NAD+ after NMN: walking and insulin tests
The NMN case gets more interesting when the outcomes leave the blood sample: a measured walk, an insulin test, and a very different experiment in mice.
Six-minute walking distance
In Yi’s trial of healthy, middle-aged adults, people received 300, 600 or 900 milligrams per day of NMN for 60 days. Blood NAD+ increased at days 30 and 60. Participants also walked farther in six-minute tests than the placebo group, and quality-of-life scores improved.
I take the walking test seriously because it examines physical performance. A questionnaire adds people’s reported experience within a controlled trial. The study’s biological-age measurement did not increase, but that measure alone cannot establish that human aging stopped. The authors’ preference for 600 milligrams per day describes their trial; it supplies no personal treatment plan.
Insulin testing in muscle
The Yoshino trial enrolled prediabetic, postmenopausal women and used 250 milligrams per day of NMN for 10 weeks. Muscle insulin sensitivity improved: muscles took up glucose better during controlled insulin testing. Body composition and HbA1c did not change.
That combination deserves careful wording. The insulin response improved, while the test left fat and muscle amounts unchanged. I credit this metabolic finding within its defined population. Claims about weight loss or stronger muscles outrun what this experiment measured.
Mills and aging mice
Mice in the Mills experiment received NMN in drinking water at 100-300 milligrams per kilogram each day for 12 months. They gained less weight as they aged and showed improvements in energy metabolism, insulin sensitivity, eye function and bone density. No toxicity was observed during the experiment.
The range of effects explains the excitement around this paper. I understand the enthusiasm: several aspects of physiology moved together. The species remains essential to the account. Human trials have yet to establish that same breadth of aging benefits, and the human evidence review describes inconsistent translation to clinical outcomes.
NMN and NAD+ metabolism
NMN is one biochemical step away from NAD+. The metabolism review places it within the pathways cells use to replenish their supply. NR reaches that step by first becoming NMN. Much swallowed NAD+ itself breaks down before it can enter cells intact.
Proximity in a pathway makes NMN an interesting candidate. A head-to-head claim of superiority would need a suitable comparison; the trials discussed here test their own ingredients and populations.
The NMN sales dispute
The earlier FDA position excluded NMN from the dietary-supplement definition because drug investigation had preceded supplement use. That position led to a sales-status dispute. It was not a general ban on the molecule.
The reading list contains no later FDA decision settling the current supplement-sales question. A bottle on a shelf carries little legal weight with me. WADA does not prohibit NMN, NR or nicotinamide; sports eligibility and supplement law are separate matters. Legal NAD offers no legal advice.