Heavy metals, a term that seems hard to associate with food. In fact, these "toxic" heavy metals have begun to slowly seep into our food.
Recently, Luo Yunbo, Dean of the College of Food Science and Nutritional Engineering at China Agricultural University, made a startling remark at the "2009 China Food Safety High-Level Forum": Compared to the frequent adulteration of food, it is difficult to experience in daily life the excessive content of toxic and harmful substances such as drug residues and heavy metals in food. However, its potential threat to our country's food safety is greater! Among them, lead and cadmium pollution problems are prominent, with 36% of dietary lead intake exceeding safety limits, especially in century eggs. The level of cadmium contamination is also high, mostly found in mollusks and crustaceans.
So, how much heavy metal are we actually eating? Where do they come from? How can ordinary people protect themselves?
Three Channels of Heavy Metal Intake
According to experts, in our daily lives, we mainly ingest heavy metals through the following three channels.
First, environmental pollution (mainly air pollution, water pollution, and soil pollution) leads to excessive heavy metals in aquatic products, fruits, and vegetables, with aquatic products being the most severely affected.
>Wang Cunxin, a seafood expert at the Institute of Oceanography of the Chinese Academy of Sciences, told reporters that in recent years, due to the discharge of some industrial wastewater into the sea, some commonly eaten seafood has also been contaminated, and has been tested to contain harmful heavy metals such as mercury and zinc. >He Hongju, a researcher at the National Engineering Research Center for Vegetables, stated that there are two main sources of heavy metals in vegetables: heavy metal elements in the soil are absorbed by plants through the soil solution, and heavy metal elements in atmospheric dust are directly absorbed through plant leaves. A professor of food safety at China Forestry University, who wished to remain anonymous, said that fruits are less contaminated by heavy metals than vegetables because the problem of irrigating vegetables with sewage is more serious, although the peels of fruits can also be affected to a certain extent.Second, food is contaminated during processing or storage.
The popcorn made in large pots by vendors on the streets in the past was quite problematic because the container coatings contained lead. Century eggs are also a type of food that is easily contaminated with lead. In the traditional preservation process of century eggs, heavy metals such as lead or copper are often added to the soaking solution to coagulate the protein. However, due to improvements in technology, this risk has now been reduced.
In food packaging, there are also some potential dangers. Dong Jinshi, Secretary-General of the Beijing Environmental Protection Tableware Association, stated that due to printing quality issues, lead in the ink of some packaging bags can "contaminate" food. For example, the tubes used for holding popcorn, and the paper bags used on the street for "Diao Sha Shao Bing" (a type of flaky pastry) and "Rou Jia Mo" (Chinese hamburger).
Third, ingesting heavy metals through daily use items.
This first involves heavy metals in drinking water. Fei Hong, the technical person in charge of the Health Drinking Water Professional Committee of the China Health Promotion Association, introduced that China's current drinking water pollution mainly has two aspects:
One is mercury pollution. Direct discharge of industrial wastewater allows mercury pollution to seep into groundwater, and it is very difficult to remove mercury when tap water is treated. This type of pollution mainly exists in some small towns where industrial wastewater is discharged relatively casually.
The second is lead pollution, which mainly comes from copper water meters, faucets, and galvanized water pipes containing lead. The longer the water pipes are used, the lower the PH value of the tap water, and the greater the degree of lead contamination.
Stainless steel and ceramic tableware used in daily life are also important sources of heavy metal contamination. Dong Jinshi stated that to prevent rust, stainless steel tableware contains a certain amount of chromium and nickel. If the surface coating of the tableware is damaged, chromium and nickel will be released, endangering human health. The colored patterns printed on the glaze of ceramic tableware also contain a certain amount of lead.
Children and the elderly are high-risk groups
What are the harmful effects of heavy metals on the human body? Jing Hao, a professor at the College of Food Science at China Agricultural University who researches food safety and toxicology, explained that chemically, metals with a specific gravity greater than 5 and a density greater than 4.5g/cm3 are called heavy metals, such as copper, lead, zinc, iron, cobalt, and nickel. The aluminum we often talk about does not belong to heavy metals. Some heavy metals such as manganese, copper, zinc, and iron are trace elements needed for human life activities, but most heavy metals such as mercury, lead, and cadmium are not essential for life activities, and all heavy metals are toxic to the human body above a certain concentration.
This harm mainly has three aspects:
First, it harms the liver. Heavy metals combine with heme in the blood, damaging the liver and leading to cirrhosis, liver cancer, etc.
Second, it damages the circulatory system. After heavy metal poisoning, blood viscosity increases and oxygen content decreases. In severe cases, it can lead to symptoms such as suffocation and shock.
Third, it harms the nervous system, inhibiting and interfering with its function.
Jing Hao emphasized that for children and the elderly, the harm of heavy metals is greater. Because children have low immunity and the elderly have a slower metabolism, it can lead to difficulty in excreting heavy metals. Therefore, these groups should pay more attention to their diet.
Guarding the entrance, staying away from heavy metals
During the interviews, all experts reminded that although heavy metals in food cannot be reduced by washing, soaking, heating, or stir-frying, as long as we guard the "entrance," we can stay away from heavy metals.
Don't eat the head and内脏 of fish
Heavy metals mainly accumulate in the internal organs and head of fish, so these parts can be discarded when eating. Soak the fish in water for as long as possible before eating, and dip it in vinegar when eating, which can promote the decomposition of harmful metals.
>In terms of aquatic species, flatfish, yellow croaker, and "Pian Kou Yu" (a type of flounder) live near the bottom of the coast and are severely polluted, while mackerel, hairtail, etc., are less polluted and relatively safe. Among freshwater fish, the degree of contamination in snakehead carp, common carp, and crucian carp is relatively greater, while grass carp, silver carp, etc., which mainly eat aquatic plants, are relatively safe.Eggplant, cauliflower, and celery pose the greatest risk
Generally speaking, the content of heavy metals in vegetables is in the order of leafy vegetables > root vegetables > fruit vegetables. Different types of vegetables also have different absorption rates for different types of heavy metals. According to current research, eggplant has a strong ability to absorb lead and cadmium, cauliflower has a strong ability to absorb chromium, and celery has a strong accumulation ability for lead, cadmium, and chromium. In terms of exceeding the standard rate, these three vegetables exceed the standard the most.
Eat more detoxifying foods
By consuming foods that support the liver and kidneys, you can assist in detoxification. For example, carrots, garlic, grapes, and figs can help the liver detoxify. In addition, it is also necessary to supplement more protein foods, such as legumes and high-fiber foods. Foods with high dietary fiber can also accelerate the excretion of heavy metals.
Choose the right tableware
When using stainless steel tableware, try not to hold salt, vinegar, soy sauce, etc. Salt has a moisture-absorbing effect and can corrode the coating. When buying tableware, you can touch it and smell it. Porcelain that feels smooth and has no ink smell is of better quality. To completely avoid risks, you can buy pure white ceramic tableware without patterns.
Reduce exposure to car exhaust
The gas produced from burning leaded gasoline, when inhaled by the human body, can lead to an increase in lead content in the body. It is recommended to close the car windows when waiting at traffic lights to prevent inhalation.
Choose environmentally friendly paints and coatings
Some paints and pigments also contain lead. If a child accidentally swallows them, acute lead poisoning may occur.