Don't Eat Canned Tuna the Second You Open It. Give It 10 Minutes.

Opened tuna can

Canned tuna gets opened and eaten straight from the can more often than not, especially when it's a quick meal. That skips a small window that actually matters — the canning and sterilization process that makes tuna shelf-stable also produces furan, a volatile compound classified as a possible carcinogen, and letting the can sit open for a bit gives it a chance to dissipate.

Water-Packed vs. Oil-Packed: The Calorie and Sodium Gap

Drained tuna alone runs about 108–120kcal per 100g. Eating the oil along with it pushes that up to 200–210kcal for the same amount. A full 150g can of olive oil-packed tuna, oil included, comes out to roughly 270kcal, 29g protein, 16g fat, and 540mg sodium.

That sodium figure is worth pausing on — 540mg is about 27% of the WHO's daily recommended sodium intake of 2,000mg, packed into a single can.

The 10-Minute Wait, and Why It Helps

Tuna in oil versus water

Furan is volatile enough that inhaling its vapor can irritate the respiratory tract. Rather than eating straight from the can, transfer the contents to a separate dish and let it sit for about 10 minutes — that window gives the furan time to evaporate into the air rather than staying concentrated in the food.

Breaking the tuna up into smaller pieces increases its surface area exposed to air, which speeds up the process, and cooking it further reduces furan content beyond that. What to avoid: crushing the can itself after opening, or heating the can directly over a flame or in a microwave.

Storing and Disposing of the Rest

Leftover tuna shouldn't stay in the can — move it to a sealed container. Covering it with perforated plastic wrap, microwaving for about 90 seconds, letting it cool, then refrigerating helps prevent spoilage. Finishing it within 3–4 days of opening is the general guideline, since the inside of an opened can is vulnerable to both microbial growth and metal corrosion once exposed to air.

Leftover oil shouldn't go down the drain — absorb it into a paper towel and dispose of it with regular trash. The empty can should be rinsed of food residue and oil before going into recycling, since a can with leftover oil or residue isn't accepted as clean recyclable material in most areas.

Giving a can of tuna 10 minutes before eating it, rather than digging in immediately, is a small habit worth building into the same routine as opening, eating, storing, and disposing of it properly. Households with young children or anyone pregnant are worth checking age-specific intake guidelines for in particular, alongside paying attention to how the leftover oil and can get handled afterward.

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