Have you ever hesitated to treat yourself to a tuna steak or a colorful sushi plate because of concerns about mercury and other heavy metals? You’re not alone — and your caution is justified. Considered one of the top ten chemicals of public health concern by the World Health Organization, mercury can cause serious medical issues, distinctly for developing fetuses during pregnancy.
While eating fish regularly is encouraged for its nutritional benefits — especially during pregnancy — global industrial processes have dramatically increased heavy metal levels in our oceans. That means more mercury in the fish that end up on our plates.
Scientists from UCLA and UC San Diego’s Scripps Institution of Oceanography may have come up with a clever solution. They’ve genetically modified a common human gut bacterium to help detoxify mercury before it can harm us. Their study, published in Cell Host & Microbe, lays the groundwork for a practical probiotic we could take just before digging into a seafood feast.
Danger of Heavy Metals in Food
But what exactly makes mercury and other heavy metals so dangerous? These substances disrupt essential cellular functions, stunt cell growth, and can lead to organ damage — particularly in the brain, liver, and kidneys. Mercury exposure is especially harmful during pregnancy, where it can interfere with fetal development.
Even low-level exposure can result in heavy metals slowly building up in the body over time. Seafood is the main dietary source of mercury, thanks to pollution from mining and other industrial activities. Once in the ocean, mercury is converted into methylmercury — a far more toxic form that accumulates in large predatory fish like tuna, swordfish, and even salmon, through a process called biomagnification.
“Despite global efforts to reduce mercury emissions and its accumulation in fish, methylmercury levels in seafood are not expected to decline anytime soon. Fish remains a major and culturally important part of the diet for many people around the world, and we hope it continues to be,” said Amina Schartup, co-author and Scripps associate professor of marine biogeochemistry, in a statement.
Read More: Climate Change and Overfishing are Making Seafood More Toxic
Upgrading Our Gut Microbes
To tackle the mercury issue, the researchers took inspiration from mercury-resistant soil bacteria. These microbes produce an enzyme that helps them detoxify mercury. The team inserted this enzyme into Bacteroides thetaiotaomicron, a common member of the human gut microbiome. After confirming the modified bacterium could remove methylmercury, they moved on to testing it in mice.
The results were encouraging: mice with the engineered gut microbe were protected from both acute and gradual mercury exposure after a diet heavy in bluefin tuna.
And what about pregnancy — the most sensitive time for mercury exposure? In a similar experiment with pregnant mice, the probiotic once again proved effective. “The gut bacteria helped to eliminate [mercury] from the body before it could enter the maternal bloodstream and access the developing offspring,” reported first author and UCLA research scientist Kristie Yu in a press release.
Probiotics Fighting Mercury
The researchers also tested their approach with salmon, which, while generally lower in mercury than other species, still poses a risk. The treatment with the modified microbe continued to show promise.
Finally, they tried a more convenient delivery method: an oral probiotic supplement. Mice fed a diet of bluefin tuna and given the engineered microbe in the form of an oral probiotic had significantly lower levels of methylmercury in their tissues.
Elaine Hsiao, co-author of the study and a UCLA professor, envisions “the possibility that people could take a probiotic to offset the risk of consuming too much methylmercury, especially when pregnant.”
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Cell Host & Microbe. An engineered gut bacterium protects against dietary methylmercury exposure in pregnant mice
World Health Organization. Mercury
Having worked as a biomedical research assistant in labs across three countries, Jenny excels at translating complex scientific concepts – ranging from medical breakthroughs and pharmacological discoveries to the latest in nutrition – into engaging, accessible content. Her interests extend to topics such as human evolution, psychology, and quirky animal stories. When she’s not immersed in a popular science book, you’ll find her catching waves or cruising around Vancouver Island on her longboard.
