EP 64: What Your Microbiome Test Really Means: Beyond "Good vs Bad" Bacteria

This episode is different.

Instead of a traditional interview, Jeremy sits down with registered dietitian Kara Siedman, a gut microbiome expert, for a live, recorded consult using his own Tiny Health stool test results.

Together, they walk through how to read and interpret microbiome data, why a single missing bacteria does not mean an unhealthy gut, and how the microbiome functions as an ecosystem rather than a checklist of "good" and "bad" bugs.

From digestive capacity and short-chain fatty acid production to pelvic floor health and protein breakdown, this episode is a practical, case-study-style walkthrough for anyone curious about what their results actually mean.

Topics include microbiome testing, stool analysis, gut health, digestion, and functional nutrition.

Kara Siedman, RDN, CDCES, is a registered dietitian with 15+ years spanning inpatient care, outpatient program development, and integrative and functional nutrition. Her work in a leading gastroenterology practice sparked a root-cause focus and a specialty in the gut microbiome, leading to collaborations with Pendulum and Microbiome Labs and now resbiotics. At resbiotic, Kara serves as Director of Partnerships and Scientific Operations, educating healthcare providers on microbiome science and the clinical use of targeted pre-, pro-, and postbiotics. She is known for translating complex research into clear, actionable guidance that clinicians can use at the point of care.

Links

• Tiny Health (stool testing platform used in this episode): tinyhealth.com
• Resbiotic: resbiotic.com
• Kara Siedman Instagram: @kara.siedman
• Resbiotic Instagram: @resbiotic
• Tiny Health Instagram: @tiny.health
• Vitality Collective Instagram: @vitalitycollectiveperformance
• Vitality Collective Linkedin: @vitalitycollectiveperformance
• Vitality Collective YouTube: @vitalitycollectiveperformance

Three Actionable Takeaways

Add more variety to your fiber sources, not just more fiber. Kara keeps a fiber chart on her refrigerator and rotates in two or three new plant foods each week. It's a small habit that builds the kind of microbial diversity your gut is designed to run on.

1. If you eat a high-protein diet, add digestive bitters before meals. When protein intake outpaces what stomach acid can break down at one sitting, the excess reaches your large intestine and creates byproducts your microbiome has to manage. Bitters help stimulate hydrochloric acid and keep that breakdown where it belongs.

2. Prioritize fermented foods over probiotic supplements. Kara recommends kimchi, sauerkraut, miso, kefir, and yogurt, not necessarily for the live bacteria themselves but for what those bacteria produce as they move through your system. Those postbiotics are where the real benefit lives.

Key Insights

• Whole genome sequencing, the technology used by Tiny Health, gives a more complete picture of the microbiome than older 16S technology. It shows not just which bacteria are present but what functions they are carrying out.

• The microbiome should be treated as a data point, not a diagnosis. Like GPS tracking in elite sport, stool testing is most useful when layered with other health markers and interpreted over time, not in isolation.

• Missing Akkermansia does not automatically mean poor gut barrier health. In the absence of metabolic disease and with strong short-chain fatty acid producing bacteria present, the gut barrier can remain intact through other mechanisms.

• Probiotics are tourists, not colonizers. The goal of probiotic supplementation is to support a specific function that is not being carried out, not to permanently seed the microbiome. Taking an Akkermansia supplement while the test showed undetectable Akkermansia illustrates this point directly.

• Having some unfriendly bacteria is normal and expected. A healthy microbiome is about balance and competition, not the elimination of all opportunistic species. The ratio matters far more than the presence or absence of individual microbes.

• Short-chain fatty acids are among the most important outputs a healthy microbiome can produce. They support immune signaling, gut barrier integrity, and an anti-inflammatory tone throughout the body.

• The microbiome plays a direct role in hormone balance through a system called the estrobolome. Specific bacteria help regulate how estrogen is processed and cleared, which matters for both men and women as they age.

• Vitamin K2 is primarily produced through bacterial fermentation in the gut. If the microbiome is not producing enough, supplementing K2 alongside vitamin D3 is worth considering, especially since dietary sources like natto are rarely consumed in Western diets.

• Bowel movement frequency that seems like a gut issue may actually have roots in pelvic floor dysfunction. A history of contact sport, back injury, or chronic stress can alter the gut-brain signaling that controls how and when the bowel empties.

• Longitudinal testing matters more than a single snapshot. The microbiome is dynamic and changes with diet, stress, travel, medication, and season. A single test gives useful direction but not a complete picture.