NAD+ Benefits: 9 Claims Checked Against the Human Trials

Quick Answer: NAD+ is a coenzyme every cell uses to turn food into energy, and its precursors, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), reliably raise it in people: by 22%, 51% and 142% in whole blood at 100, 300 and 1,000 mg of NR a day in one eight-week trial. Whether that higher level produces the benefits sold on the label is a separate question, and human trials mostly answer no. A 2025 meta-analysis found no effect on muscle mass, grip strength or walking speed in adults over 60. A 2026 meta-analysis of 15 NMN trials found no effect on weight, blood sugar, cholesterol or systolic blood pressure. The positive findings are narrower: better muscle insulin sensitivity in one trial of prediabetic women, lower inflammatory markers in two small trials, and early signals in Parkinson’s disease. Safety has been good up to 2,000 mg a day for 12 weeks.

“NAD+ benefits” lists usually run from energy and muscle to brain, skin and lifespan. Most of those claims come from mice, where raising NAD+ does change how animals age. This page takes nine of the claims and checks each one against what happened when people took NR or NMN in randomized, placebo-controlled trials. For how injections compare with pills, see our NAD+ injections vs supplements guide.

What NAD+ is, in one paragraph

Nicotinamide adenine dinucleotide (NAD+) carries electrons in the reactions that release energy from food, and it is the fuel for enzymes involved in DNA repair and cell signalling, including the sirtuins. NAD+ has been reported to decline with ageing in preclinical models, as the Birmingham trial below notes, and topping it up with precursors improves several markers of metabolism in rodents. The body makes NAD+ from forms of vitamin B3. NR and NMN are two of those forms, sold as supplements.

The scoreboard: 9 claims, what the trials found

1. It raises NAD+: the one claim that holds every time

In an eight-week trial funded by ChromaDex, which sells NR as Niagen, overweight but healthy adults took 100, 300 or 1,000 mg of NR a day. Whole-blood NAD+ rose by 22%, 51% and 142% within two weeks and stayed there. There was no flushing and no difference in side effects from placebo.

An independent University of Colorado trial gave healthy middle-aged and older adults 500 mg of NR twice a day for six weeks. NAD+ in circulating immune cells rose by about 60%. The authors concluded NR “effectively stimulates NAD+ metabolism,” and found no effect on VO2 max or treadmill time to exhaustion.

That gap, between the level going up and the body changing, is the theme of the rest of this page.

2. Muscle: no effect in older adults

This is the claim with the most direct test. A 2025 meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle pooled randomized trials of NMN and NR in people with mean ages of 60.9 to 83. NMN had no significant effect on skeletal muscle index, handgrip strength, gait speed or the five-times chair stand test, and the narrative review found no improvement in knee strength, physical performance scores or thigh muscle. The conclusion was direct: “Current evidence does not support NMN and NR supplementation for preserving muscle mass and function in adults with mean age of over 60 years.”

If muscle is your goal, the interventions that do work are resistance training and enough protein; our page on how much protein older adults need sets out the numbers.

3. Insulin sensitivity: one yes, one no

• No: forty obese, insulin-resistant men took 1,000 mg of NR twice a day for 12 weeks. Measured with the gold-standard clamp test, “insulin sensitivity, endogenous glucose production, and glucose disposal and oxidation were not improved.”
• Yes: in a 10-week trial published in Science, postmenopausal women with prediabetes who were overweight or obese took NMN. Insulin-stimulated glucose disposal and muscle insulin signalling increased after NMN and did not change on placebo.

The two trials used different precursors in different people, so they do not cancel out. They do show that “improves blood sugar” is a claim about specific groups, not a general benefit.

4. Weight and body composition: no

The obese-men trial found no effect on body composition, resting energy expenditure or fat burning. The 2026 meta-analysis of 15 NMN trials, at doses of 250 to 2,000 mg for two weeks to six months, found no significant effect on body weight or BMI.

5 and 6. Blood pressure and cholesterol: small and inconsistent

The same 2026 NMN meta-analysis found no effect on fasting glucose, HbA1c, lipids or systolic blood pressure, while diastolic pressure “decreased slightly.” A 2024 meta-analysis of 19 trials of all NAD+ precursors did find lower total cholesterol and triglycerides, but no significant effect on the other metabolic-syndrome measures, and rated the quality of evidence as “very low” to “low.”

7. Exercise capacity: weak

The Colorado trial found no change in VO2 max or time to exhaustion after six weeks of NR. A 60-day trial of 80 healthy middle-aged adults found longer six-minute walking distances at 300, 600 and 900 mg of NMN than on placebo, with the best results at 600 mg. That trial was led by staff of an NMN manufacturer, and the walking test is a measure of everyday function rather than athletic performance.

8. Inflammation: an early signal

Twelve older men took 1 g of NR a day for 21 days in a crossover trial at the University of Birmingham. NR reached their muscle and “depressed levels of circulating inflammatory cytokines,” without changing how well their mitochondria produced energy. The Parkinson’s trial below also reported lower inflammatory cytokines in blood and spinal fluid. These are marker changes in small groups, not evidence of less disease.

9. Brain health: one phase I trial

In the Norwegian NADPARK trial, 30 people newly diagnosed with Parkinson’s disease took 1,000 mg of NR or placebo for 30 days. NR raised brain NAD+ levels, measured by scanning, though the rise varied between people, and those whose brain levels rose showed changes in brain metabolism “associated with mild clinical improvement.” The authors called NR a potential neuroprotective therapy “warranting further investigation in larger trials.” It is a phase I study, designed mainly to test safety.

Is it safe?

In the trials above, NR up to 2,000 mg a day for 12 weeks and NMN up to 900 mg a day for 60 days caused no serious adverse events. The 2026 meta-analysis found NMN did not increase adverse events or liver enzymes, but all of this is short-term: no trial has run for years.

Frequently Asked Questions

What are the proven benefits of NAD+?

Raising NAD+ levels is proven: NR raised blood NAD+ by 22% to 142% depending on dose. Health benefits are not established. A 2025 meta-analysis found no effect on muscle in adults over 60, and a 2026 meta-analysis found no effect of NMN on weight, glucose or cholesterol.

Does NAD+ give you energy?

Not measurably in trials. Six weeks of 1,000 mg of NR a day did not change VO2 max or treadmill time to exhaustion in healthy middle-aged and older adults.

Does NAD+ help build muscle?

No. A 2025 meta-analysis of NMN and NR in adults over 60 found no effect on muscle mass, grip strength, gait speed or chair-stand time.

Is NMN or NR better?

Both raise NAD+, and neither has shown broad health benefits in people. The one positive insulin trial used NMN in prediabetic women; the negative one used NR in obese men, so the trials cannot be compared directly.

How long does NAD+ take to work?

Blood NAD+ rose within two weeks of starting NR and stayed raised for eight weeks. Trials of functional outcomes ran from 21 days to six months.

What are the side effects of NAD+ supplements?

None of note in short trials. NR up to 2,000 mg a day for 12 weeks and NMN up to 900 mg a day for 60 days were well tolerated, and NR did not cause flushing.

The Bottom Line

NAD+ precursors do what they say on the first line of the label: they raise NAD+, by 22% to 142% in blood. The benefits on the rest of the label mostly have not shown up in human trials. Muscle, weight, blood sugar in most groups and exercise capacity did not change. Insulin sensitivity improved in one group of prediabetic women, inflammation markers fell in two small trials, and Parkinson’s disease is the most interesting open question. If you take NR or NMN, take it knowing that the strongest evidence is for the number on the blood test.

Sources

1. Conze D, Brenner C, Kruger CL. 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. Sci Rep, 2019. PMID 31278280. 8 weeks; 100, 300 and 1,000 mg NR raised whole-blood NAD+ by 22%, 51% and 142% within 2 weeks; no flushing; ChromaDex-affiliated authors. Checked 1 October 2026.
2. Martens CR, Denman BA, Mazzo MR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun, 2018. PMID 29599478. 2 x 6-week crossover, NR 500 mg twice daily; PBMC NAD+ +~60% vs placebo; no effect on VO2 max or treadmill time to exhaustion. Checked 1 October 2026.
3. Prokopidis K, Moriarty F, Bahat G, et al. The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis. J Cachexia Sarcopenia Muscle, 2025. PMID 40275690. Mean ages 60.9 to 83; NMN no significant effect on SMI, handgrip, gait speed or 5-times chair stand; “Current evidence does not support NMN and NR supplementation for preserving muscle mass and function in adults with mean age of over 60 years.” Checked 1 October 2026.
4. Dollerup OL, Christensen B, Svart M, et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. Am J Clin Nutr, 2018. PMID 29992272. 40 men, BMI over 30, 40-70 y, NR 1,000 mg twice daily for 12 weeks; no improvement in insulin sensitivity, energy expenditure, lipolysis or body composition. Checked 1 October 2026.
5. Yoshino M, Yoshino J, Kayser BD, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 2021. PMID 33888596. 10-week RCT, postmenopausal overweight or obese women with prediabetes. Checked 1 October 2026.
6. Yang W, Huang J, Tang Z, et al. Safety and Metabolism-Related Outcomes of Oral Nicotinamide Mononucleotide Supplementation in Adults: A Systematic Review and Meta-Analysis. Nutrients, 2026. PMID 42514320. 15 trials, 250-2,000 mg/day, 14 days to 24 weeks; no effect on weight, BMI, fasting glucose, HbA1c, lipids or systolic BP; diastolic BP “decreased slightly”; no increase in adverse events or ALT/AST. Checked 1 October 2026.
7. Oliveira-Cruz A, Macedo-Silva A, Silva-Lima D, et al. Effects of Supplementation with NAD+ Precursors on Metabolic Syndrome Parameters: A Systematic Review and Meta-Analysis. Horm Metab Res, 2024. PMID 39111741. 19 RCTs; lower total cholesterol and triglycerides, no significant effect on other outcomes; evidence quality “very low” to “low”. Checked 1 October 2026.
8. Yi L, Maier AB, Tao R, et al. The efficacy and safety of beta-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial. GeroScience, 2023. PMID 36482258. 80 completers, 300/600/900 mg NMN for 60 days; six-minute walk longer than placebo, greatest at 600 mg; HOMA-IR no difference; first author affiliated with Abinopharm. Checked 1 October 2026.
9. Elhassan YS, Kluckova K, Fletcher RS, et al. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Rep, 2019. PMID 31412242. 12 aged men, 1 g NR/day for 21 days, crossover; lower circulating inflammatory cytokines; mitochondrial bioenergetics unchanged. Checked 1 October 2026.
10. Brakedal B, Dölle C, Riemer F, et al. The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson’s disease. Cell Metab, 2022. PMID 35235774. 30 newly diagnosed patients, 1,000 mg NR or placebo for 30 days; cerebral NAD+ increased (variable); altered cerebral metabolism “associated with mild clinical improvement”; lower inflammatory cytokines in serum and CSF. Checked 1 October 2026.

Featured image: illustration by HealthyMag, not a data chart.