By Dr. Mercola
Fish has always been the best source for the animal-based omega-3 fats EPA and DHA, but as levels of pollution have increased you have to be very choosy about which types of seafood you decide to eat.
If you’re not careful, the toxic effects from the pollutants in the fish will outweigh the benefits of the omega-3 fats. Meanwhile, many fish species have been overfished and are dangerously depleted. When choosing seafood for your family, it’s important to take not only your health into consideration but also that of the environment. As reported by National Geographic:1
“Fisheries for the most sought-after species, like orange roughy, Chilean sea bass, and bluefin tuna have collapsed. In 2003, a scientific report estimated that industrial fishing had reduced the number of large ocean fish to just 10 percent of their pre-industrial population.
Faced with the collapse of large-fish populations, commercial fleets are going deeper in the ocean and farther down the food chain for viable catches. This so-called ‘fishing down’ is triggering a chain reaction that is upsetting the ancient and delicate balance of the sea's biologic system.
A study of catch data published in 2006 in the journal Science grimly predicted that if fishing rates continue apace, all the world's fisheries will have collapsed by the year 2048.”
Why Farmed Fish Are Not a Good Option
Industrial fish farming, or aquaculture, is the fastest growing form of food production in the world.2 About half of the world’s seafood comes from fish farms, including in the US, and this is expected to increase. At first glance, farmed fish may seem like a good idea to help protect wild seafood populations from overfishing.
In reality, however, the industry is plagued with many of the same problems surrounding land-based concentrated animal feeding operations (CAFOs), including pollution, disease, and inferior nutritional quality.
It’s getting so bad that fish farms can easily be described as “CAFOs of the sea.” Many farmed fish are fed genetically modified (GM) corn and soy, which is a completely unnatural diet for marine life. Others are fed fishmeal, which is known to accumulate industrial chemicals like PCBs and dioxins.
Fish waste and uneaten feed litter the sea floor beneath these farms, generating bacteria that consume oxygen vital to shellfish and other bottom-dwelling sea creatures. Farmed fish waste promotes algal growth that harms the water’s oxygen content, posing risks to coral reefs and other aquatic life.
The close quarters where farmed fish are raised (combined with their unnatural diets) means disease can spread quickly, and because farmed fish are often raised in pens in the ocean, pathogens can spread like wildfire and contaminate any wild fish swimming past.
Concentrated antibiotics, pesticides, and other chemicals are also commonly used to fight diseases and parasites common to fish farms. One study found a drug used to kill sea lice also kills other marine invertebrates, can travel up to half a mile and persists in the water for hours…3
Farmed Fish May Contain Fewer Healthy Fats
If you’re eating fish you’re probably doing so, in part, to take advantage of their beneficial omega-3 fats. Fish in the wild, especially oily fish such as salmon, are a rich source of omega-3 fats. But levels of critical omega-3 fats may be reduced by about 50 percent in farmed salmon, compared to wild salmon, due to increasing amounts of grain feed.
That being said, farmed salmon are much fattier overall than wild salmon. The economic incentive to speed the growth of farmed salmon has led to the use of increasingly high-energy diets, which is why farmed grow so big.
High fat itself is not a problem, but what comprises that fat IS the problem. Farmed salmon are much higher in omega-6 fat—almost five times higher—and the typical American already gets 10 to 20 times too much omega-6 as they need.
It’s not only farmed salmon that has an unfavorable ratio of fats, either. One study published in the Journal of the American Dietetic Association found farmed tilapia and farmed catfish also have much lower concentrations of omega-3s and very high ratios of omega-6 fats to omega-3 fats. According to the study:4
“Taken together, these data reveal that marked changes in the fishing industry during the past decade have produced widely eaten fish that have fatty acid characteristics that are generally accepted to be inflammatory by the health care community.”
Further, when researchers looked into the effect of farmed trout on cardiovascular risk markers in men, they found trout raised on vegetable-based feed had a less pronounced impact on omega-3 levels.5
Farmed Fish May Be More Contaminated Than Wild-Caught Fish
"Consumption of farmed salmon at relatively low frequencies results in elevated exposure to dioxins and dioxin-like compounds with commensurate elevation in estimates of health risk."
In a global assessment of farmed salmon published in the January 2004 issue of Science, 13 persistent organic pollutants were found.8 Some of the most dangerous are PCBs, strongly associated with cancer, reproductive, and other health problems. PCB concentrations in farmed salmon were found to be eight times higher than in wild salmon.
Those contamination levels are deemed safe by the Food and Drug Administration (FDA) but not by the Environmental Protection Agency (EPA). Researchers postulated that if EPA guidelines were applied to the farmed salmon they tested, recommendations would be to restrict salmon consumption to no more than once per month.
Certain types of farmed fish, including farmed catfish imported from China and farmed shrimp from China, India, Malaysia, Mexico, Vietnam, Bangladesh, and Indonesia are on the US Food and Drug Administration’s (FDA) watch list for illegal drug residues, including antibiotics and anti-fungal compounds.9
Most Shrimp Is Farmed… and Should Be Avoided
Shrimp is the most popular seafood in the US, but the vast majority of shrimp (over 90 percent) come from industrial shrimp farms off the coasts of India, Indonesia, Thailand, Vietnam, and other countries where industry regulations may be less strict than in the US.
For example, the US does not permit the use of antibiotics in shrimp farming, but many other nations use antibiotics in their operations. It’s illegal to import shrimp raised on antibiotics into the US.
But in one recent study Consumer Reports detected antibiotics in 11 of 342 samples of imported raw farmed shrimp.10 A lack of enforcement of the laws is part of the problem. Bacteria were also detected on 60 percent of the shrimp tested, including bacteria that can cause staph infection and food poisoning, which is suggestive of poor hygiene among food processors.
Aside from potential contamination, farmed shrimp is unsustainable. Carnivorous sea animals such as prawns need fish in their diet, and dwindling fish stocks in the wild has led to illegal fishing; some of it within national park waters off the coast of Thailand—an area that now supplies much of the fish meal to feed factory farmed animals, including farmed shrimp and prawns.
Trawling for “trash fish” along the coast of Southeast Asia to meet the demand for shrimp feed is having devastating effects on the ecosystem. All sorts of tropical fish, and even rare shark species, sea sponges, starfish, and octopi end up as fish feed in this process.
They also catch small, immature fish reduces overall fish stocks, as bigger fish are left without a suitable food source. The end result is rapidly decreasing fish stocks for human consumption.
In short, the entire balance in nature is being destroyed. Illegal toxic pesticides are also routinely used to farm shrimp in some of these areas, including endosulfan, a broad-spectrum insecticide that is banned in more than 80 countries due to its environmental and human toxicity.
Shrimp Products Are Often Misrepresented
Adding to the controversy, it’s not always possible to tell whether the shrimp you’re eating is farm-raised or wild-caught. A 2014 report by the ocean conservation group Oceana revealed that over 30 percent of shrimp products sold in US grocery stores and restaurants are misrepresented.11 Fifteen percent were mislabeled in regard to production method (farm-raised or wild-caught) or species.
Farmed species were often labeled as “Gulf shrimp,” and different species were often mixed together in one bag, or otherwise mislabeled. One sample of frozen shrimp salad even contained a type of aquarium pet shrimp that is not intended for human consumption.
Ironically, if you’re looking for wild-caught shrimp, you may be best off purchasing products labeled simply as “shrimp,” as two-thirds of such packages contained wild-caught Gulf shrimp, while more than one-third of those labeled as “Gulf shrimp” were actually farm-raised. Assuming it’s labeled accurately, wild shrimp is a generally healthy and sustainable choice, but this excludes wild shrimp caught in Mexico or Louisiana. According to the Monterey Bay Aquarium’s Seafood Watch program:12
“Wild shrimp from Louisiana and Mexico are on the ‘Avoid’ list for poor management, illegal fishing or heavy bycatch loads that include sea turtles and many other species.”
Why You Should Be Wary of Canned and Sushi Tuna
The larger a fish is, the longer it has lived and the more time it has had to bioaccumulate toxins like mercury from the ocean. One study from the US Geological Survey found that ALL tuna tested contained fairly high amounts of mercury. The contamination may be even worse in restaurants, which suggests that eating restaurant tuna is a risky proposition. In a separate study, toxicological testing revealed that tuna sold in restaurants actually contained HIGHER amounts of mercury than the store-bought variety.13
The reason for this is because restaurants tend to favor certain species of tuna, such as bluefin akami and bigeye tuna, which had significantly higher levels of mercury than bluefin toro and yellowfin tuna. Unfortunately, mercury tends to accumulate to a greater degree in muscle than in fat, rendering these highly prized, leaner species of tuna more susceptible to high contamination. As for canned tuna, albacore has been found to contain about three times more mercury than light chunk tuna (0.353 ppm vs. 0.118 ppm).14
Independent testing by the Mercury Policy Project found that the average mercury concentration in albacore canned tuna was typically even greater than that, with most samples exceeding 0.5 ppm.15 The rate of mercury contamination in tuna and other Pacific fish increased 30 percent between 1990 and 2009. About 40 percent of all US exposure to mercury comes from eating contaminated tuna from the Pacific, and roughly 75 percent of all human exposure to mercury in general comes from eating fish.
Not to mention, like shrimp, tuna is also often mislabeled. According to Oceana, nearly 60 percent of the fish labeled "tuna" in the US is not actually tuna.16 And, 84 percent of “white tuna” sold in sushi venues was actually escolar, a fish associated with acute and serious digestive effects if you eat just a couple of ounces.
What Are the Best Fish to Eat?
Among the safest in terms of contamination, and the highest in healthy omega-3 fat, is wild-caught Alaskan and sockeye salmon. Neither is allowed to be farmed, and are therefore always wild-caught. The risk of sockeye accumulating high amounts of mercury and other toxins is reduced because of its short life cycle, which is only about three years.
Additionally, bioaccumulation of toxins is also reduced by the fact that it doesn't feed on other, already contaminated, fish. The two designations you want to look for on the label are: “Alaskan salmon” (or wild Alaskan salmon) and “Sockeye salmon.”
Canned salmon labeled "Alaskan salmon" is also a good choice and offers a less expensive alternative to salmon fillets. A general guideline is that the closer to the bottom of the food chain the fish is, the less contamination it will have accumulated, so other safer choices include smaller fish like sardines, anchovies, and herring. Sardines, in particular, are one of the most concentrated sources of omega-3 fats, with one serving containing more than 50 percent of your recommended daily value.17
They also contain a wealth of other nutrients, from vitamin B12 and selenium to protein, calcium, and choline, making them one of the best dietary sources of animal-based omega-3s. From a sustainability perspective, you’ll want to avoid Atlantic sardines that come from the Mediterranean in favor of Pacific sardines. According to the Seafood Watch program:18
“As a result of ineffective management and overfishing, consumers should ‘avoid’ Atlantic sardines from the Mediterranean. Instead, choose the relatively abundant and well-managed Pacific sardines from U.S. waters - a Seafood Watch ‘Best Choice.’”
Finally, no matter what type of fish you’re considering, look for varieties that have received the Marine Stewardship Council (MSC) certification. This certification assures that every component of the manufacturing process – from how the raw materials are harvested to how the product is manufactured – has been scrutinized by MSC and has been independently audited to ensure it meets sustainable standards.
All of my krill products, for example, are MSC certified, allowing you to track where the krill oil came from in the Antarctic Ocean, as each batch of krill is carefully monitored all the way through, from catch to sale. Seafood Watch can also guide you in the direction of more sustainable seafood choices. They have a searchable database to find more sustainable seafood options, and they even offer a Sustainable Seafood app for your smartphone. Other labels that signify more sustainable products include:
- Whole Foods Market Responsibly Farmed 3rd Party certification
- Fishwise: The Fishwise label identifies how the fish was caught, where it came from, and whether the fish is sustainable (or environmentally threatened).
- Seafood Safe: The Seafood Safe label involves independent testing of fish for contaminants, including mercury and PCBs, and recommendations for consumption based upon the findings.