The strange combination that could boost immunity and cognition... and even ward off colon cancer

It's certainly not your standard doctor's prescription.

But a new study suggests that bathing in hot water after eating yogurt could bring a multitude of benefits, from boosting cognition to fighting off colon cancer.

Yogurt, especially varieties with live and active cultures (probiotics), can help maintain a healthy balance and more diverse spread of good bacteria (the microbiome) in the digestive system.

The more diverse those microscopic colonies are, the better our immunity to a host of diseases from cancer to heart disease.

Maintaining a balanced microbiome through diet, particularly with probiotics such as yogurt, can also reduce inflammation, which is linked to neurodegenerative diseases like Alzheimer's, and may help slow cognitive decline.

On top of this, the same healthy bacteria can help prevent constipation by breaking down food molecules and increasing their movement through the intestines.

Meanwhile, hot baths can aid digestion by promoting vasodilation (widening of blood vessels), which improves circulation to the digestive organs and helps relax abdominal muscles, reducing cramping and bloating.

The warmth can also stimulate intestinal peristalsis (the process of wavelike muscle contractions that propel food and waste through the digestive tract) and lower stress, which is beneficial for regulating bowel movements and overall gut health.

Armed with this knowledge, researchers at Kyushu University in Japan looked at if combining these two therapeutic therapies - eating yogurt and bathing in hot water - could achieve even greater benefits to gut health.

For their study, a total of 47 healthy men and women aged 20 to 65 years were recruited for a four-month period.

The participants were then randomly assigned to one of three groups.

There was a 'control group' who did nothing different, a 'yogurt group' who were instructed to eat 180g of low-sugar yogurt after dinner daily and a 'yogurt plus hot spring group', who on top of eating yogurt everyday, also had to bathe in hot springs.

For the study the participants bathed in chloride hot springs or 'onsens' as they are known in Japan.

Chloride hot springs are mineral-rich geothermal waters containing high concentrations of chloride ions, making them saline.

These springs are often recommended for improving poor circulation, treating muscle and joint pain, relieving sensitivity to cold, and promoting relaxation.

Before and after the intervention period, the participants provided stool samples, and answered questions about their bowel movements, including stool frequency and consistency.

After eating yogurt for four months, those in the 'yogurt group' saw a significant increase in gut microbiota diversity.

Along with getting the benefit of a more diverse gut microbiome, the 'yogurt plus hot spring group' also had improved bowel movements with less complaints such as constipation or pain when passing stools.

While the direct link between hot springs and enhanced bowel movements is still being researched, one of the theories is that the warmth of the hot spring water promotes vasodilation, leading to increased blood flow to the digestive system.

Another is that hot springs help reduce stress and anxiety, which are both known to disrupt digestion.

The researchers say improved and regular bowel movements are good for overall health, as they indicate a healthy digestive system.

Other benefits, they say, include improved energy levels, and potentially lower risks of chronic conditions such as cancer.

They also make reference to the 'gut-brain axis,' which highlights the bidirectional communication between the gut and the brain.

A healthy gut is said to contribute to improved mood, mental clarity, and a reduced risk of mental health conditions like anxiety and depression.

The researchers write: 'The gut microbiome plays a fundamental role in maintaining human health, influencing various physiological processes such as digestion, metabolism, immune regulation, and even neurological functions.

'Recent research has highlighted the dynamic nature of the gut microbiota, emphasizing how diet, environmental factors, and lifestyle choices collectively shape its composition and function.'

The researchers say that their findings suggest that combining two lifestyle interventions - yogurt intake and hot spring bathing - may contribute to better health, and could potentially applied as a treatment in preventive medicine.

Professor Shunsuke Managi of Kyushu University's Urban Institute who led the research, added: 'These results are especially relevant given the growing interest in non-pharmaceutical, lifestyle-based strategies for preventive health and wellness.

'Furthermore, this research may support the development of evidence-based wellness tourism, particularly in regions known for their onsen, by providing scientific validation for health-oriented travel and services.'

The study was published in the journal Frontiers in Nutrition.