Is canned tuna in oil a bigger mercury source than tuna in water?

What's actually in it

Tuna is a top predator, so it builds up methylmercury from smaller fish. The amount in the can depends on the type of tuna (albacore is highest, skipjack is lowest), where it was caught, and how it's packed.

Mercury binds to fats. When tuna is packed in oil, the oil pulls mercury out of the fish and holds it in the can. People who drain the oil but eat the fish still get the bulk of the dose.

What the research says

A 2026 study in NPJ Sci Food tested canned tuna in oil sold across markets and measured total mercury. Many cans were close to or above safety limits, especially the bigger albacore brands. The team flagged tuna in oil as a higher daily dose than tuna in water for the same brand.

Pregnant women, kids under 12, and people who eat tuna multiple times a week had the biggest risk in the model.

Pick skipjack tuna packed in water, also sold as chunk light. Limit albacore to once a week. For little kids and pregnancy, swap to salmon or sardines, which are lower in mercury and higher in omega-3s.