Gut microbes are part of the system
which unconsciously regulating person’s behavior depending on the composition
of the type of microbes [1] the enteric nervous system that regulates our gut
is often called the body's “second brain.” This “second brain.” can take part
in neurochemistry but not in wisdom as brain is involved. This extensive
network is very efficient and vigilant; by using the same chemicals and cells
as the brain to help in digestion and also send massages to alert the brain
when something is wrong [2]. In addition to above mentioned functions, gut
microbes also produce hundreds of neuro-chemicals that the brain uses to
regulate basic physiological processes as well as mental processes such as
learning, memory and mood. [3]. For example, serotonin, most important
neurotransmitter, about 90 is produced by gut bacteria. Serotonin plays
important role in regulating both mood and GI activity. Increasing evidence has
associated gut microbiota to both gastrointestinal and extra-gastrointestinal diseases.
Several mental illnesses, such as anxiety and depression which are prevalent in
society today are caused by Dysbiosis and inflammation of the gut [4]. Recent
investigations indicate that the gut microbiome and brain are connected. The
gut microbes largely impact on cognitive function and fundamental behavior
patterns, such as social interaction and stress management [5] Experimental
evidence suggests that gut microbiota has an important role in bidirectional
interactions between the gut and the nervous system;. It interacts with central
nervous system by regulating and influencing neuro-endocrine systems associated
with stress response, anxiety and memory function. In the absence of microbes,
underlying neurochemistry is very much altered [6]. The human gut microbes
influence the brain health in the following ways: Bacteria present in the gut
stimulate directly afferent neurons of the enteric nervous system (ENS) which
send signals via the vagus nerve to the brain [7]. They produce hormones and
neurotransmitters that are identical to those produced by neuro-endocrine
system. Bacterial receptors for these hormones influence microbial growth and
virulence [8] even beneficial metabolites such as short-chain fatty acids may
exert neurotoxicity. Structural bacterial components such as
lipopolysaccharides provide low-grade tonic stimulation of the innate immune
system [9]. Excessive stimulation due to bacterial dysbiosis, small intestinal
bacterial overgrowth, or increased intestinal permeability may produce systemic
and/or central nervous system inflammation [10]. Bacterial proteins may
cross-react with human antigens to stimulate dysfunctional responses of the
adaptive immune system [11]. The gut microbes shape the architecture of sleep
and stress reactivity of the hypothalamic-pituitary-adrenal axis. They
influence clinically and therapeutically relevant to a range of disorders,
including alcoholism, chronic fatigue syndrome, fibromyalgia, and restless legs
syndrome. Their role in multiple sclerosis and the neurologic manifestations of
celiac disease is established. Nutritional tools for altering the gut
microbiome therapeutically include changes in diet, probiotics, and prebiotics
[12] (Figure 1).
An abnormal microbiota associated
with a disrupted gut barrier and the activation of the mucosal immune system
leads to the release of inflammatory mediators and other neuroactive molecules
into the systemic circulation from where they reach the brain and result in
changes in cognition and behavior. Alternately, central stimuli, such as
stress, can disrupt mucosal immunity, the gut microbiota and gut barrier
function and lead to gut dysfunction. Note: bidirectional nature of the
relationships between the gut, the microbiota and the brain. [13]. Diet
and lifestyle factors, including poor sleep quality, alcohol consumption and
inactivity, can harm the gut bacteria [14]. Alternatively, living a healthy
lifestyle characterized by regular physical activity, low stress and a variety
of whole foods is the best way to ensure healthy gut microbes. More so by
eating fresh fruits without added sugars and other additives and including
whole grains and legumes in the diet which are rich in fiber will add enough
healthy bacteria in the gut By including probiotic-rich foods such as plain
yogurt in the daily diet also promote healthy bacteria in the gut .These are
some suggestions for a healthier gut and in turn improved mood.