What have studies shown about NAD+ and aging?
Older tissue holds less NAD+. Raising the blood level hasn’t been shown to slow age.
Does NAD+ fall as people grow older?
Yes, NAD+ does fall as people grow older. Reviews put the loss between 10% and 50% in body tissue [10]. One body protein breaks down more NAD+ with age. DNA repair also spends more of the supply. Human skin showed the same drop [7]. No human study found that raising NAD+ turns back age. The loss is real, but the cure claim isn’t.
What did older human skin show about NAD+?
Small skin samples from older people held less NAD+. They also had more DNA repair work [7]. Extra repair work spends NAD+. A review found less NAD+ in skin, brain, liver, muscle, and blood. It put the fall near 10-50% across adult life [10]. The review found far more mouse studies than human ones.
The age-linked drop is clear, though its exact size isn’t.
Which age changes can lower NAD+?
Reviews give three reasons for the age-linked loss [10]. First, one protein breaks apart more NAD+ with age. Mice without that protein kept more NAD+. Their cell parts also made energy better [2]. Second, DNA damage calls for more repair. That repair work uses NAD+ [7][13]. Third, the body gets worse at rebuilding NAD+ from old parts [10].
Old cells can make nearby tissue sore and swollen. That starts even more NAD+ breakdown. In some mice with low NAD+, DNA and the cell parts that make energy stopped working together as well [5].
Can NAD+ help cell care during aging?
Some cell-care proteins need NAD+ to work [6]. When NAD+ falls, those proteins do less. In mice, greater work by one such protein went with longer life. Blood sugar and fat were also controlled better [6].
Those findings raised a simple hope. More NAD+ might restore some cell care. Mouse studies support that idea [5][6]. Human studies haven’t shown a longer life.
Has NAD+ made people look younger?
No trial has found that NAD+ changes how people look. Older human skin held less NAD+ as DNA repair rose [7]. Raising blood NAD+ has not changed people’s looks in a study. Longer life and healthier tissue appeared only in animals [6][9]. A 2025 review found little proof of benefit in people [14].
Looking younger remains an unproved claim.
What can’t NAD+ aging studies answer yet?
Human trials show that NMN and NR can raise blood NAD+ [3][4]. Neither has been shown to slow age or stop disease [14]. Most hopeful results came from mice. Mouse findings point to questions for human studies. They don’t predict what will happen to you.
A 2025 review found few useful human studies. Any health gains were small or unclear [14]. A higher blood number isn’t the same as a longer, healthier life.