With lengths of nearly 13 feet (4m) and weights of up to 2000 pounds (900 kg), tuna are one of the fastest and strongest predators in the open ocean. They are also the biggest species of mackerel and are only eaten by toothed whales, sharks, and, of course, people.
Many species of tuna are the target of small and large-scale fisheries around the world. In fact, they are one of the most commercially valuable species on the planet. One bluefin tuna was once sold for more than $700,000. Why do fisheries target this species with almost unmatched effort? Because of its high value in the high-end sushi market, many tuna populations have been wiped out by overfishing.
Because they are expensive and not very common, fish like bluefin tuna are often used in seafood fraud.
Canned tuna is a popular pantry staple enjoyed by many for its convenience, affordability and nutritional value. However, some people experience digestive issues like diarrhea after eating canned tuna. If you’ve ever wondered, “Can canned tuna give me diarrhea?” – this article will give you the facts.
Overview of Canned Tuna and Potential Risks
Canned tuna is usually made from skipjack or albacore tuna fish. It contains high amounts of protein, omega-3 fatty acids and other nutrients. However, some potential risks are associated with canned tuna:
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Histamine poisoning – Eating tuna with high levels of histamine can cause inflammation diarrhea, headache and flushing. This happens when tuna isn’t properly refrigerated after catching.
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Heavy metal contamination – Tuna contains methylmercury a neurotoxin. Consuming too much can cause neurological symptoms. Albacore (white) tuna has 3 times more mercury than skipjack (light) tuna.
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Bacterial contamination – Improper handling, storage or canning can introduce pathogens like salmonella, E. Coli and listeria, causing severe food poisoning.
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Spoiled or contaminated tuna – Tuna past its expiration or with damaged packaging can have pathogenic bacterial growth, increasing diarrhea risk
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Allergies and sensitivities – Some people may be allergic or sensitive to tuna itself, preservatives like salt or oil used in canning tuna. This can trigger adverse reactions.
So in some cases, canned tuna can indeed cause diarrhea. Let’s look at reasons why in more detail.
Common Causes of Diarrhea from Canned Tuna
Here are 5 main reasons why you may get diarrhea after eating canned tuna fish:
1. Histamine Poisoning
One of the most common causes of canned tuna induced diarrhea is histamine poisoning or scombroid poisoning.
Histamine is naturally present in fresh tuna flesh. Bacteria produce enzymes that convert amino acid histidine in tuna to histamine when tuna isn’t immediately refrigerated after being caught.
Canned manufacturers are required to control histamine levels through prompt refrigeration. However, high histamine levels can still occur if:
- Tuna isn’t gutted, chilled or frozen quickly after catching
- Storage temperature becomes too warm at some point before canning
- Defective cans allow contamination after canning
Ingesting high-histamine tuna can cause inflammation, dilated blood vessels, headache, rash, diarrhea and vomiting within minutes to a few hours.
2. Heavy Metal Toxicity
Tuna contains methylmercury, which comes from pollution of oceans. Larger, older predators like albacore tuna accumulate more mercury as it goes up the food chain.
Consuming too much methylmercury can cause neurological problems, muscle weakness, vision issues and gastrointestinal symptoms like diarrhea.
According to FDA, children under 6 should eat no more than 1-2 servings of canned white tuna per month. Others can safely consume up to 4 servings per month.
Pregnant women need to limit albacore tuna intake to about 6 oz per week to reduce risks to the fetus.
3. Bacterial Contamination
Canned tuna can harbor bacterial pathogens if:
- Raw tuna had contaminants before canning
- Faulty seals allow entry of bacteria into cans
- Cross-contamination from unhygienic handling and storage
Bacteria like Salmonella, E. coli, Staphylococcus aureus, Listeria monocytogenes and Clostridium botulinum can contaminate tuna. Consuming contaminated fish or fish products can cause severe diarrhea.
Proper cooking usually kills these bacteria. However, toxins produced by bacteria may not be destroyed by heat. Consuming contaminated tuna can still cause diarrhea despite thorough cooking.
4. Spoiled Tuna
Eating tuna past its expiration date or from damaged cans/pouches can also cause diarrhea.
Over time, tuna’s fats oxidize and proteins break down, making it unfit for consumption. Contaminants can also grow in spoiled tuna.
Bulging or leaking cans, foul odors, mushy texture, sliminess, discoloration or mold indicate spoiled tuna that shouldn’t be eaten. Consuming such tuna can cause stomach pain, nausea, vomiting and diarrhea.
5. Allergies and Sensitivities
Some people may be allergic or sensitive to:
- Proteins present in tuna like parvalbumin
- Preservatives like salt, vegetable broth or oil used in canning process
- Food additives like MSG
This can trigger immune reactions causing cramping, bloating and diarrhea after consuming even small amounts of canned tuna.
Tips to Prevent Diarrhea from Canned Tuna
Here are some tips to help prevent diarrhea from canned tuna:
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Check expiration dates – Don’t purchase or consume tuna past expiration date.
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Inspect cans – Avoid dented, leaking or bulging cans which indicate spoilage.
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Store properly – Refrigerate after opening, use within 3-4 days. Unopened cans last 2+ years in cool, dry pantry.
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Limit white tuna – Choose light over white tuna to lower mercury exposure if concerned.
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Avoid tuna daily – Eat no more than 1-2 canned tuna meals per week.
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Cook thoroughly – Ensure canned tuna reaches 165°F internally when cooking.
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Use saferVariants – Opt for low-sodium or canned in water variants.
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Know your tolerance – Limit or avoid tuna if you have sensitivity or allergy.
When to Seek Medical Care
Consult your doctor if you experience:
- Severe diarrhea lasting over 2 days
- Bloody stools
- High fever, chills, dehydration signs
- Persistent vomiting
- Muscle weakness, tingling, confusion
Get emergency help for symptoms like chest pain, trouble breathing, fainting or uncontrolled vomiting.
The Bottom Line
Canned tuna can definitely cause diarrhea in some cases due to histamine content, heavy metals, bacterial growth or allergies. However, following safe storage, hygiene, expiration dates and consumption limits can minimize risk. If diarrhea persists after eating tuna, seek medical advice, especially with concerning symptoms. Be aware of potential risks but don’t avoid tuna entirely – instead take steps to consume it more safely.
The oppor-tuna-ty for fraud…
Seafood fraud is any dishonest activity that misrepresents the product being purchased. Though seafood fraud takes many forms, of particular concern is species substitution. It’s possible to get something very different when you think you’re getting tuna because of lax labeling laws.
Oceana conducted a global review of more than 200 seafood fraud studies; 65 per cent of these studies found clear evidence of economically motivated mislabelling of products. This ‘bait and switch’ is when one type of fish, generally a cheaper or more readily abundant species, is sold as a more expensive fish.
The word “tuna” refers to 61 different species of fish that scientists usually call “tunas” or “tuna-like fish.” “In Canada, seafood labels only need to have a generic market name and the country where the seafood came from.” Naming protocols allow many different species to be listed under the same common name. There are eight species of true tuna on the Canadian Food Inspection Agency’s Fish List, and six species that aren’t tuna but can be sold under the name “tuna.” ”.
However, these species don’t have much in common. Some, like bluefin tuna, are critically endangered, while others are not. Levels of mercury also differ according not only to the species, but where it was caught. Unfortunately, in Canada consumers aren’t given the information they need to know which species they are purchasing or where it was harvested.
Photo Credit: Oceana/Thierry Lannoy and Oceana/Pilar Marin
Are you really eating tuna?
In Ottawa, Canada’s capital, Oceana Canada tested fish for DNA and found that almost half of the fish were mislabeled last summer. Four out of five samples of white tuna were actually escolar, a fish that is known as the “laxative of the sea.” The oily fish in question is not at all related to tuna, and it can make you sick with diarrhea, vomiting, and nausea. The health concerns are so severe that it is banned in Italy, South Korea and Japan.
We wish this was only a problem in Canada, but our colleagues from Oceana offices around the world have found similar examples of fraud. In Brussels, 95 per cent of bluefin tuna samples were fraudulent. And in the US, a shocking 94 per cent of white tuna samples were mislabelled, with 84 per cent of samples actually being escolar.
This “bait and switch” practice is bad for public health and safety, cheats customers, and hurts law-abiding, honest fishers and seafood businesses. It also hurts the long-term economic and environmental health of fisheries and fish populations. It can even mask global human rights abuses by creating a market for illegally caught fish.
Photo Credit: Miki Tiger
Is Canned Tuna Safe To Eat? Experts Weigh In On The Benefits Of Eating The Canned Fish | TIME
FAQ
Why do I have diarrhea after eating tuna?
What are the side effects of canned tuna?
Is canned tuna hard on the stomach?
Why you shouldn’t eat too much canned tuna?
What happens if you eat canned tuna?
As with other foods, there is a risk that canned tuna can be contaminated with pathological bacteria, such as Clostridium botulinum, Salmonella, Shigella, Campylobacter jejuni and Escherichia coli, which can cause food poisoning and even death. Symptoms can include diarrhea, vomiting and stomach cramps four to 36 hours after ingestion.
Are tuna or sardines safe to eat when one has diarrhea?
When you’re having diarrhea or recovering from it, there are a lot of foods you need to avoid. They can trigger the digestive system and exacerbate or prolong diarrhea. Some of them: sausage and sausages – tuna or sardines.
Is canned tuna toxic?
Canned tuna contains mercury, a heavy metal that can be toxic in small doses. Tuna swim in waters that contain high amounts of methylmercury, a substance that can impair the nervous system, particularly in fetuses, infants and young children.
Can you eat canned tuna?
If you eat canned tuna, choose the product with low sodium or no added salt. As with other foods, there is a risk that canned tuna can be contaminated with pathological bacteria, such as Clostridium botulinum, Salmonella, Shigella, Campylobacter jejuni and Escherichia coli, which can cause food poisoning and even death.