There are theories based on research in test tubes that increased NAD⁺ may provide tumors with energy for faster growth.
In reality, there have been no experiments in live animals showing this.
In fact, all studies in mice and humans have found no increased incidence, severity, or decreased mortality due to cancer.
In response to this question, Dr. Sinclair states: "Johan Auwerx and I only see health benefits and lifespan extension in mice when we give NR or NMN to old mice. Fasting and exercise raise NAD⁺ and they don't accelerate aging or cancer.