And it's largely considered a superfood—one of those super-healthy types of oily fish. Both the Department of Health and the Department of Agriculture recommend the consumption of at least 8.4 oz of seafood per week. The UK National Health Service and several other EU national health organizations recommend eating fish at least twice a week, as do the Institutes of Medicine and the American Heart Association, to ensure sufficient consumption of omega-3 fatty acids, which assist in everything from the function of cell receptors to hormone production, blood clotting, the reduction of inflammation and a lower risk of heart disease, stroke and other disease conditions.1
One of the leading sources of omega-3 fatty acids, salmon is also nutritious for other reasons. It's high in protein, vitamin B12, vitamin D and many minerals, including iodine and selenium, and even the beautiful orange-pink color of salmon is health related. The striking hue comes from the presence of a plant pigment called astaxanthin, which is recognized as a powerful antioxidant with anti-inflammatory properties.2
As demand for salmon rises, wild stocks are facing devastating reductions. According to the Food and Agriculture Organization of the United Nations (FAO), 80 percent of the world's wild fish stocks are fully exploited or overexploited, requiring immediate protective management. In 2015 and 2016, the annual wild catch of salmon only averaged between 700,000 and 1,000,000 tons. Since 2014, many southern European rivers have recorded historically low return rates of wild Atlantic salmon. In Alaska and the Pacific Northwest, runs of Chinook, King and other salmon species (see box, page 63) continue to decline.
As seafood is being depleted worldwide, there is a concomitant shift toward more aquaculture, better known as 'fish farming.' Salmon has been farmed since the 1980s from the North Sea of Europe to the Tasman Sea of New Zealand, wherever the cold-water conditions and currents are right. According to the Salmon Farming Industry Handbook 2017, in 2016 the total catch of wild salmon was about one-third that of farmed salmon, and comprised mostly chum, pink and sockeye varieties.
Because salmon require specific environmental and biological conditions such as proper seawater temperature and the right kind of current movement, farmed salmon is only produced off the coasts of the UK, northeastern and northwestern US, the Faroe Islands, Ireland, Norway, Chile, New Zealand and Tasmania. Atlantic salmon are also farmed inland in tanks called closed-containment systems.
Although touted as an environmentally friendly method of producing healthy edible protein for humans, largely because it has a far lower carbon footprint than other meat and poultry sources, aquaculture is in fact directly responsible for the decimation of wild populations of salmon and other fish. Since salmon started being farmed, wild salmon numbers have plummeted. In 2008, the first global assessment of the impact of farmed salmon on wild stocks revealed a 50 percent crash in wild stock numbers every generation wherever coastal salmon farms were found, mainly because the farmed fish spread diseases and parasites.3
Unfortunately, as it turns out, farmed salmon isn't just unhealthy for their wild cousins. Studies show that farmed salmon isn't all that healthy for humans either.
Wild versus farmed
The first and most disturbing difference between the two types of fish is that study after study shows that farmed salmon contains considerably higher levels of toxins. A total of 14 toxins have been found in higher levels in farmed versus wild salmon, including polychlorinated biphenyls (PCBs), dioxins, toxaphene, dieldrin, hexachlorobenzene (HCB), lindane, heptachlor epoxide, cis-nonachlor, trans-nonachlor, gamma-chlordane, alpha-chlordane, Mirex, endrin and total DDT.4 Agent Orange, the infamous herbicide and defoliator used to destroy millions of acres of jungle in Vietnam, contains another dioxin, TCDD (tetrachlorodibenzodioxin), found in higher concentrations in farmed fish today. These toxins and other dioxin-like compounds (DLCs) are certainly present in other foods we eat, but the levels in farmed salmon are higher than in any other food contained in the Food and Drug Administration's Total Diet Survey.5
Dioxins affect humans through the activation of something called the aryl hydrocarbon receptor (AhR), a transcription factor. Transcription factors are proteins involved in the process of converting or transcribing DNA for the creation of new proteins that the body needs to carry out all its essential functions. AhR is deeply involved in the development and aging processes. It is also linked to hypoxia (oxygen deficiency) and circadian rhythms. It is believed that dioxins prevent AhR from working properly, which can interfere with the normal function of the body including effects on the nervous system, immune system and reproductive system.6
Adverse health effects of dioxin and dioxin-like compounds include cardiovascular disease, diabetes, cancer, and porphyria—a group of diseases in which the build-up of organic compounds negatively affects the skin and/or nervous system, producing symptoms ranging from abdominal and chest pain to vomiting, fever, high heart rate and blood pressure.
Dioxins and DLCs additionally can cause changes in immune response and alter metabolism and growth-factor signaling. Endometriosis, early menopause, and skin, nail and tooth problems have also been reported, as well as reduced hormone production, in particular testosterone and hormones related to thyroid function.7
Farmed salmon also contain far more pesticides and herbicides than the wild variety, many of which have been shown to cause dysfunction in the endocrine system because of their powerful ability to bind to sex hormone receptors. These so-called 'endocrine disruptors' decrease the ability of natural hormones to do their work, altering normal maturation and reproductive and sexual development. They have been shown to lead to lowered sperm production and reduced fertility in men.8 Studies also link pesticide exposure to cancer—chlorinated pesticides in particular have been linked to breast cancer. For example, a long-term study of women living in New York found an increased risk of breast cancer among those who lived on land that was previously used for agriculture or within 1 mi of a hazardous waste site known to contain chlorinated pesticides.9
Another cause for concern is the introduction of genetically modified farmed salmon into the marketplace. A company called AquaBounty Technologies has spent years developing a salmon that is genetically engineered to grow faster and thus reach maturation and market more quickly. These salmon constantly produce a growth hormone—something wild salmon only produce when conditions are favorable for a growth spurt. AquAdvantage salmon is currently being sold in grocery stores in Canada and was approved by the Food and Drug Administration in 2015. It's expected to go on sale in the United States soon, pending finalization of labeling requirements.
Critics point out that few studies have been done on the safety of eating genetically modified (GM) foods, and that a lack of proof that it is dangerous doesn't mean it's necessarily safe. Indeed, so far, some studies suggest that the use of recombinant growth hormone in animals such as cows and salmon may have the potential to promote cancer. There is other evidence that the consumption of GM foods may cause problems with the kidneys, liver and pancreas, trigger reproductive issues, and negatively affect the bloodstream and immune responses.10
So why the major differences in toxicity levels between wild and farmed salmon?
You are what you eat
Don Staniford, head of the Global Alliance Against Industrial Aquaculture, was quoted as referring to salmon farms as "toxic toilets" and "reservoirs for infectious diseases and parasites" in British newspaper The Guardian. The paper also recently reported on the current crisis in Scottish salmon farming—an uncontrollable infestation of sea lice that is spreading globally, dramatically reducing harvests of farmed salmon worldwide and forcing fish farmers to use more and more chemical deterrents.11
Just as commercial agriculture—with its congested, inhumane, sewage-filled feedlots for cattle, pigs and chickens—has led to the increased use of antibiotics, pharmaceuticals and vermicides to keep rampant disease under control, the same is now true of salmon farming. Currently the go-to drug being dumped into the world's oceans via fish farms is something called emamectin benzoate, a pesticide that works by interfering with nerve impulses in the bodies of the sea lice.
According to a statement released by the Scottish Environment Protection Agency, emamectin benzoate is not supposed to harm wildlife or the environment, "provided guidelines for safe use are followed." The statement goes on to admit that emamectin benzoate can enter the human body by inhalation, skin contact or the ingestion of food or water contaminated with emamectin benzoate. Exposure may cause respiratory irritation as well as irritation of the eyes and skin.
The report goes on to say, "Animal studies suggest that exposure to emamectin benzoate may also cause tremors."12
Perhaps worse than the conditions farmed salmon are subjected to is the feed they are given. A 2005 study comparing the levels of polychlorinated biphenyls (PCBs) in wild versus farmed salmon found that the higher PCB levels in the farmed salmon "closely corresponded" to the PCB levels in the feed they were given. (PCBs are an organic chlorine compound from coolant and heat-transfer fluids.) The study also revealed that these kinds of toxins accumulated in the body over time.13 Another study concluded that the significantly higher levels of PCBs, PBDEs (polybrominated diphenyl ethers—flame retardants that contain bromine) and organophosphate found in farmed salmon came from the salmon feed.14
Farmed salmon are also fed both natural and synthetic carotenoids, the plant pigments that wild salmon naturally ingest from algae in oceans and rivers. If farmed salmon aren't given these additives, their flesh is grayish white and not salmon-colored at all—and thus unmarketable. Therefore, they are fed manufactured 'colorant products' such as 'lucantin pink' from the German chemical company BASF and 'carophyll pink' from Roche, a Swiss pharmaceutical company. Some of these products come from ground-up crustacean shells and other natural sources of astaxanthin, but others are synthetic.
Many feeds contain another carotenoid called canthaxanthin. Although both additives have been approved for human consumption, canthaxanthin used in tanning pills has been found to form crystal deposits on the retina of the human eye—a condition called canthaxanthin retinopathy—that can last seven years or more.15
If salmon consuming feed with additives and numerous known toxins end up contaminated with those same toxins, it's hardly a stretch to assume that humans ingesting the salmon—and other foods with similar toxicity profiles—will suffer the same consequences.
There is growing evidence that exposure to a wide number of chemical pollutants, herbicides and pesticides commonly found in farmed salmon (and other food products) may alter endocrine function and thus adversely affect child development. They may even be transmitted from generation to generation. For example, diethylstilbestrol (DES), a synthetic, nonsteroidal estrogen, can be passed on to children decades after the mothers are exposed to it.16
Persistent organic pollutants (POPs) such as PCBs, PBDEs and organochlorine pesticides (such as DDT, chlordane and hexachlorobenzene) found in farmed salmon easily combine with or dissolve into fat and have long half-lives, meaning that they linger around in the body long after they enter it, and this can result in obesity, male and female reproductive problems, and endocrine-related cancers.17
Recent studies also show that POPs are linked to a greater risk for developing type 2 diabetes mellitus than other established lifestyle risk factors such as poor diet and lack of exercise. In particular, chlorinated pesticides and polychlorinated biphenyls have been linked to type 2 diabetes as well as metabolic syndrome, insulin resistance and other conditions that involve the dysregulation of blood sugar levels.18
In addition, PCB exposure has been linked to asymmetrical hearing loss.19 Organochlorine pesticides themselves have been linked to Parkinson's disease and prostate and breast cancers.20 Dioxin exposure is linked to learning disabilities and ADHD.21 Unborn babies exposed to dichlorodiphenyldichloroethylene (DDE), a byproduct of DDT, in the first trimester of pregnancy may experience arrested brain development before 12 months of age.22
Emotional and social side-effects
Speaking of stress, studies show that 'handling stress' causes a rapid rise in cortisol levels in Atlantic salmon.23 Although there have been no studies so far, it's possible that the stressful conditions of salmon farms themselves—overcrowding, high levels of feces, lack of exercise, disease and medications—may well trigger higher cortisol levels in farmed salmon, which are then passed on to those who eat the meat.
All in all, between the high levels of toxins and the diseases they cause, the specter of genetic modification, medications, and the general low quality of the environment farmed salmon are subjected to, it seems that the temporary savings you might enjoy at the grocery store purchasing farmed over wild-caught salmon is far less than the exorbitant price you might end up paying down the road in health-related expenses and disease.
Know your salmon
The family Salmonidae contains many species, including some of the most highly prized fishes on the market today—the Atlantic salmon of Europe and eastern North America and the Chinook and sockeye salmon of the Pacific Northwest—along with various trout, chars and freshwater whitefishes.
Unless it is labeled 'wild' or 'wild caught,' you can assume any salmon in the grocery store—fresh, frozen, and/or prepackaged—is farm raised. Wild salmon sells at a much higher price than farmed salmon. Farmed salmon produced in European farms generally carries a heavier toxin load than salmon raised in farms in North and South America.1
Farmed salmon have almost three times the fat of wild salmon. Unfortunately, most of this fat is omega-6 fatty acids—something the typical Western diet already has in ample supply. From a dietary perspective, what salmon is most prized for is the healthy amount of omega-3 fatty acids it brings to the table.
Since farmed salmon have a ratio of omega-6 to omega-3 fatty acids that is approximately three times higher than wild caught salmon and farmed salmon are much more heavily burdened with toxins, consuming farmed salmon seems to defeat the whole purpose of eating it for health reasons.
Know what you are buying
The most commonly found salmon in grocery stores, wild stocks of Atlantic salmon are dangerously low. Most Atlantic salmon you can buy is farmed unless otherwise labeled.
Highly prized. Caught in ever-smaller batches in Alaska, British Columbia and New Zealand. Deep pink color, sweet, delicate flesh. Sometimes exported at premium prices.
Mostly caught and sold in Japan, Alaska, coastal British Columbia and Washington state. Has a denser, chewier, paler flesh and stronger taste than other salmon.
Farmed in Chile, mostly sold in Japan.
Native to Alaska and Russia, mostly exported to Japan. Prized for use in sushi. Often found canned and smoked in the EU.