NAD+ and aging: older samples held less, but replacing it hasn't proved slower aging.

The aging studies found a loss of NAD+, not a proven remedy

NAD+ supports the work that keeps your cells supplied with energy. This page covers its loss with age and tests of ways to raise the supply. Most findings about slowing aging came from mice. As tissue ages, some proteins consume more NAD+ while cells become less able to remake NAD+ from spent parts, so the supply is used faster and replaced less well than before. In mice, blocking a protein that consumes the supply or providing material to make more raised the supply. People also have less NAD+ in older tissue, but human studies haven't shown slower aging from replacing the supply.

Your treatment choices need evidence from people, beyond those mouse results.

Skin repairs were busier, and older men made less muscle NAD+

The skin study compared people of different ages; nobody received an aging treatment. In the older skin, NAD+ was lower in both forms used during energy release, yet the proteins called on to respond to DNA damage were more active in those samples ^[6]. The repair proteins spend NAD+, which helps explain finding a lower supply alongside more repair activity. More activity doesn't prove the repairs worked better. You can follow the findings in older samples.

A separate study found problems with the supply in older men's muscles.

Researchers examined muscle samples from 119 older men in three groups. Men with muscle loss had fewer of the tiny parts inside cells that release energy. Those parts also worked less well. Their muscles made less NAD+, both from fresh material and by reusing spent material ^[12]. A review links lower NAD+ with poorer energy use and illness, from yeast through people ^[5].

Those muscle samples don't show whether a pill could rebuild your muscles.

Mice kept more NAD+ when a protein could no longer consume it

These experiments concerned mice, not people choosing an aging treatment. A protein on cell surfaces uses up NAD+. With aging and inflammation, the response to injury or infection, the protein consumes more NAD+. Researchers bred mice to lack the protein; those animals retained more NAD+ in old age. The parts of their cells that release energy kept working better. Tests also found less decline in how their bodies handled food ^[2]. A later test prevented the protein from working in older mice. NAD+ increased, with improvements in tests of food use ^[9]. Those results concerned cell work and food handling; they don't establish extra strength or a longer life for you.

Another mouse experiment measured blood sugar and fat in the liver.

Apigenin is a substance found in food. In cells kept in lab dishes, apigenin blocked the protein and raised NAD+. In this experiment, mice on a high-fat diet received 100 milligrams for every kilogram they weighed, with a kilogram being a little more than two pounds of body weight. Those mice controlled blood sugar better and had less liver fat ^[10]. The amount belongs to that mouse experiment and cannot guide your care.

NMN and NR raised blood NAD+; exercise helped muscles replace it

These brief human studies can't settle the effects on your later years. For 60 days, healthy middle-aged adults received 300, 600, or 900 milligrams of NMN a day, giving their cells material to make NAD+ while researchers checked their blood and walking. Their blood NAD+ rose more than in people given placebo, a similar-looking pill containing no NMN. The NMN groups also covered more distance in a timed test and gave better answers about their health. The authors judged 600 milligrams a day best overall after checking those results, not simply the largest blood rise. No safety problems were reported ^[3]. In an eight-week NR study, the blood rise reached 142% at 1000 milligrams a day ^[4].

Walking farther in one test doesn't establish more years in good health.

Exercise was studied separately from those pills. Endurance and strength training raised a protein muscles need to reuse spent NAD+ by 12-30%. The rise was larger in older adults ^[7]. A 2025 review judged the evidence of supplement benefits in people limited. Only a few human studies had confirmed the fall with age. Researchers had also measured NAD+ in few kinds of human tissue ^[15].

Your blood reading can't show how much NAD+ every part of your body has.

Raising NAD has not shown that people look younger

The evidence doesn't show that extra NAD+ makes your skin look younger. Researchers found a lower supply in older people's skin ^[6]. Restoring the supply helped mice, which can't settle a claim about your appearance ^[2][9]. A 2025 review found few firm health benefits in people ^[15].

Those findings don't promise you younger skin or extra years.