Why High-Dose NMN May Be Backfiring — What the Research Actually Shows

David Sinclair takes one gram of NMN daily. The human trials with the best functional outcomes used 250 milligrams. Most people are somewhere in between — based on what they read, not what the research shows. This video breaks down: • What dose the major human NMN trials actually used (and what they found) • The CD38 "ceiling effect" that limits returns at high doses • The 2023 Nature Metabolism paper on NAD+ and cancer cells (and what it actually means) • Why Sinclair's one-gram dose is self-selected, not clinically derived • Peter Attia's position on NMN — and why it's also reasonable • Age-based dosing breakdown: under 45, 45–65, 65+ --- TIMESTAMPS 0:00 — The NMN dose question: is 1 gram actually better? 0:35 — Why “more NMN = more benefit” is not always true 1:28 — What this video is — and is not — saying about NMN safety 2:06 — Major human NMN trials and the doses they actually tested 3:14 — 2024 meta-analysis: where functional benefits appear strongest 3:55 — The cancer-metabolism concern around high NAD+ levels 5:21 — CD38: the “NAD+ vampire” and the ceiling effect 6:50 — Why David Sinclair takes 1 gram — and what that really means 7:37 — Peter Attia’s more cautious position on NMN 8:05 — Why age changes the ideal NMN dose 9:17 — Practical NMN dose guide by age group 9:55 — Cancer history: talk to your oncologist before NAD+ precursors 10:07 — Timing and absorption still matter regardless of dose 10:20 — Next topic: why NMN brand quality matters --- STUDIES REFERENCED • NMN 250mg RCT in older men — Keio University, 2021 (Cell Metabolism) • NMN 1,000mg trial in postmenopausal women — Washington University, 2022 • MIB-626 (NMN) high-dose trial — 2023 • NAD+ and cancer metastasis — Nature Metabolism, 2023 • NMN human trial meta-analysis — npj Aging, 2024 --- DISCLAIMER — AI CONTENT & HEALTH ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ AI CONTENT: This video features an AI-generated presenter (Dr. James Chen), AI voiceover, and AI-assisted visuals. Dr. James Chen is a synthetic AI wellness educator — not a real person or licensed physician. HEALTH: All content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare provider before starting any supplement protocol or making significant lifestyle changes — especially if you are pregnant, nursing, on medication, or managing a chronic condition. Individual results vary. Studies referenced are linked above. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ --- Longevity Lab covers the science of aging without supplement industry spin. New video every week. ```