Draining narrows the difference, but oil-packed tuna usually still has more fat and calories than water-packed tuna. Most of the packing liquid can be poured away, yet some oil remains on and within the fish. Protein stays high in both versions, so the main nutritional difference after draining is usually the amount of added fat and the energy that comes with it.
The size of that difference is not fixed. Tuna species, brand, oil type, packing method and how thoroughly you drain the can all matter. Compare equal drained weights whenever possible rather than assuming that two cans contain the same amount of edible fish.
Oil changes energy more than protein
Water contributes essentially no energy to the tuna. Oil, by contrast, is energy dense. Even after it is poured off, an oil-packed product retains some of that added fat. USDA food-composition references illustrate the scale: some drained light tuna in water entries contain around 1 gram of fat per 100 grams, while a drained light tuna in oil reference contains a little over 8 grams.
That extra fat can push an oil-packed reference close to 200 calories per 100 grams, whereas water-packed examples are substantially lower. The numbers should be treated as examples, not a universal label value. Different products can use different tuna, have different moisture content, and be formulated with or without added salt.
More fat is not automatically a drawback. Olive oil or another unsaturated vegetable oil can be a useful part of a diet. What matters is whether you want that oil already included or prefer to control the amount separately when building the meal.
What the drained comparison looks like
| Feature | Water-packed, drained | Oil-packed, drained |
|---|---|---|
| Protein | High | High |
| Total fat | Usually lower | Usually higher |
| Calories | Usually lower | Usually higher |
| Texture | Leaner, sometimes drier | Richer and more moist |
| Sodium | Brand dependent | Brand dependent |
Protein figures can look surprisingly different across databases because the amount of water in a food changes how nutrients are concentrated per 100 grams. That does not mean packing tuna in oil creates protein. It means equal weights of drained products may contain different proportions of fish, water and retained oil.
Sodium is a separate variable. Water-packed tuna may be packed in salted water or brine; oil-packed tuna may also contain added salt. A “no salt added” or lower-sodium label can matter far more for sodium intake than whether the can says water or oil.
Does extra draining remove all the oil?
No. A longer drain can remove more free oil than a quick pour, so the amount actually eaten changes with preparation. Pressing gently or letting the tuna sit in a strainer can reduce the surface liquid further. However, some oil remains associated with the tuna, and a home cook cannot accurately calculate how much was absorbed and how much was discarded.
Rinsing may remove additional surface liquid and some sodium, but it also washes away flavor and is not necessary for a properly stored commercial can. If you track calories closely, the best option is a product whose nutrition label specifies values for the drained portion, then weigh the amount you actually use.
Think about the rest of the recipe too. Tuna salad made with mayonnaise, an olive-oil dressing or avocado already contains another fat source. Starting with water-packed tuna gives you more control over that addition. If the tuna is served on its own with vegetables and lemon, retained olive oil may be exactly what gives the dish enough richness.
Which one makes more sense for you?
Choose water-packed tuna when you want a lean protein base and the lowest practical calorie contribution from the packing medium. Choose oil-packed tuna when you value a softer texture and richer flavor, or when the retained oil is replacing dressing you would otherwise add. Neither choice changes the need to look at portion size and the whole meal.
The packing medium also does not determine mercury content. Species matters much more for mercury, so an albacore can in water does not become lower-mercury simply because it is packed without oil. Likewise, the omega-3 content of the fish and the fatty-acid profile of the added oil are two different things.
The useful takeaway is that draining removes some of the nutritional gap, not all of it. Water-packed tuna is generally leaner; oil-packed tuna generally carries extra fat and calories even when drained, while both remain concentrated sources of protein.
Sources
- FoodData Central — Food composition database with entries for drained canned tuna packed in water and oil.
- Dietary Guidelines for Americans — General context for dietary fat, calorie balance and nutrient-dense food choices.