Fish is recognized as one of the healthiest of our human foods.
But due to the growing popularity of plant-based alternatives and growing concerns about the sustainability and carbon footprint of seafood, some are beginning to question whether we need fish in our diets. Since 1974, fish catches within biologically sustainable yield levels have declined from 90 percent to less than 66 percent today, according to the U.N. Food and Agriculture Organization.
And, fears of contamination of fish with the heavy metal mercury and other chemicals mean that pregnant or breastfeeding women should limit their consumption of certain fish.
So, is eating fish good or bad for your health?
Heavy metals
One of the biggest concerns about fish in recent decades has been the contamination of fish with contaminants and heavy metals that can reach harmful levels in fish.
One of these is polychlorinated biphenyls (PCBs), an industrial chemical that was banned in the 1980s but is still left in our soil and water in large quantities because of its widespread use around the world. The absorption of PCBs by the human body has the potential to produce a range of health problems, including damage to the immune system and brain. Although PCBs are present in all human foods, from dairy products to drinking water, the highest levels are generally found in fish.
Johnathan Napier, scientific director of the Rothamsted Research Institute in Hertfordshire, U.K., said it may be inconsistent with common sense to assume that PCBs can be avoided by eating less fish.
Toxic compounds accumulate in fish that may affect human health, but perhaps we should be more concerned about wild fish that are caught for human consumption,” he said. “And fish that are farmed in captivity are usually safer than wild fish because the artificially farmed feed has been cleaned or gotten rid of toxic compounds.
However, this is not absolute, and PCB levels in fish can vary with the seasons.
Although it is generally accepted that large-scale aquaculture is better for human health and the environment, there are some problems, such as farm wastewater that can pollute the ocean and farms that can be a source of spreading infectious diseases into the wild.
The NHS recommends that pregnant and breastfeeding women should limit their intake of fish that may contain PCBs, and other contaminants such as dioxins, to two servings per week. These include high-fat fish, such as salmon and sardines, and non-fat fish, such as crab and sea bass. One serving is about 140 grams.
Another concern is mercury, or mercury, a neurotoxin that may affect children’s development through the placenta. Many links have been found between mercury intake and cancer, diabetes and heart disease. While mercury is also found in other foods, such as vegetables, one study found that 78 percent of study participants got their intake of mercury from fish and seafood.
Because of the high levels of mercury in fish, the U.S. Food and Drug Administration (FDA) recommends that pregnant women limit their intake of some popular fish, including halibut and tuna, to once a week.
But Napier said concerns about the accumulation of heavy metals in fish are overblown. He said it is mainly those fish with particularly long lifespans that accumulate high levels of heavy metals in their bodies, such as swordfish, which can live 15 to 20 years. While the mercury concentration in swordfish is 0.995 parts per million (0.995 PPM), the average Life span of salmon is only four to five years, and the mercury concentration is much lower, at about 0.014 PPM. While studies of mercury levels in fish are still being conducted, the U.S. Environmental Protection Agency currently says that if a pregnant woman eats one serving of fish per week, her intake of mercury will only be a maximum of 0.46 PPM.
But the problem is destined to worsen, as evidence suggests that mercury levels in the oceans may rise as the planet warms. Studies have found that as Arctic permafrost melts, mercury sealed in the permafrost is released into the waterways.
The risk of ingesting mercury from eating fish is actually small, but the benefits gained are much greater, especially since the omega 3 fatty acids contained in marine life are particularly powerful, says Napier.
Fatty acids
Eating high-fat fish, including salmon, tuna, sardines and mackerel, can reduce the risk of cardiovascular disease, thanks to the fact that these marine fish contain two of the omega 3 (omega-3) fatty acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
Some plants that contain omega-3s, such as flaxseed and walnuts, have a third type of omega-3 fatty acid, primarily ALA. a 2014 study concluded that the heart health benefits of plant-produced omega-3s may be comparable to those of EPA and DHA from marine fish, but no other studies have been done to support this conclusion. However, you can find EPA and DHA in seaweed supplements and in edible seaweed.
Both EPA and DHA play a very important role in human metabolism, but the body cannot effectively synthesize these two fatty acids, so it’s really important to have both as part of our diet,” says Napier. “
We humans have large amounts of DHA, a fatty acid, in our brains, retinas and other specialized tissues. Along with EPA, DHA helps fight inflammation in the body, which is associated with a high risk of heart disease, cancer and diabetes.
Philip Calder, director of the Human Development and Health Research Program at the University of Southampton in the United Kingdom, said, “The findings of the data studying the effects of marine fish omega-3 on human health are consistent and compelling, all suggesting that people who regularly consume EPA and DHA fish are less likely to develop common diseases and die from them, especially heart disease. “
The alternative to not wanting to consume fish with high mercury levels to avoid harm to the body, but wanting to consume omega-3s, is to take fish oil supplements. However, a recent study conducted on behalf of the World Health Organization (WHO) found that omega-3 supplements were not as effective as consuming high-fat fish in terms of health effects.
Napier said, “The human body evolved to be fit to metabolize whole foods, not a single nutrient or a particular food component. “
Lee Hooper, a professor at the University of East Anglia in England and one of the researchers of the WHO Omega-3 Health Programme, added, “Our findings suggest that the beneficial effects (of supplements) are small in terms of reducing the probability of death from coronary heart disease. “
On average, she said, about 334 people would have to take omega-3 supplements for four to five years before one person would not die from coronary heart disease.
But there’s a problem with the study done by Hooper and others. Although some high-fat fish, such as sardines, are not very expensive, generally speaking, fish and other seafood are still part of a more expensive diet. It is widely believed that socioeconomic status affects health status, so, in short, families that eat more fish may also have higher incomes and healthier lifestyles.
Calder said researchers usually take these complex factors into account, but they can’t take into account all the factors that would skew study results. This WHO report is a comprehensive analysis of 79 studies, each of which controlled differently for the socioeconomic status of those who participated in the study.
And there were problems with the intervention trials on omega-3. In such trials, participants were randomly assigned to a group and then interventions such as measuring the amount of omega-3 supplements participants took were administered. Calder said it would be difficult to analyze, for example, what the health effects of EPA and DHA deficiencies in humans are, because the levels of omega-3 in participants’ bodies were already varied when they began participating in the trials.
In addition, the study showed that the health effects of eating fish may also differ to varying degrees for each individual, depending on the body’s ability to switch between EPA and DHA precursor forms. Calder said such differences may be related to a person’s overall diet and lifestyle, and genetic differences may also play a role.
Another reason for the varying health benefits of eating fish depends on the way the fish you eat is raised.
Omega-3s are phased in and passed throughout the marine ecosystem. Smaller fish eat ocean plankton, which are then eaten by larger fish, and eventually the entire food chain passes the omega-3 to humans. But the ecosystem for captive fish is different, and most people eat captive fish. In fish farms, thousands of fish are kept in net cages and eat what the fish farmers feed them,” says Napier. “
As in the wild, the artificially farmed fish are fed small fish. In the natural environment, however, large fish will eat a wide variety of fish. On farms, fish feed is typically fish meal made from Peruvian anchovies.
Although the global aquaculture industry is expected to continue to grow, the catch of Peruvian anchovies has reached the highest level the industry can sustain and is unlikely to increase further, Napier said. According to the UN Food and Agriculture Organization, the growing demand for fish oil supplements means that fish meal, which is used as feed for fish in farmed fisheries, is also containing less fish oil. This in turn means that the amount of omega-3s we consume from eating fish is also declining.
If aquaculture is expanding, but the amount of omega-3 fish oil that needs to go into the most important component of the human diet is completely fixed, it dilutes the amount of omega-3 in fish feed,” says Napier. would dilute the amount of omega-3 in fish feed. “
The 2016 study found that salmon raised in captivity had seen its EPA and DHA content drop by half over the past decade. Even so, captive-raised salmon still contains more omega-3 fatty acids than wild salmon, says Napier.
He explained, “Wild salmon have to migrate from the Atlantic to the river where they were born to spawn and are therefore very lean. Wild salmon can’t store fat during its migration; instead, it burns everything it eats into its stomach. “
Brain-boosting foods
In addition to omega-3s, fish has other beneficial nutrients, including the trace element selenium, which protects cells from damage and infection, iodine, which supports a healthy metabolism, and protein.
Fish has long been touted as a “brain food. A recent study suggests that this is not just because fish contains omega-3 fatty acids, but the study also found an association between omega-3 fatty acids and slower cognitive decline.
Researchers compared the brain volume of people who ate fish with those who did not and found that eating grilled fish was associated with gray matter volume in the human brain, but not with higher levels of omega-3.
Cyrus Raji, an assistant professor of radiology and neurology at the University of Washington School of Medicine, said, “Our brain volume also changes as health conditions and diseases improve. The more neurons you have, the more brain volume you have. “
The researchers compared the fish-eating habits and MRI scans of 163 participants whose average age was in their 70s. They found that compared to participants who did not eat fish, those who ate fish weekly had larger brain volumes located primarily in the frontal lobe, which is important for concentration, and in the temporal lobe, which is critical for memory, learning and cognition.
Raj said the association between eating fish and brain brain volume may be because fish has an anti-inflammatory effect because it can affect the growth of brain cells when the brain responds by slowing down inflammation.
This means that to enhance brain health to prevent Alzheimer’s disease is as simple as eating more fish in the diet,” Raj said. “To enable the brain to try to prevent dementia, Raj recommends starting to eat fish at least once a week when you are in your twenties or thirties.
Another reason fish is good for health is that it replaces unhealthy foods in our diet. Hooper says, “If we eat more fish, we generally eat less of everything else. “
However, Calder said, since there are no solid and reliable studies showing that people who don’t eat fish have major health deficits, it’s hard to say definitively that fish is essential to overall human health. But he added that it’s clear that omega-3s promote health and reduce the risk of disease.
Figuring out just how healthy fish are for humans may be a matter of opinion for a long Time to come. Because fish is not a sustainable food source, research now will probably focus on solving that problem, such as how to grow algae to produce omega-3 oils, rather than looking at fish for human health,” Calder said. “
As individuals, to help solve the seafood sustainability problem, there are options to buy the most sustainable fish species. The Ocean Conservancy, for example, has come up with a guide to good fish species, with 50 of the 133 fish on the list being the most sustainable “good” choices, and luckily Fortunately, many of these are our favorite fish, such as farmed salmon, shrimp, cod, mackerel, mussels, oysters, and farmed halibut.
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