The findings suggest that sauna bathing may temporarily mobilize immune cells that normally remain in tissues, allowing them to circulate more widely throughout the body. This increased movement could help the immune system monitor for harmful pathogens, including bacteria and viruses.

During the study, researchers observed an increase in every type of circulating white blood cell they measured. Among them were neutrophils and lymphocytes, two important groups of immune cells. Neutrophils are often among the first defenders to respond to an infection, while lymphocytes include cells that recognize specific threats, produce antibodies, and help coordinate immune responses.

The increase was temporary. Within 30 minutes after the sauna session, neutrophil and lymphocyte counts had returned to their original levels.

How Sauna Bathing May Activate Immune Defenses

“This may indicate that sauna bathing mobilizes additional white blood cells into the bloodstream from tissues, where they are then redeposited after the session. This kind of periodic release of white blood cells into the bloodstream is beneficial, as once they leave their storage sites, they are better able to patrol the body and respond to pathogens,” says Ilkka Heinonen, an Academy Research Fellow at the University of Turku.

This process is known as immune surveillance. Rather than remaining in one location, immune cells travel through the bloodstream and tissues, searching for signs of infection or other abnormalities. By temporarily increasing the number of white blood cells in circulation, the body may improve their ability to detect potential threats.

Interestingly, a similar response occurs during physical exercise. Exercise can temporarily increase the number of immune cells moving through the bloodstream, helping distribute them throughout the body. The new findings suggest that sauna bathing may produce a comparable short-term response, although this does not mean the two activities provide identical immune benefits.

Sauna Heat Also Affects Immune Signaling Molecules

The researchers also investigated whether sauna bathing influenced cytokines, small proteins that help immune cells communicate with one another. Cytokines play important roles in regulating inflammation, coordinating immune defenses, and directing the body’s response to infections.

Overall, the sauna session produced little change in average cytokine levels in the bloodstream. However, a closer examination revealed an interesting connection between certain cytokines and changes in body temperature.

“Interestingly, however, the levels of several cytokines changed in relation to how much body temperature rose during sauna bathing. No similar association was observed between white blood cell counts and changes in body temperature,” says Professor Jari Laukkanen, who led the study at the University of Eastern Finland.

In other words, some immune signaling molecules responded differently depending on how much a person’s body temperature increased. White blood cell counts, however, did not show the same relationship with rising body temperature.

This distinction suggests that sauna bathing may influence different parts of the immune system through different physiological processes.

What This Discovery Means for Sauna Health Benefits

Previous research has linked regular sauna bathing with several potential health benefits. The latest findings offer another clue about what may be happening inside the body during these sessions, particularly how heat exposure and the sauna routine affect immune cell circulation.

However, the researchers caution that the results do not establish whether sauna bathing produces lasting improvements in immune function or reduces the risk of illness. The study examined only the immediate effects of one sauna session, and the observed changes in white blood cells were short-lived.

Because the session also included a brief cold shower, the findings reflect the combined sauna and cooling routine rather than the isolated effects of heat alone.

The research involved 51 adults with an average age of 50. The findings were published in the scientific journal Temperature, which specializes in research on body temperature regulation and its effects on human physiology.

Although more research is needed to understand the long-term implications, the study reveals that even a single sauna session can rapidly change how immune cells circulate through the body, potentially offering new insight into the biological effects of this popular relaxation practice.

The supplement also appeared to be considerably easier for participants to stick with than a digital physical therapy program. Only 3.6% of those assigned to inulin alone dropped out of the study, compared with 21% of those assigned to physical therapy alone.

Published in the journal Nutrients, the findings suggest that improving gut health could become an additional strategy for managing arthritis. They also reveal an intriguing connection between the bacteria living in our digestive system, the way our bodies process pain, and muscle function.

A Simple Dietary Change Could Help Relieve Arthritis Pain

Knee osteoarthritis affects hundreds of millions of people worldwide and is a major cause of chronic pain and disability, especially among older adults. The condition develops as the tissues within the knee joint, including the cartilage that cushions the ends of bones, gradually deteriorate. This can lead to pain, stiffness, swelling, and difficulty with everyday activities such as walking or climbing stairs.

Treatment typically focuses on reducing symptoms and maintaining mobility. Pain medications can provide relief but may cause unwanted side effects, while physical therapy and regular exercise can help improve joint function. However, keeping up with an exercise program can be difficult, particularly for people already struggling with persistent pain.

The new research raises the possibility that a simple dietary supplement could provide another way to manage symptoms.

“This study raises the exciting possibility that a simple dietary change — adding a fiber supplement to your breakfast or yogurt — could meaningfully reduce pain and improve physical function,” said Dr. Afroditi Kouraki, lead author of the study from the School of Medicine at the University of Nottingham.

The supplement tested in the study was inulin, a naturally occurring fiber found in foods such as chicory root, Jerusalem artichokes, and certain other vegetables. Unlike many nutrients, inulin is not broken down by digestive enzymes in the small intestine. Instead, it passes into the large intestine, where beneficial bacteria can use it as food.

How Gut Bacteria May Influence Arthritis Pain

Researchers are increasingly discovering that the gut microbiome, the vast community of microorganisms living in the digestive tract, influences much more than digestion. These microbes interact with the immune system, produce biologically active compounds, and may even affect how the nervous system responds to pain.

Inulin is classified as a prebiotic because it nourishes certain beneficial gut bacteria rather than directly supplying living microorganisms, as probiotics do.

When bacteria ferment inulin, they produce substances known as short-chain fatty acids (SCFAs). One of the most important is butyrate, a compound that helps support the intestinal lining and can influence inflammation and biological pathways involved in pain.

The researchers found that participants taking inulin had increased levels of butyrate, suggesting that the supplement was influencing activity within the gut microbiome.

They also observed higher levels of glucagon-like peptide-1 (GLP-1), a hormone released by the gut that helps regulate blood sugar and appetite and has also been linked to pain regulation and muscle health.

GLP-1 has attracted widespread attention because it is the hormone targeted by medications such as Ozempic and Wegovy. However, the inulin supplement used in this trial was not a GLP-1 medication. Instead, researchers examined whether supporting beneficial gut bacteria could influence the body’s own production of the hormone.

One particularly interesting finding was that higher GLP-1 levels were associated with better grip strength. Although this does not establish that GLP-1 caused the improvement, it suggests that changes originating in the digestive system may be connected to muscle function as well as pain.

Fiber Supplement vs. Physical Therapy

To investigate these effects, the researchers conducted the INSPIRE trial, a six-week randomized controlled study involving 117 adults with knee osteoarthritis.

Participants were assigned to one of four treatment groups: a daily inulin supplement alone, digitally supported physical therapy exercises (PSE) alone, a combination of inulin and physical therapy, or a placebo.

This design allowed researchers to examine the effects of the supplement and exercise separately, as well as investigate whether combining them offered additional benefits.

Both inulin and physical therapy independently reduced knee pain, indicating that each approach provided meaningful symptom relief.

However, the supplement produced additional improvements that were not observed with physical therapy alone. Participants taking inulin demonstrated better grip strength and reduced pain sensitivity.

Pain sensitivity reflects how strongly the nervous system responds to potentially painful stimulation. Reducing that sensitivity could be particularly valuable for people with osteoarthritis, because persistent pain is not always explained by the amount of visible damage within a joint. Changes in how the nervous system processes pain can also contribute to discomfort.

The improved grip strength was another unexpected result, suggesting that the supplement’s effects might extend beyond the knee itself.

The researchers also found a substantial difference in how many participants completed their assigned treatments. Only 3.6% of the inulin-only group dropped out, compared with 21% of the physical therapy-only group.

This difference suggests that taking a daily fiber supplement may be easier to incorporate into a regular routine than following a structured exercise program.

A Surprising Connection Between Gut Health, Muscles, and Pain

Dr. Kouraki said: “Our findings suggest that targeting gut health with a prebiotic supplement is a safe, well-tolerated, and effective way to reduce pain in people with knee osteoarthritis. The very low dropout rate compared to the exercise group is also encouraging from a public health perspective — people were able to fit this supplement easily into their daily lives.”

Beyond the reduction in arthritis pain, the researchers are particularly interested in what the findings reveal about interactions between the digestive system, muscles, and nervous system.

The association between GLP-1 and grip strength raises the possibility of a broader biological relationship connecting gut health with physical performance and resilience as people age.

Senior author Professor Ana Valdes from the School of Medicine added: “The link we observed between GLP-1 and grip strength is particularly intriguing and points to a broader gut-muscle-pain axis that warrants further investigation. This could have implications not just for osteoarthritis, but for understanding how gut health influences aging and physical resilience more broadly.”

The findings are promising, but the trial was relatively small and lasted only six weeks. Larger studies with longer follow-up periods will be needed to establish whether the benefits persist, identify which patients are most likely to respond, and clarify the biological mechanisms responsible.

The results also do not suggest that fiber supplements should replace exercise or other established arthritis treatments. Instead, they point toward a potentially useful additional approach that could complement existing care.

A New Direction for Arthritis Treatment

The potential importance of this research becomes clearer when considering how many people live with persistent arthritis pain.

Professor Lucy Donaldson, Director of Research at Arthritis UK, said: “The pain of arthritis can severely impact quality of life. Our recent lived experience survey showed that six in ten people are living in pain most or all of the time due to their arthritis.

“Researchers are starting to explore the role of the gut microbiome in our experience of pain. This exciting preliminary research highlights how diet and physiotherapy can act in different ways to have benefits for people with arthritis. We know a variety and balance of healthy foods, including fiber, and regular physical activity matter, and we’re glad to be supporting research that explores how they work to help people with arthritis.”

For people living with knee osteoarthritis, the findings offer an encouraging possibility: a relatively simple change in daily nutrition may help reduce pain while supporting other aspects of physical health.

Perhaps most intriguingly, the research suggests that treating arthritis may involve looking beyond the joints themselves. By exploring how gut bacteria influence inflammation, pain perception, and muscle function, scientists may uncover new ways to manage a condition that affects millions of people every day.

Some autistic people tend to look at faces less frequently or make less eye contact. They may also find it more difficult to remember faces or interpret facial expressions compared with neurotypical individuals. Scientists have spent decades investigating the brain activity behind these differences. In the early 2000s, for example, researchers at Yale reported that brain regions responsible for processing faces showed lower activity in autistic individuals than in people without autism.

James McPartland, PhD, Harris Professor in the Child Study Center and director of the Center for Brain and Mind Health, studies how autistic people process faces using electroencephalography (EEG), a technique that records the brain’s electrical activity. Previous EEG studies, however, have typically examined signals from limited regions rather than analyzing activity across the entire scalp.

To gain a more complete picture, McPartland and his colleagues conducted a study involving approximately 400 autistic children, examining electrical signals recorded across the scalp. They discovered that brain activity associated with face recognition was less clearly distinguishable in autistic participants. They also identified a striking difference in development: In neurotypical children, the brain’s response to faces became more specialized with age, while autistic children did not show the same pattern.

“This is the first time we’ve leveraged the full volume of very rich information provided by an EEG recording to understand face perception and autism,” McPartland says.

How Scientists Discovered Differences in Autistic Brain Activity

McPartland compares traditional approaches to studying face recognition with attempting to understand traffic throughout an entire city by monitoring just one downtown street.

“That’s the way most research on face processing so far has worked,” McPartland says.

The new approach provides a much broader perspective, similar to observing traffic across an entire city using satellite imagery. To investigate these patterns, the researchers analyzed information collected through the Autism Biomarkers Consortium for Clinical Trials (ABC-CT). The dataset included autistic and neurotypical children across different age groups.

During the experiments, participants viewed pictures of faces and everyday objects while EEG equipment recorded their brain activity. Instead of concentrating on a small number of recording locations, the scientists examined electrical signals from all 128 electrodes positioned around each participant’s scalp.

They then applied machine learning techniques to determine whether patterns in the recordings could reveal what each child was viewing.

The results showed that brain activity provided a clearer indication of face viewing in neurotypical children than in autistic children. In other words, the electrical signals associated with seeing faces were less distinguishable in the autistic group.

“The neural activity that we measure at the scalp is just not as distinct in autistic children,” says first author Jason Griffin, PhD, assistant professor of psychology at University of Houston. Griffin previously worked as a postdoctoral researcher in McPartland’s laboratory.

The researchers also found that the ability to identify what a child was viewing from brain activity improved with age among neurotypical participants. This age related improvement was not observed in autistic children, suggesting that their neural responses to faces develop along a different pattern.

“Their face-specific processing is not following the same trajectory,” Griffin says.

Face Recognition Differences May Begin Earlier Than Previously Thought

Beyond identifying differences in brain activity, the study offers new insight into how early those differences emerge during face perception.

Recognizing someone involves multiple stages of neural processing. The sequence begins when visual information enters the eyes and continues as the brain interprets that information until a face is recognized.

Much of the earlier research on autism and face perception has concentrated on a brain signal called the N170. This measurable change in electrical activity typically occurs about 170 milliseconds after a person sees a face. Previous studies have shown that the N170 response tends to occur later in autistic individuals.

By analyzing brain activity over a wider period, the researchers found evidence that differences in face processing begin before this familiar signal appears. This suggests that autism related differences may arise at earlier stages of visual processing than researchers had previously established.

“But when you look at face processing through an approach that’s more inclusive of the full temporal range of information, we’re seeing that differences in autism occur even earlier,” McPartland says.

What the Discovery Could Mean for Autism Diagnosis and Early Support

The findings could eventually influence how researchers approach autism diagnosis and the development of supportive interventions.

Historically, some clinicians attempted to address difficulties with face perception by requiring autistic individuals to maintain eye contact. Research has since shown that forcing eye contact is not an effective solution. A better understanding of how face processing develops in the brain could help identify approaches that are more useful and appropriate.

An ongoing challenge in autism research is separating neurological differences associated with autism itself from changes that may develop through the experience of living with the condition. According to the researchers, the patterns identified in this study suggest that differences in face processing are connected to underlying developmental characteristics of autism rather than simply reflecting accumulated life experiences.

“When we’re seeing this expected refinement and specialization in non-autistic people, we’re seeing a reduced developmental change in autistic people,” McPartland explains.

Because the differences appear during development, the findings also raise the possibility that support aimed at helping autistic children interpret facial emotions could be particularly beneficial when introduced earlier in childhood.

However, the researchers emphasize that autism does not necessarily create difficulties that require intervention. Many neurodivergent people experience little or no impairment related to their autism and may neither need nor want additional support. For others, challenges with recognizing faces or understanding facial expressions can complicate everyday social interactions.

“Imagine navigating life when it’s hard for you to perceive the information in another person’s face, from navigating a playground to navigating a job interview,” McPartland says. “This is one of the critical areas that causes difficulty for many autistic people.”

New Brain Signals Could Help Improve Autism Diagnosis

Another potential application involves the search for more objective ways to assess autism. Currently, clinicians diagnose autism primarily by evaluating behavior because reliable biological tests are not yet available for routine diagnosis.

Scientists are investigating several possible biomarkers, which are measurable biological characteristics that could improve diagnostic assessments or help distinguish different groups within the autism spectrum.

The newly identified patterns of face related brain activity could contribute to that effort. By examining how these neural signals differ among individuals, researchers may eventually develop additional diagnostic tools or better identify autistic people who are likely to benefit from particular forms of support, including social skills therapy.

Although more research is necessary before these findings can be used in clinical practice, the study provides a new way to investigate how the autistic brain processes faces and how those responses change throughout childhood.

“This is a first step in introducing a new biomarker,” McPartland says.