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Dangerous Side Effects of Eating Canned Tuna, According to Science

Don’t let hives, tingling toes, and high blood pressure keep you from catching the benefits of fish.
FACT CHECKED BY Olivia Tarantino

Unless you happen to live near the sea and are pretty good with a hook and line, the easiest way to eat more fish is to open a can of tuna. Canned tuna is among the healthiest, most affordable sources of protein you can buy. The fish is rich in anti-inflammatory, heart-protective omega-3 fatty acids, contains anywhere between 20 and 25 grams of protein per can, is rich in vitamin D, and is low in carbs. As most of the American population isn't getting enough omega-3 fatty acids, including tuna in your diet is a convenient, cheap way to overcome this deficiency.

While it's important to be aware and informed about potential health hazards of eating canned fish, keep in mind that by eating a balanced diet and consuming a moderate intake of tuna per week, which the FDA recommends as 2-3 servings, you can reap the benefits of tuna without most of the side effects.

Knowing the potential dangers of canned tuna and how to avoid them may lure you back to making tunafish sandwiches for lunch once or twice a week. After all, despite the potential concerns, canned tuna is nowhere near as bad for you as these 8 Dangerous Foods that are Shortening Your Life, According to Science.


Mercury Poisoning

canned tuna bread

Also called hydrargyria, mercury poisoning is usually caused by consuming food containing the heavy metal, a known neurotoxin. "All fish have some level of mercury, but that level varies widely; canned tuna has relatively high levels of mercury so its consumption could potentially become harmful above three or so servings a week," says Andrea Paul, MD, medical advisor to Illuminate Labs. Symptoms of mercury poisoning include itching or a pins-and-needles feeling in the toes and fingertips, muscle weakness, coordination, speech and hearing impairment, and reduced peripheral vision. High mercury levels in women who are pregnant may result in central nervous system disorders in their babies.

Dr. Paul recommends switching to fish with lower levels of mercury, like wild-caught salmon, to gain the health benefits of omega-3 fatty acids without the health risks. The Food & Drug Administration (FDA) and Environmental Protection Agency (EPA) recently revised their recommendations, encouraging pregnant women and women breastfeeding to eat more low-mercury fish (up to 12 ounces weekly) to gain the health benefits. However, both agencies continue to advise that no more than six ounces of those 12 per week be white (albacore) tuna, a large fish that contains higher amounts of mercury. Canned light tuna is made mostly from skipjack tuna, a smaller species that's lower in mercury.

If you don't mind paying a little bit more for peace of mind, consider the Safe Catch brand of canned fish. Using a proprietary technology that the company founders invented, Safe Catch tests every tuna and salmon for mercury levels before buying it. The company's Safe Catch Elite tuna is 10 times lower in mercury than the FDA limit of 1.00 ppm (parts per million). Its wild albacore is 2.5 times lower than the FDA limit. Safe Catch is also cooked just once while in the can, which retains more healthy oils, says chief operating officer Kevin McCay. Other brands cook twice, first on racks where the oils drip away, then again in the cans.

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Scombroid Poisoning

can tuna

If you experience facial flushing, sweating, dizziness, and a peppery taste in your mouth and throat shortly after eating canned tuna, you could be having an allergic reaction to a bacterium in marine fish that has begun to spoil. "Scombrotoxin is a unique type of food poisoning most commonly found in tuna and mackerel fish," says food scientist Janilyn Hutchings, CP-FS (certified professional in food safety) with "The toxin is created by spoilage bacteria due to improper handling and isn't destroyed in the canning process."

Canned fish isn't the only culprit. Anglers who leave their catch too long on a dock or boat out of the cooler can trigger bacterial growth in the fish that elevates levels of the histamine that causes symptoms. Non-scombroid gamefish such as bluefish, mahi-mahi and amberjack are also associated with the toxin. Advanced symptoms include hives, diarrhea, and blurred vision. See a physician if symptoms worsen or last more than 4 to 6 hours.


BPA Toxicity

tuna fish

Animal studies and some human studies suggest that the chemical Bisphenol A (BPA), a known endocrine-disrupting contaminant, may impact your health, potentially elevating blood pressure, causing infertility, birth defects, and raising the risk of obesity, diabetes, heart disease, and cancer. "BPA is a component in some food containers, including some cans, and it's somewhat controversial," says Hutchings. The FDA made standards for food containers stricter following a 2008 National Toxicology Program report indicating the levels of BPA consumed by the U.S. Population at the time could negatively affect health. "The FDA's official stance is that the amount of BPA currently in food containers is safe," says Hutchings.

A recent study conducted by the Can Manufacturers Institute in Washington state also found that all domestically produced food cans were lined with non-BPA next-generation materials. However, less is known about cans manufactured outside of the U.S.

Related: The Unhealthiest Canned Foods on the Planet


High Blood Pressure

open faced tuna sandwich

Fresh fish is a great source of protein and heart-healthy omega-3 fatty acids, but canned tuna, while very convenient, may not be the healthiest for those with high blood pressure. "At an average of 200-300 milligrams of sodium per serving, anyone who has heart disease or diabetes can't risk eating canned tuna," says nutritionist Cassidy Gunderson, PhD, who helps her clients manage chronic disease through food as the owner of Spiro Health & Wellness, in Salt Lake City. Eating a lot of canned tuna, along with other foods high in sodium like canned soups, baked goods, and other processed foods and restaurant meals, raises your risk of high blood pressure, kidney disease, diabetes, and sleep apnea. The American Heart Association recommends that people keep their daily intake of sodium below 1,500 milligrams. Luckily for you, there are multiple no-salt-added tuna brands, which we detail in our guide: 6 Best Canned Tunas on the Market, and 4 to Stay Away From.

If you're concerned about your blood pressure, you may want to read up on these 14 Mistakes That Are Making Your High Blood Pressure Worse.

Jeff Csatari
Jeff Csatari, a contributing writer for Eat This, Not That!, is responsible for editing Galvanized Media books and magazines and for advising journalism students through the Zinczenko New Media Center at Moravian University in Bethlehem, PA. Read more about Jeff
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