Tuna and mercury- how much is too much?
Something smells fishy…
I like tuna.
I’ve been eating it for as long as I can remember, and in various ways too. Tuna melts, sandwiches, salads, on its own doused in olive oil and vinegar. Tuna has been a staple food in my life, and in the lives of many others. It’s a very inexpensive source of protein, low in fat, and is very convenient.
If you have ever heard about tuna and mercury, you’re not alone. Tuna does contain this heavy metal, but only specific types of tuna contain more than others.
https://www.delish.com/cooking/recipe-ideas/a26146096/tuna-melt-recipe/
What is Mercury? Can it be dangerous?
Mercury is a type of metal that occurs naturally in soil, rocks, and water bodies. Mercury can also be released as a by-product of industrial work such as mining. The most common exposure to humans is actually found in fish.
Is there a risk of excess mercury? Absolutely. Mercury poisoning can result in rashes, congenital disabilities, as well as death. Along with this, mercury can pose neurological, respiratory, and renal toxicity. With all this being said, Canadians are not likely to experience mercury poisoning, but, it’s important to understand that some foods can contribute to the overall mercury consumption in the body. Foods like tuna.
Is fish good for you?
Fish is really good for us. There is quite a bit of research supporting fish as a part of healthy eating behaviours in Canadians, to help you reduce your risk of dying from all causes, as well as lowering your risk of cardiovascular disease and depression. So yeah, fish rocks.
Many people head to tuna as a healthy food option, myself included. Sandwiches, salads, snacks. All can be used as a high protein convenient food if you're in a pinch.
https://www.flavcity.com/tuna-salad-recipe/
Tuna and Mercury
In nature, there is a concept called bioaccumulation. Bioaccumulation is when smaller organisms accumulate a particular substance, only to be carried over to the larger organisms that eat them. Sometimes too, those substances ingested by the smaller organisms are magnified in a process called biomagnification. In our vast bodies of water, smaller fish are exposed to certain metals and chemicals, one of them being mercury, which then ends up in the fish we eat, like tuna. Big fish eat the little fish.
Fresh/frozen vs canned
Fresh/frozen tuna, which is fish that was caught in a body of water and then eaten or frozen and consumed later, should be limited to the following amounts, according to Health Canada (this also includes shark, swordfish, marlin, orange roughy and escolar):
General Population - 150 g per week
Specified Women * - 150 g per month
Children 5-11 years old - 125 g per month
Children 1-4 years old - 75 g per month
*Specified women are limited to those who are pregnant or looking to become pregnant, as well as those who are breastfeeding.
What about canned tuna? There are two main types of canned tuna: White (generally Albacore Tuna) and light.
Albacore tuna is a bigger fish compared to what they use in light tuna.
Light tuna contains smaller and younger tuna types, which tend to have less mercury than fresh or frozen (the above types). White (albacore) tuna may have more mercury levels than what is recommended for consumption in Canada, and according to the EDF, may have 3x more mercury per serving compared to light.
So, to recap: there are two types of tuna:
White (albacore) tuna
Bigger fish
generally containing more mercury
Light tuna
Smaller fish
Less mercury
White should be limited, while light can be consumed more often.
https://www.epicurious.com/expert-advice/best-canned-tuna-brands-to-buy-article
How much white tuna (albacore) can I eat?
I would suggest, according to the information by health Canada, to stick to light tuna, or canned salmon. However, if you chose to eat the white (albacore) kind, the following guidelines should be followed:
*Specified Women - 300 grams a week
Children 5-11 years old - 150 grams a week
Children 1-4 years old - 75 grams a week
*Specified women are limited to those who are pregnant or looking to become pregnant, as well as those who are breastfeeding.
Canada limits the mercury content of all canned tuna products to 0.5ppm total mercury. Those who eat albacore tuna, particularly those who eat it every day, could be consuming too much mercury. How? Although Health Canada has a mercury limit for its products, you can still overdo it depending on the amount of mercury-containing foods you’re eating. Why stick to light? Because it contains less mercury overall, thus contributing less to your overall mercury consumption.
How much light tuna can I eat?
The following guidelines are for canned light tuna:
“The same concerns do not exist for canned "light" tuna because it contains less mercury than canned albacore tuna. Various species can be labelled as "light" tuna including skipjack, yellowfin, and tongol.”
So it seems we are able to worry less about eating canned light tuna more often compared to canned albacore tuna. There doesn’t seem to be any recommendations or guidelines for eating light tuna.
How do we know light tuna is safe?
Health Canada activity monitors the mercury concentrations in tuna sold in Canada. According to their website, the current information is up to date and hasn't warranted any official changes as of recently.
Hope you enjoyed it! Leave me a comment below if you have anything on your mind!
https://www.mashed.com/240712/what-you-should-know-before-taking-another-bite-of-canned-tuna/
References
https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/environmental-contaminants/mercury.html
https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/environmental-contaminants/mercury/mercury-fish.html
https://pubmed.ncbi.nlm.nih.gov/25969396/
https://academic.oup.com/advances/advance-article-abstract/doi/10.1093/advances/nmaa029/5811305
https://www.canada.ca/en/health-canada/services/healthy-living/your-health/environment/mercury-human-health.html
https://www.ncbi.nlm.nih.gov/books/NBK499935/
