In Part 3 of our Digestion Series, we explore the microbial reset—addressing imbalances in the digestive ecosystem before moving into gut barrier repair and microbiome rebuilding.

In Part 2, we explored how enzymes, bile, and motility help move digestion forward and support healthy digestive function. Once these processes are supported, we can turn our attention to the microbial terrain.

Before we jump into gut lining repair or microbiome rebalancing, we need to ask an important question: Is the digestive terrain ready?

Bacterial, fungal, or parasitic imbalances can occur when conditions within the gastrointestinal tract favor their persistence or overgrowth. Some microorganisms can form protective biofilms, produce biologically active compounds, and interact with the intestinal lining and immune system.

The goal of a microbial reset is not to indiscriminately “kill” microorganisms. It is to identify clinically relevant imbalances, address contributing factors, and help create a healthier intestinal environment before moving into the repair and rebuilding phases.

The Microbial Reset: Restoring Balance to the Inner Terrain

A healthy microbiome contains a diverse and dynamic community of microorganisms that interact with digestion, immune function, metabolism, and the intestinal barrier.

When this ecosystem becomes disrupted, a state commonly referred to as dysbiosis may develop. Dysbiosis describes an alteration in the composition or function of the microbiome rather than the simple presence of “good” or “bad” organisms.

Factors that may contribute to microbial imbalance include:

• Impaired digestive function
• Frequent or repeated antibiotic exposure
• Certain medications, including acid-suppressing medications
• Chronic stress and inadequate sleep
• Dietary patterns high in ultra-processed foods
• Altered gastrointestinal motility
• Certain infections and gastrointestinal conditions

Depending on the individual, clinically relevant microbial patterns may include:

Yeast and Fungal Overgrowth

Candida species normally live within the human gastrointestinal tract and other areas of the body.

Their presence alone does not necessarily indicate disease. However, under certain conditions, fungal populations may become altered or overrepresented and interact differently with the surrounding bacterial microbiome.

Small Intestinal Bacterial Overgrowth (SIBO)

SIBO occurs when excessive numbers or abnormal populations of bacteria are present in the small intestine.

Symptoms may include bloating, abdominal discomfort, changes in bowel habits, and excessive gas, although these symptoms are not specific to SIBO and can occur with many gastrointestinal conditions.

Breath testing measuring hydrogen and methane is commonly used as part of the clinical evaluation when SIBO or intestinal methanogen overgrowth is suspected.

Opportunistic Bacteria

Certain bacteria may exist within the gastrointestinal tract without causing problems but become more clinically relevant when the intestinal environment changes.

The significance of organisms such as Klebsiella, Pseudomonas, and certain Clostridia depends on the species, abundance, location, host health, symptoms, and overall microbial environment.

Intestinal Parasites and Protozoa

Organisms such as Blastocystis and Dientamoeba fragilis may be detected in stool testing.

Their clinical significance is complex. Some individuals carrying these organisms have symptoms, while others remain completely asymptomatic.

For this reason, a positive stool result does not automatically mean that an organism requires eradication. Results should be interpreted alongside symptoms, medical history, travel and exposure history, and other clinical findings.

💡 Important: Microorganisms are not simply “good” or “bad.” Many organisms can coexist with us without causing disease. What matters is the relationship between the organism, its location, the surrounding microbial ecosystem, and the health of the individual.

Microbial Imbalance and the Gut Barrier

Microbial imbalance and intestinal barrier function are closely interconnected.

Certain microbial components, metabolites, and inflammatory signals may influence the intestinal epithelium and immune system.

One example is lipopolysaccharide (LPS), a structural component of the outer membrane of gram-negative bacteria. When intestinal barrier function is disrupted, increased exposure to microbial products such as LPS may contribute to immune and inflammatory signaling.

You may also encounter biomarkers such as:

Zonulin – A protein associated with the regulation of intestinal permeability. Commercial zonulin testing is available, but current assays have important limitations and results should be interpreted cautiously.

Occludin – A protein involved in the structure and regulation of intestinal tight junctions. Although antibodies and other markers related to tight-junction proteins are sometimes included in commercial testing, their clinical interpretation remains an evolving area.

LPS – A component of gram-negative bacterial cell walls that can stimulate immune signaling. Its presence and biological effects are complex, and commercially available measurements should not be used alone to diagnose intestinal permeability.

💡 No single biomarker can tell us exactly how much microbial imbalance is affecting the intestinal lining. These findings, when used, should be interpreted alongside symptoms, medical history, conventional laboratory findings, and other clinical information.

Signs a Microbial Reset May Be Considered

Symptoms alone cannot confirm dysbiosis, SIBO, fungal overgrowth, or another microbial condition.

However, further investigation may be appropriate when someone experiences persistent symptoms such as:

• Chronic or recurrent bloating and abdominal discomfort
• Excessive intestinal gas
• Persistent constipation or diarrhea
• Significant changes in bowel habits
• Ongoing digestive symptoms following a gastrointestinal infection
• Recurrent or persistent gastrointestinal symptoms despite dietary changes
• Symptoms that consistently worsen with certain fermentable foods

Brain fog, fatigue, mood changes, skin symptoms, and food reactions are sometimes attributed to “gut dysbiosis” online, but these symptoms have many potential causes and should not automatically be assumed to originate from microbial overgrowth.

The goal is to investigate appropriately rather than treating symptoms based on assumptions alone.

Biofilms: Why Some Microbes May Be Harder to Address

Biofilms are organized communities of microorganisms surrounded by a protective extracellular matrix.

Within a biofilm, microorganisms can adhere to surfaces and communicate through chemical signaling processes, including quorum sensing.

Quorum sensing allows microorganisms to coordinate certain behaviors according to population density, including biofilm formation and the expression of particular genes.

💡 Think of it as microorganisms communicating chemically with one another and changing their collective behavior as their community grows.

Biofilms are well established in microbiology and play important roles in many infectious processes.

However, the clinical significance of gastrointestinal biofilms—and the extent to which commercially marketed “biofilm disruptors” improve outcomes for routine dysbiosis—is still an evolving area of research.

For this reason, biofilm treatment should not automatically be assumed to be necessary for every person with gastrointestinal symptoms.

A Strategic Approach to the Microbial Reset

A microbial reset is not about “killing everything.”

The goal is to address clinically relevant microbial imbalances while also considering the environment that may have allowed those imbalances to develop.

This may involve addressing factors such as:

• Gastrointestinal motility
• Digestive function
• Diet and nutrient intake
• Medication use
• Previous infections
• Stress and sleep
• Underlying gastrointestinal conditions

When treatment is appropriate, the strategy should be individualized according to the specific condition being addressed.

🌿 Herbal Antimicrobials

Certain plant-derived compounds have demonstrated antimicrobial activity in laboratory studies, and some have been investigated clinically for specific gastrointestinal applications.

Examples commonly used in integrative practice include:

• Oil of oregano
• Berberine-containing botanicals
• Garlic or allicin extracts
• Olive leaf
• Caprylic acid
• Neem
• Artemisia species

These compounds may influence microbial growth through a variety of mechanisms, including effects on microbial membranes, metabolism, adhesion, and signaling.

However, “natural” does not mean harmless or universally appropriate.

Herbal antimicrobials may interact with medications, cause adverse effects, and potentially influence beneficial as well as undesirable microorganisms.

They should therefore be selected according to the individual rather than used indefinitely as a generalized “gut cleanse.”

🧬 Biofilm Support

Several compounds are marketed or used clinically with the goal of disrupting microbial biofilms.

Examples include:

• N-acetylcysteine (NAC)
• Certain proteolytic or digestive enzymes
• Lactoferrin
• Other specialized biofilm-targeting formulations

NAC, for example, has demonstrated effects on biofilm structure in laboratory and selected clinical contexts.

However, evidence varies considerably depending on the organism, location of the biofilm, and intervention being studied.

More aggressive agents, including chelating compounds such as EDTA, require particular caution and should only be considered under appropriate professional supervision.

🧲 What About Binders?

Products such as activated charcoal, bentonite clay, and zeolite are sometimes incorporated into functional medicine protocols with the intention of binding compounds within the gastrointestinal tract.

However, claims that these products routinely remove microbial “toxins,” LPS, or mycotoxins from the body are stronger than the available human evidence supports.

Activated charcoal has established medical uses in specific poisoning situations, but this does not mean that routine charcoal supplementation is necessary or beneficial during a microbial protocol.

Binders may also interfere with the absorption of medications and nutrients and may worsen constipation in some individuals.

They should therefore be used selectively rather than considered an essential part of every microbial reset.

💧 Supporting Normal Elimination and Recovery

The body already has highly sophisticated systems for processing and eliminating metabolic waste, involving the liver, kidneys, gastrointestinal tract, lungs, and other tissues.

Rather than trying to “detox” the body aggressively, the goal should be to support normal physiological function.

This may include:

• Adequate hydration
• Regular bowel movements
• Appropriate dietary fiber when tolerated
• Adequate nutrition
• Regular physical activity
• Sufficient sleep
• Addressing constipation or impaired motility when present

Nutrients such as B vitamins, magnesium, and amino acids participate in many normal metabolic pathways, but supplementation should be based on individual needs rather than automatically prescribed as “detox support.”

Functional Testing to Guide a Microbial Reset

Testing can sometimes help clarify what is happening, particularly when symptoms are persistent, recurrent, or complex.

Depending on the clinical picture, testing may include:

Comprehensive Stool Testing

Tests such as GI-MAP, GI360, and other comprehensive stool analyses may provide information about selected microorganisms, digestive markers, inflammatory markers, and aspects of mucosal immune function.

However, results need careful interpretation.

Detecting an organism does not automatically mean that it is causing symptoms or requires treatment.

SIBO and Intestinal Methanogen Overgrowth Breath Testing

Hydrogen-methane breath testing is commonly used when SIBO or intestinal methanogen overgrowth is suspected.

Results should be interpreted alongside symptoms, preparation quality, gastrointestinal transit, and the broader clinical picture.

Secretory IgA and Other Mucosal Markers

Secretory IgA may provide information about aspects of mucosal immune activity.

Some commercial tests also offer zonulin and other intestinal barrier-associated biomarkers.

These tests have limitations and should not be viewed as standalone diagnostic tools for “leaky gut” or microbial overgrowth.

The most useful test is one that answers a specific clinical question and has the potential to change what we do next.

The Microbial Reset Is Not One-Size-Fits-All

Some individuals may benefit from short, targeted treatment, while others require a different approach based on the underlying diagnosis, symptoms, medical history, and test results.

Long-term or repeated use of antimicrobial herbs and supplements without a clear indication may have unintended effects on the broader microbiome.

This is why timing, sequencing, and reassessment matter.

A microbial reset should be individualized according to symptoms, medical history, medications, testing when appropriate, and the specific type of microbial imbalance being addressed.

It is also important not to interpret every temporary worsening of symptoms as a Herxheimer or “die-off” reaction.

Headaches, fatigue, bloating, diarrhea, constipation, or other symptoms that occur during treatment may have many explanations—including intolerance to the intervention itself.

New or worsening symptoms should be evaluated rather than automatically viewed as evidence that a treatment is “working.”

The Microbial Reset Is Only One Step

Clearing or reducing a clinically relevant microbial overgrowth is not the final goal.

Long-term digestive health depends on creating an intestinal ecosystem that supports appropriate microbial diversity, healthy digestive function, intestinal barrier integrity, and immune regulation.

Once clinically relevant microbial issues have been addressed, attention can shift toward supporting the intestinal lining and creating an environment in which a healthier microbial ecosystem can thrive.

What’s Coming Next: Part 4 – Gut Barrier Repair

In Part 4, we explore the next phase of the Digestion Series.

We look at the intestinal barrier, mucosal nutrients, herbal demulcents, probiotics and immunoglobulin support, as well as the role of nutrition, lifestyle, and appropriate testing in supporting gastrointestinal health.

Need Help Navigating a Microbial Reset?

Digestive symptoms do not always have a single cause, and microbial clearing is not appropriate for everyone.

At Raleigh Health & Wellness Center, Dr. Mary Clark, DACM, LAc., takes an individualized approach to digestive health, considering symptoms, health history, nutrition, lifestyle, medications, and appropriate testing when developing a personalized plan.

📞 Call (919) 909-5736

📍 Raleigh Health & Wellness Center
8358 Six Forks Road, Suite 204
Raleigh, NC 27615

References 

• Erdogan, A. and Rao, S.S.C., 2023. Small intestinal bacterial and fungal overgrowth. Nutrients, 17(8), p.1365.
• Fan, R., Yuan, Y., Liu, Y., Li, X. and Zhao, J., 2023. The interactions of Candida albicans with gut bacteria: a new perspective on intestinal infection. Gut Pathogens, 15, Article 559.
• Li, H., Miao, M., Jia, C., Cao, Y., Yan, T., Jiang, Y. and Yang, F., 2022. Interactions between Candida albicans and the resident microbiota. Frontiers in Microbiology, 13, Article 930495.
• Mărginean, C.O., Mares, C.R. and Săsăran, M.O., 2024. The relationship between small intestinal bacterial overgrowth and constipation in children – a comprehensive review. Frontiers in Cellular and Infection Microbiology, 14, Article 1431660.
• Pimentel, M. and Takakura, W., 2020. Small intestinal bacterial overgrowth and irritable bowel syndrome – an update. Frontiers in Psychiatry, 11, Article 664.
• Stensvold, C.R., van Lieshout, L., Lebbad, M., Alfellani, M.A. and Clark, C.G., 2024. The clinical significance of Dientamoeba fragilis and Blastocystis in human stool. Diagnostic Microbiology and Infectious Disease, 110(1), p.115045.
• Tansel, A. and Levinthal, D.J., 2023. Understanding our tests: hydrogen–methane breath testing to diagnose small intestinal bacterial overgrowth. Clinical and Translational Gastroenterology, 14(1), p.e00524.

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