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©2023 American Medical Writers Association. All rights reserved.  
ISSN 2163-5315

AMWAJournal.org     20

ABSTRACT 
There appears to be a collaborative nexus between the 
human body and its resident microbes. Research shows 
strong associations between this parallel universe of micro-
organisms and our overall health, immunity, and behavior. 
The human microbiome consists of microbes that flourish 
in different parts of the body. Our gut with all its projec-
tions spans nearly 7 kilometers in length and contains the 
largest number of microorganisms within the human body. 
An imbalance in the gut microbiome is strongly associated 
with allergies, metabolic diseases (eg, diabetes, obesity), 
neurological conditions (eg, depression, autism), respira-
tory diseases, liver diseases, and cancer. The development 
of the gut microbiome is a dynamic process that begins 
either during gestation or at birth and continuously evolves 
with human growth into adulthood. The gut microbiome is 
part of an intricate metabolic and signaling network in the 
human body. It communicates through biochemical path-
ways or axes with the skin, brain, lungs, kidneys, breast, and 
liver. A key motivation behind gut microbiome research is to 
confirm the cause-and-effect role of the gut microbiota on 
host health homeostasis. Today, gut microbiome research 
is generating excitement due to its potential to prevent and 
treat several interrelated health conditions. Conclusive evi-
dence of the role played by the gut microbiome on human 
health will furnish new avenues of treatment and better 
insights into the influence of diet, environment, antibiotics, 
and genetics on the body. This article, the first of a two-part 
review, will discuss the relevance of the gut microbiome and 
its prominent constituents, the developmental trajectory 
of the gut microbiome from infancy to adulthood and its 
mutualistic relationship with the human host.
 

Today, medical research is dominated by an overwhelm-
ing interest in the human microbiome.1 Because advances 
in health and medicine are of genuine public interest, 
results related to microbiome research are popular. In 
North America, there is a hype about the microbiome where 

nearly 94% of articles discuss only health benefits, whereas 
very few articles provide critical assessments or limitations 
of microbiome research.2 Microbiome is a term that refers 
to the ecosystem that comprises genes, metabolites, and 
associated products of bacteria, fungi, viruses, phages, and 
archaea (Box 1).3-7 There is a symbiotic relationship between 
human cells and the microbial community that dwells in 
the human body.8 In humans, there are approximately 39 
trillion microbial cells, encoding nearly 20 million microbial 
genes.3,9-12 In contrast, human bodies with approximately 30 
trillion human cells possess a little more than 20,000 human 
genes.12-14 This vast difference of a factor of 102 to 103 in 
microbial gene number has an impact on immunity, behav-
ior, and health in humans. Although studies on the effects 
of the microbiome on human health have been around for 
more than 50 years, a dedicated human microbiome project 
was initiated in 2007 by the National Institutes of Health to 

Smitha S. Dutt, PhD / Freelance Medical Writer, Editor, and Translator, Montreal, Canada

The Gut Microbiome–Human Body Symbiosis: Relevance of the 
Ubiquitous Microbial Community on Health and Development, Part 1

SCIENCE SERIES

Microbiome
An ecosystem of microorganisms (bacteria, viruses, phages, 
fungi, archaea), their genes, and metabolites in a particular 
environment. 

Microbiota
The microorganisms living in a particular environment, 
which include bacteria, viruses, fungi, archaea, and phages.

Dysbiosis
Changes to the composition of the gut microbiome  
(eg, function and taxonomy) cause dysbiosis as presented 
in a disease state. Drastic disturbances to the gut microbial 
balance are linked to diseases, such as inflammatory bowel 
disease, obesity, type I diabetes, asthma, autism, and 
allergies. Gut dysbiosis causes inflammation and immune 
reactions.

Alpha Diversity
The intraspecies diversity in a particular environment in an 
individual.

Vertical Transmission
Transfer of bacteria and genes directly from mother to child

Box 1.

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AMWAJournal.org     21The Gut Microbiome–Human Body Symbiosis

understand the physical and genetic structure of the micro-
biome.1,4,15 The first phase of this project studied the com-
position of different microbiomes (eg, skin, buccal mucosa, 
gut, feces, vaginal wall, tongue, outer ear cavity, and other 
sites) in the human body.15 A second integrative human 
microbiome project is studying the impact of 3 conditions–
prediabetes, inflammatory bowel disease, and pregnancy–
on the dynamic interaction between microbiomes and the 
human body.4,15 There is evidence of biased reporting of gut 
microbiome benefits on human health. By reporting results 
before they have been verified in large sample studies or 
randomized controlled trials, the public may be misled 
about the impact and benefits of the gut microbiome on our 
health.16,17 The following evidence-based review aims to pro-
vide a balanced overview of the gut microbiome and its role 
in the human body.

RELEVANCE OF THE GUT MICROBIOME IN THE 
HUMAN BODY
The gut or intestinal microbiome accounts for 99% (~ 1,000 
to 4,500 species) of the entire microbial flora in the human 
body (Table 1),5,11-13,18,19 making it the densest organ of 
metabolism on our planet. Research has demonstrated the 

significant role of the gut microbiome in immune system 
maturation, vitamin production, energy production from 
dietary components, breakdown of complex sugars from 
plant-derived products and human milk, protection of the 
body against pathogenic bacteria, maturation and develop-
ment of epithelial cells, and neurotransmitter production 
to facilitate communication with the brain.20-22 Processed 
foods, high-fat diet, high- protein diet, low-fiber food,  
antibiotics, alcohol, and diseases cause inflammation and 
create an imbalance in the composition or dysbiosis of 
the gut microbiome.23,24 Gut dysbiosis (Box 1) appears to 
be associated with long-term impacts on the individual’s 
health in the form of allergies (eg, hay fever), gastrointesti-
nal diseases (eg, inflammatory bowel disease [IBD], Crohn’s 
disease), metabolic diseases (eg, obesity, diabetes, and 
cancer), neurological conditions (eg, depression, autism, 
Alzheimer disease), and respiratory tract infections  
(Figure 1).4,20,25,26

ORIGINS OF THE GUT MICROBIOME
The First Stage: Seeding
The development of the gut microbiome is a dynamic pro-
cess.27 Two theories explain the seeding of the gut microbi-

Table 1. Types of Microbiota in the Gut

Bacteria Fungi Viruses and Bacteriophages Archaea
Major Phyla 
(Term Infants)

Major Phyla 
(Preterm Infants) Children Adults Infants Maternal Gut

Methanobrevibacter smithii
Methanosphaera stadtmanae

Order MethanobacterialesProteobacteria
Firmicutes
Actinobacteria
Bacteroidetes
Verrucomicrobia

Firmicutes
Actinobacteria
Bacteroidetes

Aspergillus
Tremellomycetes

Phyla
Basidiomycota
Ascomycota

Genera
Saccharomyces
Penicillum
Aspergillus
Candida

Myoviridae, 
Podoviridae, 
Microviridae, 
and 
Siphoviridae 
families

Microviridae
Circoviridae

Figure 1. The relevance of the gut microbiome 
in the human host. The 3 main roles of the gut 
microbiome are outlined in the figure. Parts of 
the figure were drawn by using pictures from 
Servier Medical Art. Servier Medical Art by 
Servier is licensed under a Creative Commons 
Attribution 3.0 Unported License (https://
creativecommons.org/licenses/by/3.0/). 
Archaea cells icon by SwissBioPics https://
www.swissbiopics.org/ is licensed under CC-
BY 4.0 Unported https://creativecommons.org/
licenses/by/4.0/. 

Impact on the health of an individual
• Immune system modulation
• Vitamin Production
• Digestion
• Neurotransmitter production
• Cytokine production
• Protection from pathogenic bacteria
• Iron absorption

Gut-Organ Axes
Gut-Skin
Gut-Brain

Gut-Brain-Skin
Gut-Liver
Gut-Lung

Gut-Liver-Kidney
Gut-Liver-Heart
Gut-Liver-Brain

Gut Dysbiosis – Health 
Conditions

• Neurological – Parkinson
disease, Alzheimer disease,
Depression, Autism

• Gastrointestinal diseases –
Inflammatory Bowel Disease
(IBD), Celiac disease

• Liver diseases – Hepatic
steatosis, Non-alcoholic fatty
liver disease (NAFLD)

• Allergies – Asthma

• Metabolic diseases – Obesity,
Diabetes

• Skin Diseases – Psoriasis,

• Cancer

Gut microbiome
(Archaea, Fungi,  

Bacteria,  
Bacteriophages,  

Viruses)

Gut-Organ Axes 
Gut-Skin

Gut-Brain
Gut-Brain-Skin

Gut-Liver
Gut-Lung

Gut-Liver-Kidney
Gut-Liver-Heart
Gut-Liver-Brain

Impact on the health of an individual
• Immune system modulation
• Vitamin Production
• Digestion
• Neurotransmitter production
• Cytokine production
• Protection from pathogenic bacteria
• Iron absorption

Gut Dysbiosis – Health 
Conditions
• Neurological – Parkinson 

disease, Alzheimer disease, 
Depression, Autism

• Gastrointestinal diseases– 
Inflammatory Bowel Disease 
(IBD), Celiac disease

• Liver diseases – Hepatic  
steatosis, Non-alcoholic  
fatty liver disease (NAFLD)

• Allergies – Asthma
• Metabolic diseases– 

Obesity, Diabetes
• Skin Diseases – Psoriasis, 
• Cancer

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https://creativecommons.org/licenses/by/3.0/
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AMWAJournal.org     22The Gut Microbiome–Human Body Symbiosis

ome in humans.8,23,28 Bacteria initially colonize the immature 
gut of infants followed by viruses and fungi.23,29,30 

Sterile womb hypothesis. This hypothesis states that the 
uterus of a pregnant person is a sterile environment, and 
microbial colonization of the fetal gut begins at birth during 
labor.8,31,32 When the amniotic sac ruptures in a vaginal birth, 
the fetus is exposed to and enveloped by the mother’s  
vaginal microbiome as it makes its way through the birth 
canal. Babies born via elective cesarean section have a gut 
microbiome that resembles the mother’s skin microbi-
ome.3,8,13,33 Infants born from an emergency C-section have 
gut microbiota that resemble the mother’s skin and vaginal 
microbiomes.3,8,13,33

 In the term infant, the gut is randomly colonized initially 
by pioneer colonizers or microbiota (Box 1) from differ-
ent sites of the mother’s body (eg, skin, mouth, gut, vagina, 
breastmilk).28,30-32 In the first week of birth, the infant’s gut 
is aerobic and has a neutral pH. Facultative anaerobic bac-
teria (growing with or without oxygen) act as pioneer colo-
nizers (Box 1, Table 2).28,31,32 They then reduce in number as 

obligate anaerobes (Table 2) begin to proliferate in the gut. 
As the infant grows, the pH of the gut changes. Facultative 
anaerobes become predominant in the gut, signaling a shift 
in oxygen conditions. These robust microbes are vertically 
transmitted (Box 1) from the mother to the child.32 After 6 
days of life, there is a transition to Bifidobacteria species 
that use human milk oligosaccharides (HMOs) as a source 
of carbon (Figure 2).3,23

In utero hypothesis. In contrast, this controversial hypothe-
sis suggests the fetal gut microbiome is seeded during ges-
tation when the fetus is exposed to the microbiota of the 
placenta or amniotic fluid. Placenta, amniotic fluid, and 
meconium–once considered sterile–are now being shown to 
be occupied by microbial communities. Preterm babies are 
exposed to amniotic fluid microbiota due to urinary infec-
tions (premature rupture of membranes) or chorioamnion-
itis (infection within the amniotic sac and the surrounding 
fetal membrane) during gestation.25,34-38

Controversies. Critics argue against the presence of micro-
biota in these sterile sites and suggest that laboratory con-
tamination may be the potential source. These microbiota 
could also seed the neonatal gut via vertical transmission 
from the mother to the fetus (eg, breastmilk).6,25,34,39

The Second Stage: Weaning
The infant’s gut microbiome undergoes a significant 
change during weaning when they are introduced to a solid 
diet.3,23,40 The gut microbiome is compelled to mature and 
increase in diversity when the complexity of carbohydrate 
and starch components increases. There is a decrease in 
Bifidobacterium and other obligate anaerobic species. This 
stage of maturation sees the predominance of the phylum 

Table 2. Seeding Microbes

Facultative anaerobes Obligate anaerobes
Term
Infants

Prevotella melaninogenica, 
Haemophilus parainfluenzae, 
Enterobacteriaceae members, 
Alistipes putredinis, 
Staphylococci, Streptococci

Bifidobacteria, Clostridia, 
Eubacteria spp, and 
Bacteroides

Preterm 
Infants

Staphylococcus, Enterococcus, 
Enterobacteraceae, 
Bifidobacterium

Delayed colonization – 
Bifidobacteria, 
Lactobacillus, and 
Bacteroides

Figure 2. Seeding and stages of development of the gut microbiome. 
Successive stages in gut microbiome development in preterm and term 
infants are outlined in the figure. Predominant bacteria at each stage of 
succession are indicated.

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AMWAJournal.org     23The Gut Microbiome–Human Body Symbiosis

Bacteriodetes and Clostridia species.23,28,31,40 The gut flora is 
distinctly different in children aged 4 months, 12 months,  
3 years, and 5 years.3,23,29,41 As the infant grows through the 
first year of life, the alpha diversity (Box 1) increases when 
solid foods are introduced in the diet (Figure 2).25,27,37

 
The Third Stage: Stabilization of Gut Flora During 
Growth Into Adulthood
There is limited information on the gut microbiomes of 
children and adolescents. The evolution of the gut microbi-
ome stabilizes in children after 5 years of age and appears 
to resemble that of adults. The 5 major phyla in an adult gut 
are Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, 
and Verrucomicrobia. Microbial content, however, differs 
and is influenced by diet, geographical location, and use 
of antibiotics.3,8,29,41-43 Bacterial genera of the adult gut do 
not resemble the genera found in children younger than 
3 years.29 With the progress to adulthood, Bifidobacteria 
abundance reduces along with subsequent enrichment of 
Firmicutes and Bacteroidetes in the adult microbiome.44

FACTORS INFLUENCING GUT MICROBIOTA
Normal development of the gut microbiome with 
increasing species diversity from birth is essen-
tial to the future health of the individual.27 Several 
factors enhance or impede the microbial balance 
in the gut.

Term Infants
In a term neonate, vaginal birth, good maternal 
health, breastmilk, and probiotics enhance the 
diversity of gut flora. Antibiotics, hospitalization, 
and smoking (Table 3) give rise to antimicrobial 
resistance genes and facilitate the growth of fac-
ultative anaerobic pathogenic bacteria.8,13,39,45,46 
The type of mother’s diet, c-section birth, formula 
feeds, bovine-milk-fortified human milk, and the 
environment (eg, living with family members, 
daycare, pets, rural or urban lifestyle, an indus-
trialized environment) influence gut flora mat-
uration in different ways.8,28,30 Gut microbiota of 
infants born via c-section and/or fed formula are 
very diverse and closely resemble mature micro-
biota of adults.23 In addition, chemical factors 
(pH, bile acid, mucus), microbial factors (adhe-
sion capability, metabolic pathways, bacterial 
enzymes), and bacteriophages influence gut 
microbiome diversity.5,21

Preterm Infants
Preterm infants show delayed development of 

microbial diversity and a distinct difference in species 
composition (Table 4) from those of age-matched term 
infants before 6 months.25,37,47 Microbial colonization may 
occur prior to birth because of complications during ges-
tation.13,33,36 Gestational age plays a major role in the initial 
colonization and microbial diversity of the preterm infant’s 
gut.47 Other factors include genetics, sex, the mode of feed-
ing (enteral; parenteral; breastfeeding), type of milk (breast-
milk; formula, donor milk); pumping and storage of milk, 
and the environment (hospital; intensive care unit; medical 
interventions; antibiotics; family members).13,27,33,37,44,45,48-51

IMPACT OF CHANGES IN MICROBIAL DIVERSITY
Gut microbiomes of children are more susceptible to 
changes in diet, environment, and antibiotics than those 
of adults. Babies born via c-section appear to be predis-
posed to developing obesity and celiac disease.8,41 Antibiotic 
treatment reduces microbiota diversity, leading to anti-
biotic-related obesity, multidrug resistance, and asthma. 
Gut health could be restored when treated with beneficial 
bacteria.23,41 The quality of microbial diversity in the gut is 

Table 3. Gut Bacteria in Term Infants

Vaginal Escherichia coli, Lactobacillus spp, Enterococcus Bifidobacteria  
(eg, Bifidobacterium breve, Prevotella spp, Bifidobacterium bifidum, 
Bifidobacterium adolecscentis, Bifidobacterium longum), Sneathia spp, 
Streptococci, Atopobium vaginae and Gardnerella vaginalis, Bacteroides, 
Fecalibacteria, Parabacteroides, Lachnospiraceae, Ruminococcaceae, 
Christensenallaceae, Roseburia, Anaerostipes

C-section Klebsiella, Clostridium, Staphylococcus, Haemophilus, Veillonella, 
Propionibacteria, Proteobacteria, Enterococcus spp, Corynebacterium spp, 
other Ruminococcaceae variants, Bifidobacterium spp↓, Lachnospiraceae, 
and Bacteroidaceae species↓

Breastmilk Enterobacter, Streptococci, Acinetobacter, Staphylococci, Bifidobacteria, 
lactic acid bacteria, Pseudomonas

Formula Clostridium difficile, Bacteroidetes (Bacteroides fragilis), Staphylococci, 
Atopobium, Enterobacteria, Enterococci, and Firmicutes Lactobacilli, 
Escherichia coli

Table 4. Gut Bacteria in Preterm Infants
C-section Enterococci, Enterobacteraceae, Staphylococci, Klebsiella, 

Mycoplasmataceae (↑ in chorioamnionitis), Bacteroidetes↓, Escherichia, 
Bifidobacteria ↓, Veillonella, Lactobacilli ↓, Coprobacilli, Desulfovibrio, 
Carnobacteria, Phascolarctobacteria, Gammaproteobacteria, 
Firmicutes, Shigella, Clostridia ↓, Atopobium ↓, Sneathia sanguinegens, 
Fusobacterium nucleatum

Breastmilk Staphylococci, Corynebacteria, Pseudomonas, Streptococci, Acinetob
Formula Bifidobacteria and Clostridiales
Antibiotics Firmicutes and Proteobacteria
Hospital-
associated

Klebsiella pneumoniae, Yersinia, Enterococci, Serratia, Granulicatella, 
Proteus, Enterobacter aerogenes, Escherichia coli 

Diet-
associated

Ruminococcus bromii, Bacteroides vulgatus, Lactococci,  
Ruminococcus obeum

Butyrate 
producers Eubacterium hallii, Anaerostipes caccae, Coprococcus eutactus

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AMWAJournal.org     24The Gut Microbiome–Human Body Symbiosis

crucial and dependent on the interplay of different factors. 
Despite breastfeeding, malnutrition reduces alpha diver-
sity (increased prevalence of Proteobacteria) and slows 
down growth in children.3,23,29,43 A Western diet of low-fi-
ber and high-fat processed foods increases the presence of 
Bacteroides and reduces overall alpha diversity. Numerous 
health conditions (eg, obesity, IBD, cancer) appear to be 
associated with reduced alpha diversity.23,52 In contrast, 
high-fiber diets increase microbial diversity and over-
all health in rural populations in Asia and Africa.23,40,41,52 
Geographical location appears to influence microbial  
diversity. People living in industrialized urban areas  
exhibit lower gut microbial diversity than those who live  
in rural areas.42,52

GUT MICROBIOME NETWORK
The gut microbiome does not act in isolation. Instead, 
microbiota or its metabolites travel to other sites of the 
human body and interact with their microbiomes through 
bidirectional or multidirectional pathways. This complex 
network explains the influence of the gut microbiome on 
our immunity, health, and even our emotions (Figure 1). 
Some of the gut axes are gut-liver,24 gut-lung,10,24,53,54 gut-
brain, gut-skin, gut-liver-kidneys,24 and gut-brain-liver.24 
Disruption to the normal functioning of these axes results in 
diseases such as chronic kidney disease, hepatic encepha-
lopathy, and cardiovascular disease, nonalcoholic fatty liver 
disease, chronic obstructive pulmonary disease, asthma, 
and cystic fibrosis.10,24,53,54 These conditions are often linked 
to gastrointestinal diseases. This article will focus on the gut-
skin, gut-brain, and the gut-breastmilk axes.

Gut-Skin Axis
The biochemical interactions between the skin and gut 
microbiomes are bidirectional.28 A dysbiotic gut microbi-
ome may induce changes to the skin microbiome with the 
release of proinflammatory cytokines. This allows gut bac-
teria or their metabolic byproducts and toxins to enter the 
systemic blood circulation. The gut bacteria reach the skin 
and affect the integrity of the skin barrier. The resulting 
inflammation has been linked to chronic skin disorders  
(eg, psoriasis, acne, alopecia).55,56

Gut-Brain Axis
According to preclinical research, there are bidirectional 
interactions between the gut, brain, and the gut microbiome 
(GBM). The gut-brain axis comprises the autonomic ner-
vous system, the gut microbiota with its metabolic products, 
the enteric neuroendocrine system, the hypothalamic-pi-
tuitary-adrenal system, the enteric nervous system, and the 
gut-associated immune system.36,57 Research has shown that 

bacteria, their metabolites, and immune cells have access 
to the brain through the blood brain barrier (BBB).22,58 
Gut bacteria belonging to the genera Bifidobacteria, 
Streptococci, Escherichia, Lactobacilli, and Enterococci reg-
ulate the production of neurotransmitters (eg, GABA, sero-
tonin, and acetylcholine), which pass through the BBB and 
modulate brain signaling directly or indirectly. Interactions 
between the nervous system and the immune system are 
also affected. People suffering neurological, psychiatric, and 
degenerative conditions (eg, depression, anxiety) also dis-
play perturbations in the diversity of their gut microbiome 
(eg, IBD, chronic abdominal pain).22,57-59

Gut-Brain-Skin Axis
The gut-brain-skin axis is gaining relevance in the consistent 
link between skin conditions (psoriasis, acne) and mental 
health (depression). The central nervous system (CNS) is 
regulated by neurotransmitters transmitted from the gut 
microbiota through the vagus nerve. Neurotransmitters 
facilitate the interactions between the nervous system and 
immune responses to skin inflammation. Mental health 
conditions (eg, depression) and skin conditions (eg, pso-
riasis) generate cytokines (eg, IL6) from the brain and the 
skin. This causes inflammation. Simultaneously, CNS condi-
tions (eg, depression or anxiety) appear to cause gut dysbi-
osis and increase the permeability of the gut epithelial cells 
(leaky gut). Gut microbiota and their metabolites enter the 
bloodstream and trigger inflammation on the skin and in 
the brain.58,60

Human Breastmilk – Enteromammary Hypothesis
Breastmilk may play a role in seeding the infant microbi-
ome. A quarter of the infant’s gut microbiota is obtained 
from breastmilk, which influences its development over the 
individual’s lifetime and protects against potential aller-
gies.61,62 The enteromammary hypothesis suggests that bac-
teria travel from the mother’s gut to the lactating breast and 
create the breastmilk microbiome. However, this hypothe-
sis is based on a small sample size.51,61,63 Human breastmilk 
contains bioactive compounds (secretory immunoglobulin 
A,64 growth factors, >200 HMOs, cytokines), immunolog-
ical compounds, nutrients, and maternal gut microflora. 
Bioactive compounds help to develop a robust immune 
system in the infant.8,44,61 As prebiotics and a source of bio-
active compounds, HMOs are digested by microbiota, such 
as Bifidobacteria, in the large intestine because humans 
lack the enzymes to metabolize HMOs in the small intes-
tine. HMOs (elaborate sugar complexes) are a major source 
of brain nourishment and prevent the growth of infectious 
pathogens.8,44,61 The components of breastmilk change 
dynamically at each developmental stage of the infant.65

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AMWAJournal.org     25The Gut Microbiome–Human Body Symbiosis

CONCLUSION
Despite strong associations, the vital question persists: does 
a health condition cause gut dysbiosis, or is the reverse 
true?22,23 This topic is ripe for debate as misinformation 
influences public opinion. Unfortunately, it has been noted 
that the general population prefers to acquire information 
from nonmedical independent sources.17 Popular content 
(eg, articles or videos) lack reliable peer-reviewed sources 
to support their claims on the benefits of products, such as 
probiotics or yogurt, on human health.2,17 However, respon-
sible reporting is warranted. Accurate data interpretation 
could influence future health policies.1 To preserve scientific 
integrity, it is our responsibility as medical writers to ensure 
that facts and research findings on the gut microbiome are 
validated and appropriately disseminated. Data from large 
randomized clinical trials should be cautiously interpreted 
by assessing the relevance of statistical tests used or by dis-
tinguishing associations from cause-and-effect. When sta-
tistical data are accurately interpreted in the larger context 
of the human population, the significance of the results 
is more convincing. Although gut microbiome research is 
under the influence of the “health halo,” we cannot deny the 
existence and the involvement of this extensive microbial 
community in human health.2 Established as an integral 
part of the complex, interconnected human signaling net-
work, the gut microbiome and its manipulation could soon 
form a key aspect of the diagnostic and treatment landscape.

Acknowledgments
I thank Dr Naomi Bishop for her insightful comments and 
for her review of the article.

Author declaration and disclosures: The author notes no  
commercial associations that may pose a conflict of interest in 
relation to this article.

Author contact: smitha.dutt@gmail.com

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