What is the controversy with NAD+?

NAD+ is a substance every cell in the body needs for energy and repair. Your NAD+ levels decline as you age, through a combination of reduced production and increased consumption. Many researchers view this as a contributing factor in ageing.

NAD+ supplements, such as NMN or NR (different forms of the same precursor), measurably raise your NAD+ levels in blood and tissues. That much is reasonably well established. In mouse and worm studies, higher NAD+ also led to a longer, healthier lifespan. But an animal result is not yet a human benefit, and that is precisely where the debate lies.

Because higher NAD+ levels in humans have so far not reliably translated into noticeable health gains. Whether your fitness, memory or metabolism genuinely improves has not been demonstrated. Existing human studies are too small and too short to draw firm conclusions^1,2,3.

There is also a concrete safety signal. In cell and mouse studies, NMN protected pancreatic cancer cells against several chemotherapy agents and supported tumour growth. NAD+ supplements such as NAM showed a similar but weaker effect. Whether this applies to humans is not yet known, but anyone with active cancer or an elevated risk would be wise to discuss this with a doctor first⁴.

The biology is also more complex than was long assumed. Your gut bacteria process supplements in ways that influence how they work. Furthermore, each cell contains multiple separate NAD+ pools, for example in the mitochondria and the cell nucleus, each regulated independently. This makes it difficult to predict exactly what a supplement does. On top of that, several lead authors of influential review articles have financial ties to companies that sell these supplements, through patents, advisory roles or equity stakes^5,6. That does not automatically make their work wrong, but it is something to factor in.