Does the harm from mercury in seafood outweigh the benefits of eating fish?

02.03.2018

The NHS recommends eating 2-4 servings of fish a week as part of a healthy diet. Fish is a good source of protein, vitamins and omega-3 fatty acids, the heart healthy ‘good’ fats’ that are required for normal brain function. However the risk of exposure to mercury and other toxic pollutants which are now found in our oceans have scared many people away from eating fish.

Here’s what you need to know to eat fish and stay healthy. 

Exposure to Mercury

Decades of industrial mercury emissions around the world have contaminated our oceans. After absorption by fish the mercury is processed into a toxic substance called methylmercury; that once in our bloodstream goes right to our brains . According to the World Health Organization, at the right dose and duration of exposure, methyl mercury can attack the nervous system, imparing a person’s memory, ability to learn, and behaviour; it can also have fatal effects on the digestive and immune systems and can cause severe birth defects and developmental delays in infants exposed to mercury when in the womb.

How to minimze risk to mercury exposure

Smaller fish like sardines, herring and tilapia   have much lower amounts of mercury and can be eaten without concern.

Having said this due to the varying amounts of mercury in different types of fish, there are ways to minimise risk.

Big fish with longer life spans like swordfish, Chilean sea bass and tuna tend to bioaccumulate mercury and are the most prevalent source of human mercury exposure. Smaller fish like sardines, herring and tilapia   have much lower amounts of mercury and can be eaten without concern.

Shellfish can also be full of toxins because they are scavengers and feed on industrial deposits, sewage, and the waste of other fish, filtering it through their bodies. Try to minimise your intake of clams, lobsters, oysters, shrimp and scallops if you want to avoid excess toxins from shellfish.

Preservatives

Many fish are sprayed with potentially harmful preservatives such as polyphosphates, sulfites, and sodium benzoate to enhance the appearance and flavour of the fish and to prolong shelf life.

Preservatives are another worry when it comes to eating fish, especially as they are not required to be on the labels of the fish we buy. Many fish are sprayed with potentially harmful preservatives such as polyphosphates, sulfites, and sodium benzoate to enhance the appearance and flavour of the fish and to prolong shelf life. The dangers of consuming these preservatives in the long term are still undetermined. Therefore use your judgment and speak to your fish monger to ensure that you’re getting high quality fish without preservatives.

Wild fish vs farmed fish

Omega -3 content

Most farm raised fish have the same level of beneficial omega-3 fatty acids as wild fish. Although location and environmental changes can affect the diet of a wild fish in general they eat smaller fish that are rich in omega-3s. Meanwhile the amount of omega-3s present in farmed fish is dependent on the farmer’s choice of food pellets, which in most farms are high-protein fish and/or soy pellets.

Problem with farmed fish – toxins

The fish are kept in overcrowded tanks where they can barely move let alone swim and are at a high risk of catching a disease.

A high number of fish farms do not operate responsibly. The fish are kept in overcrowded tanks where they can barely move let alone swim and are at a high risk of catching a disease. As a result they are often given antibiotics as well as commercial dyes to make them appear a healthy colour. Moreover, the food pellets they are fed can contain harmful toxins that are transferred to the consumer.

Therefore wild caught fish is generally the better option in my opinion ;the money you save on farmed fish is not worth the potential health risks.

Fish to eat

Based on mercury contamination and omega 3 levels the following fish seem to have the greatest health benefits:

Oily fish :

  • Anchovies
  • Herring
  • Salmon
  • Sardines
  • Salmon
  • Trout

White fish: (not as high in omega-3s but have minimal mercury contamination

  • Cod
  • Pollock

Fish to minimise consumption

Oily fish :

  • King mackerel
  • Swordfish
  • Fresh Tuna

White fish:

  • Halibut
  • Snapper
  • Haddock
  • Shark
  • Canned tuna

Shellfish like clams, lobsters, oysters, shrimp and scallops, fish whose colour has been preserved with dyes and farmed fish (unless from a responsible fish farm) should all be minimised.

How much to eat

  • Average adult (and boys under the age of 16) should limit their intake of oily fish to 1-4 servings a week.
  • Girls under the age of 16 should limit their intake to 2 servings a week and should avoid all the fish on the ‘Fish To minimise consumption ‘ list
  • Pregnant and breast feeding women and those trying to get pregnant should have no more than two servings of oily fish a week and should avoid all the fish on the ‘Fish To minimise consumption ‘ list
  • There are currently no maximum recommended amounts for white fish so if you stick to the fish to eat list of white fish you should be fine.

Final thoughts… the benefits outweigh the risks

Fish really is one of the healthiest and most nutritious foods you can eat; the benefits of eating fish far outweigh the risks…when you are mindful about which fish you eat, the size of the fish, and where it has come from. Studies have shown that eating fish twice weekly is as effective as taking a fish oil capsule every day.

 

 

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author: Tania Weil

Tania Weil - Fitness Coach

boxandburn@taniaweil.co.uk
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