You may have heard claims that C15:0 (pentadecanoic acid) is the first essential fat discovered in 90 years, a powerful longevity booster, and a game-changer for metabolic health. But how much of this is backed by solid science? In this episode, I sit down with Dr. Bill Harris, a leading expert in fatty acid research, to critically evaluate the evidence behind C15:0. We break down the population studies linking it to health benefits, the key clinical trials testing its effects, and whether the marketing around Fatty15 is ahead of the actual data. In this episode, we cover: What exactly is C15:0, and how does it compare to other fats? The claim that C15:0 is an essential nutrient—does it meet the criteria? The current evidence on C15:0 and its impact on cholesterol, glucose, and inflammation Does C15:0 supplementation mimic omega-3s, metformin, or rapamycin? The broader issue of patenting a naturally occurring compound For more details and supporting studies, visit the full show notes. Introduction to Pentadecanoic Acid (C15:0) (00:00) Evaluating the Claims of C15:0 (02:05 Comparing C15:0 with Other Fatty Acids (03:12) Health Implications of Dairy Fats and the Essentiality of C15:0 (05:02) Scientific Evidence and Studies on C15:0 (13:12) Interpreting Clinical Trial Results, Cholesterol, and the Tango Trial (27:59) Cholesterol and the Tango Trial (28:28) Comparing C15:0 to Omega 3s (32:02) Future Research Directions for C15:0 (37:46) Longevity Claims and Patents (42:30) Final Thoughts and Conclusion (49:44) 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.  Eight Sleep Upgrade your sleep with the Pod 4 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. Eimele Eimele Essential 8 is a comprehensive multivitamin that is scientifically formulated to complement your plant-rich diet, increase and sustain your energy, and support the immune system, as well as heart and brain health. Follow this link for 20% off one-time purchases and subscriptions. 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. 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: @simonhill • Twitter: @theproof • Facebook: The Proof with Simon Hill Nourish your gut with my Plant-Based Ferments Guide and download my Two-Week Meal Plan.