NAD Supplements: Can They Really Slow Aging?

Why are NAD supplements attracting anti-aging interest?

In an October 8 book review in The BMJ, Richard Smith examines Seamus O'Mahony's critique of the longevity industry and its promises. The article is commentary about the field, rather than a clinical trial. It raises a practical question for consumers: does a product have evidence that people become healthier, or primarily evidence that it changes a laboratory measurement? [BMJ book review](https://www.bmj.com/content/395/bmj-2026-101072).

Nicotinamide adenine dinucleotide, usually written NAD+, participates in energy metabolism and supports enzymes involved in cellular maintenance. Nicotinamide riboside, or NR, and nicotinamide mononucleotide, or NMN, are compounds the body can use to produce it. A systematic review published in Aging Research Reviews found that human supplementation studies commonly increased NAD-related measurements, while effects on clinical and functional outcomes varied. This distinction matters: demonstrating that a substance reaches a biological pathway is an early research milestone, not proof of healthier aging. [Systematic review of NAD supplementation](https://doi.org/10.1016/j.arr.2026.103057).

What have human trials of NR and NMN actually found?

A 2018 randomized, blinded crossover trial in Nature Communications enrolled 30 healthy adults aged 55 to 79; 24 completed the study. Participants received NR and placebo for six weeks each. NR increased NAD-related measures and was generally well tolerated during the study, but researchers did not find improved blood glucose regulation or insulin sensitivity. The trial supported further investigation of physiological effects; its size and duration could not establish protection against diseases developing over many years. [Martens and colleagues' NR trial](https://doi.org/10.1038/s41467-018-03421-7).

A separate trial published in Science in 2021 studied 25 postmenopausal women with prediabetes and overweight or obesity. After 10 weeks, NMN improved a laboratory measure of insulin sensitivity in skeletal muscle. However, benefits did not extend across the other metabolic outcomes assessed, including body composition and liver insulin sensitivity. This was a potentially useful biological finding in a specific population. It did not demonstrate diabetes prevention, establish benefits for healthy adults generally, or measure whether participants lived longer. [Yoshino and colleagues' NMN trial](https://doi.org/10.1126/science.abe9985).

What evidence would justify stronger longevity claims?

The next research question is whether biochemical changes translate into outcomes people can recognize: maintaining mobility, avoiding illness, preserving independence or living longer. These outcomes are related, but they are not interchangeable. A treatment might improve one aspect of function without extending life. The mixed clinical findings identified in the NAD supplementation review therefore support continued investigation, while leaving broad consumer claims about reversing aging unproven. [Review of clinical and preclinical evidence](https://doi.org/10.1016/j.arr.2026.103057).

Safety also needs a longer view. Good tolerability during a small, brief trial cannot exclude uncommon adverse effects or problems emerging after years of use. Results obtained with a particular ingredient and formulation also do not automatically apply to every supplement blend. For someone considering these products, the useful discussion with a clinician concerns the intended benefit, existing conditions, other medicines and the evidence for that exact intervention. The early NR trial offers information about short-term tolerability, but cannot establish the safety of lifelong supplementation. [NR trial methods and safety findings](https://doi.org/10.1038/s41467-018-03421-7).