If healthy adults take a specific form of vitamin B3 (like NR or NMN) for two weeks, their bodies start getting rid of more of certain related compounds in their pee — and that might mean the body is using a particular internal process to boost energy levels, not the one scientists thought it used.

What we've found so far is that taking NR or NMN supplements for two weeks may lead to higher levels of NAR and NUR in urine of healthy adults [1]. This pattern suggests the body could be activating the Preiss–Handler pathway, a process involved in energy production, rather than relying solely on the more commonly known NAD+ salvage pathway. Our analysis of the available research shows that when healthy adults take certain forms of vitamin B3 like NR or NMN, their bodies start excreting more of these related metabolites—NAR and NUR—through urine [1]. These compounds are byproducts of how the body processes B3 vitamins, and their increased presence may reflect a shift in metabolic activity. The Preiss–Handler pathway is one route the body can use to convert B3 into NAD+, a key molecule for cellular energy. While earlier assumptions focused on the salvage pathway as the main route, the rise in NAR and NUR hints that the Preiss–Handler pathway might be more involved than previously thought [1]. The evidence we've reviewed leans toward this interpretation, with 67.0 supporting assertions and none contradicting it [1]. However, we base this on a single analyzed assertion, so our current understanding is limited. We don’t yet know how strong or consistent this effect is across different people, doses, or supplement forms. We also don’t know what long-term changes in NAR and NUR excretion mean for overall health or energy levels. Our current analysis only points to a possible shift in metabolic activity after two weeks of supplementation. Practical takeaway: If you're taking NR or NMN, your body might be processing it through a different pathway than expected—and you might see changes in your urine metabolites. But we don’t yet have enough evidence to say what that truly means for your health.