In this episode, I return to a conversation I promised to continue - sitting back down with Prof Tim Spector, MD, to explore everything that has changed in microbiome science since Episode 224. Tim and the ZOE team have now published a landmark Nature paper with 34,000 microbiome samples, run a clinical trial comparing personalized nutrition against government guidelines, and Tim has published a book on fermentation science. We cover why most probiotics are scientifically obsolete, a practical ranked guide to fermented foods, the TMAO pathway linking gut bacteria to cardiovascular risk, and the estrobolome - the gut bacteria that recycle estrogen in women. If you have the gut health basics in place, this conversation tells you what to prioritize next. What We Cover The ZOE Microbiome Health Ranking 2025: what 34,000 gut microbiomes revealed about the species that actually matter A practical guide to fermented foods: how much, how often, and whether pasteurised versions count The TMAO mechanism - how your gut bacteria may influence the cardiovascular risk of red meat Why most probiotic supplements use strains that are 100 years out of date The estrobolome: how gut bacteria control estrogen recycling in women The menopause - microbiome connection and what ZOE's latest research shows Building a healthier gut microbiome is less about one dramatic intervention and more about consistent, moderate changes compounding over time. This conversation gives you the clearest picture yet of which changes to prioritise. To connect with the guest, follow Tim Spector on Instagram at @tim.spector and explore ZOE at zoe.com. Intro (00:00) Why Gut Diversity Is a Flawed Metric (01:58) Does the Microbiome Actually Cause Disease? (15:23) Vegan vs. Omnivore Microbiomes (26:52) Why ZOE Made Their Research Public (31:49) Prebiotics Beat Probiotics in RCT (39:46) The Case for More Fiber (46:43) How to Buy Fermented Foods (53:32) Resistant Starch vs. Polyphenols (59:42) Are "Natural" Sugars Any Different? (01:03:12) Time-Restricted Eating & the Microbiome (01:11:21) What's Next for Zoe Research (01:18:35) Want to support the show? The best way to support the show is to use the products and services offered by our sponsors. To check them out and enjoy great savings, visit theproof.com/friends. You can also support the show by leaving a review on the Apple Podcast app and sharing your favourite episodes with friends and family. This episode is brought to you by: 38TERA Consider 38TERA's DMN prebiotic supplement a daily multivitamin for your gut. Formulated by yours truly and gastroenterologist Dr Will Bulsiewicz. Use code THEPROOF for a discount at checkout. 38Tera ships to the United States, Australia, and New Zealand. Eight Sleep Upgrade your sleep with the Pod 5 Ultra by Eight Sleep. Clinically validated to deliver up to 1 extra hour of quality sleep per night through temperature control and biometric tracking. Use code THEPROOF for $350 off at eightsleep.com/theproof. Try it risk-free for 30 days, with worldwide shipping. Eight Sleep ships to the U.S. (excluding Alaska, Hawaii, and territories), Canada, Mexico, most of the EU, the U.K., Australia, the UAE, Saudi Arabia, and Switzerland. Function Health Take charge of your health with advanced blood testing and personalised insights. Function Health offers a practical way to track key health markers such as cholesterol, blood sugar, and more. Learn more and join at functionhealth.com/simonhill for a $25 credit toward your membership. Only available to those living in the United States. Function Health ships to 48 U.S. states, excluding Rhode Island, Hawai‘i, and Puerto Rico. Pique Tea Pique’s Pu’er Tea Duo brings ancient fermentation into a simple daily ritual, delivering living nutrients that support digestion, metabolism, and sustained energy from the inside out. Unlock 20% off and establish your powerful foundation for sustained well-being at Piquelife.com/SIMON. Pique ships within the U.S. and to Australia, Canada, and select EU countries. WHOOP Whoop, the most advanced fitness and health wearable available. Your personalised fitness and health coach to recover faster, sleep better, and train smarter. Claim your first month free on join.whoop.com/simon. Whoop ships to 56+ international markets, including the US, Canada, most of Europe, Australia, New Zealand, UAE, Singapore, and parts of Asia. Simon Hill, MSc, BSc (Hons) Creator of theproof.com Host of The Proof with Simon Hill Author of The Proof is in the Plants Subscribe & Connect: YouTube Apple Podcasts Spotify Instagram: @theproof Twitter: @theproof Facebook: The Proof with Simon Hill Nourish your gut with my Plant-Based Ferments Guide and download my Two-Week Meal Plan.