The one thing every trial agrees on: swallow NMN or NR and blood NAD+ goes up, usually doubling within weeks 1. Everything past that number is where the field splits.
The felt effects are small and specific. Trained amateur runners got more efficient at sustained effort, though top-end power didn't move 2. Men over 65 walked a bit faster, 1.50 up to 1.60 m/s 3. The famous 25% insulin-sensitivity win came from a 25-person trial whose placebo group had more than double the liver fat at baseline, on the one variable that most predicts the result 4; a separate NR trial found nothing 5. Memory tests didn't budge 6.
The longevity claim is a bet, not a finding. No human trial has measured lifespan, dementia, or fracture risk. It rests on mouse data and on the biology being plausible 7. At $30โ60 a month, you're buying a cheap option on that story, nothing more.
If you decide it's worth the money, keep it cheap and simple.
What three months actually delivers.
- Weeks: a number in your blood rises. You can't feel it.
- Two to three months: if you train hard, long efforts may feel a touch more sustainable 2. If your walking pace has slowed with age, it may edge back up 3. Nobody around you notices.
- Years: the longevity payoff, if it exists, shows up in things no trial has yet caught. This is the part you're betting on. You won't feel it.
The biggest NAD+ lever is the one nobody sells. Hard cardio and lifting drive the enzyme that rebuilds NAD+ in muscle, and a few weeks of training can rival what months of a supplement do to blood NAD+. Eating in a shorter window pushes the same lever, as does plain niacinamide at pennies a day. For the training edge, creatine has stronger evidence and a longer safety record; for the longevity bet, the same yearly spend does more on sleep, strength, and omega-3.
The fine print โ when to skip it, and what people get wrong
Short-term safety is clean, with no serious events up to 3,000 mg/day NR over 8โ12 weeks 10. The multi-year data simply doesn't exist.
"NMN is better than NR." No head-to-head trial shows it on any clinical endpoint; the premium isn't backed by data.
"Raising NAD+ reverses aging." The blood rise is real; its effect on your aging trajectory is the open question, and the hard-endpoint trials mostly came back null.
"The FDA banned NMN." It was briefly excluded over a drug-development filing, then reinstated in September 2025 11. Lawful again; the whole episode was about regulatory mechanics, and said nothing about safety or efficacy.
- 1Martens CR, Denman BA, Mazzo MR, et al. (2018). Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nature Communications. link
- 2Liao B, Zhao Y, Wang D, et al. (2021). Nicotinamide mononucleotide supplementation enhances aerobic capacity in amateur runners: a randomized, double-blind study. Journal of the International Society of Sports Nutrition. link
- 3Igarashi M, Nakagawa-Nagahama Y, Miura M, et al. (2022). Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men. npj Aging. link
- 4Yoshino M, Yoshino J, Kayser BD, et al. (2021). Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. link
- 5Remie CME, Roumans KHM, Moonen MPB, et al. (2020). Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans. American Journal of Clinical Nutrition. link
- 6Orr ME, Kotkowski E, Ramirez P, et al. (2024). A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment. GeroScience. link
- 7Imai S, Guarente L (2014). NAD+ and sirtuins in aging and disease. Trends in Cell Biology. link
- 8Grozio A, Mills KF, Yoshino J, et al. (2019). Slc12a8 is a nicotinamide mononucleotide transporter. Nature Metabolism. link
- 9Schmidt MS, Brenner C (2019). Absence of evidence that Slc12a8 encodes a nicotinamide mononucleotide transporter. Nature Metabolism. link
- 10Conze D, Brenner C, Kruger CL (2019). Safety and metabolism of long-term administration of NIAGEN (nicotinamide riboside chloride) in a randomized, double-blind, placebo-controlled clinical trial of healthy overweight adults. Scientific Reports. link
- 11FDA (2025). Response to citizen petition on ฮฒ-nicotinamide mononucleotide; NMN not excluded from definition of dietary supplement. link
Related in the handbook (4)
- โ If you're weighing a longevity supplement, creatine is the cheap, well-proven one โ NAD precursors are the speculative bet next to it.
- โ Both are supplements where dose and indication matter; omega-3 has a narrow but proven use, NAD precursors are still a longevity bet.
- โ The blunt counterpoint: the strength work this money could fund beats any anti-aging pill on the shelf for staying strong into old age.
- โ NMN and NR are pricey and lightly regulated. If you're betting on them, pay for a brand that's actually been tested.
NAD+ Precursors (NMN and NR)
One pill, once or twice a day. About the easiest habit on the shelf.
Quality brands run roughly $30โ60 a month โ call it $500 a year. Not nothing, for a supplement whose payoff is uncertain.
The biology is clean, the human trials aren't. Blood levels rise reliably; whether that translates to anything you'd actually notice is still open.
A handful of small trials show walking pace and submaximal endurance ticking up after a few months. Don't expect to feel like a different person.
The aging biology is real โ a key fuel molecule falls with the decades โ but no human trial has shown the supplement actually adds years. A bet, not a guarantee.
Trained runners squeezed a bit more out of their cardio after six weeks. If you're training, it might shift the floor of a hard session a notch.