Recently, the New York City Department of Health advised residents to be cautious when eating crab roe, citing its high content of environmental pollutants such as polychlorinated biphenyls (PCBs), dioxins, and cadmium, which may increase cancer risk. With the season for Chinese mitten crabs upon us, the question arises: should we or should we not eat this delicacy?
Crab roe and paste are chemical accumulators
Many people eat crabs for the delicious roe and paste. However, according to a recent report by a Chinese-language newspaper in the U.S., the New York City Department of Health has listed crab roe and paste as parts to be avoided, as these areas concentrate chemical substances. The department reminded that the cooking juices from crabs should not be used for sauces and should not be given to children to avoid affecting their development.
Nutrition experts point out that in terms of nutritional value, seafood and freshwater fish are indeed good choices. They are mostly low in fat and high in protein, and their content of trace elements such as zinc, copper, selenium, and iodine is also relatively high.
However, nutrition experts also note that seafood and freshwater fish pose considerable health risks, including parasites, pathogenic bacteria, environmental pollution, allergic reactions, and elevated uric acid levels. The danger mentioned by the New York Department of Health this time is persistent environmental pollutants.
Environmental pollution refers to pollutants from the farming environment entering the food. Aquatic products like fish, shellfish, shrimp, and crabs are constantly in the water, inevitably absorbing pollutants from it. Algae and plankton in the water absorb pollutants from the sediment and water; fish, shrimp, crabs, and shellfish then easily swallow these pollutants from the algae and plankton, concentrating them in their own bodies.
Many toxic and harmful pollutants are chemically stable and do not break down for over a century, remaining in the environment. After seeping into soil and water sources, they inevitably enter plants and animals. These pollutants are easy to ingest but difficult to excrete. A contaminated animal accumulates more pollutants with each day it lives; the longer it lives, the more it accumulates. Generally, pollutant concentrations increase tenfold or more with each step up the food chain, which is the "law of biological magnification" for pollutants.
On the other hand, crustaceans and shellfish have a natural tendency to accumulate certain heavy metals. If the water contains a certain level of pollution, it can become magnified many times over in seafood and freshwater fish.
Furthermore, nutrition experts remind that there is no such thing as farmed crab in the United States, so all crabs there are wild. However, because wild plants and animals are not inspected, their safety and quality are not controlled. In contrast, farmed crabs and crayfish are relatively safer. This is because farming waters are included in regulatory oversight, are usually located away from industrial production areas and chemical waste pollution zones, and have monitoring mechanisms for product safety and quality, making them generally more reassuring.
Four tips for eating crab safely
So, what can be done about the environmental pollutants in seafood and freshwater fish?
Nutrition experts point out that the reason environmental pollutants are so troublesome is precisely because their chemical properties are stable, and they cannot be removed by cooking. However, while the pollution problem in delicious seafood cannot be completely avoided, there are many ways to protect ourselves from the actual harm caused by environmental pollution.
First, purchase food from reliable sources. Do not eat wild food indiscriminately, do not buy food of unknown origin, and prioritize food with a traceable source.
Second, consume in moderation. To avoid excessive intake of environmental pollutants, seafood and freshwater fish should be eaten in moderation and not in large quantities. According to the recommendations of the Chinese Nutrition Society, a daily intake of about 40-75 grams (excluding shell, spines, etc., pure meat weight) will not lead to excessive protein intake, nor will the environmental pollutants from seafood reach a harmful level.
Moreover, the human body has strong detoxification and excretion capabilities. As long as the intake of harmful substances is limited to what the body's detoxification system can handle, it will not cause actual harm. It is a very unsafe practice for many people to overindulge in seafood and freshwater fish to the point of being "helped in and out by a wall."
Third, reduce the frequency of consumption, that is, eat it less often. If the body hasn't had time to process and excrete the pollutants from the last meal before new ones arrive, it is inevitable that a cumulative toxicity problem will arise from persistent pollutants. Finally, maintain a balanced diet by eating more foods rich in dietary fiber, vitamins, and phytochemicals. Much dietary fiber can help the body excrete heavy metals and fat-soluble pollutants, while vitamins and some phytochemicals can help the detoxification system work at full efficiency.