Canned tuna is not bad for you when eaten in reasonable amounts. It’s one of the most affordable sources of lean protein and omega-3 fatty acids available, and for most adults, two to three servings per week falls well within safe limits. The main concern is mercury, but the risk depends heavily on which type of tuna you buy and how often you eat it.
What You Get From a Can of Tuna
A 3-ounce serving of canned tuna packed in water delivers 16 to 20 grams of protein, depending on the species. Albacore (sold as “white tuna”) sits at the higher end with about 20 grams, while skipjack (sold as “chunk light”) comes in around 16 grams. Either way, that’s a significant portion of most people’s daily protein needs from a single can that costs a couple of dollars.
Canned tuna also provides omega-3 fatty acids, the type linked to heart health. Water-packed canned tuna contains 0.26 to 0.34 grams of EPA and DHA per serving. That’s modest compared to fresh bluefin tuna (up to 2.4 grams), but enough to contribute meaningfully if you eat it a few times a week. It’s also a source of vitamin D, B12, selenium, and iodine.
A large study of older adults found that eating tuna or other baked/broiled fish one to two times per week was associated with a 20% lower risk of heart failure. Eating it three to four times weekly was linked to a 31% lower risk. Those benefits disappeared for fried fish, so how you prepare it matters.
The Mercury Question
Mercury is the legitimate concern with canned tuna, and the answer isn’t the same for every can on the shelf. Fish absorb methylmercury from the water they swim in, and larger, longer-lived species accumulate more. The FDA tracks mercury levels across commercial fish, and the difference between the two main types of canned tuna is significant:
- Canned light tuna (skipjack): 0.126 parts per million mercury on average
- Canned white tuna (albacore): 0.350 parts per million mercury on average
Albacore contains nearly three times the mercury of skipjack. If you eat canned tuna regularly, choosing light tuna over white is the single easiest way to reduce your exposure.
The FDA classifies canned light tuna as a “Best Choice” fish, meaning most adults can safely eat two to three servings per week. Albacore falls into the “Good Choice” category, with a recommended limit of one serving per week. Bigeye tuna is the only variety the FDA says to avoid entirely due to high mercury levels, though it rarely shows up in cans.
How Selenium Offsets Mercury Risk
Tuna contains selenium, a mineral that binds to mercury in the body and forms a compound that can’t be absorbed. This effectively neutralizes some of the mercury before it deposits in tissue and causes harm. Researchers use a metric called the Selenium Health Benefit Value to assess whether a fish species has enough selenium to offset its mercury. A positive score means the selenium outweighs the mercury risk.
Skipjack tuna scores 19.61 on this scale, and even bigeye tuna (the highest-mercury variety) scores 11.47. Both are comfortably positive. This doesn’t mean mercury is irrelevant, but it does mean tuna’s built-in selenium content provides a meaningful buffer that many people don’t know about.
What Chronic Mercury Exposure Looks Like
For context on why mercury limits exist: adults exposed to harmful levels of methylmercury over time can develop symptoms including memory problems, depression, numbness, muscle weakness, difficulty walking, changes in vision or hearing, and a metallic taste in the mouth. These symptoms can appear gradually or develop suddenly. Reaching these levels from canned tuna alone would require eating far more than the recommended amounts over a sustained period, but it’s the reason guidelines exist, particularly for vulnerable groups.
Who Needs to Be More Careful
Pregnant and breastfeeding women can still eat canned tuna, but the FDA recommends sticking to two to three servings per week from the “Best Choice” list (which includes canned light tuna) or one serving per week from the “Good Choice” list (which includes albacore). A serving during pregnancy is defined as 4 ounces.
Children need smaller portions scaled to their age: about 1 ounce for ages one to three, 2 ounces for ages four to seven, 3 ounces for ages eight to ten, and 4 ounces at age eleven. The FDA recommends two servings per week from the “Best Choice” list for kids. Mercury is more concerning for developing nervous systems, which is why the portions are smaller, not because children should avoid tuna altogether.
Sodium Is Higher Than You’d Expect
One downside of canning that often gets overlooked is sodium. Fresh tuna contains about 13 milligrams of sodium per ounce. Canned tuna packed in water jumps to 70 milligrams per ounce, and oil-packed tuna hits 118 milligrams per ounce. For a full 3-ounce serving, that’s roughly 210 milligrams from water-packed and 354 milligrams from oil-packed, before you add anything else to your meal. If you’re watching your sodium intake, water-packed is the better option, and draining the liquid thoroughly helps.
BPA in Can Linings
Most metal food cans use an interior coating to prevent the food from contacting the metal directly. Traditionally, these coatings contained BPA, a chemical that mimics estrogen in the body. A Health Canada survey found that canned tuna products had the highest BPA levels among all canned foods tested, with an average of 137 nanograms per gram and individual samples ranging as high as 534 nanograms per gram. The variation between products was enormous: some cans of the same brand tested at 32 nanograms per gram while others hit 507.
Many manufacturers have shifted to BPA-free linings in recent years, though the alternatives aren’t always well studied either. If BPA is a concern for you, look for brands that specifically label their cans as BPA-free, or consider tuna sold in pouches, which typically don’t use the same type of lining.
Water-Packed vs. Oil-Packed
Beyond sodium, the packing liquid also affects the omega-3 content you actually get. Water-packed tuna retains more of its omega-3s (0.26 to 0.34 grams per serving) compared to oil-packed tuna after draining (0.09 to 0.26 grams). The vegetable oil used in oil-packed varieties can leach some of the fish’s own omega-3s into the packing liquid, which you pour down the drain. If you’re eating tuna for heart-health benefits, water-packed gives you more of what you’re after. Oil-packed tuna has a richer flavor and works better in certain recipes, but it comes with more calories, more sodium, and fewer omega-3s per serving.