Mercury occurs in a number of forms and, in large enough doses, can cause a toxic effect on the lungs, brain and kidneys.
The most common way this occurs is through the ingestion of mercury, called methylmercury, when eating seafood.
This is particularly a problem for young children and pregnant or breastfeeding women as high levels of mercury can affect the child’s neurological development, as well as lead to a number of other quite serious health problems.
Mercury Moves Up The Food Chain
Fish and shellfish absorb methylmercury through water pollution and unfortunately it is excreted very slowly.
This means long-living fish higher on the food chain tend to contain higher levels of mercury.
This includes swordfish, northern pike and king mackerel, but as most people don’t tend to eat these fish regularly, most talk centers around the two most common consumed fish: tuna and salmon.
Health agencies recommend eating one portion of oily fish per week due to its health benefits (protection against heart disease for example), and while fresh tuna is considered to be an oily fish it loses these beneficial properties during the canning process.
Tuna – The Not-So Fish Low In Mercury – Buyer Beware
Mercury levels in canned tuna vary enormously, another reason for pregnant or breastfeeding women to be cautious, particularly if they eat tuna regularly.
Albacore tuna, or white tuna, is a popular species but often contains up to three times the mercury levels of light chunk tuna (usually Shipjack tuna).
Some canned light tuna contains Yellowfin tuna, and this is reported to have much higher mercury levels than some other species, such as Eastern little tuna which is cheaper and low in mercury but not widely popular due to its strong taste.
Another suggestion for keeping mercury levels down is to try ‘troll caught’ tuna as these fish tend to be younger (and therefore haven’t built up high levels of mercury) than ‘long-line caught’ fish.
All of this is not to say that we should avoid tuna altogether but that it is advisable to keep track of how much we consume on a weekly basis. Guidelines vary but typically suggest anywhere between 2-4 regular cans (or up to two tuna steaks) for people above 50Kg, while pregnant or breastfeeding women, and children, should limit their intake to one can per week, with overall weekly fish consumption at two cans/portions weekly. *Note: Regular cans are 6oz.
Pacific Salmon #1 Low Mercury Fish
Let’s now turn our sights to salmon… the good news is when it comes to canned salmon, mercury levels are generally found to be far lower than in canned tuna and don’t come with the same health warnings.
An added benefit to salmon is its high levels of omega-3 fatty acids, with one regular can providing an entire week’s worth!
Try Alaska wild salmon, or wild salmon caught along the Pacific coast of the USA (Atlantic salmon is exposed to greater levels of pollutants).
Farmed Salmon, The Bad Guy Again
Farmed salmon is also thought to contain higher levels of pollutants, including mercury, than Alaskan or Pacific salmon so if you do choose farmed salmon try to stick to organic produce and investigate its origin.
Or why not branch out and try Atlantic mackerel or anchovies – both are on the low mercury fish list and are high in beneficial omega fatty acids.
When buying tuna read the label and find out exactly what you’re eating, and if you eat tuna on a regular basis perhaps switch to salmon (or other low mercury fish) whenever possible. Salmon has less associated risks, is beneficial to health, and in my opinion much more delicious: fin-tastic.
*This article was authored by professional blogger, Amy Corcoran