Tuna vs Sardines: Nutrition and Canned Portions

Canned tuna and sardines are convenient sources of complete protein, but they differ in fat content, calcium, omega-3 fatty acids and mercury exposure. Tuna packed in water is usually a leaner choice, while sardines with edible bones can supply considerably more calcium and marine omega-3 fats.

The type of tuna matters. Canned light tuna, including skipjack, must not be treated as equivalent to albacore, yellowfin or bigeye tuna when discussing mercury. The packing medium matters too: fish in water, oil and tomato sauce can have different nutritional values.

Actual nutrition data: canned tuna versus sardines

The following figures come from two specifically identified USDA SR Legacy food descriptions. They refer to 100 g of drained edible fish, not the complete weight of a can.

For comparisons based on drained edible portions, the separate guides to tuna and sardines help distinguish canned product types.

Sources: USDA light tuna data and USDA Atlantic sardine data. The underlying dataset is USDA SR Legacy; these are food-description values, not independently measured nutrition labels for every current product.

There is an important limitation: the tuna is packed in water without added salt, while the sardines are packed in oil. Both are drained, but they do not have the same packing medium. Consequently, this table is a real-world comparison of two clearly defined canned products, not a controlled test isolating fish species. For a strict same-medium comparison, choose two actual cans packed in water and use their respective drained-product labels.

The measured database entries show 0.89 g more protein and 92 fewer calories for the light tuna per 100 g. The specified sardine entry supplies far more calcium, primarily because its softened bones are included.

What happens with real edible portion sizes?

A package's net weight and drained weight are not necessarily the same. A 120 g can containing 90 g of drained fish supplies nutrition based on those 90 g if the liquid is discarded.

Using the USDA entries above:

The per-serving values are calculated from the real USDA per-100-g entries, not independently measured servings. Values have been rounded.

Serving nutrient = reference value per 100 g × edible serving weight / 100.

If you eat the oil, tomato sauce or other packing liquid, calculate that separately or use a label that describes the entire consumed product. Do not use drained-fish values for a serving that includes all the oil.

Lean protein versus oily fish

With the specified USDA entries, tuna provides about 22.0 g protein per 100 kcal, compared with about 11.8 g for sardines.

That makes this canned light tuna a more concentrated protein source relative to calories.

Sardines, however, contain considerably more total fat, including valuable long-chain marine omega-3 fatty acids EPA and DHA. Their nutritional advantage cannot be assessed by protein-per-calorie calculations alone.

Actual EPA and DHA concentrations vary with species, location and processing. Avoid treating total fat as an exact omega-3 measurement.

If you want maximum protein with fewer calories, light tuna in water can be practical. If you are seeking oily fish and calcium from edible bones, sardines serve a different purpose.

Why sardine bones change the calcium comparison

The referenced Atlantic sardines provide 382 mg calcium per 100 g, versus 11 mg in the specified tuna entry.

This substantial difference is partly explained by the edible softened bones included in the sardine food description.

Boneless sardines may contain significantly less calcium. Check the actual product rather than assigning the same calcium figure to every sardine can.

The iron values in these particular entries also differ: 2.92 mg in sardines versus 1.53 mg in light tuna per 100 g.

These numbers are tied to the described products and should not be generalized to all tuna and sardines.

Mercury: the tuna species makes the decision different

The FDA/EPA fish advice identifies sardines and canned light tuna, including skipjack, as Best Choices. Albacore/white tuna and yellowfin tuna are Good Choices, while bigeye tuna belongs to Choices to Avoid for the populations covered by its advice.

This is a major reason not to describe every can simply as "tuna."

Historical FDA monitoring data reported these approximate average mercury concentrations:

Source: EPA/FDA technical fish advice data.

These are monitoring averages from sampled fish, not guaranteed concentrations in an individual can. The data are historical and sample coverage differs by species. They nevertheless illustrate why tuna identification is important.

See the FDA/EPA fish consumption advice for population-specific recommendations, especially for pregnancy, breastfeeding and children. Applicable German or French national recommendations may differ.

For someone eating canned fish frequently, varying species and favouring appropriate lower-mercury choices can be more useful than repeatedly choosing an unidentified tuna species.

Salt, oil and the can label

The tuna entry in the first table specifically contains no added salt. The sardine entry has a different formulation, so its higher sodium value must not be interpreted as evidence that all sardines naturally contain more sodium than tuna.

Compare actual labels per 100 g. In the EU, salt is normally declared rather than sodium.

For oil-packed cans, check whether the declared values refer to the drained fish or to the product as sold. Drained fish can retain some oil.

For accurate nutrition tracking, weigh the edible fish after draining, then count any packing medium actually consumed. A tuna product in oil can be much more energy-dense than the water-packed tuna in this comparison.

Cost: calculate the drained edible amount

The cheapest-looking can is not necessarily the best value.

Suppose two hypothetical packages are offered:

These are hypothetical prices, not current supermarket observations.

Cost per 100 g drained = can price / drained grams × 100.

You can also calculate cost per 30 g protein using verified protein data from the product label. This is useful for budgeting, but it does not account for omega-3 or calcium benefits.

Choosing between the two

Both fish work in salads, sandwiches, potato dishes and quick meals. Tuna has a milder, flaky texture; sardines have a stronger flavour and richer texture.

A balanced meal can include either fish alongside vegetables, whole grains or legumes.

Sources and interpretation

• USDA FoodData Central — underlying food-composition data.
• Light tuna, drained, USDA-derived values — 116 kcal and 25.51 g protein per 100 g.
• Atlantic sardines, drained with bones, USDA-derived values — 208 kcal and 24.62 g protein per 100 g.
• FDA/EPA advice about eating fish — species-specific mercury categories.
• FDA/EPA technical monitoring data — historical average mercury concentrations.

The nutrition comparison uses real database entries for differently packed products. Portion calculations are derived from those entries. Only the clearly identified shopping example is hypothetical. Check actual labels, drained weights and local fish advice before making an individual decision.