Prolonged military-style training causes changes to intestinal bacteria, increases inflammation

May 5, 2017, American Physiological Society

A new study finds that long periods of physiological stress can change the composition of microorganisms residing in the intestines (intestinal microbiota), which could increase health risks in endurance athletes and military personnel. The study, published ahead of print in the American Journal of PhysiologyGastrointestinal and Liver Physiology, is the first to study the response of the intestinal microbiota during military training. The manuscript was chosen as an APSselect article for May.

Healthy intestines are semi-permeable and act as a defense both to let nutrients into the bloodstream and keep bacteria and other potentially harmful substances out. Physical stress can increase (IP), which allows more materials out of the intestines and raises the risk of inflammation, illness and symptoms such as diarrhea.

A group of 73 Norwegian Army soldiers participated in a military-style cross country skiing exercise. Over four days, the group skied approximately 31 miles (51 km) while carrying 99-pound (45 kg) packs. The researchers collected blood and stool samples before and after the training exercise. The soldiers took 24-hour urine tests before the exercise and on the third day of the trek, before which they drank a solution of water mixed with the artificial sweetener sucralose and mannitol, a sugar alcohol. The human body does not break down sucralose during digestion, but gets rid of the sweetener through urination. Levels of excreted sucralose are commonly used as a marker for IP.

The and the composition of substances produced during metabolism (metabolites) in the soldiers' blood and stool changed significantly by the end of the aggressive training period. Sucralose excretion rose considerably, indicating an increase in IP. Concentrations of several compounds that are products of bacterial metabolism of amino acids and fat decreased in the stool, and levels of more than half of the different compounds found in the volunteers' blood changed during the session. Changes in IP were associated with changes in inflammation, the composition of the intestinal microbiota before training and changes in several metabolites possibly derived from the microbiota. "[Previous] human studies have demonstrated that drastic changes in diet impact intestinal microbiota composition by altering the availability of metabolic substrates for . Our findings contrast with those reports in demonstrating alterations in microbiota composition that most likely were not solely attributable to diet, and which were more pronounced than is commonly reported in human diet studies," the researchers wrote.

Intestinal microbiota appear to be one influencing factor in the gut's response to . "Our findings suggest that the intestinal microbiota may be one mediator of IP responses to severe physiologic stress, and that targeting the microbiota before exposure may be one strategy for maintaining IP," the researchers wrote.

Explore further: Gut bacteria affect ageing

More information: J. Philip Karl et al. Changes in intestinal microbiota composition and metabolism coincide with increased intestinal permeability in young adults under prolonged physiologic stress, American Journal of Physiology - Gastrointestinal and Liver Physiology (2017). DOI: 10.1152/ajpgi.00066.2017

Related Stories

Gut bacteria affect ageing

April 19, 2017
It loses its pigments, its motor skills and mental faculties decline, it gets cancer – the turquoise killifish (Nothobranchius furzeri) struggles with the same signs of old age that affect many other living creatures. Researchers ...

Researchers find unhealthy gut microbes a cause of hypertension

February 3, 2017
Researchers have found that the microorganisms residing in the intestines (microbiota) play a role in the development of high blood pressure in rats. The study is published in Physiological Genomics. It was chosen as an APSselect ...

Food and antibiotics may change microorganisms in gut, causing IBS

January 27, 2017
A recent review of research suggests that changes to the microorganisms (microbiota) in the gastrointestinal (GI) tract may be a cause of irritable bowel syndrome (IBS). The review article is published in the American Journal ...

Intestinal bacteria alter gut and brain function

March 1, 2017
Research from McMaster University has found that bacteria in the gut impacts both intestinal and behavioural symptoms in patients suffering from irritable bowel syndrome (IBS), a finding which could lead to new microbiota-directed ...

Changes in gut microbiota after unhealthy diet may protect from metabolic disease

March 17, 2017
An unhealthy diet changes the composition of the gut flora and it is generally assumed that this maladaptation called "dysbiosis" triggers disease. A study by Matteo Serino and his colleagues at the Université Paul Sabatier ...

Stress during pregnancy related to infant gut microbiota

January 26, 2015
Women who experience stress during pregnancy are likely to have babies with a poor mix of intestinal microbiota and with a higher incidence of intestinal problems and allergic reactions. This could be related to psychological ...

Recommended for you

Gradual release of immunotherapy at site of tumor surgery prevents tumors from returning

March 21, 2018
A new study by Dana-Farber Cancer Institute scientists suggests it may be possible to prevent tumors from recurring and to eradicate metastatic growths by implanting a gel containing immunotherapy during surgical removal ...

Immune cells in the retina can spontaneously regenerate

March 21, 2018
Immune cells called microglia can completely repopulate themselves in the retina after being nearly eliminated, according to a new study in mice from scientists at the National Eye Institute (NEI). The cells also re-establish ...

Cold can activate body's 'good' fat at a cellular level, study finds

March 21, 2018
Lower temperatures can activate the body's 'good' fat formation at a cellular level, a new study led by academics at The University of Nottingham has found.

Switch discovered to convert blood vessels to blood stem cells in embryonic development

March 20, 2018
A switch has been discovered that instructs blood vessel cells to become blood stem cells during embryonic development in mice. Using single-cell technology, researchers from the Wellcome Sanger Institute in Cambridge and ...

Don't blame adolescent social behavior on hormones

March 19, 2018
Reproductive hormones that develop during puberty are not responsible for changes in social behavior that occur during adolescence, according to the results of a newly published study by a University at Buffalo researcher.

Stem cells treat macular degeneration

March 19, 2018
In July 2015, 86-year-old Douglas Waters developed severe age-related macular degeneration (AMD). He struggled to see things clearly, even when up close.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.