Try to eat as little as possible of these kinds of fish, and the heavy metal content may exceed the standard!

Chinese like to eat fish, but with the improvement of living standards, people's requirements for dietary safety are getting higher and higher, many people are worried about fish, aquatic products will have heavy metal pollution, such as the risk of mercury pollution, how to choose fish, how to eat healthier? These questions, let's answer them one by one~

The benefits of eating fish are not just for the brain

As a kind of "white meat", fish has a lower content of calories and saturated fat, and a relatively higher content of minerals such as calcium than pork, beef and mutton, which can be used as a high-quality protein source during weight loss and fat loss.

In addition, the glutamic acid and aspartic acid rich in fish meat are umami amino acids, which give fish its own umami taste. This allows us to cook fish without going through heavy oil, heavy salt, high sugar deep processing, just steamed or boiled soup, it can be delicious and attractive.

In addition, many fish (especially fatty marine fish and some freshwater fish) have a high content of unsaturated fatty acids such as DHA, which is also beneficial to promote the development and health of brain cells and visual cells.

Comparison of the nutrient content of fish with pork and beef
class	Protein (g/100g)	Fat (g/100g)	钙（mg/100g）	热量（kcal/100g）
sea bass	18.6	3.4 (Saturated Fat 0.8)	138	105
Pork (lean)	20.3	6.2 (Saturated Fat 2.48)	6	143
Beef (lean)	21.3	2.5 (Saturated fat 1.4)	5	113

In addition, many fish are not low in vitamin D, while other common foods are not high in vitamin D. For people who are deficient in the sun and vitamin D in their foods, it is good to eat more fish.

Is there heavy metals in fish?

Which fish are higher in heavy metals?

Some heavy metals in the water body, such as mercury, lead, arsenic, cadmium, etc., can be continuously enriched in the fish body through the water body or algae containing heavy metals, and the metabolization time is very long.

Historically, large fish in the deep sea were thought to be more susceptible to heavy metal contamination than freshwater fish. There is some truth to this conclusion, and it is also supported by the corresponding research results [1]. However, heavy metal pollution in fish is also related to factors such as different sea areas, fish species and age.

On a global scale, there is such a general pattern:

Carnivorous fish have higher levels of heavy metals than omnivorous and herbivorous fish;

Larger fish have higher levels of heavy metals than smaller fish;

Older fish have higher levels of heavy metals than younger fish.

Large carnivorous fish such as sharks, swordfish, tilefish, mackerel, bigeye tuna, and marlin are listed as "not recommended" (high mercury) by the US Food and Drug Administration [2].

Different sea areas also have an impact on the weight metal content of fish.

According to a study findings, in the case of the mainland, the mercury levels in wild fish in the Bohai Sea region of the East China Sea are higher than those in farmed fish, and in the South China Sea, the mercury levels in marine farmed fish are higher than those in wild fish [3]. At the same time, carnivorous fish such as grouper, goldfish, catfish, and mandarin fish showed high levels of mercury in this survey, which is also in line with the general pattern we mentioned earlier.

The Centre for Food Safety (CFS) also has tips on mercury levels in fish, including carnivorous fish with high mercury content, such as alfonsino snapper, swordfish, tilefish, bigeye tuna, blue flag tuna, sailfish, shark, etc. This is similar to the "not recommended" category given by the US Food and Drug Administration [4].

In addition, it is important to remind everyone that even if the same fish is the same, you should avoid choosing too much weight, mainly because a larger weight means that the fish is older, not only the meat is not necessarily tender, but it is also easy to enrich more heavy metals through eating and drinking.

The stock copyright picture, reprinting and using may cause copyright disputes

However, it is reassuring to know that the above survey results also point out that the mercury content of mainland aquatic products is far below the national standard limit as a whole.

The risk of health exposure is generally acceptable at the 1.6 μg/kg body weight weekly tolerable intake of food methylmercury published by the Joint Expert Committee on Dietary Exposures and Food Additives, considering that fish intake is not up to standard in the continental population, and that the overall health exposure risk is acceptable [3].

Whether it is the U.S. Food and Drug Administration, the Hong Kong Center for Food Safety, or the dietary guidelines for mainland residents, the low-mercury and high-DHA fish recommended include: salmon, sea bass, sardines, anchovies, large yellow croaker, tilapia, etc. Some shellfish, such as clams, crabs, oysters, scallops, etc., are also safe for low mercury, and they are also available at a low price.

I want to stay away from heavy metals as much as possible

There is also a particular way to eat

In addition to familiarizing yourself with which fish may be higher in heavy metals, there are also some tips to minimize our risk of ingesting heavy metals during the cooking process.

1

Try to avoid the several large fish that are not recommended above

2

Pair it with ingredients that promote the excretion of metals from your body weight

The human body has the ability to remove and expel heavy metals. As long as you don't eat a lot of fish with high heavy metal content for a long time, the possibility of causing harm is generally not great. If you can add some foods that promote the excretion of heavy metals by the human body during the cooking process, such as coarse grains rich in dietary fiber, vegetables and fruits, you can better prevent injuries.

3

Variety of foods

We can give full play to the advantages of food diversification, not only to reduce the use of fish that may contain heavy metals, but also to give full play to the health effects of different types of nutrients in different foods, so as to minimize, share and offset the health risks that may be caused by heavy metal intake.

For example, if we are worried that the presence of heavy metals will harm the brain and nervous system, we can do this by eating more foods that are good for brain and nervous system health, such as salmon rich in DHA, plain nuts, etc. If you are worried that heavy metals will increase the metabolic burden on the liver, you can eat more fresh fruits and vegetables rich in vitamin C.

All in all, food diversification is beneficial in terms of enriching nutrition, preventing chronic diseases, and combating the health hazards of heavy metals.

Finally, the intake of fish should also be limited in quantity. According to the recommendations of the Dietary Guidelines for Chinese Residents, normal adults are recommended to eat fish twice a week, about 300~500 grams. When cooking fish, it is better to steam it, and try to avoid frying and grilling, so as not to destroy the unsaturated fatty acids in the fish, and also prevent the increase in the content of carcinogens due to frying and grilling.

bibliography

[1] Ye Haimei, Wu Yongning. Comparison of Heavy Metal Indexes in Fish and Processed Products[J]. Chinese Journal of Food Hygiene, 2009, 21(3): 273-276.

[2]https://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm115644.htm

[3] Xu Xi, Yan Chonghuai.Analysis of total mercury pollution characteristics and health exposure assessment of aquatic products in China[J]. Chinese Journal of Food Hygiene, 2022, 3(17): 104-109.

[4]https://www.cfs.gov.hk/sc_chi/index.html

Planning and production

Author丨Wang Lu is a registered dietitian

Audit丨Ruan Guangfeng, Director of the Science and Technology Department of Kexin Food and Nutrition Information Exchange Center

Planning丨Yang Yaping

Editor丨Yang Yaping

Reviewer丨Xu Lai Linlin