Your neighbor is 74 and has started NMN capsules after a podcast said they keep older legs young. He wants to keep walking to the market on his own and asks whether there is real evidence behind the claim. Do human trials show NMN helps older people walk faster or stay stronger?
Not convincingly. Four small placebo-controlled trials in Japan found that NMN, a building block the body turns into NAD, reliably raised NAD levels in the blood. Their results for walking and strength were mixed: a few secondary measures improved, one trial missed its main goal, and the one trial in frail older men found no gain at all. All four had co-authors who worked for companies, including food and ingredient makers. Regular exercise remains the approach with strong evidence.
What four trials in older adults measured
A University of Tokyo team led by Igarashi gave healthy older men NMN or a placebo for 6 or 12 weeks. NMN raised NAD and related compounds in the blood and caused no harmful effects. Gait speed and left-hand grip showed what the authors called nominally significant improvements that should be confirmed in larger studies, and body composition did not change. Three authors worked for Mitsubishi Corporation Life Sciences, an ingredient company.
A University of Tsukuba study by Kim and colleagues split 108 older adults into four groups: NMN or placebo, taken in the morning or the afternoon, for 12 weeks. Sit-to-stand times improved in every group, including those on placebo, which is a reminder that simply joining a study can change results. The afternoon NMN group showed the largest effect for leg function and for daytime drowsiness.
A 2024 trial by Morifuji and colleagues, three of whom worked for the food company Meiji, enrolled 60 older adults for 12 weeks. Its main measure, a stepping test, showed no difference between NMN and placebo at 4 or 12 weeks. Among secondary measures, the NMN group took less time to walk 4 meters and scored better on a sleep questionnaire.
The smallest study tested the people most likely to want help. Akasaka and colleagues in Osaka enrolled 14 men with diabetes, average age 81, who already had weak grip or slow walking. After 24 weeks, grip strength and walking speed changed no more with NMN than with placebo, although NMN was well tolerated.
How to read a mixed set of small studies
When a trial misses its main goal, a better result on a secondary measure is a lead to test again, not a finding. These trials were short, small, run in one country, and all involved company researchers. A higher NAD reading in the blood shows the capsule was absorbed; it does not show that legs got stronger. Supplement quality also varies, and NAD-related products sold as research chemicals are labeled not for human use and were not what these trials tested.
What reliably helps older legs
MedlinePlus describes four types of exercise for older adults: endurance activities such as brisk walking or dancing, strength work with weights or resistance bands, balance exercises that help prevent falls, and flexibility stretches. It suggests starting slowly if you have not been active and checking with a health care provider about what is right for you. For a neighbor who wants to keep walking to the market, a physical therapist or a local strength-and-balance class has far better evidence than a capsule. If he keeps taking NMN, he should tell his doctor so it is on his medicine list. Not medical advice.
Sources
- Igarashi M et al. Chronic nicotinamide mononucleotide supplementation elevates blood NAD levels and alters muscle function in healthy older men. NPJ Aging, 2022 (PubMed)
- Kim M et al. Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults. Nutrients, 2022 (PubMed)
- Morifuji M et al. Ingestion of beta-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adults. Geroscience, 2024 (PubMed)
- Akasaka H et al. Effects of nicotinamide mononucleotide on older patients with diabetes and impaired physical performance. Geriatr Gerontol Int, 2023 (PubMed)
- MedlinePlus: Exercise for Older Adults
Related reading
- Raising NAD blood markers is not proof of anti-aging
- Walking for blood pressure, with and without nicotinamide riboside
- What a 2026 NMN trial in low platelets tested
By The Everyday Brief. AI-assisted drafting with automated source and editorial checks. Sources fetched 2026-10-23 PT. Not medical advice.