Fish: The Untold Story

By Robyn Chuter

  • Fish consumption has been linked in epidemiological research to a higher risk of breast cancer and heart disease.
  • Fish is the major dietary source of exposure to persistent organic pollutants which are linked to diverse health issues including impaired immune function, liver damage and Parkinson’s disease.
  • In most people, fish consumption is the major source of mercury exposure. Mercury is a neurotoxin linked with anxiety, attention deficit, and dementia.
  • Antibiotics and antibiotic-resistant bacteria are found in farmed fish, as they are in other intensively-reared animals.

When I counsel clients seeking weight loss, disease prevention or reversal, improved mood – and anything else they want to fix – to cut down on or entirely eliminate their animal product consumption, most can accept pretty easily that the great weight of scientific evidence supports this advice.

But then the question always comes up: “What about fish? Isn’t fish good for me?”

In the past I used to recommend moderate fish and seafood consumption for those who still wanted to include some animal foods in their diet, figuring it was safer than chicken or meat.

I no longer give that advice, and here’s why:

Over the years, numerous large, well-designed studies have indicated that fish consumption poses significant risks to health. But none of these studies have received widespread coverage in the popular media, which constantly pushes the line that fish is heart-healthy, an excellent source of omega 3 fats, and a good source of lean protein.

What risks were found? Well, how about a roughly 50% higher risk of breast cancer in women who eat the most fish, compared to women who eat little or no fish (1)?

Or a 2-fold higher risk of heart attack and a 2.9-fold higher risk of cardiovascular death in men with a high intake of nonfatty freshwater fish (2)?

Or a 30% higher risk of coronary death in Finnish male smokers with the highest intake of omega-3 fatty acids from fish (3)?

What’s in fish that makes it a health risk?

1) Persistent organic pollutants (POPs):

The world’s oceans are now brimming with toxic chemicals such as PCBs, dioxins and dieldrin. Some of these are no longer in use (such as PCBs and dieldrin, whose prodution was banned in 2001 because of their adverse health effects), yet they remain in our environment because they strongly resist biodegradation.

They get into the ocean either through direct discharge from factories, or by contaminating ground water or river water that eventually ends up in the ocean. There they are absorbed by phytoplankton, which are eaten by zooplankton, which are eaten by tiny fish, which are eaten by bigger fish, and so on and on, up the food chain.

These contaminants are fat-soluble, so they concentrate in the fatty tissues of the animals that eat them, and biomagnify (reach higher and higher concentrations in animals) at every step up the food chain.

Humans are at the top of the food chain, so every time we eat fish, we’re copping the full load of contaminants that that fish has accumulated over its lifetime.

So what’s the problem with that?

PCBs (polychlorinated biphenyls) are endocrine (hormone) disrupters that cause liver damage; interfere with normal sexual development within the womb, impair immune function, motor skills and short-term memory in babies whose mothers ate fish high in PCBs; and increase the risk of liver, biliary tract and breast cancer (4).

Dioxins also cause liver damage, are endocrine disrupters and probable carcinogens (cancer-causing agents). They adversely affect metabolism of haem (the oxygen-carrying protein in red blood cells), serum lipid levels, sperm count and motility, and the function of the thyroid gland and immune system, and may cause diabetes (5).

European researchers concluded that

“… if the recommended LC n-3 PUFAs [long chain polyunsaturated fatty acid – i.e. DHA and EPA] intake would be based on fish consumption as the only extra source, the majority of the study population would exceed the proposed health based guidance values for dioxins and dioxin-like substances.” (6)

Dieldrin is linked with the development of Parkinson’s disease, breast cancer, and immune, reproductive, and nervous system damage. Male babies born to women who were exposed to dieldrin during pregnancy have a higher risk of undescended testes (7).


Farmed_vs_wild_salmon_contaminantsThe chart at left shows levels of some POP contaminants found in wild-caught (green bars) and farmed (red bars) salmon (8). As you can see, farmed salmon has higher levels of all of these contaminants than wild salmon.

However, exposure to any amount of these contaminants is risky, particularly as there is no research on the combined effects of these chemicals. Toxicology tests only investigate the effects of one chemical at a time, but many toxic substances have a synergistic effect – that is, exposure to very small amounts of multiple chemicals may cause just as much harm as a large exposure to just one chemical, especially if those small exposures are repeated on a regular basis… such as eating a can of salmon several times per week.

As the researchers who produced the chart concluded,

“Risk analysis indicates that consumption of farmed Atlantic salmon may pose health risks that detract from the beneficial effects of fish consumption” (8).

2) Mercury:

All fish and seafood contain methylmercury, and most of the mercury load in most people’s bodies comes from fish consumption, not amalgam fillings or thiomersal, the mercury-containing preservative used in many vaccines (9, 10).

Mercury is linked with infertility, neurological and mental disorders (including anxiety, attention deficit, and dementia), high blood pressure and endocrine disorders; and mercury levels are also strongly correlated with the risk of heart attack (11, 12, 13, 14, 15).

Mercury levels vary from one fish species to another, with large fish such as shark, swordfish and king mackerel being the most polluted.

But as with the POPs, persistent low-level exposure is just as dangerous as occasional high exposure, because mercury takes months to eliminate from the human body, and if more is ingested before previous doses are eliminated, then it starts to accumulate – particularly in the brain and kidneys.

3) Antibiotic residues and antibiotic-resistant strains of bacteria:

Like other factory-farmed animals, farmed fish are routinely given antibiotics to prevent infectious diseases from spreading like wildfire through the densely-stocked pens. Residues of these antibiotics contaminate not only the flesh of the farmed fish, but also wild fish and shellfish living in or travelling through the vicinity of the fish farm (16).

Use of antibiotics has been linked to a higher risk of breast cancer (17) and prostate cancer (18); chronic low-level intake of antibiotics through the food supply may also be a risk factor for cancer.

Antibiotic-resistant strains of bacteria including E. coli, Salmonella, and Serratia species bacteria cause food poisoning, respiratory diseases and urinary tract infections.

Furthermore, antibiotic-resistant bacteria can transfer the genes that confer their antibiotic resistance to other bacteria – including ones living in your body, making these formerly harmless bacteria capable of causing serious disease for which there may be no effective treatment (16).

The bottom line is, it is simply not worth exposing yourself to the serious, even life-threatening hazards posed by POPs, mercury and antibiotic-resistant bacteria, when every nutrient that fish contains, can be obtained from other, safer food sources that offer a range of beneficial nutrients.

The short-chain omega 3 fat alpha-linolenic acid (ALA) occurs in abundance in flaxseeds (also known as linseeds), chia, hemp seed, walnuts, pepitas (pumpkin seeds) and green leafy vegetables. ALA can be converted into the long-chain omega 3s EPA and DHA, which occur in fish, although the efficiency of this conversion varies from person to person. The good fats in these foods come packaged up with cancer-fighting lignans, fibre, and powerful antioxidants, none of which occur in fish.

If you want to safely boost your intake of ready-formed DHA and EPA, you can take a supplement derived from algae. As a matter of fact, that’s where fish get their long chain omega 3 fats. The algae are grown in controlled conditions, ensuring they are free of mercury, POPs and other contaminants. There are many vegan-friendly algal DHA and EPA supplements available, including Opti3, Nuique Omega 3 and Source Naturals Vegan Omega 3s.