Are NAD Precursors Just for Old People?
No, NAD precursors are not just for when you get old.
For sure, aging is one condition that drives down NAD levels, in animals and humans alike. And when it comes to reproductive health, the effects of aging begin earlier than it might appear. But aging is not the only thing that drives down NAD levels.
NAD levels can be reduced episodically and temporarily, too, by a wide variety of common metabolic stresses, such as overeating, obesity, alcohol consumption, vigorous exercise, sun exposure, time zone disruption, postpartum, viral infection, reactive oxygen, DNA damage, bright light, even loud noises:
NAD+ consumption is not constant. Under some circumstances, such as...upon DNA damage, NAD+ is consumed at a higher rate and, therefore, NAD+ synthesis rates also need to increase to maintain NAD+ levels..." ---
That's because your body initiates repair processes in response to various metabolic insults, and those repair processes consume NAD, leaving you, at least temporarily, with less.
This study found that when NR was not available to muscle cells that had been injured -- not due to old age -- repair time was delayed:
During regeneration, muscle stem cells (MuSCs) from [mice with both NRK1 and NRK2 knocked out] hyper-proliferate but fail to differentiate. Double NRK Knockout also alters the recovery of NAD+ during muscle regeneration as well as mitochondrial adaptations and ECM remodeling required for tissue repair. These metabolic perturbations result in a transient delay of muscle regeneration which normalizes during myofiber maturation at late stages of regeneration via over-compensation of anabolic IGF1-Akt signaling.