The Diary of a CEOThe No.1 Poo & Gut Scientist: If Your Poo Looks Like This Go To A Doctor! Dr Will Bulsiewicz
CHAPTERS
- 0:00 – 9:00
Why Gut Health Now: Setting the Stakes
The episode opens with a teaser about poop shapes and health, then introduces Dr. Will Bulsiewicz and frames gut health as central to modern disease. He outlines the idea of a gut health epidemic and why a healthy microbiome is non-negotiable for overall health.
- •Poop appearance can be a red-flag indicator requiring medical attention.
- •We’re living through an epidemic of gut-related issues that extend far beyond digestion.
- •A healthy gut microbiome is essential to being a “healthy human.”
- •Dr. B’s background: chemistry degree, top-tier medical training, gastroenterology, clinical research, and role as ZOE’s US medical director.
- 9:00 – 23:00
Meet Your Microbial Superorganism
Dr. B explains what gastroenterologists do (“guts and butts”) and breaks down what the gut microbiome is, where microbes live, and how we co-evolved with them. He describes humans as ‘superorganisms’ whose survival depends on microbial partners.
- •Gastroenterologists specialize in the intestines and colorectal area.
- •Gut microbes include bacteria, fungi, viruses, and parasites; ~38 trillion live mainly in the colon.
- •Microbes begin colonizing us around birth, especially via the birth canal.
- •Humans co-evolved with microbes; removing them (e.g., Bubble Boy) reveals how essential they are.
- •Microbes are integral to digestion, immune training, metabolism, mood, cognition, and hormone regulation.
- 23:00 – 34:00
Individual Microbiomes, Shared Diseases
The conversation turns to how individual and variable microbiomes are, even among identical twins, and how this ties into disease. Dr. B suggests many seemingly separate conditions share a common denominator: a damaged gut microbiome.
- •Human DNA is ~99.99% identical, but microbiomes can be 75% different even in identical twins.
- •Diet, environment, and lifestyle heavily shape microbial composition.
- •Every GI patient Dr. B sees has microbiome disruption; their other diagnoses (diabetes, depression, hypertension, autoimmunity) also map to gut issues.
- •He rarely needs a stool test to infer gut damage when the medical history is clear.
- 34:00 – 45:00
The Gut Barrier, Immunity, and Chronic Inflammation
Dr. B details how 70% of the immune system sits along the intestinal wall and how a fragile, one-cell-thick barrier separates immune cells from trillions of microbes. When this barrier breaks, chronic inflammation emerges; microbes and their metabolites are key to repair.
- •Immune cells dwell in the intestinal walls rather than primarily in bone marrow.
- •The epithelial layer and tight junctions create a thin but critical barrier.
- •Barrier breakdown allows microbial products into the bloodstream, driving chronic inflammation.
- •The gut barrier renews every 3–4 days and requires microbial help and SCFAs to regenerate strongly.
- •Microbes replicate roughly every 20 minutes, amplifying dietary choices quickly.
- 45:00 – 57:00
Food as Medicine: Microbes, Fiber, and Rapid Change
Using a 2014 Nature paper, Dr. B shows how dramatic dietary shifts rapidly reprogram microbes. He stresses that the gut is forgiving but responds directly to what we eat, with fiber and plant diversity being central levers.
- •We eat ~1.3 kg of food daily, vastly outweighing any drug exposure.
- •A 5-day all-plant vs. all-animal diet study showed microbiome changes within 24 hours.
- •The gut is forgiving; positive choices can quickly improve microbial balance.
- •Microbes eat what we eat: different foods ‘water’ different microbial families.
- •High plant diversity—around 30 plants/week—correlates with higher microbial diversity (American/British Gut Projects).
- 57:00 – 1:09:00
Plant Diversity, Fermented Foods, and DIY Microbe Farming
The hosts discuss practical ways to expand plant variety and introduce fermented foods. Dr. B explains fermentation as a controlled transformation creating foods rich in probiotics, prebiotics, and postbiotics, and cites studies showing fermented foods boost microbiome diversity.
- •Most Westerners eat about 10–15 plant types per week; aiming upward toward 30 is beneficial.
- •Incremental increases (e.g., from 10 to 15 plants) are more sustainable than drastic jumps.
- •Fermented foods (sauerkraut, kimchi, traditional pickles, etc.) significantly increase microbiome diversity in RCTs.
- •Fermentation is microbes transforming food, creating probiotic organisms, prebiotic substrates, and postbiotic compounds.
- •Real pickles and sauerkraut rely on natural microbes plus brine, not vinegar-only shortcuts.
- 1:09:00 – 1:24:00
Prebiotics, Probiotics, Postbiotics and the Power of SCFAs
Dr. B clarifies the terminology around pre-, pro-, and postbiotics and argues that postbiotics—especially short-chain fatty acids—are the true workhorses. He explains how SCFAs repair the gut barrier, modulate immunity and metabolism, and even reach the brain.
- •Prebiotics = compounds in food that beneficially feed microbes; probiotics = live microbes proven beneficial; postbiotics = beneficial compounds they produce.
- •Not all microbe-feeding carbohydrates (e.g., sugar) are prebiotics; benefit to humans is required.
- •SCFAs (butyrate, acetate, propionate) from fiber are central postbiotics that rebuild the gut barrier.
- •SCFAs influence immune function, insulin sensitivity, lipid metabolism, and cross the blood–brain barrier.
- •SCFA supplements are emerging but likely cannot fully replicate benefits of a high-fiber diet.
- 1:24:00 – 1:41:00
Metabolism, Weight, and Why Calories Aren’t the Whole Story
The discussion shifts to metabolism, weight regulation, and how microbes impact energy handling. Dr. B highlights twin and mouse fecal transplant studies that undermine simplistic calories-in/calories-out thinking and show microbial control over fat storage and burning.
- •Metabolism is the body’s management of energy (e.g., blood sugar, blood fats, visceral fat).
- •ZOE’s Predict 1 study shows microbiome profiles are critical predictors of glycemic and lipid responses to meals.
- •In transplant studies, mice given stool from obese vs. lean twins adopted their donor’s body type on identical diets.
- •Microbiomes geared to produce more SCFAs improve insulin sensitivity, reduce fat storage, and may cause more calories to be excreted in stool.
- •Calorie restriction can ‘work’ short term but slows metabolism, promotes muscle loss, and causes rebound weight gain (yo-yo effect).
- 1:41:00 – 2:01:00
Poop as a Vital Sign: Transit Time and the Bristol Scale
Dr. B reframes stool as a vital sign for gastroenterologists, akin to heart rate for cardiologists. He introduces ZOE’s Blue Poo study, explains gut transit time thresholds, and walks through the Bristol Stool Scale types 1–7 and what they reveal about health.
- •About 60% of stool is microbial; its appearance reflects microbiome status.
- •Blue Poo studies (blue muffins) show transit time under 14 hours is very fast; over 58 hours is very slow; 24–48 hours is typical.
- •Transit time correlates with microbiome diversity, cardiovascular risk, visceral fat, and fiber intake.
- •Bristol types 3–5 (especially 4) are ideal; 1–2 indicate constipation; 6–7 indicate diarrhea.
- •Fiber uniquely can normalize both constipation and diarrhea, but increases must be gradual to avoid symptoms.
- 2:01:00 – 2:37:00
Fecal Transplants, Microbial Extinction, and Poop as Future Medicine
The conversation explores fecal microbiota transplantation (FMT), its current use in C. diff infections, and its mixed results in other diseases. They discuss donor specificity, capsule-based delivery, and scientists’ concerns about microbial extinction and the need to bank ancestral microbiomes.
- •FMT via colonoscopy or capsules can cure recurrent C. diff and occasionally induce remission in ulcerative colitis.
- •Some FMT responders in UC shared a single donor, suggesting disease-specific ‘super donors.’
- •Future daily ‘poop capsules’ could act as super-probiotics to reconstitute entire ecosystems, but require strict regulation.
- •Traditional and tribal populations show far greater microbial diversity; Westerners have lost many species.
- •Researchers are biobanking stool from remote populations and even ancient coprolites to preserve and possibly reintroduce lost microbes.
- 2:37:00 – 3:12:00
Microbiome, Mood, Trauma, and Human Connection
Dr. B delves into the gut–brain axis, early-life microbiome development, and the profound impact of trauma and relationships. He explains how neurotransmitters, the vagus nerve, and postbiotics link gut to brain, and how unprocessed trauma can block gut healing despite perfect lifestyle habits.
- •95% of serotonin and ~50% of dopamine are produced in the gut; over 30 neurotransmitters originate there.
- •The vagus nerve is a “super phone line” between gut and brain.
- •Short-chain fatty acids can cross the blood–brain barrier, influencing mood and focus; increasing SCFAs improved focus in children.
- •C-sections, lack of breastfeeding, antibiotics, and early adoption alter infant microbiomes and raise later risk of obesity and immune issues.
- •Childhood trauma measurably changes microbiota, stress response, and brain activation; addressing trauma often unlocks rapid gut recovery.
- •Cohabiting, emotionally connected couples share more microbes and have healthier microbiomes than isolated or disconnected individuals.
- 3:12:00 – 3:40:00
Alcohol, Ozempic, and the Fiber Deficit
The hosts tackle alcohol’s harms, the hype around Ozempic and similar GLP‑1 drugs, and how fiber offers a safer, wider-ranging alternative. Dr. B argues we’re skipping the foundational step—diet and lifestyle—by reaching for pharmacological shortcuts with hidden long-term costs.
- •Alcohol is antimicrobial; blood alcohol levels rise in parallel with inflammatory endotoxin (LPS), indicating gut barrier damage.
- •Hangovers likely reflect microbiome injury and systemic inflammation more than simple dehydration.
- •Semaglutide (Ozempic/Wegovy) mimics GLP‑1, reducing appetite but causing digestive side effects and requiring long-term use; long-term safety is unclear.
- •High-prebiotic, high-fiber diets naturally stimulate GLP‑1 and PYY, increasing satiety without drugs.
- •95% of Americans are fiber-deficient; average intakes (15–18 g) fall far below recommended levels, contributing to obesity and chronic disease.
- •Large meta-analysis (Andrew Reynolds) shows higher fiber intake reduces cardiovascular events, diabetes, multiple cancers, and improves key biomarkers.
- 3:40:00 – 4:26:00
Colors, Shapes, and What Your Poop Is Telling You
Returning to stool, Dr. B systematically reviews stool shapes (Bristol 1–7) and colors and what each can signify for health, including colon cancer warning signs. He emphasizes when blood or tarry black stool absolutely warrant medical evaluation.
- •Bristol 4 is the ‘dream’ poop: smooth, soft, sausage-like; 3–5 are generally fine.
- •Bristol 1–2 (pellets or clustered marbles) indicate constipation; 6–7 indicate diarrhea.
- •Big Poo Review (142,000 UK participants) linked Bristol 4 to higher plant and fiber intake; constipation correlated with higher fat/animal product intake.
- •Bile makes stool brown; white stool suggests bile duct blockage; greasy yellow can indicate fat malabsorption (e.g., pancreatic issues).
- •Green stool can arise from infections or large intakes of green smoothies; blue from blueberries or food dye (Blue Poo test).
- •Bright red blood or tarry, foul-smelling black stool can signal GI bleeding or colorectal cancer and should always prompt medical evaluation.
- •Colon cancer rates are rising in younger generations; fiber and SCFAs confer strong protection, with risk dropping per 5 g fiber increment.
- 4:26:00 – 4:56:00
Generational Microbiomes, Lifestyle Transfer, and Sexual Attraction
Dr. B explains how low-fiber diets erode microbial diversity across generations and how we pass both microbes and lifestyle to our children. The discussion then explores how hormones and even pheromones tie sexual function and attraction back to gut health.
- •Mouse studies show low-fiber diets cause stepwise microbial diversity loss across generations; later fiber reintroduction can’t fully restore the original richness.
- •We don’t just inherit genes; we inherit maternal microbes and family lifestyle patterns that shape disease risk.
- •The estrobolome (gut microbes handling estrogen recirculation) links dysbiosis to breast, ovarian, and endometrial cancers and endometriosis.
- •Specific microbes influence testosterone and androgens; PCOS likely has a strong gut component.
- •Libido, erectile function, and presumably female sexual desire are hormonally tied and therefore microbiome-linked.
- •Animal data suggest pheromones and even kissing-related attraction are influenced by gut microbes; microbial matchmaking may underlie some of our ‘chemistry’ judgments.
- 4:56:00
Practical Framework: F-GOALS, Sprouts, and Daily Microbiome Nutrition
The episode wraps with Dr. B’s practical eating framework (F-GOALS), the power of sprouts, and his view on supplements including his own prebiotic product. He reiterates that he wants abundance and sustainability, not restrictive dieting, and that many powerful interventions are free.
- •F-GOALS: Fruit; Fermented; Greens & (whole) Grains; Omega‑3 seeds (chia, flax, hemp, walnuts); Aromatics (onion/garlic); Legumes; Shrooms/Seaweed/Sprouts.
- •Fruit has been unfairly demonized; higher fruit intake correlates with lower diabetes risk and weight loss.
- •Legumes are underappreciated superfoods: rich in fiber, resistant starch, and polyphenols; strongly linked to longevity.
- •Sprouts (e.g., broccoli sprouts) concentrate phytochemicals 50–100x adult plants, offering major benefits in tiny quantities.
- •Not all fiber is the same; soluble vs insoluble matter less than getting a wide variety from plants.
- •Dr. B’s 38 Tera product is a clinically-dosed prebiotic powder aimed at improving stool form, diversity, and digestive symptoms; he still emphasizes diet first.
- •Final actionable summary: eat diverse plants and fermented foods, move your body, sleep well, nurture human connection, and look at your poop.
