Recently, Japan has been criticized by many countries for the discharge of Fukushima nuclear wastewater into the sea, and the main concern is related to the contamination of seafood. Today, Japan abruptly announced that Fukushima blackfish is banned from the market because of excessive radioactive materials.
It is reported that this decision broke the situation that the restrictions on the listing of seafood in the sea area of Fukushima Prefecture were completely lifted since February last year.
In February this year, the Fukushima Prefectural Fisheries Cooperative Association found that the radioactive material contained in the body of the black scorpion in the prefecture exceeded the standard during the trial salvage operation, and has taken the initiative to stop the marketing of the black scorpion.
For this news, several popular science vss in aquatic fisheries on Weibo also made an introduction, and Li Angdu's father fish explained that the accident was again "クロソイ", the scientific name of this fish is Xu's Flat Squid /Sebastes schlegelii, which inhabits the near-shore rocky reef area and has no long-distance migratory habits.
The biological man who opened the aquarium in the V@, who is famous for recognizing fish, said that Hsu's flats live near the shore, and he also mentioned that Fukushima's seafood and agricultural products have long been synonymous with street rats and garbage goods in Japanese supermarkets in Japan.
After the Fukushima nuclear power plant accident in 2011, the seafood in the local waters was exposed to the news of excessive nuclear radiation from time to time, and until now many countries still prohibit the import of seafood products produced in Fukushima, Japan.
Fish has long been considered one of the healthiest foods we can eat.
But with the rise of alternative plant-based fish meat, coupled with growing concerns about ocean sustainability and carbon footprint, whether we need fish in our diets is becoming a question. The Food and Agriculture Organization of the United Nations reports that fish stocks in the biosustainable range have fallen from 90 percent to less than 66 percent today, according to the Food and Agriculture Organization of the United Nations.
At the same time, concerns about mercury and other pollutants mean that, for example, women who are pregnant or breastfeeding are advised to eat less of certain fish.
So, is eating fish healthier, or does it bring more health risks?
heavy metal
One of the biggest concerns in recent decades has been that fish can carry harmful levels of pollutants and metals.
One of the most concerned is polychlorinated biphenyls (PCBs). Although PCBs were banned in the 1980s, before they were banned, these industrial chemicals were already used in large quantities around the world and still lingered in our soils and waters. PCBs can have adverse health effects on everything from the immune system to the brain. Although PCBs are found in everything from dairy products to drinking water, the highest levels of PCBs are found in fish.
Fish carry pollutants and metals that can reach harmful levels
Joseph Napier, head of science at the Lausanne Research Centre in Hertfordshire, England, said limiting PCB intake from fish could be counterintuitive.
For wild fish that are directly caught for food, the potential problem of toxic compound accumulation in their bodies is more worthy of attention. Because fish are farmed, the food we feed them from the ocean has been washed to remove toxic substances, so farmed fish are generally safer than wild fish.
However, this is not always the case. PCB levels also fluctuate with the seasons.
Although we generally believe that farming fish is more beneficial to our health and the environment, large-scale aquaculture also has its own problems, such as causing marine pollution, becoming a hotbed of disease, and transmitting diseases to wild fish.
The Uk's National Health Service (NHS) has recommended that pregnant and lactating women should reduce their intake of fish that may be more abundant in PCBs or other pollutants (e.g., dioxins), such as reducing the number of servings per week to around 140 g per serving. These fish include oily fish such as salmon and sardines, as well as non-oily fish such as crabs and sea bass.
Because oily fish such as herring have higher levels of toxins (i.e., PCBs), pregnant women should not consume more than two servings of these fish per week.
Another source of concern is metallic mercury, a neurotoxin that can enter the placenta and affect infant development. There are numerous links between mercury intake and cancer, diabetes, and heart disease. While other foods, such as vegetables, also contained mercury, one study found that 78 percent of the subjects' mercury intake came from fish and seafood.
The mercury levels in fish are high enough for the U.S. Food and Drug Administration (FDA) to recommend that pregnant women limit their intake of certain common fish, including halibut and tuna, to no more than once a week.
But Napier also said the concerns about the accumulation of heavy metals in fish are somewhat exaggerated. The problem, he said, exists only in particularly long-lived fish, such as swordfish. Swordfish can survive for 15 to 20 years. Swordfish have a mercury content of 0.995 PPM, while salmon with an average lifespan of 4 to 5 years have a mercury content of about 0.014 PPM. Although research is still ongoing, the U.S. Environmental Protection Agency has proposed that for pregnant women, the average allowable amount of mercury per meal is 0.46 PPM if consumed once a week.
However, the problem is getting worse. As the global climate warms, there is evidence that mercury levels in the oceans may rise. The study found that as the permafrost of the Arctic gradually melts, the mercury contained in it also flows into the waterways.
Although the risk of mercury is small, we get much more benefits from fish, especially marine omega-3 fatty acids.
fatty acid
Oily fish, including salmon, tuna, sardines and mackerel, are rich in the marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Therefore, it is widely believed that consuming these oily fish can reduce the risk of cardiovascular disease.
Some plants are also rich in omega-3s, such as flaxseeds and walnuts. However, these plants are also rich in a third fatty acid, α-linolenic acid (ALA). A 2014 study concluded that the heart health benefits of plant Omega-3s may be no less than those of EPA and DHA, but no other study has supported this argument. However, both algae supplements and edible seaweed are rich in EPA and DHA.
EPA and DHA both play an important role in the body's metabolic processes, but we cannot effectively produce these two fatty acids in our bodies. Therefore, it is very important to make them part of our daily diet.
Our brain, retina, and other special tissues contain large amounts of DHA. Together with EPA, DHA helps us fight inflammation in our bodies, which is often associated with a higher risk of heart disease, cancer and diabetes.
Philip Calder, head of human development and health at the University of Southampton in the UK, said: "Demographic data studying the health benefits of marine omega-3s have always been consistent and convincing, and also show that people who consume more EPA and DHA have a lower risk of dying from common diseases, particularly heart disease. ”
One way to supplement Omega-3s while avoiding the potential harm caused by ingesting metal mercury is by taking fish oil supplements. However, a recent study commissioned by the World Health Organization (WHO) that, after looking at the efficacy of omega-3 supplements in various health outcomes, found that taking these supplements did not produce the same effects as edible oily fish.
Although you can get Omega-3 from fish oil supplements, it is not as effective as directly consuming oily fish.
Our bodies are accustomed to metabolizing whole foods, rather than a small subset of specific nutrients.
Lee Hopper, one of the researchers at the WHO study and a reader at the University of Eastern Anglia, added: "Our study found that omega-3 supplements have limited efficacy in reducing the risk of death from coronary heart disease. ”
About 334 people took Omega-3 supplements for four or five consecutive years before one person could not die of coronary heart disease.
But there is still a problem with population studies like those conducted by Hopper. Although some oily fish, such as sardines, are not expensive, fish-related diets are generally more expensive. It is also widely believed that socioeconomic status affects health outcomes. So, families who eat more fish may also have higher incomes and healthier lifestyles.
Researchers often take these confounding factors into account, but they may not be able to take into account every factor that may affect the results of a study. The WHO report is a review of 79 studies, each of which will differ in the way in which participants' socioeconomic status is controlled.
Fish-related diets are generally more expensive – so are those who eat more fish generally earn higher and healthier?
However, there are also problems with intervention trials. An intervention trial is when subjects are randomly assigned to a small group and then evaluated for intervention behavior (e.g., taking omega-3 supplements). Calder said it was also difficult to analyze the potential health effects of EPA and DHA deficiencies through intervention trials because subjects had different levels of omega-3s before the trial began.
In addition, studies have shown that the health effects of fish on each person may also be different, depending on each person's ability to transform EPA and DHA precursor forms. Calder said the difference may be due to a person's overall eating habits and lifestyle, but genetic differences can also be a factor.
Another factor that affects the health benefits of fish is the way fish is cultured.
Marine ecosystems are rich in Omega-3: small fish eat marine plankton, big fish eat small fish, and finally the entire food chain passes Omega-3 to humans. But the ecosystem of farmed fish is different, and most of us actually eat farmed fish. Napier said: "In aquaculture farms, it is just thousands of fish kept in one cage. Farmers feed them what they eat. ”
Like their companions in the wild, farmed fish usually eat smaller fingerlings. However, what is different is that in the wild, big fish can eat a wide variety of small fish. Fish on farms often eat food made from Peruvian anchovies.
Even if global aquaculture is expected to maintain growth, the aquaculture industry is already fishing for anchovies in order to survive. According to the Food and Agriculture Organization of the United Nations, the increasing demand for fish oil supplements means that the amount of fish oil contained in the fish feed used to feed farmed fish is decreasing, which in turn means that the content of Omega-3 in the farmed fish we eat is also decreasing.
The increasing demand for fish oil supplements means that the content of Omega-3 in the farmed fish we eat is decreasing.
The amount of fish oil produced in the ocean each year is limited, and we have just a few. If aquaculture continues to grow and the total level of fish oil, the most important nutrient you need to add to people's diets, remains the same, the amount of fish oil in fish feed can only be diluted continuously.
A 2016 study found that EPA and DHA levels in farmed salmon fell by half in a decade. Even so, Napier said, farmed salmon still contains more Omega-3 than wild salmon. "Wild salmon in the Atlantic Ocean are famous for migrating fish; they're actually a lean animal," he said. Wild salmon rarely hoard fat, and they consume all the calories they eat. ”
Brain-healthy food
In addition to Omega-3, fish has other beneficial nutrients, including selenium (which protects cells from damage and infection), iodine (which maintains a healthy metabolism), and protein.
Fish has long been known as a "brain food". A recent study suggests that fish have this reputation, not only because they are rich in omega-3 fatty acids (although some studies have found a link between omega-3s and delaying cognitive decline).
After comparing the brain capacity of people who regularly ate fish and those who didn't eat fish, the researchers found that grilled fish was associated with more gray matter, not omega-3 content.
Cyrus Raj, an assistant professor of radiology and neurology at the University of Washington School of Medicine, said: "Health improvements or diseases can alter the volume of our brains. The more neurons in the brain, the greater the brain volume. ”
The researchers studied 163 subjects whose average age was in their 70s and nearly 80 years old. After comparing their fish-eating habits with MRI scans, the researchers found that subjects who ate fish every week had a larger brain volume than those who did not eat fish—mainly concentrated in the frontal lobe (an area important for attention concentration) and the temporal lobe (important for memory, learning, and cognition).
The relationship between fish and the brain may be due to the fact that fish have anti-inflammatory effects, as this process affects brain cells when the brain responds to relieving inflammation.
This means that you can improve your brain health and prevent Alzheimer's by eating fish in a simple way. To beat dementia as much as possible, Raj suggests that after turning twenty or thirty, people should start eating fish at least once a week.
Another reason why fish is good for health is that it can replace the less healthy foods in our diets. Hopper said: "If we eat more fish, then naturally, we eat less other food. ”
Another reason why fish is good for health is that it can replace the less healthy foods in our diets.
But, Calder said, because there is no strong study showing that people who don't eat fish have obvious health problems, it's hard to assert that fish is essential for people's overall health. However, there is no doubt that Omega-3 can improve health and reduce the risk of developing the disease.
But how healthy fish really is could be a topic of long-term debate. Since fish is not a sustainable food source, research will now focus on solving this sustainable problem, such as how to get more algae and more fish oil, rather than delving into fish.
Of course, individuals can make their contribution by choosing the most sustainable fish. For example, a guideline from the Marine Conservancy lists the best fish, and 50 of the 133 species of fish are listed as the most sustainable. Fortunately, good "options" include the favorite farmed salmon, prawns, cod, mackerel, mussels, oysters and farmed halibut.
News synthesized from: fast technology, Sina technology