Forever Health

Introduction

Something is quietly draining your brain. By the time most people reach their mid-50s, the cellular levels of a critical molecule called NAD+ (nicotinamide adenine dinucleotide) have fallen by roughly 50% compared to young adulthood — and that decline continues steadily into later life. Once considered little more than a metabolic coenzyme, NAD+ is now at the center of some of the most promising aging and neurodegeneration research in the world.

A sweeping review highlighted in a March 24, 2026 ScienceDaily report concluded that restoring NAD+ levels through precursor supplementation — most notably nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) — could slow biological aging and may represent a therapeutic target for Alzheimer’s and Parkinson’s disease. Early clinical trials are reporting improvements in memory, physical movement, and metabolic health markers. For anyone concerned about cognitive longevity, this is a story worth paying attention to.

What the Experts Are Saying

Dr. David Sinclair, Professor of Genetics at Harvard Medical School and co-director of the Paul F. Glenn Center for the Biology of Aging, has been one of the most prominent scientific voices linking NAD+ to the aging process. Appearing on the Huberman Lab podcast, Sinclair explained his Information Theory of Aging — the idea that aging is fundamentally a loss of epigenetic information, and that NAD+-dependent enzymes called sirtuins are the molecular guardians responsible for maintaining it. “Sirtuins need NAD+ to function properly. Without it, aging is accelerated,” Sinclair has stated. He personally supplements with approximately one gram of NMN per day, and his 2024–2025 protocol continues to include NMN alongside resveratrol, metformin, and vitamin D.

Dr. Andrew Huberman, neuroscientist and professor at Stanford University, reports taking both NMN (1–2 g/day) and NR (500 mg/day) for sustained mental and physical energy. His discussions with longevity physician Dr. Peter Attia add important nuance: while both experts acknowledge strong mechanistic links between NAD+ and cellular health, Attia emphasizes that definitive human evidence for lifespan extension remains incomplete, calling for larger, longer-term clinical trials before sweeping recommendations can be made.

Dr. Rhonda Patrick, biomedical scientist and host of FoundMyFitness, highlights preliminary data showing NMN improved cognitive deficits and restored cerebral blood flow in aging mouse models — early signals that the brain may be among the primary beneficiaries of NAD+ restoration. Patrick notes that NMN and NR differ in tissue uptake profiles and may work synergistically when combined.

Dr. Mark Hyman, physician and bestselling author of Young Forever, frames NAD+ as one of three foundational longevity supplements, noting that it “inhibits inflammation, increases metabolism, and increases insulin sensitivity” — a triad of benefits particularly relevant for aging brains.

The Science Behind It

NAD+ acts at the intersection of three major aging pathways. First, it is the essential cofactor for sirtuin enzymes (SIRT1–SIRT7), the “longevity enzymes” that regulate gene expression and epigenetic maintenance — the foundation of Sinclair’s Information Theory of Aging. Second, NAD+ is consumed by PARP enzymes during DNA repair. As cells accumulate damage with age, PARP activity rises, consuming up to 90% of available NAD+ in some studies, creating a vicious cycle of depleted sirtuins and accelerated epigenetic drift.

Third, NAD+ supports mitochondrial energy production in neurons. Reduced availability in the aging brain correlates with impaired synaptic transmission and accumulation of amyloid-beta and tau — hallmarks of Alzheimer’s pathology. Preclinical studies show NR reduces amyloid burden and improves cognition, while NMN restores cerebrovascular function and brain blood flow. Clinically, a November 2025 randomized trial published in eClinicalMedicine (The Lancet) assessed high-dose NR (2,000 mg/day) in adults with post-COVID cognitive symptoms and found measurable NAD+ elevation alongside early positive cognitive signals.

Key Benefits

• Elevated cellular NAD+ levels: Both NMN and NR consistently raise circulating NAD+ by 50–150% above baseline in clinical studies, with doses of 500 mg–2,000 mg/day demonstrating a strong safety profile and minimal side effects across multiple trials.
• Neuroprotection and cognitive support: Preclinical evidence shows NAD+ restoration reduces amyloid-beta pathology, improves cerebral blood flow, and supports neuronal energy metabolism — pathways directly implicated in Alzheimer’s and Parkinson’s disease prevention.
• DNA repair and genomic stability: By replenishing NAD+ consumed by PARP enzymes during DNA repair, precursor supplementation helps maintain genomic integrity and may slow the epigenetic drift that drives cellular aging.
• Metabolic and cardiovascular improvements: Human trials report reductions in blood pressure and arterial stiffness (with NR in middle-aged men), improved muscle insulin sensitivity in prediabetic women (with NMN), and reduced inflammatory cytokines in elderly men.
• Mitochondrial energy and exercise capacity: NAD+ is essential for oxidative phosphorylation; restoring levels supports mitochondrial function in muscle and brain, with some participants reporting improved sustained energy and physical performance.
• Circadian rhythm regulation: NAD+ levels oscillate with the circadian clock and are required for SIRT1-mediated regulation of core clock genes — meaning adequate NAD+ may support healthier sleep-wake cycles alongside cognitive function.

How to Get Started

Both NR and NMN are available over the counter, with clinical trials using doses ranging from 250 mg to 2,000 mg per day. A common starting point is 500–1,000 mg/day of either compound. Take your precursor in the morning with food to align with the body’s natural NAD+ synthesis rhythms. David Sinclair prefers sublingual NMN powder for faster absorption, though oral capsules appear effective as well. Refrigerating NMN preserves potency, as it degrades at room temperature. Some protocols combine both NR and NMN at lower individual doses given their differing tissue uptake profiles. Discuss any interactions with your physician, especially if you are taking metformin or other medications.

What to Watch Out For

The evidence, while exciting, is still maturing. Most human studies are short-term, rely on surrogate biomarkers, and lack the long-duration hard endpoints needed to confirm lifespan or healthspan benefits — a point Peter Attia emphasizes. Flushing, mild nausea, and digestive upset are the most common side effects at higher doses. Some researchers have raised theoretical concerns about NAD+ supplementation and cancer proliferation, as certain tumors upregulate NAD+ synthesis; consult your oncologist if you have a relevant history. The FDA has periodically revisited NMN’s regulatory status, so verify current rules and purchase from reputable, third-party-tested brands. No supplement replaces the lifestyle behaviors — exercise, quality sleep, caloric moderation — that most robustly raise NAD+ on their own. Always consult your physician before starting, particularly if pregnant, nursing, or managing a chronic condition.

Watch the Full Expert Videos

Dr. Andrew Huberman & Dr. David Sinclair (Huberman Lab): The Biology of Slowing & Reversing Aging

Dr. Andrew Huberman & Dr. David Sinclair — Essentials (Huberman Lab): Essentials: The Biology of Slowing & Reversing Aging

Dr. Mark Hyman: The 3 Daily Supplements Everyone Should Be Taking For Longevity

Dr. Andrew Huberman & Dr. Peter Attia (Huberman Lab): Supplements for Longevity & Their Efficacy — Full Episode

Dr. Rhonda Patrick & Dr. David Sinclair (FoundMyFitness): The Theory of Aging, NAD+ Boosters (NR and NMN), Sirtuins, and More