This study, conducted by researchers at the University of Tokyo, used a placebo-controlled, randomized, double-blind design to evaluate the effects of NMN supplementation. Twenty healthy elderly men over the age of 65 participated in a trial where they received 250 mg/day of NMN for either 6 or 12 weeks.
The results were striking: NMN supplementation significantly increased NAD⁺ levels in the blood, and these healthy seniors experienced marked improvements in muscle strength and physical performance!
📄 Note: This paper is currently under peer review as a preprint submitted to the top journal Nature.
🚶♂️ Muscle Strength Boost: Seniors Become More Agile
To evaluate changes in physical performance, the researchers tested participants’ skeletal muscle mass and strength. Although detailed model analyses did not detect changes in muscle mass, over the 12-week period, NMN significantly improved muscle strength and performance.
Compared to their pre-supplementation state, the elderly men showed clear increases in gait speed and grip strength. The placebo group confirmed these improvements were truly attributable to NMN.
📊 Figure: NMN supplementation enhances muscle strength and physical performance
Interestingly, NMN’s preference for improving muscle tissue is consistent with findings from clinical trials in the US and China [2, 3]. Together, these studies suggest NMN’s core target may lie in skeletal muscle rather than in adipose tissue, as some earlier studies hypothesized [4, 5].
In fact, this study also assessed changes in visceral fat distribution but found no significant differences.
📊 Figure: NMN supplementation had no effect on visceral fat (red regions = visceral fat; blue regions = subcutaneous fat)
👂 Improved Hearing: Seniors Regain Sharpness
Beyond mobility, the study also examined aging-related indicators such as hearing function. After NMN supplementation, participants showed significant improvements in right-side hearing ability.
This effect may be due to NMN’s activation of the SIRT3 protein, which regulates the redox ratio of reduced glutathione within mitochondria [6-8].
📊 Figure: NMN’s effect on hearing function
⚖️ The Disappointments: No Improvement in Insulin Sensitivity or Cognition
From a philosophical perspective, every coin has two sides. If a trial’s results seem too perfect, we might question whether negatives were overlooked.
This human trial also brought some less encouraging news:
-
NMN did not improve insulin sensitivity
-
No measurable improvements in cognitive function were observed
The gold-standard oral glucose tolerance test (OGTT) showed no significant changes in insulin sensitivity markers such as HOMA-IR, adiponectin, or interleukin-6 (IL-6).
Similarly, other blood indicators—triglycerides, cholesterol, glucose, insulin, and C-peptide AUC curves (reflecting the amount of a substance in circulation over time)—showed no meaningful changes.
📊 Figure: Many blood markers, including insulin sensitivity, remained unchanged
In contrast, an April 2024 clinical trial in the US had found NMN to significantly improve insulin resistance in muscle tissue [2]. However, this Japanese trial involved healthy elderly participants with no pre-existing metabolic issues, making direct comparisons between the two studies difficult.
Also, while a previous animal study by “NMN pioneer” Professor David Sinclair found NMN significantly enhanced cognitive performance in aged mice [9], this human trial failed to replicate that finding.
Future research will hopefully clarify these discrepancies and uncover the full scope of NMN’s effects.