This article explores the emerging scientific understanding of how the diversity of life in soil—its biodiversity—influences human health, with a particular focus on the gut connection. You will learn how microorganisms from healthy soils can reach and interact with your body, the biological pathways involved, and why this relationship matters for immune function, nutrition, and overall well-being. We’ll examine the central role of the gut microbiome as a mediator, discuss the limits of self-diagnosis, and explain how personalized insight into your microbial ecosystem can inform a more tailored approach to health.

Introduction: Soil Biodiversity, Human Health, and the Gut Connection

Framing the Topic: What Soil Biodiversity Means for People

When we think of biodiversity, we often picture rainforests, coral reefs, or charismatic animals. Yet, one of the planet's most critical reservoirs of biodiversity lies beneath our feet: the soil. A single teaspoon of healthy soil contains billions of microorganisms, including bacteria, fungi, protozoa, and nematodes. This complex, living ecosystem is fundamental to plant growth, nutrient cycling, and ecosystem stability. But its importance extends far beyond agriculture and ecology. A growing body of research suggests that the microbial richness of soil is intricately linked to human health, primarily through its influence on our own internal microbial communities, especially those residing in the gut.

The Primary Objective: Linking Environmental Microbiota to Personal Gut Health

The primary objective of this exploration is to connect the dots between the external microbial environment and our internal one. We are not sterile beings isolated from our surroundings; we are constantly exchanging microbes with the environment through the food we eat, the air we breathe, and the surfaces we touch. This article aims to clarify how the quality and diversity of environmental microbes, particularly from soil, can shape the composition and function of the human gut microbiome, which is a key determinant of health and disease.

What You'll Learn and How to Use This Guide

You will learn about the biological pathways connecting soil to the human body, the concept of the "soil–gut axis," and the mechanisms by which environmental exposure may support gut barrier integrity, immune education, and metabolic health. We will discuss why individual responses vary greatly and why symptoms alone are an unreliable guide. Finally, we will cover how modern tools like gut microbiome testing can provide a personalized snapshot of your internal ecology, offering insights that generic advice cannot. Use this guide as a foundation for understanding the broader context of your health and for making more informed decisions about diet, lifestyle, and potential diagnostic steps.

Core Explanation: How Soil Biodiversity Shapes Human Health

From Soil to the Human Body: The Main Pathways (Food, Water, Air, and Contact)

Microbes from soil enter the human ecosystem through several interconnected routes. The most direct pathway is through food: consuming plants (fruits, vegetables, herbs) and, indirectly, animals that have interacted with soil, bringing along trace amounts of environmental microbes. Minimally processed, organically grown produce may harbor a more diverse array of these microbes. A second pathway is through water, as rainfall and irrigation can transfer soil microbes into groundwater and waterways. Third, we inhale soil-derived microbes and their metabolites as part of dust and airborne particles. Finally, direct physical contact with soil—through gardening, playing, or walking barefoot—facilitates transfer through the skin.

The Soil–Gut Axis: How Environmental Microbes Influence Gut Ecosystems

The concept of the "soil–gut axis" describes a dynamic, two-way relationship between the microbial communities in soil and those in the human gastrointestinal tract. The hypothesis posits that exposure to a diverse array of environmental microbes, including those from soil, can help "seed" and diversify the gut microbiome. These incoming microbes may not always colonize permanently, but their transient presence and the genetic material they carry can influence the metabolic activity and immune interactions of the resident gut community. This exposure is thought to be a crucial part of training and regulating the immune system from early life onward.

Key Concepts: Diversity, Function, and Transfer of Microbes Across Environments

Three key concepts underpin this connection. First is diversity—both in soil and in the gut. Higher microbial diversity is generally associated with ecosystem resilience and health. Second is function. It's not just which microbes are present, but what they *do*. Soil microbes perform functions like nitrogen fixation; gut microbes produce essential metabolites like short-chain fatty acids. Some functional genes are shared across these environments. Third is the transfer process, which is influenced by modern lifestyle factors like sanitation, processed diets, and reduced time spent in natural environments, potentially limiting this ancient exchange.

Why This Topic Matters for Gut Health

The Gut Microbiome as a Central Mediator of Health

The gut microbiome is now recognized as a virtual organ that interacts with nearly every system in the body. It aids in digesting food, synthesizing vitamins, regulating the immune system, maintaining the integrity of the gut barrier, and communicating with the brain via the gut-brain axis. Its state of balance or imbalance (dysbiosis) is linked to a wide spectrum of conditions, from digestive disorders and allergies to metabolic and mental health challenges. Therefore, factors that shape the gut microbiome, including environmental inputs, are of paramount importance to overall health.

Mechanisms by Which Soil-Derived Microbes May Influence Gut Function

Soil-derived microbes may support gut health through several mechanisms. Immune modulation is a primary pathway. Exposure to diverse environmental microbes is thought to promote immune tolerance, helping the body distinguish between harmless substances and genuine threats, which may reduce inappropriate inflammatory responses. Secondly, some soil bacteria may contribute to barrier integrity by influencing the production of mucus or strengthening the tight junctions between gut lining cells. Thirdly, they can impact host metabolism by contributing enzymes that help break down complex compounds or by interacting with resident microbes to influence the production of beneficial metabolites like butyrate.

Environmental Exposure as a Modulator of Microbial Diversity in the Gut

Lifestyle plays a decisive role in the composition of our gut microbiota. Compared to urbanized populations, studies of traditional, agrarian communities consistently show higher gut microbial diversity, which is attributed to closer contact with natural environments, diverse diets rich in fibrous plants, and different hygiene practices. This suggests that controlled, safe exposure to a variety of environmental microbes—akin to what soil biodiversity offers—can be a significant modulator, helping to maintain a rich and functional gut ecosystem that is more resilient to disruption.

Related Symptoms, Signals, or Health Implications

Digestive Symptoms That May Reflect a Soil–Gut Connection

While not diagnostic, certain persistent digestive issues may indirectly reflect a gut ecosystem that lacks diversity or resilience, which could be influenced by limited environmental microbial exposure. These can include chronic bloating, gas, irregular stools (constipation or diarrhea), and emerging food sensitivities. An imbalanced gut microbiome may struggle with efficient fermentation, proper motility, and maintaining a healthy mucosal barrier, leading to such symptoms.

Systemic Signals and Immune-Related Symptoms

The immune system's development and function are deeply intertwined with microbial exposure. Signals that may be connected to broader microbial dysregulation include unexplained low-grade inflammation (e.g., elevated CRP), a history of recurrent infections, or increased frequency of autoimmune flares. The "hygiene hypothesis" and its modern extensions suggest that insufficient microbial challenge during early life and adulthood may contribute to faulty immune regulation.

Skin, Allergy, and Respiratory Signals Linked to Microbial Ecology

The skin and respiratory tract have their own microbiomes and are also points of contact with the environment. Conditions like eczema, allergies (both food and environmental), and asthma have been associated with altered microbial communities. The foundational immune education that comes from diverse microbial exposure, potentially via the gut, may influence the risk and severity of these atopic conditions.

Mood, Energy, and Cognitive Signals That Can Connect to Gut Microbiome Health

Through the gut-brain axis, the microbiome influences neurotransmitter production, systemic inflammation, and stress hormone response. Consequently, feelings of persistent low energy, brain fog, or low mood can sometimes be linked to an underlying gut microbiome imbalance. While these symptoms have multifactorial causes, gut health is an important component to consider in a holistic assessment.

Individual Variability and Uncertainty

How Geography, Diet, Lifestyle, and Exposure History Shape Microbiome Baselines

Every person's microbiome is as unique as a fingerprint, shaped by a lifetime of exposures. Geography influences the local soil and environmental microbiota. Diet is a powerful driver, providing both substrates for gut microbes and introducing new ones. Lifestyle factors like occupation, pet ownership, and frequency of outdoor activity dictate the level and type of environmental contact. Critically, early-life exposure history—including birth mode, infant feeding, and childhood environment—sets a long-term trajectory for immune and microbial development.

Genetic and Developmental Factors Influencing Microbiome Responsiveness

Host genetics can influence the gut environment, such as mucus composition and immune receptor variants, which in turn shapes which microbes thrive. Furthermore, developmental windows, particularly in infancy and early childhood, are periods of heightened plasticity where microbial exposures have a more profound and potentially lasting impact on immune programming. This means two individuals with identical soil exposure may harbor different microbial communities and experience different health outcomes based on these intrinsic factors.

Embracing Uncertainty: Why One-Size-Fits-All Conclusions Don't Apply to Gut Health

Given this immense variability, it is crucial to embrace uncertainty. The relationship between soil biodiversity and human health is probabilistic, not deterministic. An intervention like gardening or eating organic vegetables may benefit one person's gut ecology noticeably, while another sees minimal change. There is no universal "prescription" for microbial health. Effective strategies must be personalized, taking into account an individual's unique baseline, history, and current state.

Why Symptoms Alone Do Not Reveal the Root Cause

Distinguishing Symptoms from Drivers of Health Outcomes

Symptoms like bloating or fatigue are the body's outward signals of an internal imbalance, but they are not the imbalance itself. They are the "smoke," not the "fire." The same symptom can stem from a multitude of different underlying drivers—various patterns of microbial imbalance, different metabolic deficiencies, distinct immune activations, or non-microbial causes altogether. Relying solely on symptoms is like trying to diagnose a car's problem only by an odd sound; it points you in a direction but doesn't identify the exact faulty part.

Case Perspectives: Why Similar Symptoms May Arise from Different Microbial Patterns

Consider two individuals with chronic bloating. For Person A, it might be driven by an overgrowth of bacteria that produce excess gas in the small intestine. For Person B, it might be due to a deficiency of microbes that produce methane, slowing gut transit. Both present with "bloating," but the underlying microbial patterns and, therefore, the appropriate dietary or lifestyle adjustments, could be opposites. Guessing based on symptoms alone can lead to ineffective or even counterproductive actions.

The Risk of Jumping to Conclusions Without Microbiome Context

Without insight into the specific microbial landscape, efforts to improve gut health through diet, probiotics, or environmental exposure are often based on trial and error. This can lead to frustration, wasted resources, and the potential to inadvertently exacerbate an imbalance. For example, increasing fiber—generally a healthy choice—can worsen symptoms for someone with a specific type of bacterial overgrowth. Personalized context is key to moving from guesswork to informed strategy.

The Role of the Gut Microbiome in This Topic

The Gut Microbiome as the Primary Mediator Between Soil Biodiversity and Health

The gut microbiome is the crucial intermediary in the soil–health connection. It is the internal environment that receives, filters, and integrates signals from the external microbial world. When we talk about soil biodiversity influencing immunity or inflammation, we are largely describing effects that are channeled through changes in the gut microbiome's composition and its metabolic output. Therefore, understanding one's personal gut ecosystem is the most direct way to gauge how environmental factors are being processed and what their net effect might be.

How Microbial Balance Supports Barrier Function, Immune Regulation, and Nutrient Metabolism

A balanced, diverse gut microbiome performs essential services. It supports the gut barrier by fueling the cells that line the colon with short-chain fatty acids (SCFAs) like butyrate, keeping the lining robust and impermeable to toxins. It regulates the immune system by training immune cells and producing anti-inflammatory signals. It also modulates metabolism, extracting energy from food, synthesizing vitamins (like B and K), and influencing bile acid and hormone signaling. Disruptions in these core functions can have wide-ranging health consequences.

The Concept of Resilience vs. Vulnerability in the Gut Ecosystem

Think of the gut microbiome as a forest ecosystem. A diverse forest with many species (high microbial diversity) is more resilient to a stressor like drought or fire—it can recover and maintain function. A monoculture forest (low diversity) is vulnerable; a single pest can wipe it out. Similarly, a diverse gut microbiome is better able to resist perturbations from antibiotics, poor diet, or stress, and return to a healthy state. Soil-derived microbial exposure may be one factor that contributes to building this ecological resilience.

How Microbiome Imbalances May Contribute

Dysbiosis in the Soil–Gut Continuum: What Patterns to Look For

Dysbiosis refers to an imbalance in the microbial community. In the context of the soil–gut continuum, relevant patterns might include a noticeable lack of overall diversity, or the underrepresentation of specific bacterial groups known to be associated with environmental exposure and health, such as certain Actinobacteria or Bacteroidetes species. An overgrowth of potentially pro-inflammatory microbes alongside a depletion of SCFA producers is another common pattern of dysbiosis.

Functional Consequences: Shifts in Key Metabolic Outputs

The real impact of dysbiosis lies in altered function. Key consequences include:

• Reduced SCFA Production: Lower levels of butyrate, propionate, and acetate can compromise gut barrier integrity and immune regulation.
• Altered Bile Acid Metabolism: This can affect fat digestion, cholesterol levels, and signaling pathways throughout the body.
• Pro-inflammatory Immune Messaging: An imbalanced microbiome may promote the release of inflammatory cytokines (like TNF-α, IL-6) instead of regulatory ones.

Visualizing Imbalance: Diversity, Evenness, and Key Taxa Relevance

Advanced microbiome analysis moves beyond a simple list of bugs. It visualizes health through metrics like:

• Alpha Diversity: The richness and evenness of species within your gut. Generally, higher is better.
• Beta Diversity: How your microbial community compares to reference populations (e.g., healthy cohorts).
• Relative Abundance of Key Taxa: The proportions of major bacterial phyla (like Firmicutes/Bacteroidetes ratio) and specific health-associated genera (e.g., Faecalibacterium prausnitzii, a major butyrate producer).

How Gut Microbiome Testing Provides Insight

Overview of Microbiome Testing Options

Modern testing, such as the detailed analysis provided by comprehensive gut microbiome tests, uses genetic sequencing to identify the bacteria, archaea, and fungi present in a stool sample. 16S rRNA sequencing profiles bacterial and archaeal communities at the genus level. Shotgun metagenomics provides a more granular view, identifying microbes to the species or strain level and allowing analysis of their functional genes. Some panels also include markers for gut inflammation, digestive function, and yeast overgrowth.

What Each Test Can Tell You About Gut Ecology and Function

A high-quality microbiome report provides a personalized map of your gut ecology. It can tell you your level of overall microbial diversity, highlight the presence or absence of beneficial keystone species, identify potential overgrowths, and infer metabolic pathways (like SCFA production potential). It provides objective data that moves the conversation beyond generic assumptions to the specifics of your internal environment.

Important Limitations and Caveats in Interpretation

Microbiome testing is a powerful snapshot, not a crystal ball. It has limitations: results show who is there and what they might be capable of doing, not their real-time activity in your gut. The microbiome has natural day-to-day and seasonal variability. Different labs may use different methods and reference databases. Most importantly, interpreting this complex data requires context—your diet, health history, and symptoms—and is best done with the guidance of a knowledgeable healthcare practitioner.

What a Microbiome Test Can Reveal in This Context

Linking Test Results to Potential Soil Exposure and Environmental Factors

While a test cannot directly measure your soil contact, it can reveal a gut microbial profile that is either rich or poor in bacteria typically associated with environmental sources. Extremely low overall diversity, coupled with a lack of specific taxa common in non-Westernized populations, might suggest a lifestyle with limited environmental microbial exchange. This objective data can start a meaningful conversation about whether increasing safe, diverse environmental exposure could be a beneficial part of your health strategy.

Interpreting Results for Personalized Action Plans

The true value of testing lies in creating a personalized plan. If results show low SCFA producer abundance, you might focus on increasing specific types of dietary fibers (prebiotics). If a certain pathobiont is elevated, you might temporarily avoid foods that feed it. If diversity is low, strategies might include diversifying your plant food intake and considering activities that increase environmental contact. This moves you from a generic "eat more fiber" to a targeted "increase inulin and resistant starch to support your low Bifidobacterium."

Translating Complex Data Into Practical Steps

The complexity of microbiome data can be daunting. This is where working with a clinician, nutritionist, or the support resources often paired with advanced testing platforms becomes invaluable. They can help translate the report's findings into a clear, phased action plan involving dietary tweaks, lifestyle modifications, and potentially probiotic or prebiotic considerations, all tailored to your unique results and health goals.

Who Should Consider Testing

Individuals With Persistent or Unexplained Gut Symptoms

If you have experienced chronic digestive discomfort—bloating, pain, irregular bowel habits, gas—that hasn't resolved with basic dietary changes, a microbiome test can offer clues that standard medical tests might miss. It helps identify potential microbial patterns driving the symptoms.

People With Immune-Related Signals, Allergies, or Inflammatory Patterns

For those managing conditions like eczema, seasonal allergies, autoimmune disorders, or unexplained inflammation, understanding the gut microbiome's role can provide a critical piece of the puzzle. The test can reveal an immune-modulatory profile that informs a broader therapeutic strategy.

Parents or Caregivers Considering Pediatric Gut Health and Early-Life Exposures

Interested parents seeking to understand their child's gut health foundation, especially in the context of modern, sanitized environments, may find value in testing. It can provide a baseline and guide decisions about diet, outdoor play, and pet exposure to support healthy microbial development.

Researchers, Wellness Enthusiasts, or Individuals Pursuing Personalized Health Insight

Anyone with a deep curiosity about their own biology and a desire to move beyond population-based health advice to data-driven personalization can benefit from the objective insight a microbiome test provides. This includes professionals in the health and wellness field seeking to understand the platform science for their clients, which is a focus of our B2B partnership program.

Decision-Support Section (When Testing Makes Sense)

Practical Criteria for Considering a Microbiome Test

Consider testing if: you have persistent symptoms (lasting months) without a clear diagnosis; you've tried generic gut health protocols with limited success; you are embarking on a major dietary or lifestyle change and want a baseline; or you simply have a strong, informed curiosity to understand your inner ecology as part of a proactive health journey.

How to Prepare for Testing

To get the most accurate snapshot, follow the lab's pre-collection instructions carefully. This often involves avoiding probiotics for a set period, stopping antibiotics well in advance if possible, and maintaining your typical diet before collection. Note any recent medications, supplements, travel, or significant stressors, as these can influence results. Accurate documentation provides crucial context for interpretation.

How to Use Results: Communicating With Healthcare Providers

Share your report with your doctor, gastroenterologist, or registered dietitian. Frame it as a source of data to inform your collaborative discussion, not a standalone diagnosis. A qualified practitioner can help correlate microbiome findings with your clinical history and other lab work to develop a cohesive, personalized health plan.

Interpreting Results Responsibly

Avoid the temptation to over-interpret single data points or label bacteria as universally "good" or "bad." Focus on the bigger picture: diversity metrics, functional inferences, and broad patterns. Use the results to generate hypotheses about what might be supporting or hindering your gut health, and then test those hypotheses through guided, incremental changes, monitoring how you feel along the way.

Clear Concluding Section Connecting the Topic to Understanding One's Personal Gut Microbiome

Key Takeaways: Uncertainty, Personalization, and the Value of Baseline Insight

The link between soil biodiversity and human health is a fascinating and important field of science, mediated primarily through the gut microbiome. The core takeaways are: the relationship is highly individualized, symptoms are poor proxies for internal microbial states, and the modern lifestyle may limit beneficial microbial exchanges. In this context, gaining a baseline understanding of your personal gut microbiome through testing is a powerful step toward personalized health, replacing guesswork with knowledge.

How to Translate Microbiome Information Into Daily Choices

Armed with personalized insight, you can make more informed daily choices. This could mean consciously increasing the variety of plants in your diet to feed specific beneficial bacteria, spending more time gardening or in nature, or choosing fermented foods that align with your microbial needs. It transforms abstract health advice into a targeted, meaningful practice.

Final Considerations: Integrating Testing Into a Holistic Health Plan

A gut microbiome test is one tool in a holistic health toolkit. Its greatest power is realized when its insights are integrated with other aspects of health—nutritious eating, stress management, quality sleep, and regular physical activity. For those on a longitudinal journey, retesting over time can track progress and show how your internal ecosystem responds to your lifestyle interventions, creating a powerful feedback loop for sustained well-being.

Key Takeaways

• Soil biodiversity, the immense variety of life in soil, is connected to human health primarily through its influence on the gut microbiome.
• Exposure to diverse environmental microbes may support a resilient, well-functioning gut ecosystem by contributing to immune education and microbial diversity.
• The gut microbiome acts as a central mediator, translating environmental signals into effects on barrier function, immunity, and metabolism.
• Individual responses to environmental exposure vary dramatically based on genetics, diet, lifestyle, and early-life history.
• Digestive and systemic symptoms (like bloating or inflammation) are common but non-specific; they do not reveal the underlying microbial pattern causing them.
• Gut microbiome testing provides an objective, personalized snapshot of your internal microbial landscape, revealing diversity, key species, and functional potential.
• This data can move gut health strategies from generic guesswork to targeted, personalized action plans involving diet, lifestyle, and environmental exposure.
• Testing is particularly useful for individuals with persistent unexplained symptoms, immune-related issues, or a deep curiosity about personalized health.
• Interpretation should be done with professional guidance to avoid over-simplification and integrated into a broader holistic health strategy.
• Understanding your microbiome is a step towards reclaiming an ancient connection with the environment in a modern, informed way.

Frequently Asked Questions (FAQs)

1. Can I just eat dirt to improve my gut health?
No, this is not recommended. Consuming raw soil can expose you to harmful pathogens, parasites, and chemical contaminants. The goal is safe, indirect exposure through activities like gardening (and then washing hands before eating) and consuming a variety of minimally processed, soil-grown plants.

2. Does this mean organic food is better for my microbiome?
Organic farming practices generally promote higher soil biodiversity. While studies are ongoing, consuming organically grown produce may introduce a more diverse array of environmental microbes and expose you to fewer pesticide residues, which some research suggests can negatively impact gut bacteria.

3. If I live in a city, is my gut microbiome doomed?
Not at all. Urban living presents different microbial exposures, not necessarily all bad. You can actively support your microbiome by eating a wide variety of fiber-rich plants, spending time in urban parks, having houseplants or a pet, and choosing outdoor activities when possible.

4. How is this different from the "Hygiene Hypothesis"?
The hygiene hypothesis focused largely on the reduced incidence of childhood infections leading to more allergies. The concept of the "soil–gut axis" and "old friends" hypothesis expands this, emphasizing the positive, regulative role of continuous, lifelong exposure to diverse, largely non-pathogenic microbes from our natural environment, not just the absence of pathogens.

5. Will taking a probiotic replace the need for soil exposure?
Probiotics are specific, isolated strains. They can be beneficial for certain purposes but do not replicate the immense diversity and ecological complexity gained from environmental exposure. Think of probiotics as targeted tools, while diverse environmental contact helps build the overall resilience and richness of your "microbial garden."

6. Can microbiome testing diagnose a specific disease?
No. Microbiome testing is not a diagnostic tool for diseases like Crohn's, ulcerative colitis, or IBS. It is an insight tool that reveals associations and patterns. It can show dysbiosis commonly linked with such conditions, but diagnosis requires clinical evaluation by a physician using standard medical tests.

7. How stable are microbiome test results? If I test again in a month, will it be the same?
Your core microbiome is relatively stable in adulthood but can shift with major changes in diet, medication (especially antibiotics), travel, stress, or illness. For tracking progress from an intervention, it's generally recommended to wait at least 2-3 months between tests to see meaningful changes.

8. Are the bacteria from soil the same ones that colonize my gut?
Most soil microbes are transient passengers; they may not permanently colonize the gut. However, their passage can still have significant effects by transferring genes (via horizontal gene transfer) to resident bacteria, stimulating the immune system, or producing metabolites that alter the gut environment.

9. What's more important for my gut: diet or environmental exposure?
They are deeply interconnected. Diet provides the primary fuel (prebiotics) for your gut bacteria and introduces some new microbes. Environmental exposure provides a different, complementary source of microbial diversity. Both are important pillars for maintaining a robust and diverse gut ecosystem.

10. Is there an "ideal" gut microbiome profile?
There is no single ideal profile. A healthy microbiome is best characterized by high diversity, the presence of key beneficial species known for producing health-promoting metabolites, and the absence of significant overgrowths of pathogenic or pro-inflammatory organisms. The "ideal" is personal and functional, meaning it supports your unique health without causing symptoms.

11. Can improving my gut microbiome help with mental health issues like anxiety?
Research into the gut-brain axis is very active. While the microbiome is not a sole cause or cure for mental health conditions, an imbalanced gut can contribute to systemic inflammation and alter neurotransmitter production, which may exacerbate symptoms. Supporting a healthy gut is considered an important component of a holistic approach to mental well-being.

12. Should children be exposed to more dirt?
Safe, supervised play in natural environments (like parks, gardens, forests) is increasingly seen as beneficial for children's immune and microbial development. The key is allowing exploratory play and then practicing basic hygiene like handwashing before meals, rather than attempting to keep children in sterile environments.

Keywords

Soil biodiversity, human health, gut microbiome, gut health, microbial diversity, soil-gut axis, dysbiosis, immune system, microbiome testing, environmental microbiota, short-chain fatty acids, gut barrier, personalized nutrition, microbial ecology, probiotics, prebiotics, inflammation.