Tuna is one of the most protein-dense foods available, with roughly 20 to 24 grams of protein per 100 grams of muscle meat and very little fat. But protein is just the starting point. Tuna contains a complex mix of beneficial nutrients, omega-3 fatty acids, and trace contaminants like mercury that are worth understanding, especially if you eat it regularly.
Protein and Fat Content
Tuna is overwhelmingly lean protein. The white muscle tissue (the bulk of what you eat) contains about 23–24% protein in skipjack and 21–22% in yellowfin, with less than 1% fat. That makes a standard 3-ounce serving around 20 grams of protein and under a gram of fat. Few other affordable protein sources come close to that ratio.
The belly flap is the fattiest cut, but even there, fat content stays below 2%. Tuna skin is the exception, running 7 to 9% fat, though most people don’t eat it. The practical takeaway: whether you’re eating canned chunk light or a fresh yellowfin steak, you’re getting a high-protein, low-fat food.
Omega-3 Fatty Acids
Despite being low in total fat, tuna provides meaningful amounts of EPA and DHA, the two omega-3 fats linked to heart and brain health. The amount depends on the type. A 3-ounce serving of canned light tuna (typically skipjack) delivers about 190 milligrams of combined EPA and DHA. Fresh yellowfin provides less, closer to 100 milligrams per serving.
For context, major health organizations generally recommend 250 to 500 milligrams of EPA and DHA per day. Two servings of canned light tuna would get you there. Fattier fish like salmon deliver more per bite, but tuna remains a solid and inexpensive source, particularly in canned form.
Vitamins and Minerals
Tuna is notably rich in a few micronutrients. Just 3 ounces of canned tuna supplies up to 50% of the recommended daily intake of vitamin D, a nutrient many people fall short on, especially in winter months or northern climates. Tuna is also a strong source of B vitamins, particularly B12 and niacin, which play central roles in energy production and nerve function.
Selenium is another standout. This mineral acts as an antioxidant and supports thyroid function, and tuna is one of the richest dietary sources. The selenium content in tuna is high enough that it consistently exceeds the mercury content on a molecular level. This matters because selenium can bind to mercury in the body, potentially limiting mercury’s ability to cause harm. Researchers have calculated a “health benefit value” for different tuna species based on this selenium-to-mercury ratio. All four major commercial species (skipjack, yellowfin, albacore, and bigeye) showed a clear molar excess of selenium over mercury, with skipjack scoring highest.
Mercury Levels by Species
Mercury is the most discussed contaminant in tuna, and levels vary significantly by species. Canned light tuna, which is mostly skipjack, averages 0.126 parts per million (ppm) of mercury. Canned albacore (labeled “white tuna”) averages 0.350 ppm, nearly three times higher. Bigeye tuna, often sold as sushi-grade, carries the highest levels and is the only common tuna species the FDA recommends avoiding entirely.
The FDA classifies tuna into three tiers based on mercury. Canned light tuna (including skipjack) falls in the “Best Choices” category, meaning two to three 4-ounce servings per week is considered safe for adults, including pregnant and breastfeeding women. Albacore and yellowfin land in “Good Choices,” limited to one serving per week for those same groups. Children’s portions are smaller: about 1 ounce for toddlers, scaling up to 4 ounces by age 11.
Histamine in Mishandled Tuna
Fresh tuna that hasn’t been kept cold enough can develop high levels of histamine, a compound that causes a reaction called scombroid poisoning. Symptoms resemble an allergic reaction: flushing, headache, nausea, and sometimes hives, typically starting within minutes to hours of eating.
Fresh tuna normally contains less than 1 milligram of histamine per 100 grams. Levels as low as 20 mg/100 g can trigger symptoms in sensitive individuals. The FDA sets the hazard threshold at 50 mg/100 g. The key variable is temperature. Histamine formation is minimal when fish stays refrigerated and negligible below 32°F (0°C). Once histamine forms, cooking won’t destroy it. This is why proper cold-chain handling matters more for tuna than for many other proteins. Canned tuna is not a concern here, since it’s processed quickly after catch.
Purines and Gout Risk
Tuna, like most fish and seafood, is a moderate-to-high purine food. Purines are natural compounds that your body converts into uric acid. In most people this is harmless, but for those with gout or elevated uric acid levels, high-purine foods can trigger painful flare-ups. Finfish and shellfish generally range from about 110 to 260 milligrams of total purines per 100 grams, with tuna falling within that spectrum. If you have gout, limiting tuna to occasional small portions is a reasonable approach.
Microplastics in Canned Tuna
A 2022 study analyzing commercial canned tuna found microplastic particles in every sample tested. Tuna packed in water contained roughly 692 particles per 100 grams, while tuna in oil had about 442 per 100 grams. The vast majority of these particles (90%) were extremely small, between 1 and 50 micrometers, invisible to the naked eye.
These numbers sound alarming, but microplastics are now found in most foods, tap water, and even the air we breathe. The long-term health effects of ingesting them at these levels are still not well understood. For now, microplastic exposure from tuna is part of a broader environmental reality rather than a tuna-specific concern.
Canned Light vs. Canned White
If you’re standing in a grocery aisle deciding between the two most common options, here’s the practical breakdown:
- Canned light tuna (skipjack): higher in omega-3s per serving, lower in mercury (0.126 ppm average), classified as a “Best Choice” by the FDA, and typically cheaper.
- Canned white tuna (albacore): firmer texture, milder flavor, but nearly three times the mercury (0.350 ppm average), classified as a “Good Choice” with a lower recommended serving limit.
Both deliver comparable protein. For people eating tuna several times a week, canned light is the safer long-term option. For occasional meals, the difference is less meaningful.