Selenium is an essential micronutrient that supports antioxidant and immune functions, yet how its metabolism is regulated by interactions between host and gut microbiota remains unclear. In a recent study, researchers from Japan used rats to investigate how gut microbiota and the host jointly manage selenium metabolism. Their findings reveal that gut microbiota actively transform selenium into various metabolites that influence selenium utilization, detoxification, and excretion, and that the host's selenium intake affects bacterial diversity.
Selenium (Se) is an essential trace mineral found in everyday dietary items, such as seafood, meat, and whole grains. Our bodies depend on it for many biological functions, from the synthesis of antioxidant enzymes to immune system regulation. However, Se is unusual among nutrients in that the quantity window between too little and too much is quite narrow. Se deficiency has been linked to weakened immunity, while excess intake can increase the risk of type 2 diabetes and cardiovascular disorders. This makes understanding how the body absorbs, processes, and eliminates Se especially important.
One piece of this puzzle that has received relatively little attention is gut microbiota—the community of microorganisms that live in our digestive tract. Scientists have known for years that gut microbiota can interact with Se in various ways, and that Se levels in the host can affect the overall composition of the gut's microbial community. However, these two observations have rarely been studied together, leaving a gap in our understanding of how Se metabolism is shaped by bidirectional interactions between the host and gut microbiota. Since Se intake recommendations are applied broadly, yet individual gut microbiomes vary considerably, current nutritional guidelines may be missing important information.
Against this backdrop, a research team led by Assistant Professor Kazuaki Takahashi from the Graduate School of Horticulture, Chiba University, Japan, investigated the intricate bi-directional relationship between Se metabolism and the gut microbiota. Their study, made available online on April 8, 2026, and published in Volume 79 of the journal Food Bioscience on May 1, 2026, was co-authored by Ms. Momoka Yamagata and Dr. Yasumitsu Ogra, both from Chiba University.
The team used rats raised under three different conditions: Se-deficient, Se-adequate, and Se-excessive. Some animals retained their normal gut microbiota, while others received antibiotics to suppress gut microbiota activity. The researchers then tracked Se metabolism using a specialized labeling approach, which enabled them to distinguish newly administered Se from the quantity already present in the body. Using this technique, they analyzed Se-containing compounds found in urine, feces, and serum, as well as gut microbial diversity and composition.
The results showed that Se intake significantly reshaped the gut microbiota. Rats receiving excess Se had distinct microbial communities and increased bacterial diversity compared with Se-deficient rats. The researchers also found evidence that gut bacteria adapted their metabolic activity in response to Se exposure, especially pathways linked to methylation, a chemical process often involved in detoxification.
One of the most striking findings involved trimethylselenonium ion (TMSe), a Se-containing compound excreted in urine. Rats with intact gut microbiota produced substantially more TMSe under Se-excess conditions than animals whose microbiota had been suppressed with antibiotics. The team also observed increased production of selenomethionine, a Se-containing amino acid, in the feces of animals with intact gut microbiota. "Gut microbiota supplies unique selenometabolites, which differ from the original dietary substrates to the host," remarks Dr. Takahashi. In other words, gut microbes appear to metabolize and produce their own Se-derived compounds that can alter how the nutrient behaves inside the body.
Notably, the team also found that gut microbiota influenced how efficiently Se was incorporated into important biomolecules known as selenoproteins. Animals with suppressed gut microbiota incorporated Se into these proteins more efficiently, suggesting that microbes may compete with the host for Se or convert it into forms that are less biologically useful. At the same time, microbial metabolism of Se may help protect the body from excess exposure by promoting the formation and excretion of less toxic compounds.
Taken together, the findings of this study point toward a more complex picture of nutrition, in which micronutrient metabolism depends not only on diet, but also on the activity of gut microbes. Although the work was conducted in rats, the researchers suggest that the results could eventually help guide new approaches for personalized nutrition and therapies. "Gut microbiota-targeted interventions offer a means to modulate the systemic utilization of Se. This work will hopefully pave the way for the design of more effective nutrient intake strategies," concludes Dr. Takahashi.
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About Assistant Professor Kazuaki Takahashi
Dr. Kazuaki Takahashi obtained a PhD from the Graduate School of Pharmaceutical Sciences, Chiba University, Japan, in 2020. After working as a JSPS Research Fellow from 2020 to 2022 at Chiba University, he became an Assistant Professor at the Graduate School of Horticulture. His main research interests lie in the metabolism of essential micronutrients and the bioactivities of their metabolites in plants and animals. He has published over 10 papers on these topics.
Funding:
This work was partly supported by JSPS KAKENHI Grant Nos. JP23K13901, JP24H00749 and JP24K21304.
Reference:
Authors: Kazuaki Takahashi1, Momoka Yamagata1, and Yasumitsu Ogra2
Affiliations: (1) Graduate School of Horticulture, Chiba University; (2) Graduate School of Pharmaceutical Sciences, Chiba University
