In a recent Netflix documentary Don’t Die: The Man Who Wants to Live Forever, tech entrepreneur Bryan Johnson showcases his daily routine, which includes taking over 50 supplements a day—among them are NAD precursors.
These supplements aim to boost NAD, a molecule essential for energy production in our cells. The idea behind this routine is simple: as we age, NAD levels in muscles drop—by as much as 30%—so boosting them might help slow aging and maintain strength.
But new research from the University of Copenhagen suggests that this may not be necessary after all. A team of scientists led by Associate Professor Jonas Treebak published a study in Cell Metabolism showing that even when NAD levels were reduced by 85% in the skeletal muscles of mice, it had no noticeable effect on their health, strength, or aging process.
NAD, short for nicotinamide adenine dinucleotide, is important because it helps mitochondria (the energy factories of our cells) make ATP, the energy currency of the body.
It’s involved in many other cellular functions too, so it’s been a popular target in anti-aging research. But there’s still a lot scientists don’t fully understand, including how low NAD can go before it starts to affect muscle function or metabolism.
To answer this, the Copenhagen team genetically engineered mice whose NAD levels could be sharply lowered only in their skeletal muscles after they reached adulthood.
This clever approach allowed the researchers to isolate the effects of NAD depletion in mature muscle, rather than confounding it with developmental issues that might arise if NAD were low from birth.
The results were surprising. Despite having extremely low NAD levels in their muscles, the mice had no reduction in muscle size, strength, or endurance. Their mitochondria, gene activity, protein levels, and even DNA markers associated with aging remained normal.
The mice lived their lives with no obvious signs of early aging or metabolic issues due to the NAD drop in muscle.
The only differences seen were slight increases in stress signals during exercise and small changes in how their bodies used energy. But these didn’t translate into any real decline in performance or health.
Sabina Chubanava, who helped lead the study as part of her Ph.D. and postdoctoral research, explained that these results challenge the belief that NAD decline directly causes muscle weakness and aging. In fact, muscle function appears to be quite resilient, even when NAD is severely reduced—much more than the typical decrease seen with aging.
So what does this mean for the growing trend of NAD supplements? While the molecule is undeniably important, this study suggests that taking NAD-boosting supplements might not provide the muscle benefits that many hope for—at least not in healthy individuals.
The findings don’t rule out benefits in people with muscle diseases or other conditions, but they cast doubt on the idea that boosting NAD alone can prevent normal age-related decline.
In short, while NAD still plays a key role in cell function, this research suggests that the body may be more adaptable than previously believed. For now, the science does not support the hype around NAD supplements as a guaranteed path to youthful muscles or longer life.
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The research findings can be found in Cell Metabolism.
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