The Ideal NAD Level for Your Cells: What the Latest Human Studies Reveal
Longevity scientist Dr Jin Xiong She joins Modern Healthspan to unpack what recent human studies really say about NAD. He explains why NAD declines non-linearly with age, why blood tests can be misread, which precursors actually raise NAD, and the cellular range he now considers ideal to aim for.
Overview
In this hour-long conversation with host Richard, Dr Jin Xiong She — founder and chief scientific officer at Jinfiniti Precision Medicine — reviews the latest human data on NAD and aging. He pushes back on a widely discussed paper claiming whole-blood NAD does not change with age or lifestyle, arguing its narrow age range cannot answer a lifelong question.
Drawing on tens of thousands of samples, he describes NAD as declining non-linearly: very high in toddlers and teens, dropping sharply between ages 20 and 30, then only gently thereafter. He explains how health status and ethnicity strongly shape a person's baseline, so a single "normal" number rarely fits everyone. Turning to supplementation, he compares nicotinamide, NMN, NR and niacin, noting that plain nicotinamide is a weak precursor while NMN and NR raise NAD far more, and multi-ingredient formulas more still.
He cautions that niacin, though potent, can push NAD to risky highs linked to inflammatory metabolites. He also explains why intravenous NAD, despite its popularity, shows no measurable rise in blood NAD in his testing. Finally, he shares the cellular range he now considers ideal and frames NAD support as an ongoing daily practice rather than a one-time fix. As always, this is educational wellness content, not medical advice.
Key quotes
5Nicotinamide is actually a very, very poor NAD precursor.
The most rapid and sharp decline of NAD levels actually happens around 20 to 30 years of age.
Niacin is actually the most potent NAD precursor — better than NR, better than NMN.
The half-life of NAD in the bloodstream is 6 hours, so after 24 hours you have 5% left.
Ideally, we want to get our NAD levels between 55 and 80 micromolar. That's the sweet spot for most individuals.
Key ideas
9A much-discussed paper, read carefully
A recent human study concluded that whole-blood NAD does not change with age or lifestyle. Dr She argues the data are fine but the interpretation overreaches, because a narrow adult age range cannot answer a lifelong question.
NAD declines non-linearly
Levels are very high in toddlers and teens, drop most sharply between ages 20 and 30, then decline only gently into the 70s, 80s and 90s. The steepest fall happens far earlier than many assume.
Health and ethnicity shape your baseline
Health conditions tend to lower NAD, and ethnicity matters a lot: he reports Caucasian adults averaging around 27-28 micromolar, Chinese around 22-23, and Malaysian, Korean and Indian groups in the mid-teens to low 20s.
Why narrow-range extrapolation misleads
Comparing only over-30 versus under-30 adults says little about whether NAD falls across a whole lifetime. Generalising that limited window into 'NAD doesn't decline with age' is, he argues, scientifically unjustified.
Lifestyle effects are real but modest
Exercise and protein supplementation move NAD only slightly, so those specific findings are roughly right. He cautions that publication bias rewards provocative headlines that over-generalise from thin data.
Measuring NAD reliably is a craft
Freezing and thawing degrade NAD, and assays are not harmonised between labs, so numbers cannot be compared across systems. Blood-spot testing, careful calibration and a stabilising buffer keep results consistent within one method.
NMN and NR beat plain nicotinamide
Around 1,000 mg of nicotinamide raises NAD only about 10%, with just ~30% of people responding. The same dose of NMN or NR raises NAD roughly 40-50%, and multi-ingredient formulas can push it higher still.
Niacin is potent but comes with risk
High-dose niacin can raise NAD around 500%, reaching about 150 micromolar. Those very high levels are linked to inflammatory metabolites (4PY and 2PY) and vascular inflammation, so more is not better.
The ideal cellular range
He describes a minimum around 40 micromolar, an ideal sweet spot of 55-80, little added benefit above 80-100, and a level near 150 to avoid. Like vitamin D, this target is expected to be refined as more data arrive.
Practical takeaways
7- 1
NAD can dip earlier than you'd think 6:30
Because the sharpest decline appears around ages 20-30, paying attention to NAD may matter well before middle age.
- 2
A single number rarely fits everyone 11:30
Health status and ethnicity shift baseline NAD, so interpret any one reading in the context of the whole person rather than a universal 'normal.'
- 3
Choose precursors thoughtfully 39:00
NMN and NR generally outperform plain nicotinamide for sustained support, which is worth knowing when comparing products.
- 4
Type, delivery and dose all count 44:00
The right product plus the correct dose determines results, and what works well for one person may not for another.
- 5
Don't assume IV drips raise cellular NAD 53:30
In his testing, intravenous NAD showed no measurable rise in blood NAD, so it's worth setting expectations before pursuing it for longevity or performance.
- 6
Aim for a target, not just 'higher' 1:00:00
A range of 55-80 micromolar is described as the sweet spot; pushing far above it offers little extra benefit.
- 7
Treat NAD support like a daily nutrient 1:04:30
Levels drift down when you stop, so consistency is framed as more important than any single short-term bump.
Topics & chapters
14The nicotinamide surprise
An opening look at why nicotinamide barely raises long-term NAD, and an introduction to the guest.
The paper that questioned NAD decline
A widely discussed study claiming whole-blood NAD doesn't change with age or lifestyle.
How NAD really declines
The non-linear pattern from toddlers and teens through the sharp drop at 20-30.
Health status and ethnicity
Why baseline NAD varies so much between people and populations.
Why the conclusion overreaches
The problem of generalising a narrow adult age range to a whole lifetime.
Lifestyle, exercise and publication bias
Small real effects of exercise and diet, and how headlines can mislead.
Microbiome and muscle NAD
Gut bacteria's role and how blood NAD tracks changes in muscle.
Preserving and measuring NAD
Freezing, blood-spot testing, calibration and why assays aren't comparable across labs.
NMN vs NR vs nicotinamide
Comparing how much each precursor actually raises NAD.
Formulas and the three dosing factors
Multi-ingredient blends, and why product type, delivery and dose all matter.
Niacin: potent but risky
The most powerful precursor, its toxic-high concern and inflammatory metabolites.
Intravenous NAD reality check
Rapid clearance, no measurable blood rise, and where IV may still help.
The optimal NAD range
Minimum 40, ideal 55-80, and the levels to avoid.
Testing cadence and daily consistency
When to retest and why NAD support works like a daily micronutrient.