A typical tuna steak weighing 6 ounces (170 grams) packs around 50 grams of protein, making it one of the most protein-dense foods you can eat. Raw yellowfin tuna contains about 24 grams of protein per 100 grams, and that concentration increases slightly after cooking as moisture evaporates.
Protein by Serving Size
Most tuna steaks sold at grocery stores and fish counters weigh between 5 and 8 ounces. Here’s what you’re getting in terms of protein, based on cooked yellowfin tuna:
- 4 oz (113g): roughly 33 grams of protein
- 6 oz (170g): roughly 50 grams of protein
- 8 oz (227g): roughly 66 grams of protein
A single 6-ounce tuna steak covers nearly all the daily protein a 150-pound adult needs, and it does so for only about 220 to 240 calories. That protein-to-calorie ratio is hard to beat. A chicken breast of the same size delivers a similar amount of protein but typically has slightly more calories if cooked with any fat, while a 6-ounce sirloin steak comes in around 42 grams of protein with considerably more fat.
How Species Affects Protein Content
Not all tuna steaks are created equal, though the differences are modest. Bluefin tuna, the fattier species prized in sushi restaurants, delivers about 50.8 grams of protein in a cooked 6-ounce fillet. Yellowfin lands just behind at 49.6 grams for the same portion. Skipjack, more commonly found in canned tuna than as steaks, provides about 24 grams per 3-ounce cooked serving.
The practical takeaway: if you’re buying a fresh or frozen tuna steak, it’s almost certainly yellowfin or occasionally bluefin, and the protein content is essentially the same between them. Bluefin has more fat, which means slightly more calories per serving, but the protein difference is negligible.
Why Tuna Protein Is Especially Useful
Protein quality matters as much as quantity. Tuna scores between 0.9 and 1.0 on the PDCAAS scale, which measures how well your body can digest and use a protein source. A perfect score is 1.0, and tuna sits right at the top alongside eggs and dairy. Fish protein digestibility ranges from 77% to nearly 99%, with fresh tuna landing at the high end of that range.
Tuna is also rich in leucine, the amino acid that plays the biggest role in triggering muscle repair and growth. Fresh tuna provides about 1.9 grams of leucine per 100 grams. Research on muscle maintenance suggests that roughly 2.5 to 3 grams of leucine per meal is the threshold for maximizing muscle protein synthesis, so a 6-ounce tuna steak clears that bar easily with over 3 grams of leucine in a single serving. This makes tuna steaks a particularly effective post-workout meal or a strong choice for older adults looking to preserve muscle mass.
Tuna Steak vs. Canned Tuna
If you’re comparing a tuna steak to canned tuna, the protein content per ounce is similar, but not identical. Canned white tuna packed in oil provides about 22.6 grams per 3-ounce serving, while canned white tuna in water drops to about 20.1 grams for the same amount. A 3-ounce portion of cooked yellowfin steak gives you roughly 25 grams.
The bigger difference is portion size. A standard can of tuna holds about 5 ounces drained, while a restaurant tuna steak is typically 6 to 8 ounces. You’re simply eating more fish with a steak, which means more total protein per meal. The texture and flavor also differ enough that most people find it easier to eat a large portion as a steak than from a can.
Mercury and How Often to Eat Tuna Steaks
Tuna steaks come from larger fish that accumulate more mercury than smaller species. The FDA categorizes yellowfin and albacore tuna as “Good Choices,” meaning one serving per week is appropriate for most adults. Bigeye tuna, sometimes sold as “ahi” alongside yellowfin, falls in the “Choices to Avoid” category due to highest mercury levels. Canned light tuna (usually skipjack) is a “Best Choice” with lower mercury, safe for two to three servings per week.
If you’re eating tuna steaks regularly for the protein, sticking to one or two servings per week and rotating in other high-protein fish like salmon, cod, or sardines keeps mercury exposure low while maintaining a strong protein intake from seafood. Pregnant or breastfeeding women should be especially mindful, keeping “Good Choice” fish to one 4-ounce serving per week.