This is why fish is not a health food

Read Time:   |  23rd March 2020

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If everyone around you thinks fish is good for them, Dr Justine Butler reveals that may not be the truth


Ever wondered why fish isn’t healthy?

We need fats – but good fats called essential fatty acids for our cell membranes, brain and nervous system. They help regulate blood pressure, blood-clotting, immune and inflammatory responses and are ‘essential’ because our bodies can’t make them, we must get them from food.

ALA is an omega-3 essential fatty acid found in flaxseeds, rapeseed, soya, walnuts and their oils. We convert it in our bodies into the longer-chain omega-3s EPA and DHA. These are also found in oily fish, which they obtain from algae. Conversion rates of ALA into EPA and DHA in the body can be low, which is why some people insist that fish oils are far better and essential for health.

UK guidelines tend to support this view, recommending that we should eat at least two 140g portions of fish a week, one of which should be oily. It contributes to the widespread belief that eating oily fish or taking omega-3 supplements reduces our risk of heart disease, stroke and death. The research tells a different story.

Cochrane reviews are regarded as the highest standard in evidence-based research. A 2018 review found that increasing EPA and DHA from oily fish or supplements had little or no effect. These findings are consistent with many other high-quality reviews. They also found that ALA may slightly reduce the risk of cardiovascular events and arrhythmia (abnormal heart rhythm). Another 2018 review, this time from the British Journal of Nutrition, found that higher ALA intakes were linked to a reduced risk of heart disease. So it seems you’re better off with plant-based omega-3s.

Some studies show that oily fish, particularly fish oil supplements, can have the opposite effect of that claimed and increase the risk of cardiovascular events. The American Heart Association say this might be explained by the damaging effects of methylmercury, an environmental contaminant found in fish. A study of men in eastern Finland, where mercury levels in fish are high, found that the level of mercury in their hair and the amount of fish they ate were linked to increased risk of cardiovascular death.

All the world’s oceans are contaminated with toxic pollutants such as methylmercury, polychlorinated biphenyls and dioxins and many act as damaging neurotoxins. They can accumulate as you move up the food chain, especially in oily fish, cancelling out any beneficial effects of omega-3s.


Fish and pregnancy

We have the extraordinary position where women in the UK who are pregnant or breastfeeding are advised to eat oily fish because the omega-3s it contains can help a baby’s nervous system develop. On the other hand, all girls and women who are breastfeeding, are pregnant or who are planning a pregnancy – and even those who may one day in the future want to have a child – are warned not to eat more than two portions of oily fish a week!

The reason is that pollutants in the fish may build up and seriously affect the baby’s development in the womb. And there are more warnings – children, pregnant women and women trying to get pregnant are also told to avoid eating shark, swordfish or marlin because they contain more mercury than other fish and this can damage a developing baby’s nervous system. So, damned if you do, damned if you don’t!

Oily fish include: herring, pilchards, salmon, sardines, sprats, trout and mackerel. The list of fish to limit/avoid has been extended to include some white fish that may also contain similar pollutant levels – sea bream, sea bass, turbot, halibut and huss (dogfish). And this is supposed to be a health food!

Pollutants are not the only problem as filter-feeding shellfish, such as mussels and oysters, can accumulate bacteria and viruses from the environment and, if eaten raw, can pose a direct threat to health. Norovirus is one of them and can cause fever, nausea, vomiting, cramping and diarrhoea.


Many outbreaks are linked to shellfish contaminated from human faecal sources. Norovirus infections spread easily from person-to-person contact or simply by touching surfaces that have been contaminated with the virus and then touching your mouth. Current UK estimates suggest one in every 219 people are infected every year, suggesting gross under-reporting.

The hepatitis E virus causes around five per cent of acute hepatitis cases. The World Health Organisation says that, since 2000, there have been clusters of infection not associated with travel to areas where the virus is prevalent.

In the UK, there has been a steep rise in cases over the last decade. Livestock, such as pigs, can act as reservoirs and high levels have been found in wastewater and manure from pig units, highlighting the potential for it to enter watercourses and then accumulate in shellfish.

Something fishy with farms

Fish farms now provide over half of all fish consumed by humans, but are certainly not the answer. These overcrowded, unnatural pens transmit disease and cause water pollution, choking marine life with persistent organic pollutants, antibiotics, chemicals from parasitical treatments, anaesthetics, disinfectants, feed additives, metals and anti-foulants.

Farmed fish tend to contain less omega-3s, as they are fed omega-6-rich vegetable oils in addition to fishmeal and fish oils. Yes, fish are caught to feed farmed fish and livestock!

Our oceans are being decimated and ancient coral reefs destroyed at an unprecedented level by fishing on an industrial scale.

Marine ecosystems are collapsing as bottom-trawlers plough through sea beds, with up to 90 per cent of some fish species having been depleted, decimating populations of large-bodied marine animals who depend upon them. This domino effect could disrupt ocean ecosystems for millions of years to come.

The nonsensical belief that fish cannot feel pain still prevails, despite abundant science showing that fish experience conscious pain in the same way as mammals and birds. Pain is an essential element of evolution, teaching creatures the things to avoid.

Surprisingly for an island nation, fish is not a popular food in the UK, with the average adult consuming just 54g of oily fish per week. The good news is you don’t have to destroy the oceans, inflict pain or eat neurotoxins and carcinogens to get your omega-3s.

Plant foods can provide more than enough to keep your heart healthy and combat inflammatory conditions such as arthritis. You can take an algal-based vegan supplement supplying EPA and DHA without the risk of contamination and none of the ethical and environmental concerns raised by eating fish. Help our oceans become healthy and leave fish alone!

Dr Justine Butler is the Senior Health Researcher at Viva!Health. Viva!Health is part of the vegan charity Viva! It monitors scientific research linking diet to health and provides accurate information on which to make informed choices about the food you eat.

Find more information about the animal impact of non-vegan diets here.

Written by

Dr. Justine Butler

Dr. Butler is Viva! Health's senior researcher and writer focussing on all matters relating to vegan nutrition. Dr. Butler graduated from Bristol University with a PhD in molecular biology and a BSc First Class (hons) in biochemistry from UWE before joining Viva! in 2005.

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