Small microbes live in the human gut. They help digest food, support the immune system, and how the body uses energy. Scientists now think they may also affect muscle strength.
Muscles often weaken with age. Exercise and diet help, but researchers believe gut bacteria may play a role.
Scientists noticed that a microbe appeared more often in people with strong muscles.
Researchers from the University of Almeria, the University of Granada, and the Leiden University Medical Center began studying this connection.
An amazing relationship within the gut
The research team focused on bacteria belonging to the Roseburia genus. These microbes are already known to help the gut produce beneficial compounds during digestion. New findings suggest they may also support muscle health.
Jonathan Ruiz, professor at the Department of Physical Education and Sport at the University of Granada and researcher at the Joint University Institute for Sport and Health (iMUDS), explained the wider meaning of the results.
“Taken together, our findings provide strong evidence to support the existence of a gut-muscle axis in which this well-known bacterium positively modulates muscle metabolism and muscle strength,” Ruiz said.
That’s what human testing has shown
To find the connection, the researchers studied stool samples from two groups of volunteers.
The first group included 90 healthy young men between the ages of 18 and 25. The second group included 33 older adults aged 65 or older.
Participants completed several physical fitness tests. This included arm strength, leg strength, and upper body strength through chest muscle testing.
The experts also measured maximal oxygen consumption, a common way of assessing cardiorespiratory fitness.
Beneficial bacteria in the gut
Among the many groups of bacteria in the gut, Roseburia Standing higher levels of these microbes were shown to be associated with greater muscle mass and strength.
especially one type, Sweet Rosemaryshowed a clear correlation with physical fitness. Older adults who carried the bacteria showed 29% greater grip strength than those who did not.
In young adults, higher amounts of the same microbe correlate with stronger grip strength and cardiorespiratory capacity.
of other members Roseburia Families showed different patterns. Roseburia intestinalis In young adults it is related to leg and upper body strength, whereas Glaburia flesh and Human life The physical indicators measured in the study have no meaning.
Indications from mouse experiments
Human data revealed a strong association, but the researchers wanted to see if the bacteria could directly affect muscle function. To test this idea, they turned to lab mice.
Scientists first reduced the animals’ natural gut microbes by using antibiotics. Then, they introduced human strains Roseburia to mice once a week for eight weeks.
The results were amazing. Mice that received the bacteria showed about a 30% increase in grip strength on their faces compared to animals that did not receive the treatment.
The muscles themselves have also changed. Treated mice developed large muscle fibers and a greater proportion of type II muscle fibers in the soleus muscle of the calf.
These fast twitch fibers are closely related to strength and power. The researchers also observed changes in proteins and enzymes involved in muscle energy production.
Why does it decrease with age?
An important explanation emerged when the scientists compared young and old participants. of the Roseboria bacteria Occurs less frequently in older adults.
This reduction may explain why muscle mass declines later in life. If these microbes play a role in muscle metabolism, their loss may weaken the muscle-supporting system.
“This opens up the possibility that the bacteria under investigation could be used as a probiotic to help maintain muscle strength during aging,” explained Borja Martínez Tellez, researcher at the University of Almeria.
The idea is simple but promising. Instead of targeting the muscles directly, scientists may help maintain the body’s strength by supporting certain gut microbes.
Questions that still need answers
The research team emphasized that many questions remain unanswered. In mouse experiments, human strains Roseburia It does not stay permanently in the animal’s gut.
Scientists have not directly examined biological pathways such as inflammation or nerve signals between the muscles and the nervous system.
Future research still needs to answer an important question. Does Roseburia inulinivorans help build strong muscles, or do strong people simply have this bacteria in their gut?
Even with this uncertainty, the results suggest something interesting. Guts and muscles may be more connected than scientists realize.
The full study is published in the journal gut.
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