A 100 g serving of cooked tuna (about 3 oz) provides roughly 130 calories and 28 g of protein, per USDA FoodData Central. Canned in water is similar and very lean. Tuna is a top low-fat protein. Canned in oil adds calories from the oil — drain it or pick water-packed to keep it lean. Because some tuna has mercury, guidance suggests limiting certain types for pregnant people; vary your protein sources.
Key facts:
- 100 g tuna: ~130 kcal, ~28 g protein
- Water-packed is leanest
- Oil-pack adds calories
- Vary sources for mercury