Ep 52: The Microbiome Explained | How Gut Health Shapes Immunity, Performance, and Vitality with Kara Siedman

Episode Summary

You have one trillion cells in your body and ten trillion bacterial cells that make up your microbiome, meaning you're literally one-tenth human. Kara Siedman, a registered dietitian and diabetes educator working at the intersection of biotech and wellness, explains why the microbiome is the foundation everything else is built on. From the gut X axis connecting your microbiome to every system in your body, to the surprising difference between probiotics and postbiotics, to why 80% of people are walking around with some form of dysbiosis, this conversation breaks down complex science into actionable insights. We explore why coconut oil might be sabotaging your gut health, how chewing your food is more important than any supplement, and what Jeremy's microbiome test revealed about missing keystone species. This is about understanding that when you can't figure out what's wrong, the answer often starts in the gut.

 

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Guest Bio

Kara Siedman, RDN, CDCES, is a registered dietitian with 15+ years spanning inpatient care, outpatient program development, and integrative/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 resbiotic. 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's known for translating complex research into clear, actionable guidance that clinicians can use at the point of care.

 

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Links

• Kara Siedman on Instagram: Active with gut health advice and microbiome education

• Kara Siedman on LinkedIn: Connect for microbiome discussions and professional insights

• Resbiotic: Company website for precision biotic formulations and research

• Resbiotic Social Media: Follow for gut health advice and microbiome science

 

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Three Actionable Takeaways

1. Think of your microbiome as the central hub and foundation for all aspects of health, not just digestion. The gut X axis influences everything from brain function to immune health to metabolic disease, so when you can't figure out what's wrong with your health, start by looking at the gut.
   
   

2. Focus on adding diversity to your diet rather than taking things away, because what you feed your microbiome matters more than trying to seed it perfectly. Sprinkle chia seeds or basil seeds into foods you're already eating, add a second vegetable to your plate, mix half brown rice with your white rice, or throw beans and nuts on your salad to increase the variety of fibers feeding different bacterial strains.
   
   

3. Look at your personal or family health history to choose targeted probiotic or prebiotic support rather than taking a generic one-size-fits-all approach. If metabolic disease runs in your family or you're dealing with specific symptoms like poor sleep, anxiety, or skin issues that might signal microbiome dysfunction, seek out strains and formulations studied for those specific outcomes.
   
   

 

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Key Insights from the Conversation

• You have one trillion human cells and ten trillion bacterial cells in your body, making you literally one-tenth human and nine-tenths microbial

• The gut X axis describes the bidirectional communication between your gut microbiome and every other system in your body, not just the brain

• There is no sterile part of the body except for a very thin mucosal layer protecting your immune system from your microbiome, and unique microbiome neighborhoods exist in your gut, skin, lungs, and eyes

• The hygiene hypothesis suggests we're living in an antimicrobial world that wasn't made for our microbial ecosystem, and people with more robust microbiomes often live with dogs or work in gardens

• Not all fiber is prebiotic fiber, and getting your 25 to 50 grams of fiber from a single source like psyllium husk won't provide the diversity your different bacterial strains need

• Postbiotics are either bioactive compounds produced by probiotics like butyrate, or purposely heat-treated probiotics that retain targeted benefits despite being non-viable, acting like "ghost biotics"

• The biggest myth about microbiome health is that you have to have GI issues, when poor sleep, anxiety, skin problems, brain fog, and even fatty liver in someone eating well can all be signs of dysbiosis

• Short-chain fatty acids like butyrate can cross the blood-brain barrier, promote systemic reductions in inflammation, and impact immune system function throughout the body

• Probiotic strains are like dog breeds where all dogs are the same species but a Yorkshire Terrier and a Pit Bull have completely different characteristics, which is why strain-specific research matters

• When probiotics die or become heat-treated, they can retain targeted benefits as postbiotics, which explains why fermented foods sitting on shelves still show profound microbiome benefits in studies

• Seventy percent of your immune system is in your gut, where immune cells determine what's friend or foe, and microbiome dysfunction can lead to loss of oral tolerance and food sensitivities

• COVID outcomes correlated strongly with microbiome health, where worse microbiome dysfunction led to worse complications regardless of other health markers

• The mucosal barrier in your large intestine is actually two layers thick with the inner layer being the only truly sterile area of the body

• Lipopolysaccharides from gram-negative bacteria can drive systemic inflammation if they breach the mucosal barrier, creating low-grade chronic inflammation felt throughout the body

• Chewing is the first critical step of proper digestion because saliva contains amylases that start breaking down carbohydrates, and if you chew bread long enough it will turn sweet

• Consuming too much protein in one sitting without adequate stomach acid and digestive enzymes can lead to proteolytic fermentation where unfriendly bacteria produce inflammatory byproducts like ammonia

• Coconut oil creates a much greater endotoxic response and rise in lipopolysaccharides compared to omega-3 fatty acids or monounsaturated fats

• Eighty percent of people are walking around with some form of dysbiosis, making it critical to ensure adequate stomach acid and digestive enzymes when consuming high-protein diets

• Stool testing is just a snapshot in time and your microbiome shifts and changes, which is why newer longitudinal sampling methods taking multiple samples per day provide better insights

• Missing keystone species like Akkermansia on a test doesn't necessarily mean you don't have it, as you could be making your own strains not detected by the test or it could be on life support needing proper feeding

• Probiotics are generally tourists or Airbnb guests that come in, provide benefits, and leave rather than colonizing, though we don't understand why some people show colonization and others don't

• Whole genome sequencing technology shows not just who is present in your microbiome but what functions they're performing, unlike older 16S testing that can identify presence but not activity