Packages of bluefin tuna sashimi on display. (Photo by Justin Sullivan/Getty Images)
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A newly-engineered probiotic can help reduce levels of mercury and make it safer to eat fish, according to new research from UCLA and UC San Diego’s Scripps Institution of Oceanography.
The group of researchers used a gut bacterium to engineer a probiotic fed to mice with a diet high in bluefish tuna and found that it resulted in lower levels of methylmercury – a more concentrated and toxic form of mercury – than would have occurred otherwise. When tested on pregnant mice, the researchers similarly found lower levels of methylmercury in maternal and fetal tissues and lower signs of mercury toxicity in the fetal brain.
While the probiotic didn’t fully prevent methylmercury from accumulating in the mice’s bodies, it reduced the potency of methylmercury enough to prevent adverse outcomes in the fetal brain, said Elaine Hsiao, an author of the paper and a biology professor at UCLA. This means that there’s potential for an engineered probiotic like the one used in the study to make it safer for people, including pregnant women and children, to consume fish typically high in mercury, such as tuna and swordfish, said Hsiao.
Researchers specifically tested the probiotic on pregnant mice because of the potential implications for pregnant humans. Mercury is especially toxic to pregnant women, fetuses and children in early ages, according to the World Health Organization, and is commonly ingested through fish and other seafood. When mercury is in the ocean, it transforms into methylmercury, and as bigger fish eat smaller fish with methylmercury levels, the overall mercury levels compound. This means that when humans consume these bigger fish, they risk consuming mercury levels that are dangerous to human health.
The WHO estimates that between 1 and 17 out of 1000 children in some subsistence fishing populations showed cognitive impacts caused by consuming fish containing mercury. More than 75,000 newborns in the United States each year may have increased risk of learning disabilities associated with exposure to methylmercury in the womb, the Environmental Protection Agency estimated.
“The hope is that in the long run, this microbiome-based treatment can be an option for people who experience high methylmercury exposure,” Hsiao said, pointing to people who rely on fish as a primary part of their diet (one example of this is people who live in Asia and Oceania and depend more heavily on fish than do folks in other parts of the world). Hsiao also said the probiotic could help people who live in areas with power plants and mines and are exposed to mercury through their environment.
The study was funded partially by federal funds from the National Institutes of Health, which Hsiao said is critical to continue research like this. The researchers are now exploring the ways in which the probiotic can be more effective, Hsiao said, with the goal of moving toward human studies.
