghai Ocean University advises that the following kinds of fish are best eaten less often.

■ Large predatory fish, which may accumulate heavy metals

The U.S. Food and Drug Administration classifies fish into three major categories based on contamination with heavy metals such as mercury. Chen Shunsheng further subdivided them according to conditions in our country:

Not recommended for consumption: Atlantic mackerel, bigeye tuna, and other large predatory fish.

Large predatory fish, which may accumulate heavy metals. As contamination moves along the food chain, the concentration of pollutants such as heavy metals contained in plankton in the water, small herbivorous fish, and large predatory fish increases step by step, showing a clear biological magnification effect.

General recommendation: marine fish such as grouper, silver cod, yellow croaker, halibut, and so on, as well as omnivorous freshwater fish such as grass carp, silver carp, bighead carp, and carp.

Best recommendation: pomfret, freshwater perch, tilapia, rohu tilapia, salmon, and other herbivorous fish or upper-layer freshwater fish such as grass carp and Wuchang bream.

■ Colorful fish, with potential poisoning risks

The better a fish looks on the outside, the stronger its toxicity often is. For example, coral fish: the ciguatoxin it carries is highly heat-stable; cooking cannot destroy it. If accidentally eaten, it may cause nausea, vomiting, and diarrhea, and even nerve paralysis and breathing difficulties. In severe cases, it may be life-threatening.

■ Sashimi (raw fish), easy to get infected with parasites

In freshwater fish such as crucian carp and bream, there are parasites shared by humans and animals, such as liver flukes, lung flukes, and tapeworms. Eating them raw may allow the parasites to grow inside the human body, damaging the digestive system, immune system, and so on.

Therefore, freshwater fish must absolutely not be eaten raw. Marine fish that have lived in freshwater or brackish water also must not be eaten raw. For example, wild salmon that migrates to the freshwater estuary may likely be parasitized with Angiostrongylus cantonensis and sparganum tapeworm.

Eating sashimi may also infect pathogenic bacteria such as Vibrio parahaemolyticus, Salmonella, Vibrio cholerae, which can lead to vomiting, diarrhea, and other symptoms. In severe cases, it may be life-threatening.

In addition, sashimi may also carry viruses such as hepatitis A virus and norovirus, which can cause hepatitis, acute gastroenteritis, and so on.

It is recommended to eat fish only after cooking. If you really want to eat it raw, it is recommended to choose marine fish that has lived in the sea all along. After buying it home, freeze it first (at below 0°C, i.e., −20°C) for about a week, which can help kill Angiostrongylus cantonensis.

■ Overly pan-fried or deep-fried fish: more harmful substances

Fish are rich in polyunsaturated fatty acids, which help protect the cardiovascular system and improve brain health. However, after being fried at high temperatures, these “good fatty acids” undergo oxidation reactions, generating various fatty acid oxidation products, heterocyclic amines, polycyclic aromatic hydrocarbons, and more.

Among them, heterocyclic amines have very strong mutagenic and carcinogenic properties. Also, after frying, the fat content of fish increases, which is not good for controlling blood lipids.

■ Dried fish with a rancid smell: high risk of spoilage

Dried fish are rich in polyunsaturated fatty acids and are prone to oxidative spoilage, resulting in a rancid smell. After eating, it may cause digestive system symptoms such as nausea, vomiting, abdominal pain, and diarrhea. Long-term consumption may also induce digestive ulcers, fatty liver, and cancer, among others.

In addition to smelling it, when buying dried fish you should also pay attention to appearance. Generally, dried fish of better quality are yellowish-white in color. Some dried fish have slightly scorched yellow edges; the fish slices are flat, the slice shape is intact, and the tissue fibers are clearly visible.

■ Poorly cured salted fish: may cause cancer

Salted fish have a high salt content, and they also contain a certain amount of nitrites. Long-term consumption in large quantities may cause cancer.

However, salted fish are not completely impossible to eat. It is recommended to choose products that are well cured. Their surface should be glossy and have the rich, inherent fish aroma. After fermentation by beneficial bacteria, the nitrite content is low, so eating a small amount occasionally is safe.

Poorly cured salted fish often turn black; beneficial bacteria are destroyed and the nitrite content is high. Try not to eat them.

These fish are fattest in winter and spring

An expert at the National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, Zhang Shuangqing, said that winter and spring are the early stage of reproduction for many fish, so they are more plump and flavorful.

■ Ribbonfish

In winter, ribbonfish migrate from north to south to overwinter, forming a “ribbonfish run.” At this time, ribbonfish have rich oils and fats, thick flesh, and a delicate taste.

Ribbonfish belong to deep-sea fish and are rich in protein, polyunsaturated fatty acids, and relatively abundant nutrients such as calcium, phosphorus, iron, iodine, and vitamins B1, B2, and vitamin A. Among these, the calcium content is particularly plentiful.

■ Crucian carp

Crucian carp is a type of freshwater fish that is relatively cold-tolerant. In winter, it can still feed in the water. In order to store energy to withstand the cold, it eats itself especially fat and sturdy in winter. It has a high protein content, and the levels of lysine and threonine—amino acids essential to the human body—are also relatively high.

■ Yellow croaker

Each year, from the middle of the 11th lunar month to the first lunar month is the winter fishing season for yellow croaker, when the flavor is excellent.

Yellow croaker has relatively prominent levels of phosphorus and iodine. They help maintain vitamin A needed for vision and DHA needed for brain development, and the DHA content (0.33 grams of DHA per 100 grams of fish meat) is much higher than that of ordinary fish. The flesh is soft and elastic, and the taste is fresh and fragrant.

■ Freshwater perch

In winter, as temperatures drop, the growth of algae and bacteria in fish ponds is greatly reduced, making the water clearer. The earthy “muddy” smell of perch is also significantly reduced. Perch with fewer spines and tender meat tastes much like mandarin fish, but among freshwater fish, perch has a comparatively higher DHA content, while mandarin fish’s DHA content is negligible.

■ Grass carp

Every year from the Winter Solstice to the end of the year, in fish ponds in the plains south of the Yangtze River, grass carp not only grow big and fat but also have a low price. Grass carp’s protein content can reach 20.1%. In addition to containing plenty of vitamin A, it is also rich in selenium, an essential trace element for the human body (37.69 micrograms/100 grams).

To eat fish for health, you also need to know how to cook

Different cooking methods for fish have different effects on health, and the fish they are suitable for also differ.

Most recommended: steamed or lightly stewed in clear broth

While effectively preserving polyunsaturated fatty acids and multiple nutrients in fish, it does not put an excessive burden on the body.

Suitable for steaming: catfish, perch, mandarin fish, yellow croaker, and so on. These fish have fewer bones, tender flesh, and excellent taste with a mild fishy smell.

General recommendation: make fish soup and braise

The former is simmered for a longer time, which may destroy some nutrients; the latter often includes a lot of oil and salt.

Common for fish soup: snakehead fish, yellow croaker, crucian carp, and so on. Flavor compounds can be well dispersed in the soup, making it rich, smooth, and delicious.

Suitable for braising: carp, silver carp, eel, grass carp, ribbonfish, and so on.

Least recommended: pan-frying and deep-frying in oil

The retention rate of omega-3 fatty acids is lower after deep-frying or pan-frying, and cholesterol oxidation is more serious. At the same time, cooking at overly high temperatures also generates various harmful substances such as fatty acid oxidation products, heterocyclic amines, and polycyclic aromatic hydrocarbons.

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