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📘 Gut Health Library • Cornerstone

Understanding the Gut Microbiome

Learn how the gut microbiome influences digestion, immunity, Candida, IBS, SIBO, leaky gut, and overall health—and discover practical ways to restore microbiome balance naturally.

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Written & Clinically Reviewed by Eric Bakker, N.D. • Last Updated: July 2026 • 12 min read

📘 Gut Health Library • Cornerstone

Understanding the Gut Microbiome

Learn how the gut microbiome influences digestion, immunity, Candida, IBS, SIBO, leaky gut, and overall health—and discover practical ways to restore microbiome balance naturally.

Evidence-Based

Gut Microbiome Focused

Root Cause Approach

Start My Free Gut Health Assessment

Written & Clinically Reviewed by Eric Bakker, N.D. • Last Updated: July 2026 • 12 min read

What is the Gut Microbiome?

Your gut microbiome is the diverse community of trillions of bacteria, fungi, viruses, and other microorganisms that live primarily in your digestive tract.

These gut micro-organisms including beneficial bacteria help digest food, produce essential nutrients, support the immune system, protect the gut barrier, and influence many aspects of digestive and overall health.

When your microbiome becomes imbalanced—a condition known as gut dysbiosis—it may contribute to digestive disorders such as Candida overgrowth, IBS, SIBO, and leaky gut, as well as inflammation and reduced immune function.

In This Guide, You Will Learn

  • What the gut microbiome is and why it plays a vital role in health.
  • How beneficial bacteria support digestion, immunity, and the gut barrier.
  • What causes gut dysbiosis and its common symptoms.
  • How the microbiome is linked to Candida, IBS, IBD, SIBO and leaky gut.
  • Ways to restore a microbiome through diet, probiotics, prebiotics, and lifestyle.
  • When gut testing may be helpful and the best next steps for recovery.
Gut Microbiome At a Glance
  • Contains trillions of bacteria
  • Mostly bacteria, but also fungi, viruses and archae

Main Role

  • Digestion
  • Nutrient Production
  • Immune Regulation
  • Gut Barrier Protection
  • Protection against Pathogens
  • Gut-Brain Communication

When Imbalanced

  • Candida Overgrowth
  • IBS
  • SIBO
  • Leaky Gut

Can Be Improved By

  • Diet
  • Lifestyle
  • Probiotics
  • Prebiotics

What You’ll Learn

Microbiome Basics

Digestive Health

Gut Dysbiosis

Related Conditions

Restoring Balance

Quick Glance

Focus Gut Microbiome

Microbes Bacteria • Fungi • Viruses • Archae

Imbalance Dysbiosis

Functions Digestion • Immunity • Barrier

Recovery Diet • Probiotics • Lifestyle

At a Glance

Focus • Gut Microbiome

Microbes • Bacteria • Fungi • Viruses • Archae

Imbalance • Dysbiosis

Functions • Digestion • Immunity • Barrier

Recovery • Diet • Probiotics • Lifestyle

What You’ll Learn

Microbiome Basics

Digestive Health

Gut Dysbiosis

Related Conditions

Restoring Balance


Quick Facts About the Gut Microbiome

Key Fact

Why It Matters


Your digestive tract contains trillions of microorganisms.


They help regulate digestion, immunity and metabolism.


Most gut can be are either beneficial or harmless.


Only a small proportion become problematic when balance is lost.


Diversity is more important than simply having “more bacteria.”


A varied microbiome is has been shown to be more resilient and stable.


Antibiotics can significantly disrupt the microbiome.


Recovery may take weeks, months or years depending on the person.


Diet has one of the greatest influences on gut bacteria.


Fibre-rich whole foods help nourish our beneficial bacteria.


Our gut microbiome changes throughout life.


Positive lifestyle changes can improve gut health at almost any age.

Clinical Pearl


Throughout my years of clinical practice, I’ve rarely seen a person’s digestive problems occur in isolation. A patient presenting with Candida overgrowth in most all cases has signs of gut dysbiosis. Someone with IBS frequently may have poor gut microbial diversity.

Yet another person presenting with SIBO including cramping pain and bloating, or someone struggling with food intolerances may also have poor digestive function and an unhealthy gut ecosystem.

Rather than treating these as completely separate or isolated conditions, I’ve always found it much more effective to establish the cause, understand the health of the microbiome first, and then work with the patient to bring about balance and harmony.


Why Understanding Your Gut Microbiome Is So Important

For many centuries, most digestive disorders were viewed as isolated diseases affecting a person’s individual digestive organs. If someone experienced bloating, the focus was often placed mainly on their stomach or bowel. If recurrent infections developed, attention turned to their immune system. Skin conditions were considered dermatological problems. Fatigue was viewed independently. And mood disorders? Well, they belonged to neurology, psychology or even psychiatric department.

Today, we understand that these systems are far more interconnected than we previously believed, and one of the key links connecting them is the gut microbiome.

Research over the past ttwenty years alone has completely transformed our understanding of the human digestive tract. Scientists now recognise that the gut is home to an incredibly diverse community of microorganisms that constantly interact with the immune system, nervous system, endocrine system, metabolism and intestinal barrier.

These bacteria don’t simply live inside us—they actively participate in maintaining our health and wellbeing. This is one of the biggest reasons why the gut microbiome has become one of the fastest-growing areas of medical research worldwide.

This cornerstone guide has been designed to give you a complete understanding of the gut microbiome in plain and basic English.

Rather than focusing on a single digestive condition, we’ll explore the entire ecosystem and explain how it influences many aspects of health.

By the End of This Guide You’ll Understand

  • How the human gut microbiome develops.
  • Why beneficial bacteria are essential for optimal health.
  • What gut dysbiosis really means and what it causes.
  • How Candida, IBS, SIBO and leaky gut are all connected.
  • Which functional tests can help assess your gut health.
  • Practical ways to restore your microbial balance naturally.
  • Which dietary and lifestyle factors have the greatest impact.

Whether you’re beginning your gut health journey or have struggled with digestive problems for years, understanding the microbiome provides the foundation for making informed decisions about your health.

What the Gut Microbiome is More Than Just Gut Bacteria

The term gut microbiome refers to the enormous community of microorganisms living throughout the digestive tract, particularly within the large intestine (colon).

These microorganisms include:

  • Beneficial bacteria
  • Harmless bacteria
  • Yeasts
  • Fungi
  • Viruses
  • Archaea
  • Other microscopic organisms

Together, they form one of the most complex ecosystems found anywhere in nature.

Scientists estimate that the human gut contains tens of trillions of microorganisms, representing hundreds—possibly thousands—of different species.

While individual microbes are microscopic, together they perform an astonishing range of biological functions that are essential for human health.

Without them, normal digestion, immune regulation and nutrient production would be severely compromised.

Frequently Asked Questions

Find answers to the most common questions about digestive symptoms, diagnostic testing, possible underlying causes, and how to distinguish between common gut health conditions. For more detailed information, explore the in-depth guides throughout the Gut Health Library.

Poor gut health can cause a wide range of digestive and whole-body symptoms. Common digestive complaints include bloating, excess gas, abdominal discomfort, constipation, diarrhoea, indigestion, and food intolerances. However, gut problems may also contribute to fatigue, brain fog, skin conditions, sugar cravings, and changes in mood or energy levels.

Because many digestive disorders share similar symptoms, it’s important not to assume a single cause. Conditions such as Candida overgrowth, IBS, SIBO, leaky gut, and gut microbiome depletion can present in similar ways. Understanding your symptoms is the first step towards identifying the underlying cause and choosing the most appropriate treatment.

Yes. Candida overgrowth, Irritable Bowel Syndrome (IBS), and Small Intestinal Bacterial Overgrowth (SIBO) often share symptoms such as bloating, abdominal pain, excess gas, diarrhoea or constipation, and food sensitivities. This overlap can make diagnosis challenging. While these conditions have different underlying causes, they may also occur together, particularly when the gut microbiome has been disrupted.

A careful review of your symptoms, medical history, diet, and appropriate testing can help distinguish between them. Rather than focusing on one diagnosis, it’s important to consider the health of the entire digestive system

Symptoms vary considerably from person to person and often overlap with other digestive disorders. There is no single symptom that confirms Candida overgrowth. Many people experience bloating, digestive discomfort, sugar cravings, recurrent yeast infections, oral thrush, fatigue, or brain fog, but these symptoms can also occur with IBS, SIBO, food intolerances, and other digestive disorders. Diagnosis should never rely on symptoms alone. A comprehensive assessment may include your medical history, risk factors such as recent antibiotic use, dietary habits, physical examination, and, when appropriate, laboratory testing. Looking at the complete clinical picture is usually far more reliable than relying on one symptom or one test.

Some of the most common symptoms may include:

  • Bloating
  • Excess gas
  • Sugar cravings
  • Fatigue
  • Brain fog
  • Oral thrush (white tongue)
  • Itching (skin, ears, scalp, feet, genital area, rectal, etc.)
  • Vaginal thrush
  • Skin irritation or rashes
  • Digestive discomfort

These symptoms are not specific to Candida imbalance and can also occur with IBS, SIBO, food intolerances and other gut conditions. For this reason, in my clinical experience, symptoms alone cannot confirm a diagnosis.

Leaky gut, also known as increased intestinal permeability, is thought to occur when the intestinal lining becomes more permeable than normal. People often report bloating, food sensitivities, digestive discomfort, fatigue, and changes in bowel habits.

Some research suggests that increased intestinal permeability may play a role in certain digestive and immune-related conditions, although its exact significance is still being investigated. Because these symptoms overlap with many other gut disorders, a thorough assessment is essential before assuming leaky gut is the primary cause of ongoing health problems.

Yes, absolutely. Yes. A healthy gut microbiome plays an important role in digestion, nutrient metabolism, immune function, and maintaining the intestinal barrier. When beneficial bacteria become depleted—a state often referred to as dysbiosis or gut microbiome imbalance—people may experience bloating, gas, constipation, diarrhoea, food intolerances, and recurrent digestive complaints.

Antibiotic use, poor diet, chronic stress, infections, and certain medications can all affect the balance of the gut microbiome. Supporting microbial diversity is often an important part of improving long-term digestive health.

The most appropriate test depends on your symptoms and medical history. Healthcare practitioners may recommend stool testing to assess digestive function and the gut microbiome, breath testing for SIBO, blood tests to investigate nutritional deficiencies or inflammation, or other specialised laboratory investigations where clinically appropriate. Not everyone requires extensive testing, and many diagnoses begin with a careful clinical assessment. Selecting the right investigation is often more valuable than performing multiple unnecessary tests.

Stool testing and breath testing evaluate different aspects of digestive health. Comprehensive stool tests examine digestive function, inflammation, beneficial bacteria, opportunistic organisms, parasites, and other markers of gut health. Breath testing is primarily used to investigate Small Intestinal Bacterial Overgrowth (SIBO) by measuring hydrogen and methane gases produced after consuming a specific sugar solution. These tests answer different clinical questions and are often complementary rather than interchangeable. The most appropriate choice depends on your symptoms and suspected condition.

Yes. It is not uncommon for people to experience more than one digestive disorder simultaneously. For example, Candida overgrowth may occur alongside IBS, SIBO, dysbiosis, or increased intestinal permeability. These conditions often influence one another because they share common risk factors, including antibiotic use, poor diet, chronic stress, and disruption of the gut microbiome. A comprehensive assessment helps identify contributing factors so that treatment can address the underlying causes rather than focusing on only one diagnosis.

Persistent digestive symptoms should always be assessed by a qualified healthcare professional, particularly if they are severe, worsening, or accompanied by unexplained weight loss, persistent vomiting, rectal bleeding, fever, difficulty swallowing, anaemia, or a family history of bowel disease or colorectal cancer. These symptoms may indicate conditions that require prompt medical investigation. Even when serious disease has been excluded, ongoing bloating, abdominal discomfort, constipation, diarrhoea, or food intolerances deserve a proper assessment to help identify the underlying cause.

Recurring digestive symptoms often indicate that an underlying issue has not been fully addressed. While temporary improvements may occur, long-term recovery usually requires identifying contributing factors such as dietary habits, gut microbiome imbalance, recurrent infections, chronic stress, food intolerances, medication use, or other digestive conditions. Rather than simply managing symptoms, focus on understanding why they continue to return. Working with an experienced healthcare practitioner and following a structured, evidence-informed approach can help identify the root cause and support lasting improvements in digestive health.

Eric’s Clinical Perspective

After 39 years of working with patients, I’ve found that the people who get the best results usually begin with a clear understanding of what’s causing their symptoms.

  • They avoid jumping to conclusions based on symptoms alone.
  • They recognise that many digestive conditions share similar signs and symptoms.
  • They use testing when it’s appropriate, rather than relying on guesswork.
  • They look for underlying causes instead of simply treating symptoms.
  • They work with reliable, evidence-based information to make informed decisions.

This Symptoms & Diagnosis Hub is designed to help you better understand your symptoms, explore possible causes, learn about diagnostic options, and take the next step with greater confidence. Eric Bakker, N.D.

Not sure where to start?

Take the free 5-minute Gut Health Assessment to identify one of five gut types, understand the possible root causes of your symptoms, and receive personalised next steps for recovery..

Start My Free Gut Health Assessment

Not sure where to start?

Take the free 5-minute Gut Health Assessment to identify one of five gut types, understand the possible root causes of your symptoms, and receive personalised next steps for recovery..

Start My Free Gut Health Assessment

Still Not Sure What’s Causing Your Symptoms?

Complete our Free Gut Health Assessment to identify possible patterns, understand which digestive conditions may be contributing to your symptoms, and receive personalised guidance based on your answers.

Key Takeaways

  • Many digestive conditions, including Candida, IBS, SIBO, leaky gut, and gut microbiome depletion, share similar symptoms.
  • Bloating, gas, constipation, diarrhoea, fatigue, brain fog, and food intolerances are common signs of underlying gut health problems.
  • An accurate diagnosis begins with a careful assessment of symptoms, medical history, and individual risk factors, not symptoms alone.
  • Stool tests, breath tests, blood tests, and other investigations may help identify the underlying cause when clinically appropriate.
  • More than one gut health condition can occur at the same time, making differential diagnosis an important part of effective care.
  • Early recognition and appropriate investigation can help guide more targeted treatment and support long-term digestive health.
  • Explore the guides throughout this library to better understand your symptoms and take the next step towards improving your gut health.

Scientific References & Evidence Base

The information in this Symptoms & Diagnosis Hub is based on current clinical guidelines, peer-reviewed research, and evidence from recognised medical and functional medicine sources. These references support the evaluation of digestive symptoms, differential diagnosis, laboratory testing, and gut health assessment. Additional citations are provided throughout the individual articles linked from this page.

Evidence Base

This guide integrates evidence from gastroenterology, infectious disease, microbiome research, nutrition, and functional medicine. It combines conventional diagnostic approaches with evidence-informed functional assessment to help readers better understand persistent digestive symptoms and their possible causes.

Clinical Guidelines & Scientific Resources

Laboratory & Diagnostic Resources

  • Centers for Disease Control and Prevention (CDC)
  • National Institutes of Health (NIH)
  • National Center for Biotechnology Information (NCBI)
  • American Society for Microbiology (ASM)

Functional Medicine & Integrative Testing

  • Institute for Functional Medicine (IFM)
  • Genova Diagnostics (GDX)
  • Diagnostic Solutions Laboratory (GI-MAP)
  • Doctor’s Data (DDI)
  • Mosaic Diagnostics (formerly Great Plains Laboratory)

Major Databases

Medical Disclaimer
The information on Candida.com is provided for educational purposes only and should not be considered medical advice. Always consult a qualified healthcare professional before making decisions about your health, particularly if you have a medical condition, are pregnant or breastfeeding, or take prescription medications. Never delay or disregard professional medical advice because of information you have read on this website.