What is NAD? The coenzyme, the plus sign and the B3 connection

No. The 2018 study gave 1,000 mg of nicotinamide riboside daily for 6 weeks and was built mainly to test tolerability and feasibility (per Martens et al., 2018). Blood pressure and arterial stiffness were secondary measures, so the suggestive changes are signals for a larger trial, not findings.

Weeks, not years. The 2018 randomized trial gave 1,000 mg of nicotinamide riboside daily for 6 weeks (per Martens et al., 2018), which is long enough to see NAD+ rise and far too short to show whether that rise changes health over time.

The plus sign denotes the oxidized form. NAD+ picks up electrons to become NADH, then hands them off and returns to NAD+. Both forms are always present and what matters biologically is the ratio between them, which is a detail most supplement marketing skips entirely.

Because the decline could be a cause of age-related dysfunction or a consequence of rising repair demand as damage accumulates (per Abdellatif et al., 2021). Restoring the level would help in the first case and not necessarily in the second, and no trial has yet told the two apart.

NAD cycles constantly between NAD+ and NADH, and the ratio between the two matters more than either form alone. Trials therefore measured NAD metabolites with laboratory methods, which is also why no consumer test has a validated interpretation.

To show that oral nicotinamide riboside reaches human blood at all, across 100 mg, 300 mg and 1,000 mg single doses (per Trammell et al., 2016). That bioavailability result is why precursors, not NAD+ itself, became the research form, and it measured metabolites, not any health outcome.

Declining NAD with age is the observation the whole category rests on, and it is reported consistently across tissues and species. What is less settled is how much of the decline is a cause of aging rather than a consequence of it, which is the question the interventions are really testing.

Not usefully. There is no standard clinical test, no reference range you could interpret, and blood measurement does not necessarily reflect what is happening inside tissues. Any product promising to show your NAD level going up is measuring something whose meaning has not been established.

The B3 vitamers in food, principally niacin and nicotinamide, are the raw material, and they are abundant in meat, fish, poultry, mushrooms and fortified grains. Exercise and avoiding chronic overnutrition are the behavioral levers most often cited. None of that has been shown to change an outcome by raising NAD specifically.

They raise NAD metabolites, which is the best-established claim in the category. What they have not shown is a robust functional benefit in people. A review of the field concluded these compounds are safe and well tolerated and may raise the NAD metabolome, while only limited data support clinical benefit.

Cost for an unproven benefit, and a product market with documented purity problems. Direct oral NAD+ is also the least sensible form, since it is a large molecule that is broken down in digestion, which is why almost all the research uses precursors instead.

Intravenous delivery genuinely bypasses the digestion problem, which is a real mechanistic advantage. What it does not have is comparable trial evidence for safety and efficacy by that route. Bypassing the gut is a mechanism, not a demonstrated outcome, and IV clinics are the loudest voice in this space.

Neither has demonstrated superiority on a clinical outcome, because neither has clinical-outcome data to compare. NR has the longer human trial record. NMN has the more direct position in the pathway and a more turbulent regulatory history.

Possibly not, and that is the uncomfortable center of this category. Trials measured biochemistry rather than subjective experience, so a product can succeed at its stated job and change nothing you would notice. Anyone promising you will feel it has gone beyond the data.