Why eating tuna, can be dangerous?

Tuna is frequently eaten by humans, but this can be a health hazard. This fish contains within its body a toxic agent called mercury.[1]

Mercury can damage the nervous system and many organs.[2] This is because it binds to the sulfur in our proteins, affecting their function.[3]

Tuna contains a form of mercury called methylmercury,[4] which can remain in our bodies for many years.[5] Mercury can be dangerous to the fetus as it crosses the placenta.[6]

The reason this fish contains a lot of mercury, is that, it consumes smaller fish, which also contain mercury, but in less quantity.[7] Because mercury accumulates in the body,[8] mercury levels in tuna can reach high levels.[9]


Mercury is so dangerous that, in a city in Japan called Minamata, cats died after suffering severe behavioral problems, and many people either died very painfully and agonizingly, or were left with severe neurological problems.[10] This occurred after contamination of the fish in the area.[11]

Discrimination problems against people from Minamata have occurred over the years, because they are considered “contaminated.”[12]

This is a version which has been translated from Spanish and edited for clarity. The original is titled: “¿Por qué comer atún, es peligroso?” To see the original, click the title in Spanish.


1. Ali Bashiri Dezfouli et al., “Evaluating Total Mercury and Methyl Mercury Contents in Canned Tuna Fish of the Persian Gulf,” Iranian Journal of Pharmaceutical Research 17, no. 2, (2018): 585, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5985176/.

2. Michael L. Bishop, Edward P. Fody, and Larry E. Schoeff, Clinical Chemistry: Principles, Techniques, and Correlations, (New Delhi: Wolters Kluwer, 2013), 409.

3. Ibid.

4. Bashiri, “Mercury Contents,” 585.

5. Bishop, “Clinical Chemistry,” 409.

6. Ibid.

7. “Mercury in the food chain,” Government of Canada, Date modified: 2013-07-09, https://www.canada.ca/en/environment-climate-change/services/pollutants/mercury-environment/health-concerns/food-chain.html.

8. Ibid.

9. Girish Kumar, “Mercury Concentrations in Fresh and Canned Tuna: A Review” Reviews in Fisheries Science & Aquaculture 26, no 1 (2018):111, https://doi.org/10.1080/23308249.2017.1362370.

10. David E. Sanger, “Japan and the Mercury-Poisoned Sea: A Reckoning That Won’t Go Away,” The New York Times, January 16, 1991.

11. Ibid.

12. Ibid.

Photograph credit:

Photo by Karolina Grabowska from Pexels

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