Longevity supplements: what absorption and NAD+ results can tell you

Text written with the help of AI.

Better absorption and a higher blood level can show that a supplement has a biological effect. They do not, by themselves, show that it preserves health or extends life. The distinction becomes clearer when the claim is tied to the outcome a human study measured.

Magnesium: how much more was absorbed?

Magnesium is an essential nutrient. US recommended daily intakes for adults over 40 are 320 mg for women and 420 mg for men, including magnesium from food. Those are nutritional requirements, not doses shown to slow ageing. Assessing whether someone needs more also takes clinical context: serum magnesium does not reliably represent all the magnesium in the body, but a normal result is not evidence of a hidden deficiency. NIH Office of Dietary Supplements

A small trial of prebiotic fibre illustrates how to read an absorption claim. In a randomised crossover study of 11 postmenopausal women, average magnesium absorption was 30.2% with placebo and 33.9% with short-chain fructo-oligosaccharides. The difference was 3.7 percentage points, or about 12% relative to the placebo value. It was not a threefold increase. Tahiri and colleagues, 2001

A second crossover study in 15 postmenopausal women reported increased magnesium and calcium absorption with an oligofructose-enriched inulin mixture; responses varied between participants. Holloway and colleagues, 2007

These trials studied particular fibres and mineral absorption. They did not compare magnesium supplement formulations or establish that improved absorption prevents disease. When a product promises “better absorption”, the useful questions are what was absorbed, how large the difference was, and whether the claimed health benefit was measured.

NMN: a biological response and a functional test

Nicotinamide mononucleotide, or NMN, is a precursor used to produce NAD+, a molecule involved in cellular metabolism. Raising its measured concentration establishes a biological response. Whether that response improves function requires a separate test.

In a 2026 placebo-controlled trial, adults aged 65 and over took 1,250 mg of NMN daily for 24 weeks. NAD+ and related metabolites increased. The researchers found no significant improvement in hearing, the primary outcome, or in physical performance. Some apparent secondary changes did not remain statistically significant after adjustment for multiple comparisons. The supplier funded the study, and three authors were company employees. Igarashi and colleagues, 2026

An earlier trial tested 250 mg daily for ten weeks in 25 postmenopausal women with prediabetes and overweight or obesity. It found improved muscle insulin sensitivity using a controlled laboratory procedure, while body composition and several routine metabolic measures did not improve relative to placebo. Yoshino and colleagues, 2021

The trials involved different participants, doses and outcomes. The insulin-sensitivity finding should remain an insulin-sensitivity finding; it cannot establish better hearing, stronger legs or longer life. Equally, the later trial does not prove that NMN can never have a clinical benefit. Neither trial demonstrated that it extends human life.

A blend: evidence for the finished product

A sachet containing many ingredients may be easier to use than several separate products. To assess a health claim for that mixture, evidence about its individual ingredients is insufficient: the finished formula needs to be tested.

DoNotAge’s company-hosted report describes a 60-day randomised trial comparing its 15-ingredient formulation with placebo. It says 30 adults enrolled, 28 completed the study, and questionnaire scores for wellbeing and fatigue improved more in the supplement group. DoNotAge Research Team, undated report

This is preliminary evidence. The company authored and hosts the report; the published methods do not give exact ingredient doses, the analysis covers completers, and people taking prescription medicines for chronic conditions were excluded. Those limits matter when considering its relevance to older adults. The reported questionnaire changes do not establish disease prevention or slower ageing. A comparison with placebo also cannot show that all 15 ingredients are needed; that would require a direct comparison with a simpler formulation.

What the evidence can guide

Before trying a product, name the benefit you want and look for a human study that measured it in a relevant population. Check the formulation, dose, duration and outcome. If the evidence ends at absorption or NAD+, it leaves the health benefit you care about unresolved.

Personal observations may help you decide whether a product is tolerable or worth continuing. They cannot establish that it slows ageing. Safety also depends on circumstances: supplemental magnesium can cause diarrhoea, interact with medicines and pose greater toxicity risks when kidney function is impaired. A pharmacist or clinician can review the full product list in those situations. NIH Office of Dietary Supplements

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