Selenium in Tuna

Protects Against Mercury

Yellowfin tuna was first shown in 1972 to protect against mercury toxicity, not cause it. Further studies by Dr. Howard Ganther and his team at the University of Wisconsin led them to conclude that the rich levels of selenium in tuna were responsible for the protective effect.  Selenium, an essential element in our diet, is vital to the body's antioxidant system and proper immune system function. It has anti-cancer effects and is known to detoxify metals including mercury. It has been shown to protect against mercury in every animal model tested.  If the ratio of selenium to mercury determines if a food is safe, what are the ratios in Hawaii fish?

In a Hawaii Seafood Project study supported by NOAA, Dr. John Kaneko of PacMar Inc. in Honolulu and Dr. Nick Ralston of the Energy and Environmental Research Center in North Dakota analyzed selenium and mercury in 15 pelagic fish species caught near Hawaii.  They found that all of the tuna and billfish species and most other pelagic fish species contained an excess of health promoting selenium over mercury content. Mako shark was the only fish in the study that had more mercury than selenium. For this reason, most Hawaii fish are not only a healthy source of high quality protein and omega-3 fatty acids, they are also excellent sources of selenium. Our favorite fish are more likely to protect against mercury toxicity, than cause it.

The good news for Hawaii seafood lovers-the selenium is in every bite!


Regardless of the amount of mercury, if the selenium level is higher, the fish is safe to eat. In the above figure, molar concentrations of  mercury and selenium in 15 Hawaii fish species are expressed as means ± standard deviations.
Reprinted from "Pacific Islands Fishery News", Winter 2008
Newsletter Of The Western Pacific Regional Fishery Managment Council
J. John Kaneko * Nicholas V. C. Ralston