What’s your gut feeling?
Your gut may hold
the secret to your anxiety, heightened stress levels and depression. Here’s how
it works
Bacteria and birth history
The foetus in the mother’s womb is protected from all
bacteria by the placenta. So, when and where do we acquire these microbes from?
How a baby takes birth determines the kind of microbial flora that flourishes
in his/her gut.
Natural birth results in the colonisation of the gut
with unique beneficial bacteria acquired from the mother’s birth canal, whereas
a C-section causes the gut to be colonised by bacteria present on mother’s
skin, hospital instruments, etc. Also, whether a baby is breast fed or formula
fed largely determines the kind of bacteria that grow in the infant’s gut.
Breast milk contains substances that promote the growth of beneficial bacteria
in the body. For instance, mother’s milk contains substances called Human Milk
Oligosacchrides (HMOs) that are used as sources of energy by good bacteria to
grow. These bacteria feed on HMOs and not only aid in its digestion, but also
release substances as by-products that play an essential role in both the
physical and mental development of the child.
How does it affect your health?
The gut microbes maintain a mutualistic relation with
our body, i.e., the microbes use energy from the food we take and in turn
improve our physical and mental health. They aid in the digestion of complex
substances like cellulose, which normally cannot be digested by the body. Their
presence in the gut enhances metabolism by extracting maximal energy from the
remnants of digested food in the gut.
Gut microbes have also been shown to secrete substances
like Vitamin K2, which can neither be supplemented through diet, nor produced
by the body. The microbes strengthen the body’s immune system and keep a check
on the levels of pathogens in the body. Hence, maintaining a good number of
these beneficial bacteria in the gut is essential for overall well-being.
Mind matters
Another interesting and revealing finding is that
these bacteria in the gut have been shown to have an impact on one’s
psychological state, especially emotions and mood.
Studies have shown that both increased number of bad
bacteria and the absence of good bacteria in the gut can lead to increased
anxiety, and depression.
A disturbed gut microbiome has been shown to be
associated with increased stress levels, autism, Alzheimer’s Disease etc. On
the other hand, an increase in number of good bacteria has been seen to be
correlated with a state of relaxation and well-being.
Watch what you eat
The composition of the gut microbiota changes during
initial years after birth and stabilises by the time a child is five or six
years old. However, diet, environment and lifestyle have an impact on the
balance and diversity of microbes in the gut.
Whereas a healthy, well balanced, fibre-rich diet
ensures that all the gut bacteria get the fuel necessary for their growth, an
unbalanced, high fat and low fibre diet leads to reduced diversity of these
microbes by depriving them of specific substances needed for their survival.
Studies have also established that mice fed on high
fat diets experienced increased inflammation, reduced immunity, had thinner gut
linings (leaky gut), and showed symptoms of obesity, insulin resistance,
greater susceptibility to infections, etc. Interestingly, it has also been
shown that transplantation of bacteria from gut of a healthy mouse into the gut
of a mouse kept on a high fat diet helped restore the diversity of microbes in
its gut and resulted in an improvement in insulin resistance and immunity, and
reduced obesity. Also, microbes transplanted from gut of an obese mouse into that
of a germ free mouse (special experimental mice grown in germ free conditions
such that their gut has no bacteria) lead to development of obesity and
metabolic disorders in the mouse, thereby indicating that these microbes may
have a causative role to play in the development of these disease states.
Hence, a healthy lifestyle promotes growth of good bacteria in the gut, and
these bacteria, in turn, aid in maintaining good health.
Probiotics trump antibiotics
Many other factors influence the gut microbiome. For
example, the overuse of antibiotics has been shown to negatively impact the
composition of microorganisms in the gut. Excessive use of antibiotics leads to
death of not only the disease causing bacteria but also the good bacteria,
culminating in reduced diversity of microbes in the gut. This may result in gut
dysbiosis.
Hence, non-prescribed and indiscriminate use of
antibiotics should be prevented as it can deprive the gut of the good bacteria
and negatively impact health. It is to prevent this situation that doctors
prescribe probiotics, that is good bacteria in a capsule, or prebiotics, that
is dietary substances that promote the growth of good bacteria in the gut as a
part of the antibiotic course regime. Similarly, excessive alcohol intake, smoking,
sedentary lifestyle, all, have been shown to negatively impact the gut
microbiota.
It follows from this that a healthy lifestyle
comprising of balanced diet, regular exercise, meditation and avoidance of
alcohol, artificial sweeteners, carbonated drinks, junk food etc. would help in
the proliferation of the good bacteria. This would also reduce the bad bacteria
in the human gut.
The author is a researcher in the department of
biological sciences at the Tata Institute of Fundamental Research.| Harshita Kaul
MM2DEC17
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