Your Gut Is Running the Show: What the Microbiome Really Does for Your Health

By Dr. Holly German 

You’ve probably heard the word ‘microbiome’ tossed around — in health articles, on probiotic labels, maybe even at your last doctor’s appointment. But what does it actually mean, and why does it seem like scientists are connecting it to just about every health condition imaginable?

Here’s the short answer: your microbiome deserves the attention. Decades of research — accelerating rapidly in the last few years — have confirmed that the trillions of bacteria, fungi, and other microorganisms living in your gut are doing far more than helping you digest your lunch. They’re influencing your mood, your hormones, your skin, your metabolism, and your immune system. Understanding how this works isn’t just fascinating science — it’s genuinely useful for anyone trying to feel better.

Let’s break it down.

What Is the Microbiome?

Your microbiome is the community of microorganisms — primarily bacteria — that live in and on your body, with the vast majority residing in your large intestine. We’re talking about roughly 38 trillion microbial cells, which is about the same number as human cells in your body. They’re not passengers — they’re active participants in nearly every system in your body.

When this community is diverse and balanced, it supports health in ways we’re only beginning to fully understand. When it’s disrupted — a state called dysbiosis — the effects can ripple outward in surprising and far-reaching ways.

The Gut-Brain Connection: Your Mood Lives Here Too

One of the most surprising — and well-researched — areas of microbiome science is the gut-brain axis. Your gut and brain are in constant, two-way communication via the vagus nerve, your immune system, and chemical messengers called neurotransmitters.

Here’s the part that tends to surprise people: about 90% of your body’s serotonin — the neurotransmitter most associated with mood stability and wellbeing — is produced in the gut, not the brain. Your gut microbes play a direct role in regulating that production, along with GABA, dopamine, and other brain chemicals.

The clinical implications are significant. Studies show that probiotics — sometimes called psychobiotics when used for mental health — can enhance cognitive function and reduce depressive symptoms by restoring microbial balance. This doesn’t mean gut health replaces mental healthcare, but it does mean that for many people, the gut is an important piece of the puzzle that often gets overlooked.

What disrupts the gut-brain axis? Chronic stress, antibiotic use, poor sleep, ultra-processed food, and low dietary fiber are among the biggest culprits.

Your Microbiome and Your Metabolism

Weight management is rarely as simple as “eat less, move more” — and the microbiome is one of the reasons why. Research has consistently shown that the composition of gut bacteria differs significantly between lean and obese individuals, and between those with and without type 2 diabetes.

Gut microbes influence metabolism in several important ways:

• They regulate how efficiently your body extracts energy from food
• They produce short-chain fatty acids (SCFAs) like butyrate, which improve insulin sensitivity and support healthy blood sugar regulation
• They influence hormones like GLP-1 — the same pathway targeted by medications like Ozempic — which signals fullness and regulates glucose
• Dysbiosis is associated with increased systemic inflammation, which drives insulin resistance

This doesn’t mean your microbiome is entirely to blame for weight struggles, but it does suggest that treating metabolic issues without addressing gut health may be leaving an important lever unpulled.

Hormones, Reproductive Health, and the Estrobolome

You may not have heard the term “estrobolome” before, but if you experience hormonal imbalances — irregular cycles, PMS, PCOS, perimenopausal symptoms, or recurring vaginal infections — it’s worth knowing about.

The estrobolome refers to the collection of gut microbial genes responsible for metabolizing estrogen. Specific gut bacteria produce an enzyme called beta-glucuronidase, which deconjugates estrogens in the digestive tract, allowing them to be reabsorbed into the bloodstream. When the microbiome is in balance, this process keeps circulating estrogen at appropriate levels. When dysbiosis disrupts it, the results can be significant:

• Too little recycling leads to estrogen deficiency — worsening menopausal symptoms, low libido, and mood instability
• Too much reabsorption leads to hyperestrogenism — which is associated with conditions like endometriosis, fibroids, and estrogen-dominant PMS
• PCOS is specifically associated with reduced abundance of short-chain fatty acid-producing microbes and altered Lactobacillus levels in the vaginal microbiome

The vaginal microbiome deserves a mention of its own. A healthy vaginal environment is dominated by Lactobacillus species, which produce lactic acid and maintain the acidic pH that protects against infections. Gut health, diet, stress, and hormonal shifts all directly influence vaginal microbial balance — meaning recurring BV, yeast infections, or urinary tract infections may have a gut component that conventional treatment alone doesn’t address

Skin Conditions and the Gut-Skin Axis

If you’ve ever noticed that your skin flares up when you’re stressed, eating poorly, or after a course of antibiotics, you’ve experienced the gut-skin axis firsthand. This bidirectional relationship between gut microbiome health and skin conditions is one of the fastest-growing areas of research in dermatology.

Clinical evidence now links gut microbiome dysbiosis to a range of common skin conditions:

• Acne vulgaris — specific gut bacterial imbalances appear to promote the systemic inflammation that drives breakouts
• Eczema (atopic dermatitis) — altered gut microbial diversity in early life is a strong predictor of eczema development
• Psoriasis — gut dysbiosis drives the immune dysregulation that characterizes this condition
• Rosacea — increasingly associated with gut inflammation and altered microbiome composition

This means that for many patients with chronic skin concerns, looking at the gut — rather than just applying topical treatments — can produce more lasting results.

Other Conditions Linked to Microbiome Health

The research doesn’t stop there. Growing evidence connects gut microbiome health to:

• Autoimmune conditions — including rheumatoid arthritis, Hashimoto’s thyroiditis, and lupus
• Cardiovascular disease — through microbiome-produced compounds like TMAO that affect arterial health
• Chronic fatigue — via inflammation, mitochondrial function, and nutrient absorption
• Allergies and asthma — especially when microbiome disruption occurs early in life
• Cognitive decline — with emerging links between gut dysbiosis and Alzheimer’s disease

What Can You Do to Support Your Microbiome?

The good news is that the microbiome is responsive. It can shift meaningfully within days with the right interventions. Here’s what the research supports most consistently:

1. Eat for diversity

A diet rich in a wide variety of plants — vegetables, fruits, legumes, whole grains, herbs (including herbal teas), and spices — is the single most consistently supported way to build a diverse, healthy microbiome. Aim for 30 or more different plant foods per week.

2) Prioritize fiber

Fiber is what your gut bacteria eat. Specifically, prebiotic fibers found in foods like garlic, onions, leeks, asparagus, oats, and green bananas feed the beneficial strains that produce short-chain fatty acids. Diversity is key as different prebiotics feed different probiotics. Most Americans get far less fiber than their microbiome needs.

3) Include fermented foods

Foods like yogurt, kefir, sauerkraut, kimchi, miso, and kombucha introduce live beneficial bacteria and have been shown in clinical trials to increase microbial diversity and reduce inflammatory markers.

4) Minimize microbiome disruptors

Antibiotics (when avoidable), ultra-processed foods, artificial sweeteners, chronic stress, and poor sleep all negatively impact microbiome diversity. Not all of these are avoidable, but being aware of them — and actively rebuilding after disruptions — matters.

5) Consider targeted probiotic supplementation

Not all probiotics are created equal. Different strains have different effects, and the research is increasingly strain-specific. At Rocky Mountain Natural Medicine, we help patients identify the right probiotic support based on their individual health picture — whether that’s mental health, hormonal balance, skin concerns, or metabolic health.

A Naturopathic Perspective

At Rocky Mountain Natural Medicine, the microbiome has always been central to how we think about whole-body health. Long before gut health became a mainstream conversation, naturopathic medicine recognized the digestive system as a foundation of vitality — what we call the “terrain” from which health or disease emerges.

The emerging science is confirming what clinical experience has shown for decades: you cannot separate gut health from mental health, hormonal health, skin health, or metabolic health. They are interconnected, and addressing one often means addressing the others.

If you’re dealing with persistent symptoms that haven’t responded to conventional approaches, the microbiome may be a missing piece of your puzzle. We’d love to help you explore it.

Ready to learn more? Schedule a visit with one of our naturopathic doctors at Rocky Mountain Natural Medicine in Fort Collins. We offer comprehensive functional assessments that include gut health evaluation and personalized microbiome support plans.

Sources & Further Reading

1. Filardo S, Di Pietro M, Sessa R. “Current progresses and challenges for microbiome research in human health: a perspective.” Frontiers in Cellular and Infection Microbiology. 2024;14:1377012. doi:10.3389/fcimb.2024.1377012

2. “The Bidirectional Relationship Between the Gut Microbiome and Mental Health: A Comprehensive Review.” PMC/NCBI. 2024. PMC12007925. Available at: pmc.ncbi.nlm.nih.gov

3. Semo D, Reinecke H, Godfrey R. “Gut microbiome regulates inflammation and insulin resistance: a novel therapeutic target to improve insulin sensitivity.” Signal Transduction and Targeted Therapy. 2024. doi:10.1038/s41392-024-01746-y

4. “Microbial regulators of physiological and reproductive health in women of reproductive age.” npj Biofilms and Microbiomes. Nature Publishing Group. 2025. doi:10.1038/s41522-025-00839-y

5. “Gut Microbiome Dysbiosis and Its Impact on Reproductive Health: Mechanisms and Clinical Applications.” PMC/NCBI. 2025. PMC12195147. Available at: pmc.ncbi.nlm.nih.gov

6. Chai J, Deng F, Li Y, Wei X, Zhao J. “The gut-skin axis: interaction of gut microbiome and skin diseases.” Frontiers in Microbiology. 2024;15:1427770. doi:10.3389/fmicb.2024.1427770

7. “Unraveling the Gut-Skin Axis: The Role of Microbiota in Skin Health and Disease.” Cosmetics. MDPI. 2025;12(4):167. doi:10.3390/cosmetics12040167

8. “The role of intestinal microbiota and its metabolites in the occurrence and intervention of obesity.” PMC/NCBI. 2025. PMC12081357. Available at: pmc.ncbi.nlm.nih.gov