No Evidence Shows That Oral NAD+ Supplementation Increases NAD+ Levels in Humans

Key Takeaways:

• No published human studies show that oral NAD+ supplementation increases NAD+ levels, a conclusion recently acknowledged by the National Advertising Division (NAD) of the Better Business Bureau (BBB). 

• NAD+ cannot directly enter cells—it must first be broken down into smaller precursors, which cells then use to rebuild NAD+.

• Clinically studied NAD+ precursors are the most efficient way to effectively boost NAD+ levels in humans.

Nicotinamide adenine dinucleotide (NAD+) is an essential molecule that powers cellular energy production, supports DNA repair, and plays a central role in healthy aging. Over the past few years, NAD+ has become one of the most talked-about molecules in wellness and longevity science. Naturally, this has led many supplement companies to market “oral NAD+” products, claiming they can directly raise NAD+ levels in the body. While the concept is appealing, the scientific evidence does not support these claims.

As we age, NAD+ levels naturally decline, sparking interest in ways to restore them. No published human studies have shown that oral NAD+ supplementation increases NAD+ levels. This conclusion is supported by several published studies and review articles,^1,2 and was recently reinforced by the National Advertising Division (NAD), an independent self-regulatory body overseeing truth in advertising. The NAD specifically noted the absence of published human data showing that oral NAD+ increases NAD⁺ levels, stating:

“...there did not appear to be any human clinical studies on the oral ingestion of NAD+, whether liposomal or otherwise.”

The reason is straightforward: NAD+ cannot directly cross cell membranes. Its large size and two negatively charged phosphate groups prevent it from entering cells intact. Instead, the body must produce NAD+ internally from smaller, more stable building blocks—known as NAD+ precursors, including nicotinamide riboside (NR). Once inside the cell, these precursors are used to reassemble NAD+, allowing it to perform its essential biological functions.

For consumers looking to meaningfully support NAD+ levels, the science consistently points to clinically studied NAD+ precursors, not oral NAD+ itself. These precursors have been proven to raise NAD+ in human cells and tissues, providing a reliable, evidence-based way to support cellular health and vitality.

For a deeper dive into why direct NAD+ supplementation is inefficient and to learn the most effective ways to increase NAD+, read our in-depth article: Why You Can't Take NAD+ Directly—and the Best Precursor to Boost NAD+ Effectively.

1. Vinten, K. T., Trętowicz, M. M., Coskun, E., Weeghel, M. van, Cantó, C., Zapata-Pérez, R., Janssens, G. E., & Houtkooper, R. H. (2025). NAD+ precursor supplementation in human ageing: clinical evidence and challenges. Nature Metabolism, 1–17. https://doi.org/10.1038/s42255-025-01387-7
   
2. Nikiforov, A., Dölle, C., Niere, M., & Ziegler, M. (2011). Pathways and Subcellular Compartmentation of NAD Biosynthesis in Human Cells FROM ENTRY OF EXTRACELLULAR PRECURSORS TO MITOCHONDRIAL NAD GENERATION*. Journal of Biological Chemistry, 286(24), 21767–21778. https://doi.org/10.1074/jbc.m110.213298