gut microbiota

The human gastric intestinal tract
(GIT) is inhibited by a vast number of microbiota that performs a number of
functions to keep the body healthy. These microorganisms in your gut create a
barrier against infections or harmful substances from the outside world trying
to infiltrate your body. Microbiota also helps with metabolism, absorption of
nutrients, building and maintaining of the epithelium and supporting the immune
system. GIT diseases such as Irritable Bowel Syndrome (IBS) and Inflammatory
Bowel Disease (IBD) are linked to an imbalance of gut micriobiota. Wider
systemic metabolic conditions such as type 2 diabetes and obesity are also
associated with imbalanced gut microbe.


The human gut is house to more than
1 000 species of bacteria. Microbial settlement begins at birth and there are a
number of external and internal factors influencing the human gut micriobiota.  External factors include the microbial load
of the immediate environment, what food is eaten, feeding habits, and the
composition of the maternal microbiota you inherit form your mom. Dietary and
temperature-related stresses can influence the sequence of microbes. Internal
factors include intestinal pH; microbial interactions; environmental
temperature; physiological factors, such as peristalsis; bile acids; host
secretions and immune responses; drug therapy; and bacterial mucosal receptors (Bull & Plummer, 2014)


Interesting enough there is a gut–brain axis that is a communication
system allowing integrates neural, hormonal, and immunological signaling
between the gut and the brain. This offers the intestinal microbiota a direct route
to access the brain. The brain will then command gastrointestinal functions in
response. Gut microbiota is thus important to brain function. It was found that
gut microbe could even influence anxiety and depression.  A study showed that stress influences the
composition of the gut microbiota and affects communication between the gut
microbiota and the central nervous system. This way stress can influence the
integrity of the gut epithelium and altering the habitat of the intestinal
microbiota promoting changes in microbial composition and metabolism leading to
poor absorption of food, slow digestion and high risk of infections.


It is well known that prebiotics, probiotics
and a high-fiber diet rich in fruits, vegetables, legumes and whole grains have
a positive effect on the gut microbes. Lately exercise was also added to this list
as recent studies suggested
that exercise could increase the amount of beneficial microbial species,
improve the microflora diversity, and improve the development of non-harmful
bacteria. All of this improves human health.


Low intensity exercise can influence the GIT by decreasing
the transient stool time, thus reducing the contact time between harmful
bacteria and the gastrointestinal mucus layer. Exercise has protective effects,
reducing the risk of colon cancer, diverticulosis, and inflammatory bowel
disease. Exercise may reduce inflammatory infiltrate and protect the structure
and integrity of the intestine (Monda et al.,


A study done on 40 elite, professional rugby players found exercise
has a beneficial impact on gut microbiota diversity and the rugby players had
lower inflammatory status than the two control groups (Clarke et al., 2014)


Another study done on
36 mice that were fed a normal or high-fat diet for 12- weeks and randomly
assigned to exercise or inactive groups also found better gut integrity and
more beneficial bacteria in the
exercise group.  Specific
microbiota were observed in the exercise group, including Faecalibacterium
prausnitzi, Clostridium spp., and Allobaculum spp. These microbes may provide protection to the gut through
oxygen detoxification of harmful bacteria.

The good microbiota present in the exercising mice promotes a
healthy digestive tract by producing butyrate and lowering the oxygen tension
in the lumen. (Campbell et al., 2016)



The microbiota has significant effects on metabolic
functions. It produces short-chain fatty acids (SCFAs), such as n-butyrate,
acetate, and propionate, which, can increase the nutrients availability and
provide more energy in the body.  SCFAs
are involved in the gut-brain axis, and it signals the brain to release
appetite reducing hormones called peptide YY to help with satiety and neurotransmitters
to convey the feeling of happiness. It also acts as signaling molecules to
regulate immune and inflammatory responses. N-butyrate reduces mucosal
permeability, allowing fewer harmful bacteria to enter the body (Monda et al.,


In a third study, 32 sedentary adults (18 lean, 14 obese) were
subjected to 6 weeks of training followed by a 6-week period of inactivity (Allen et al.,
2017). The participants trained for 30-60 minutes at moderate to
high intensity for 3 days/week during the training period and continued with
their habitual diet. The results of the study indicated a change in beneficial
gut microbiota in the lean group during training. They found an increase in
SCFA especially butyrate but the positive effect was reversed after the
exercise was stopped.


Diversity is
important in all ecosystems to promote stability and performance. A variety of
microbiota also seems to be beneficial for the human body and may become a new
indicator of health and disease. Exercise alone has shown to increase the amount of
beneficial microbial species, improve the microflora diversity, and improve the
development of commensal bacteria.



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