A new ally against tooth decay: Arginine offers sweet relief

New human clinical trial proves arginine, an amino acid, can modify plaque formation on teeth, thereby protecting against dental caries

Editorial Office of West China School of Stomatology, Sichuan University

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New human clinical trial finds arginine can prevent caries due to bacterial plaques by reducing the acidity, altering the plaque structure and reducing harmful bacteria in the plaques

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Credit: "Smile because you want to" by mac.rj from https://www.flickr.com/ Image source link: https://openverse.org/image/11223fba-ca36-41af-a006-0d799ba95aa7?q=smile&p=28

Fermentation of sugars in our food by the numerous bacteria in our mouth produces acids that destroy our teeth to form caries cavities. These bacteria reside in plaque-like communities called “dental biofilms”. Arginine, an amino acid naturally found in our saliva, has been shown to be helpful in preventing tooth decay. A few beneficial bacteria have an arginine deiminase system (ADS) that helps break down arginine to form alkali that can neutralize the acids. Increased availability of arginine helps in the multiplication of these beneficial bacteria, while at the same time inhibiting the growth of acid-producing bacteria. Recently, studies conducted outside the human body also showed that arginine availability changes the composition of dental biofilms.

To further prove these findings in the human mouth, a team of dentists and researchers led by Post.doc. Yumi C. Del Rey and Professor Sebastian Schlafer from Aarhus University in Denmark have conducted a clinical trial and published their findings in the International Journal of Oral Science.

They recruited 12 participants with active caries and prepared specialized dentures that allow for the collection of intact biofilms, spanning both sides of the jaw. The participants were instructed to dip the dentures in a sugar solution for 5 minutes, immediately followed by distilled water (as placebo) or arginine for 30 minutes, one on each side. This was to be repeated three times a day, with arginine treatment done on the same side each time. “The aim was to investigate the impact of arginine treatment on the acidity, type of bacteria, and the carbohydrate matrix of biofilms from patients with active caries,” explains Sebastian Schlafer, professor at the Department of Dentistry and Oral Health. After 4 days, when the biofilm was developed, the dentures were removed for detailed analysis.

A special pH-sensitive dye called “C-SNARF-4” was used to analyze the acidity of the collected biofilms in different locations. Biofilms treated with arginine showed a significantly higher pH (lower acidity) at 10 and 35 minutes after a sugar challenge. “Our results revealed differences in acidity of the biofilms, with the ones treated with arginine being significantly more protected against acidification caused by sugar metabolism” says the first author, Yumi C. Del Rey.

Then, carbohydrate-binding proteins called lectins, tagged with a fluorescent dye, were used to stain two common carbohydrate components of the biofilms: fucose and galactose. These components make up a large portion of dental biofilms and may contribute to the creation of “acidic pockets” inside them. With arginine treatment, an overall reduction was seen in the amount of fucose-based carbohydrates, possibly making the biofilm less harmful. In addition, there was a change in the structure of the biofilm, with galactose-containing carbohydrates decreasing at the bottom and increasing at the top.

Further, to determine which bacteria were present in the biofilm, they sequenced all bacterial genomes using a technique called “16S rRNA gene sequencing”. Though biofilms treated with arginine and placebo were predominantly dominated by Streptococcus and Veillonella species, arginine significantly reduced the mitis/oralis group of streptococci, which produce acid but are not strong producers of alkali, and slightly increased streptococci with considerable arginine metabolism, thereby improving the pH. Overall, arginine made the biofilms less harmful by reducing their acidity, altering their carbohydrate structure, and reshaping the microbiome within them.

Dental caries, being prevalent across all ages and regions, could be combated using strategies such as supplementation of arginine in toothpastes or oral rinses for people who are more susceptible to them. Arginine, being an amino acid naturally produced in our body and present in dietary proteins, is harmless and could find application even in children.

 

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Reference
DOI: 10.1038/s41368-025-00404-5

 

 

About the University
Aarhus University in Denmark is a leading global research institution recognized for excellence in the health sciences, dentistry, and microbiology. The university fosters strong interdisciplinary collaboration between clinical researchers and molecular scientists, enabling high-impact studies that translate laboratory discoveries into real-world healthcare solutions. Within the Department of Dentistry and Oral Health at Aarhus University, researchers are internationally respected for advancing knowledge on oral microbiomes and caries prevention. With a robust translational research ecosystem and state-of-the-art facilities, Aarhus University continues to generate critical insights that shape modern dental care and improve oral health outcomes worldwide.

Website: https://dent.au.dk/about-us

 

About Professor Sebastian Schlafer from Aarhus University
Professor Sebastian Schlafer at Aarhus University leads research on dental biofilms, focusing on their extracellular matrix, composition, structure, and metabolic activity—key factors in oral diseases such as caries. He develops novel strategies to control harmful oral bacteria while preserving beneficial species. In addition to his research, he teaches cariology, operative and aesthetic dentistry, and dental materials.

 

About Post.doc Yumi Chokyu Del Rey from Aarhus University
Yumi C. Del Rey is a researcher at Aarhus University specializing in oral microbiology and dental biofilms. Her work focuses on how microbial communities, their architecture, and metabolic activity contribute to dental caries. Using techniques such as pH ratiometry, lectin-based imaging, and 16S rRNA sequencing, she investigates how treatments like arginine reshape biofilm acidity and composition. As first author of the recent clinical study, she contributes to advancing mechanism-based strategies for caries prevention.

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Journal

International Journal of Oral Science

DOI

10.1038/s41368-025-00404-5 

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Arginine modulates the pH, microbial composition, and matrix architecture of biofilms from caries-active patients

A high-protein diet can defeat cholera infection

The right foods can fight serious bacterial disease

University of California - Riverside

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Casein, found in cheese, inhibits the ability of cholera bacteria to colonize the gut.

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Credit: Frank Schulenburg

Cholera, a severe bacterial infection that causes diarrhea and kills if untreated, can be defeated with a diet high in protein, according to a new study from UC Riverside.

Specifically, the study found that diets high in casein, the main protein in milk and cheese, as well as wheat gluten, could make a dramatic difference in the amount of cholera bacteria able to infect the gut. 

“I wasn’t surprised that diet could affect the health of someone infected with the bacteria. But the magnitude of the effect surprised me,” said Ansel Hsiao, UCR associate professor of microbiology and plant pathology and senior author of the study published in Cell Host and Microbe. 

 “We saw up to 100-fold differences in the amount of cholera colonization as a function of diet alone,” Hsiao said. 

Knowing that food has a strong effect on the community of bacteria and other microbes naturally living in the gut, the researchers initially set out to understand whether infectious, invasive microbes would be similarly affected by diet.

The researchers tested diets high in protein, high in simple carbohydrates, and high in fat on cholera’s ability to colonize the gut of an infected mouse. High-fat diets did little to slow the infection, and carbohydrates showed limited effects. But the dairy and wheat gluten diets virtually shut the pathogen out.

“The high-protein diet had one of the strongest anti-cholera effects compared to a balanced diet. And not all proteins are the same,” Hsiao said. “Casein and wheat gluten were the two clear winners.”

Looking more deeply into these results, the researchers found the proteins suppress a microscopic syringe-like structure on the surface of cholera bacteria used for injecting toxins into neighboring cells. When this structure, called the type 6 secretion system, or T6SS, is muted, cholera has a difficult time killing other bacteria and taking up space in the gut.

Cholera remains a public health threat in parts of Asia and Sub-Saharan Africa with limited clean water access. Treatment typically focuses on rehydration. Antibiotics can shorten the illness, but they don’t neutralize the toxins cholera leaves behind.

Overuse of antibiotics also carries the risk of creating bacteria that no longer respond to drugs. Though antibiotic-resistant cholera is not an imminent threat, the quick-to-adapt nature of bacteria means a drug could quickly and sometimes unexpectedly change cholera’s behavior.

“Dietary strategies won’t generate antibiotic resistance in the same way a drug might,” Hsiao said.

For now, dietary strategies could offer a low-cost, low-risk tool to reduce the severity or likelihood of infection in vulnerable human populations.

“Wheat gluten and casein are recognized as safe in a way a microbe is not, in a regulatory sense, so this is an easier way to protect public health,” Hsiao said. 

And although these findings come from mice, Hsiao expects high-protein diets would have similar effects for humans, so he would like to test these results on human microbiomes in the future, as well as on other infectious bacteria. 

“Some diets will be more successful than others, but if you try this for pathogens other than cholera, I suspect we’ll also see a beneficial effect,” Hsiao said. “The more we can improve peoples’ diets, the more we may be able to protect people from succumbing to disease.”

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Journal

Cell Host & Microbe

DOI

10.1016/j.chom.2025.11.004 

Article Title

Diet modulates Vibrio cholerae colonization and competitive outcomes with the gut microbiota

 

A more accurate way of calculating the value of a healthy year of life

Researchers propose a new metric that could help improve the cost-effectiveness of healthcare policies

Tokyo University of Science

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This plot shows how the value of a QALY change as an individual gets older according to four different scenarios. Each scenario illustrate that a possible trajectory of an individual’s quality of life (QoL) over their lifetime. For example, scenario 1 contemplates a slow but steady decline in QoL from age 50 onwards. Meanwhile, scenario 4 contemplates a very pronounced decline at the age of 60 before stabilizing into a slow and steady decline afterwards.

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Credit: Dr. Kazuya Ito from Tokyo University of Science, Japan Image source: https://doi.org/10.1038/s41598-025-29794-6

Decades of advances in medical technology and public health are causing global populations to age. While achieving longer lives is certainly a net positive, this demographic shift is placing an ever-growing strain on national budgets, and many countries around the world are struggling to maintain sustainable healthcare systems. Japan, which boasts as one of the world’s longest life expectancies, faces an especially big hurdle, with healthcare expenses projected to nearly double by 2040.

To meet this challenge, governments must make informed and scientifically grounded decisions on how to allocate resources effectively. A widely used metric to guide such decisions is the quality-adjusted life years (QALY), which measures the value of a healthcare intervention by factoring in both the length and quality of the life gained. Though useful, this metric has a fundamental flaw in that it is often calculated as a uniform ‘one-size-fits-all’ number. It thus fails to account for the different health needs, remaining life expectancy, and quality of life (QoL) experienced across different age groups, meaning a year of good health is often valued the same for a 20-year-old as it is for an 80-year-old.

To tackle this limitation, a research team led by Professor Ryuta Takashima from the Department of Industrial and Systems Engineering, Tokyo University of Science (TUS), Japan, has developed a new framework for evaluating the monetary value of the QALY. Their study, published online in the journal Scientific Reports on December 01, 2025, presents a model based on the ‘value of a statistical life (VSL)’—a measure of society’s willingness to pay for a reduction in mortality risk—and applies it to socioeconomic data from Japan. This work was co-authored by Assistant Professor Kazuya Ito and Mr. Yusuke Tanizawa from TUS, the latter of whom completed his Master's course in 2024.

The core of their methodology lies in adjusting the QALY value based on two key factors: age and lifetime QoL scenarios. The team modeled several distinct QoL scenarios to represent the non-uniform ways an individual’s health status can decline throughout their life. By dividing the value of gaining an extra year of life by the QoL at any given age, they created a new VSL-based QALY that varies with both a person’s age and their health trajectory.

The analysis of data from Japan yielded three key findings. First, while the conventional QALY estimate of 5 million JPY (Japan’s current figure) was consistent with the team’s averaged QALY, their model revealed that the true value varies significantly by age. They found that policies targeting younger individuals should be evaluated with a lower QALY value to be deemed cost-effective, whereas policies targeting older individuals may be effective even at a higher cost per QALY. This implies that the benefits from a life expectancy gain increases with age–the older population recognizes the value of additional expectancy earlier than the younger population.

Second, the results clarify the economic benefits of promoting good health throughout life. The researchers demonstrated that the monetary value of one QALY is actually the lowest in scenarios where individuals maintain a high QoL for a longer duration. In other words, when most of the population is healthy, the relative monetary value of gaining one additional year of perfect health decreases.

Third, by modeling policy cost reduction effects, the team showed that policies, which succeed in extending healthy life expectancy lead to a significant reduction in social healthcare costs. Shifting a larger proportion of the population toward scenarios of sustained good health could thus lower the average QALY value significantly, reducing the budget required to achieve nationwide health benefits.

Overall, this innovative approach moves beyond the limitations of a uniform QALY, allowing for a more accurate and nuanced cost-benefit analysis. “Our findings help clarify the value of extending healthy lifespan according to QoL and age, making it possible to present measures for the rational allocation of medical resources,” explains Prof. Takashima.

The team also emphasizes that their model can be applied to any region by using the target area’s specific socioeconomic data, providing a powerful tool for policymakers everywhere. “In a future world of aging populations and declining birth rates, the intrinsic value of the QALY is likely to increase over time. The policy evaluation example presented here for Japan serves as a model case for deriving the monetary value of the QALY under such a situation, offering valuable insights into future global demographic shifts,” concludes Prof. Takashima.

This research ultimately highlights that the smart, long-term solution to rising healthcare costs is not just treating the sick, but actively extending the years people spend in good health.

 

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Reference      
DOI: 10.1038/s41598-025-29794-6  

 

About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

 

About Professor Ryuta Takashima from Tokyo University of Science
Dr. Ryuta Takashima is a Professor at the Department of Industrial and Systems Engineering in Tokyo University of Science, Japan. He received his Master's and Ph.D. degrees from the Graduate School of Engineering at The University of Tokyo. He has authored over 50 research papers and contributed to conferences, book chapters, and editorials. His research areas include energy economics, health economics, and policy science, especially the application of industrial engineering, operations research, and economics theories to energy, environmental, and healthcare policies. He is also an Executive Director of the Global Infrastructure Fund Research Foundation, Japan, and a Board Member of the Public Opinion Poll for Nuclear Energy in Japan.

Funding information
This study was supported in part by the Mitsubishi Foundation Grant Number 202430031 and Health Labour Sciences Research Grant 23HB1001.

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Journal

Scientific Reports

DOI

10.1038/s41598-025-29794-6 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Deriving Monetary Value of Quality-Adjusted Life Years through Life Extension from the Value of a Statistical Life