Should you be concerned about mercury levels in fish and seafood available here in Spain?

This week’s FounderFit Q&A is nutrition related:

Should we worry about mercury levels in fish?

Ben, Co-Founder of

Fish and Seafood feature regularly in the FounderFit KPIs (Key Performance Ingredients) – They are high in protein, packed with omega 3 fatty acids, and loaded with essential vitamins and minerals.

Sadly it has come to light that many fish species also contain mercury, a heavy metal toxic to humans. Levels of mercury have been increasing in our rivers and seas due to pollution from human activity.

So the question is, do the nutritional benefits of eating fish and seafood caught or sold in Spain outweigh the risks of mercury contamination?

What are the effects of mercury on human health?

Mercury is toxic to the central and peripheral nervous systems – Exposure to high levels can be fatal, though this would likely only occur via industrial accident.

The levels encountered in fish and seafood are typically far too low to pose any real danger to a healthy adult consuming fish at “normal” levels (a few times per week).

This doesn’t mean that mercury containing fish and seafood isn’t an issue though – It can pose a serious health risk to unborn babies and young children whose nervous systems are still developing.

Health Effects of Mercury via the WHO

Who should avoid mercury containing fish and seafood?

In Spain, the Agencia de Seguridad Alimentaria (AESAN) makes the following recommendations with regards to the consumption of fish:

Women who are pregnant, planning to conceive or breast feeding

Avoid consuming high mercury fish
3-4 portions per week of lower mercury fish and seafood

Children under 10 years old

Avoid consuming high mercury fish
3-4 portions per week of lower mercury fish and seafood

Children between 10-14 years old

Limit high mercury fish to 120g PER MONTH
3-4 portions per week of lower mercury fish and seafood

General Population

3-4 portions per week of any fish and seafood.

Mercury levels in fish
Expecting mothers and young children should worry about mercury levels in fish and seafood.

Which species of fish contain the highest levels of mercury?

It is the large predatory fish at the top of the food chain that contain potentially worrying levels of mercury.

This is because mercury accumulates within a fish throughout its life – once ingested it can’t be excreted.

A small fish at the bottom of the food chain can only consume so much mercury. When a big fish comes along and eats a small fish, it has just ingested a small fish lifetime’s worth of mercury in one meal. Next an even bigger fish comes along and wolfs down big fish and a couple of his pals… You get the picture!

The prime suspects that you’ll find in Spain’s markets and fishmongers where you may need to worry about are:

High Mercury Fish in Spain

  • Swordfish (Pez Espada/Emperador)
  • Red Tuna (Atún Rojo)
  • Sharks and Dogfish (Tiburón, Cazón, etc)
  • Pike (Lucio)

Better to stick to these smaller fish which are lower on the food chain:

Low Mercury Fish in Spain

Haddock, Anchovy/ Herring, Cod, Bacaladilla, Cockle, Mackerel, Squid, Shrimp, Crab, Cañadilla, Stoker, Carp, Clam, Cuttlefish, Crayfish, Coquina, Dorada, Sprat, Prawn, Horse mackerel, Lobster, Shrimp, European sole, Sea bass, Mussel, Merlan, Hake/Whiting, Razor, Ostion, Harvestfish, Flounder, Cuttlefish, Octopus, Quisquilla, Salmon, Sardine, Sardinella, Sardinopa, Solla, and Trout

Abadejo, Anchoa/Boquerón Arenque, Bacalao, Bacaladilla, Berberecho, Caballa, Calamar, Camarón, Cangrejo, Cañadilla, Carbonero/Fogonero, Carpa, Chipirón, Chirla/Almeja, Choco/Sepia/Jibia, Cigala, Coquina, Dorada, Espadín, Gamba, Jurel, Langosta, Langostino, Lenguado europeo, Limanda/Lenguadina, Lubina, Mejillón, Merlan, Merluza/Pescadilla, Navaja, Ostión, Palometa, Platija, Pota, Pulpo, Quisquilla, Salmón atlántico/Salmón, Salmón del Pacífico, Sardina, Sardinella, Sardinopa, Solla, y Trucha

Any fish that are not listed can be considered as “moderate” mercury level.

What can be done to prevent mercury contaminating the seas and rivers?

Mercury is a naturally occurring element found in the Earth’s crust, and therefore there will always be some small level of mercury found in fish and seafood.

The worrying levels that can be found in the larger predatory species nowadays however is due to large quantities of mercury being released into the environment via human industrial activity.

What are the major sources of mercury pollution in the sea and what can we do about it?

  1. Coal Fired Power Stations

    Burning coal for energy is a major source of mercury pollution (along with many other deadly environmental toxins). We need to support and campaign for cleaner, safer, more sustainable power.

  2. Eliminate use of mercury in gold extraction and other industrial processes

    Historically mercury has been used widely in the extraction of gold in small mining operations. Aside from the environmental pollution dangers it is highly toxic for the workers. Better, safer techniques have been available for sometime but haven’t been implemented everywhere due to lack of education or funds.

  3. Phase-out the use of non-essential mercury containing products

    From batteries, to thermometers, to dental fillings and cosmetics, mercury has been used in a wide range of different consumer products. It is important that we find alternatives or do without. It is also critical that old mercury containing items are disposed of properly. Never just throw your old batteries or electrical goods in the bin – dispose of them correctly!

Plenty of tasks there for budding entrepreneurs to get working on…

In the meantime, keep eating plenty of small oily fish such as sardines, mackerel and anchovies, along with regular portions of shellfish, cephalopods and crustaceans to keep body and brain healthy and those creative juices flowing!

Ben Gilloz

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