Tuna is one of the most nutrient-dense proteins you can eat. A 4-ounce serving of white tuna delivers nearly 27 grams of protein, and it comes packed with omega-3 fatty acids, selenium, and B vitamins. The short answer is yes, tuna is good for you, but the type you choose and how often you eat it matters more than most people realize.
What Makes Tuna So Nutritious
Tuna’s reputation as a health food rests on two pillars: high-quality protein and omega-3 fatty acids. The protein content rivals chicken breast, but tuna brings something chicken doesn’t. The omega-3s in tuna, specifically DHA and EPA, play direct roles in heart and brain health that most other lean proteins simply can’t match.
Tuna is also one of the richest dietary sources of selenium, a mineral your body uses to build antioxidant enzymes and support thyroid function. This selenium content turns out to be important for another reason: it helps offset the mercury that tuna also contains. In tuna, the selenium-to-mercury molar ratio ranges from 1.3 to 20, meaning there’s always more selenium than mercury. Selenium binds to mercury and forms compounds that are far less toxic than mercury alone, reducing your body’s actual exposure.
Heart Health Benefits
The cardiovascular case for eating tuna is strong. People who eat fatty fish a few times per week have roughly half the risk of dying from coronary heart disease and about one-third the risk of dying from a heart attack compared to people who eat no fish at all. Even modest intake helps: eating fish just one to three times per month is associated with a 21% lower risk of coronary heart disease death.
The omega-3 fatty acids in tuna lower triglycerides and raise HDL (good) cholesterol. In the largest randomized controlled trial on the topic, involving over 11,000 patients with existing heart disease, daily fish oil supplementation led to a 20% reduction in death from any cause and a 45% reduction in sudden cardiac death over 3.5 years. The American Heart Association recommends at least two servings of fatty fish per week as part of a heart-healthy diet.
Brain and Memory Benefits
DHA, the omega-3 fatty acid most concentrated in tuna, is a structural component of brain tissue. Your brain depends on dietary intake to maintain adequate levels, which means people who eat little seafood may be running on a deficit.
A six-month randomized controlled trial gave healthy young adults (ages 18 to 45) either DHA supplements or a placebo. Those taking DHA showed measurable improvements in both episodic memory and working memory speed. The benefits broke down interestingly by sex: women showed the strongest gains in episodic memory, while men improved most in working memory reaction time. These were healthy young people, not elderly participants with cognitive decline, suggesting that DHA benefits the brain across the lifespan.
The Mercury Question
Mercury is the main reason people hesitate about tuna, and it’s a legitimate concern, but it’s also more nuanced than the typical warning suggests. Mercury levels vary dramatically depending on the species of tuna you’re eating.
Skipjack tuna, which is what most “chunk light” canned tuna contains, has the lowest mercury levels at 0.05 to 0.22 parts per million. At those concentrations, one to two meals per week falls within safe limits. Albacore (sold as “white” canned tuna) and bigeye tuna carry significantly more mercury, ranging from 0.22 to 0.95 ppm, and are best limited to about one meal per month.
The FDA and EPA recommend that adults eat two to three servings of fish per week from the lowest-mercury options, or one serving per week from moderate-mercury choices like albacore. Pregnant and breastfeeding women should stick to 8 to 12 ounces per week of lower-mercury seafood. For children, the guidance is two servings per week from the lowest-mercury fish. In practical terms, this means canned light tuna (skipjack) is a regular rotation food, while albacore and bigeye are occasional choices.
Canned in Water vs. Oil
Most people eat tuna from a can, and the packing liquid changes the nutritional profile more than you might expect. A 5-ounce can of tuna in water has about 120 calories. The same size can packed in oil jumps to 280 calories, more than double. Sodium is also higher in oil-packed tuna: roughly 118 mg per ounce compared to 70 mg per ounce in water-packed versions.
Here’s the surprising part: tuna canned in water actually retains more omega-3s than tuna canned in oil. Per ounce, water-packed tuna contains 56 mg of DHA compared to just 29 mg in oil-packed. The vegetable oil used in canning likely pulls some of the fish’s natural omega-3s out of the flesh. If you’re eating tuna specifically for heart and brain benefits, water-packed is the better choice on every metric.
Choosing Sustainable Tuna
How your tuna was caught affects both the environment and, to some degree, what ends up in the can. Pole-and-line fishing catches tuna one fish at a time near the ocean surface, resulting in very low bycatch (unintended catches of other marine life) and zero contact with seabed habitats. It’s considered one of the most selective fishing methods available.
Look for the Marine Stewardship Council (MSC) blue label on cans, which certifies that the fishery meets sustainability standards for fish stock health, environmental impact, and management practices. MSC-certified fisheries that use fish aggregating devices (FADs) must now track and retrieve those devices or use biodegradable versions. Many brands now print their fishing method on the label. “Pole and line” or “troll caught” are the most environmentally friendly options, while “FAD-free” purse seine is a reasonable middle ground.
How to Get the Most From Tuna
Your best routine is to eat canned light (skipjack) tuna once or twice a week, packed in water. This gives you the protein and omega-3 benefits while keeping mercury exposure well within safe limits. If you prefer the milder taste of albacore, treat it as a once-a-week choice rather than a daily staple.
Fresh tuna steaks, typically yellowfin or ahi, fall in the moderate mercury range similar to albacore. They’re a great source of protein and omega-3s for an occasional meal but aren’t ideal as your everyday fish. Mixing tuna with other low-mercury seafood like salmon, sardines, or shrimp gives you the broadest range of nutrients while keeping mercury well in check.