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Mercury is a heavy metal that, for some years now, has begun to cause concern for human health. The fact that it is present in fish products, especially in tuna, has created alarm among people as it is very common on our tables. We need to understand why tuna contains mercury and what the potential dangers are and the subjects most at risk for a topic that is widely debated. A study conducted on animal models, however, would explain that a bacterium that is normally found in the intestine and considered harmless, could be modified to such an extent as to be able to drastically reduce the absorption of mercury thanks to some enzymes that would neutralize the metal.
All Phases of The Study
Published in Cell Host & Microbe, the researchers of the study conducted on mercury come from the University of Los Angeles and San Diego. During the research they thought of trying to exploit the qualities of some species of bacteria capable of resisting a heavy metal such as mercury. By doing so and continuing the research, they tried to modify the structure of the bacterium by selecting two enzymes that can render methylmercury harmless. In this case it would be transformed into mercury by eliminating the molecule of the methyl group that makes it a toxic substance.
The bacterium in question is called Bacteroides thetaiotaomicron, so the researchers inserted the DNA sequences that encode these enzymes into the aforementioned bacterium, which is normally found in the intestines of humans and rodents. Through an in vitro test, the scientists replaced the intestinal microbiota of mice with the modified bacterium. By administering large doses of methylmercury, wanting to simulate acute exposure to the metal, they came to the conclusion that after three hours the levels had dropped significantly and that, after four days, they had dropped even more.
Why Mercury Is Found in Tuna and How Much of It Can We Eat?
Before continuing with what could be a very important discovery, it is right to explain how mercury is found in tuna and fish products. Human activities, industries, and the use of fossil fuels do nothing but increase the concentration of mercury in the oceans. Microorganisms in the sea transform mercury into methylmercury, which, as specified above, is the toxic form of this metal and which accumulates in the marine food chain. Since tuna is a large predator, by eating smaller fish (which have accumulated methylmercury), it concentrates everything in its organism in greater quantities.
European regulations have set maximum limits for mercury that can be ingested from fish products. For tuna, the maximum limit is 1mg/kg. It is important to note that canned tuna may have a higher concentration of mercury than fresh tuna because it loses water during processing, thus concentrating the heavy metal. Ingesting too much mercury could cause muscle problems, worsening eyesight, memory loss and difficulty concentrating. Pregnant women are considered a risk category because the effects of mercury could have repercussions on the fetus.
The Probiotic of the Turning Point
Returning to the study and the modified bacterium, to increase certainty the scientists gave the laboratory animals a diet based on red tuna (the species containing the most mercury). This time too the results were satisfactory and confirmed the effectiveness of Bacteroides thetaiotaomicron which allowed to reduce methylmercury also in the brain and liver, organs where it is generally deposited more. Most of the tests carried out also with other fish, were positive but we have not yet reached maximum certainty.
They are trying to put new research into practice with as many experiments. If they confirm the potential of what has been discovered so far, they could obtain a solution to a problem that has always been unsolved and to which no one has been able to give exhaustive explanations. Experts recommend taking specific probiotics that could neutralize the risks, especially for the most at-risk categories such as pregnant women.
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