What works better to raise NAD+: NMN or NR?

The only direct head-to-head comparison study in humans (65 healthy adults, randomised) shows that NMN and NR raise blood NAD+ levels to virtually the same extent after 14 days of supplementation. There is therefore no statistically detectable winner. Nicotinamide, a cheaper related compound, performed worse: after 14 days there was no significant sustained rise in NAD+, only a short-lived, transient effect.

Both compounds do genuinely raise NAD+. In an earlier pilot study, NR showed an almost 2.7-fold higher blood NAD+ concentration after a single dose, and the increase was dose-dependent. That pilot study was partly funded by the manufacturer of NR, which may be relevant when interpreting the results. For NMN, a separate randomised study in overweight adults (aged 45 and over, 2000 mg/day for 28 days) confirms that NAD+ concentrations rise substantially; in that study, weight, blood pressure and LDL cholesterol also fell significantly, although muscle strength and insulin sensitivity did not improve.

How does it work exactly? The same comparative study offers a clue that NMN and NR act partly through gut bacteria: these convert both compounds into nicotinic acid, which then produces NAD+. Whether this is precisely what happens in living human tissue has not yet been fully established, but it suggests that the state of your gut microbiome plays a role.

The question of whether higher NAD+ levels also lead to measurable health benefits, such as improved fitness, vascular function or disease prevention, remains unanswered. Review studies note that the effects in humans have so far been smaller than was expected on the basis of animal research. Both supplements were well tolerated at the doses and study durations investigated, but little is yet known about long-term safety at high doses.