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Why most probiotic supplements use strains that are 100 years out of date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)

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Simon Hill, MSc, BSc (Hons)

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New microbiome science | Dr Tim Spector