Tuna nutrition facts at a glance

A 3-ounce serving of tuna is typically high in protein and very low in carbohydrates. Canned light tuna packed in water is usually one of the leanest options, with roughly 70 to 100 calories and about 15 to 20 grams of protein per serving, depending on the product and whether it is drained. Fresh tuna steaks are similar in protein but can be a little higher in calories depending on the cut.

Tuna is naturally carb-free and usually low in sugar. The fat content is also low in many tuna varieties, although albacore and tuna packed in oil can contain more fat and calories than light tuna packed in water. If you are tracking macros, always check the label because drainage, oil packing, and added ingredients can change the numbers.

What tuna provides besides protein

Tuna is best known for protein, but it also contributes several important nutrients. It contains B vitamins, especially niacin and vitamin B12, which help with energy metabolism and red blood cell formation. Tuna also provides selenium, a mineral involved in antioxidant defense and thyroid function, plus phosphorus and potassium in varying amounts.

Because tuna is a fish, it also contains heart-healthy omega-3 fats, though the amount depends on the species. Fatty fish usually provide more omega-3s than very lean fish. If you want a tuna meal that supports recovery after exercise, pairing tuna with fiber-rich carbs and vegetables can make it more balanced.

Canned tuna vs fresh tuna

Fresh tuna steaks and canned tuna are both nutritious, but they are not identical. Fresh tuna is often less processed and may taste richer, while canned tuna is more convenient, shelf-stable, and usually cheaper. Nutritionally, both are strong protein sources.

The biggest differences are often sodium and added fat. Tuna canned in water is usually lower in calories than tuna canned in oil, while some packaged tuna salad products can be much higher in sodium and calories because of mayonnaise or seasoning. If you are trying to lose fat or keep meals lighter, water-packed tuna is usually the easier choice.

Mercury, sodium, and how much tuna is smart to eat

The main caution with tuna is mercury. Larger tuna species, especially albacore, generally contain more mercury than canned light tuna. Mercury matters most for pregnant people, breastfeeding people, young children, and anyone eating tuna often. Choosing lower-mercury fish more often and rotating seafood choices is a good strategy.

Sodium is the other label detail to watch. Some canned tuna is relatively low in sodium, but flavored packets, seasoned tuna, and tuna mixed into prepared salads can be much higher. If blood pressure is a concern, compare labels and choose no-salt-added or lower-sodium versions when possible.

Tips

• Choose water-packed tuna if you want the lowest calorie option.
• Drain tuna well to reduce extra calories and sodium from the liquid.
• Rotate tuna with other seafood and protein sources to limit mercury exposure.
• Use tuna with vegetables, beans, or whole grains for a more filling meal.
• Check the label for serving size, sodium, and whether the tuna is light or albacore.