NAD+ levels decline 50% between age 20 and 60, primarily due to increased CD38 expression in aging immune cells. Quercetin is one of the most potent natural CD38 inhibitors identified, with IC50 values in the 10–50 μM range achievable with phytosome supplementation. Combined with NMN (which replenishes NAD+ via the salvage pathway), this creates a supply-and-demand NAD+ optimization stack.

How much does the quercetin + NMN combination increase NAD+ vs NMN alone?

Human trial data for the combination does not yet exist. Mechanistically, quercetin should prevent CD38 from consuming the NAD+ that NMN produces, resulting in greater net NAD+ accumulation — but the magnitude is not quantified in humans.

Can I substitute NR (nicotinamide riboside) for NMN?

Yes. NR and NMN both effectively raise NAD+ levels; they differ in transport mechanisms (NR uses nucleoside transporters; NMN may use a different pathway). Both are appropriate. NR is typically lower cost per effective dose.