Water-packed tuna comes out ahead for most health goals. It retains more of the omega-3 fatty acids that make tuna worth eating in the first place, delivers far fewer calories per serving, and carries a lower load of certain contaminants like bisphenols. That said, oil-packed tuna is not nutritional junk. It offers better protection against lipid oxidation during storage, and for people who are not watching calories or who use the oil in cooking, it can be a perfectly reasonable choice. The real answer depends on what you are optimizing for.
Omega-3 Retention Favors Water
The main nutritional reason most people eat tuna is its omega-3 fatty acid content, particularly EPA and DHA. These are the fats linked to cardiovascular and brain health benefits, and the packing medium has a surprisingly large effect on how much of them end up in your body. Water-packed tuna products have been found to contain higher EPA and DHA content per serving, with DHA alone ranging from about 90 to 770 milligrams depending on the product. The omega-6 to omega-3 ratio in water-packed products ran roughly 1:3 to 1:7, meaning omega-3s heavily dominated. In oil-packed products, that ratio flipped to about 3:1 to 4:1, with omega-6 fats taking the lead.1PubMed Central. The skinny on tuna fat: health implications – Section: Results
Why does this happen? It comes down to simple diffusion. When tuna sits in vegetable oil for months, fat-soluble compounds migrate between the fish and the surrounding oil. The tuna absorbs some of the packing oil’s fatty acids (typically linoleic acid if it is soybean oil, or oleic acid if it is olive oil), and some of the fish’s own omega-3s leach out into the surrounding oil. Research has confirmed that oil filling mediums increase levels of fatty acids from the oil while decreasing polyunsaturated fatty acids like EPA and DHA in the fish flesh itself.2PubMed Central. New Perspectives on Canned Fish Quality and Safety on the Road to Sustainability – Section: 3.1. Impacts of Seafood Canning Chain on Quality When you drain an oil-packed can, you pour a significant share of the tuna’s original omega-3s down the sink along with the oil.
Water does not cause the same exchange. Because omega-3s are fat-soluble, they stay put in the fish tissue rather than dissolving into the water. Draining a water-packed can removes mostly water and some water-soluble compounds like certain minerals, but the omega-3 profile of the fish remains largely intact. For anyone eating tuna specifically for heart-health benefits, this difference alone tilts the balance toward water.
Calories and Fat Content
The calorie gap between the two is substantial. A drained serving of water-packed tuna typically runs around 100 to 120 calories, with the vast majority coming from protein and only a small amount from fat. The same serving of oil-packed tuna, even after draining, often lands in the 150 to 200 calorie range, because the fish absorbs oil during storage that you cannot fully drain away. Energy from fat in canned tuna products can range from as low as 3 percent to as high as 33 percent of total calories, and the oil-packed products cluster at the high end of that range.1PubMed Central. The skinny on tuna fat: health implications – Section: Results
If you eat the oil along with the tuna rather than draining it, the calorie count rises further still, sometimes doubling compared to a water-packed serving. For people using tuna as a lean protein source for weight management, water-packed is the straightforward winner. But calories from oil are not inherently harmful. If you are eating tuna as part of a salad and plan to dress it with oil anyway, or if you are underweight and trying to increase caloric intake, the extra energy in oil-packed tuna is not a problem. Context matters.
The Draining Problem
Many people assume that draining the oil from a can of oil-packed tuna brings its nutritional profile close to the water-packed version. That assumption is wrong on two counts. First, as discussed above, some of the oil is absorbed into the fish during storage and cannot be drained out, so the calorie and fat content remain elevated. Second, draining the oil removes omega-3s that have migrated out of the fish and into the oil. You lose both ways.
With water-packed tuna, draining is relatively benign from a nutritional standpoint. You lose some dissolved sodium and trace minerals, but the protein and fat profile of the fish stays essentially the same. If you are the type of person who always drains a can before eating, water-packed gives you a much better return on what remains in the can.
One practical nuance worth noting: if you use oil-packed tuna and consume the oil as part of a recipe, perhaps tossing it into a pasta sauce or using it to dress a salad, you recapture those lost omega-3s. The fatty acids did not disappear; they just moved into the oil. The health disadvantage of oil-packed tuna is partly a function of the common habit of discarding the packing medium.
Mercury Levels Are the Same Either Way
A common worry is whether the packing medium affects mercury content. It does not. Mercury in fish is bound to proteins in the muscle tissue, not dissolved in the surrounding liquid, so switching between oil and water does not change your mercury exposure. Research comparing mercury concentrations in canned tuna found no significant differences between oil-packed and water-packed products.3PubMed. Mercury in canned tuna: white versus light and temporal variation
The factors that do affect mercury levels are the species of tuna and the size of the fish. Albacore (“white”) tuna consistently carries more mercury than skipjack (“light” or “chunk light”) tuna, because albacore is a larger, longer-lived species that accumulates more mercury over its lifetime. If mercury is your primary concern, switching from albacore to skipjack makes a real difference. Switching from oil to water does not.
Bisphenols Tell a Different Story
While mercury behaves the same regardless of packing medium, certain chemical contaminants do not. Bisphenol A (BPA) and related compounds, which can leach from can linings, appear to interact differently with oil versus water. A study monitoring bisphenols in canned tuna from Italian markets found that bisphenol levels ranged from about 19 to 187 nanograms per gram in the tuna itself and from roughly 6 to 67 nanograms per milliliter in the oil medium. No bisphenols were detected in the water medium at all. At least one bisphenol was found in about 83 percent of tuna samples packed in oil, while about 67 percent of samples packed in water showed BPA alone. And when researchers tested the liquid itself, about 21 percent of oil medium samples were positive for at least one bisphenol, compared to zero percent for the water medium.4PubMed. Monitoring of bisphenols in canned tuna from Italian markets
The likely explanation is chemistry: BPA and its analogues are more soluble in oil than in water, so they migrate more readily from the can lining into an oily environment. This does not mean oil-packed tuna is dangerous. The detected levels were generally low, and a single serving is unlikely to cause harm. But for people trying to minimize cumulative BPA exposure, particularly pregnant women or parents feeding young children, the finding gives water-packed tuna another small advantage.
Lipid Oxidation Favors Oil
Here is where oil-packed tuna earns some points back. When tuna is packed in water or brine, the fats in the fish are more vulnerable to oxidation, the chemical process that makes fats go rancid and produces potentially harmful byproducts. Research has found that the highest levels of lipid oxidation markers were in tuna packed in brine, indicating less protection for the fish’s fats in a water-heavy environment.5Journal of Agricultural and Food Chemistry. Effect of Packing Media on the Oxidation of Canned Tuna Lipids. Antioxidant Effectiveness of Extra Virgin Olive Oil – Section: RESULTS AND DISCUSSION The unsaturated fatty acids in tuna tend to gather at the boundary between oil and water, and aqueous free radicals in the water phase can attack them more easily.
Oil, by contrast, creates a more protective environment. This is especially true when the packing oil is extra virgin olive oil, which contains natural antioxidants like polyphenols that further shield the fish’s fats from breakdown. Brine may also increase the formation of cholesterol oxidation products, likely because salt and the enhanced heat transfer in brine during the canning process promote oxidation.2PubMed Central. New Perspectives on Canned Fish Quality and Safety on the Road to Sustainability – Section: 3.1. Impacts of Seafood Canning Chain on Quality
In practical terms, this matters most for shelf life and product quality. A can of oil-packed tuna that has been sitting in your pantry for a year may have a better-preserved fat profile than a water-packed can of the same age. Oxidized fats can contribute off-flavors and, in theory, are not ideal for long-term health. Still, the levels of oxidation in commercially canned tuna, even in water, remain within safe limits. This is a quality consideration more than a safety concern for most consumers.
The Type of Oil Changes the Equation
Not all oil-packed tuna is equal. Most budget brands in North America use soybean oil, which is high in omega-6 linoleic acid. Because the fish absorbs some of this oil during storage, the omega-6 to omega-3 ratio in the final product shifts in an unfavorable direction. Many Western diets already contain far more omega-6 than omega-3, so adding more through your tuna is not ideal.
Tuna packed in olive oil, which is more common in European and Mediterranean brands, presents a somewhat different picture. Olive oil is predominantly oleic acid, a monounsaturated fat, rather than the polyunsaturated omega-6 linoleic acid found in soybean oil. This means the omega-6 to omega-3 ratio does not shift as dramatically. Olive oil also brings those natural antioxidants that protect the fish’s fats from oxidation during storage.5Journal of Agricultural and Food Chemistry. Effect of Packing Media on the Oxidation of Canned Tuna Lipids. Antioxidant Effectiveness of Extra Virgin Olive Oil – Section: RESULTS AND DISCUSSION If you are going to buy oil-packed, olive oil is the better option from both an oxidation and a fatty acid standpoint.
That said, even olive oil-packed tuna will lose some EPA and DHA to the packing medium through the same diffusion process. The loss is somewhat smaller than with soybean oil, but it still happens. And the calorie addition from olive oil is roughly the same as from any other oil. So while olive oil narrows the health gap, it does not close it entirely.
Sodium Is Worth Checking Either Way
Water-packed tuna often means brine-packed, and brine means salt. A typical serving of water-packed tuna can contain anywhere from 200 to over 400 milligrams of sodium, depending on the brand. Oil-packed varieties sometimes have less added salt because the oil provides flavor on its own, but this is not universal. Some oil-packed products add plenty of salt too.
The takeaway is that packing medium alone does not determine sodium content. You need to read the label. If sodium is a concern, look for products labeled “no salt added” or “low sodium,” which are available in both water-packed and oil-packed versions. Draining and rinsing water-packed tuna can reduce its sodium content meaningfully, which is harder to do effectively with oil-packed tuna since the oil clings to the fish.
Who Should Choose What
The best choice depends on your goals and how you plan to eat the tuna:
- Weight management: Water-packed, drained. It delivers the most protein per calorie with minimal added fat.
- Omega-3 intake: Water-packed, since the fish retains more EPA and DHA. If you prefer oil-packed, consume the oil rather than draining it to recapture some of the lost omega-3s.
- Minimizing contaminants: Water-packed shows lower bisphenol levels in the packing medium, giving it a slight edge for people trying to limit BPA exposure.
- Flavor and cooking: Oil-packed, especially in olive oil, has a richer taste and works well in pasta dishes, salads, or anywhere you would add oil anyway. If the oil serves as your dressing, the extra calories are not “wasted.”
- Long pantry storage: Oil-packed products may maintain a slightly better fat quality over extended storage due to reduced oxidation.
Tuna Species Matters More Than Packing Medium
For all the attention given to water versus oil, the species of tuna in the can often has a larger impact on your health than the liquid surrounding it. Skipjack tuna, the most commonly canned variety worldwide, is lower in mercury and generally less expensive. Albacore, marketed as “white” tuna, has a firmer texture and milder flavor but accumulates more mercury because it is higher on the food chain. Yellowfin falls somewhere in between.
The omega-3 content also varies by species and even by season, since the fat content of wild fish fluctuates with water temperature, diet, and reproductive cycle. A can of skipjack in water might deliver very different DHA levels than another can of skipjack in water from a different catch. Research found DHA content varying nearly tenfold across different canned tuna products, from about 90 to 770 milligrams per serving, driven partly by species and partly by processing differences.1PubMed Central. The skinny on tuna fat: health implications – Section: Results That range is enormous and dwarfs the difference between water-packed and oil-packed versions of the same product.
If maximizing omega-3 intake is your priority, selecting a species with higher natural fat content and choosing water over oil gets you closer to the goal than either variable alone. But the honest truth is that canned tuna labels rarely tell you how much EPA and DHA a specific can contains, so you are making a probabilistic choice rather than a precise one. Eating canned tuna regularly in any form still puts you well ahead of someone who eats no fish at all.