A standard 5-ounce can of tuna packed in water contains about 30 grams of protein, while the same size can packed in oil delivers around 40 grams. That makes tuna one of the most protein-dense foods you can buy, with roughly 89% of its calories coming from protein alone.
Protein by Serving Size and Type
How much protein you get depends on whether you’re eating canned or fresh tuna, and whether your can is packed in water or oil. Here’s how they compare based on USDA data:
- Canned tuna in water (5 oz): 30 grams of protein
- Canned tuna in oil (5 oz): 40 grams of protein
- Fresh tuna, cooked (3 oz): approximately 25 grams of protein
On a per-ounce basis, canned tuna in oil provides about 8 grams of protein, while canned tuna in water provides about 6 grams. The difference comes down to how the packing medium affects moisture content. Oil-packed tuna retains less water during processing, which concentrates the protein (and calories) per ounce. If you’re counting calories alongside protein, water-packed tuna is the leaner option. If you simply want the most protein per can, oil-packed wins.
How Tuna Compares to Other High-Protein Foods
Tuna stands out even among foods known for being protein-rich. Per 100 grams, tuna provides 29 grams of protein, and 89% of its total calories come from protein. Chicken breast is close at 31 grams per 100 grams, but only 73% of its calories are from protein because it carries slightly more fat. Egg whites hit 85% of calories from protein, but you’d need to eat a large volume of them to match what a single can of tuna provides.
For people trying to hit a high protein target without overshooting their calorie budget, tuna is hard to beat. A 5-ounce can of tuna in water has roughly 150 calories and 30 grams of protein. Getting the same amount of protein from chicken breast would cost you closer to 180 to 200 calories.
Protein Quality, Not Just Quantity
The protein in tuna is exceptionally high quality. It contains all nine essential amino acids your body can’t make on its own, making it a complete protein. When scientists measure protein quality on a standardized scale (where 1.0 is a perfect score), tuna and most fish products score between 0.9 and 1.0. That puts tuna on par with eggs and dairy for how efficiently your body can use it.
Tuna is also particularly rich in leucine, the amino acid most responsible for triggering muscle protein synthesis. A 3-ounce serving of cooked skipjack tuna contains nearly 2 grams of leucine, which meets or exceeds the threshold most research identifies for maximizing the muscle-building signal after a meal. White tuna canned in oil is nearly as high at 1.8 grams per 3-ounce serving.
Does Canning Reduce the Protein?
The canning process involves high heat and pressure, which raises a fair question: does it damage the protein? Research on canned albacore tuna found that while sterilization and long-term storage slightly reduced the raw protein content (mostly by shifting the ratio of protein to fat in the can), it did not reduce protein digestibility or biological value. In practical terms, your body absorbs and uses the protein from canned tuna just as effectively as protein from fresh tuna. A can that’s been sitting in your pantry for a year is nutritionally comparable to one you bought last week.
How Much Tuna You Can Safely Eat
Tuna does contain mercury, so eating it every day in large amounts isn’t ideal. The EPA and FDA recommend eating 2 to 3 servings per week of fish from the “Best Choices” category, which includes canned light tuna (typically skipjack). Albacore or “white” tuna has higher mercury levels and falls into the “Good Choices” category, where the recommendation drops to 1 serving per week. A serving is 4 ounces.
For pregnant or breastfeeding women, the guidance is 8 to 12 ounces of lower-mercury seafood per week, which can include canned light tuna as part of a varied mix. The broader Dietary Guidelines for Americans recommend at least 8 ounces of seafood per week for the general population. Sticking within these ranges lets you take full advantage of tuna’s protein density without meaningful mercury risk. Rotating between canned light tuna and other low-mercury fish like salmon, sardines, or shrimp is a simple way to keep your intake varied.