Almost every NAD product references ageing. It is worth understanding precisely what the underlying observation is.
The observation
Studies measuring NAD in tissue have generally found lower concentrations in older subjects than in younger ones. This has been reported across several tissue types and in both animal and human samples.
What that establishes
A correlation. Older tissue tends to show less NAD.
What it does not establish
It does not establish that lower NAD causes the things we associate with ageing. Correlation in biology frequently runs both ways, or is driven by a third factor entirely. Declining NAD could be a consequence of other age-related changes rather than a cause.
It also does not establish that raising NAD by any particular route reverses or slows anything. That would require intervention studies in people, measuring outcomes that matter, with adequate controls.
Why we are careful
The step from "levels decline with age" to "take this and feel younger" skips several pieces of evidence that do not currently exist. We are not going to pretend otherwise, and you should be sceptical of brands that do.
