Sardines have less mercury than tuna, and the selenium in sardines chemically binds to mercury, reducing its presence in the body.
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Sardines contain significantly lower levels of mercury compared to larger predatory fish such as tuna, and the selenium present in sardines binds to and reduces the bioavailability of trace mercury.
Correlational — new studies may shift this
Observational4 moderate-quality studies link this claim to the outcome, but causation is not established.
What the research says
4 studies reviewedSupporting (4)
Cross-Sectional Study2025
Sardines have much less mercury than tuna, and this study shows tuna has a lot of mercury while smaller fish like herring have much less — so sardines likely do too. But the study didn't check selenium, so we can't say for sure if it neutralizes mercury.
Cross-Sectional StudyHuman2025
This study found that sardines from Lake Victoria have very low levels of toxic metals like lead and cadmium — much lower than safety limits. This supports the idea that sardines are safer to eat than big fish like tuna, which tend to have more mercury. But it didn't check selenium or how it might bind to mercury.
Cross-Sectional Study2005
Sardines have way less mercury than tuna, and they have lots of selenium — a mineral that helps bind to mercury and make it less harmful. So eating sardines is safer than eating tuna when it comes to mercury.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
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Score breakdown, mechanism chain, raw evidence, ideal studies needed & 4 supporting studies
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