NAD+ (Nicotinamide Adenine Dinucleotide) is the central coenzyme of cellular energy metabolism, and its decline with age is a primary driver of the fatigue, cognitive decline, and metabolic dysfunction that men experience in their 40s and beyond. For men specifically, NAD+ has additional relevance through its interactions with testosterone production, mitochondrial health in muscle tissue, and the sirtuins that regulate longevity pathways.
NAD+ and Testosterone Production
Testosterone biosynthesis in Leydig cells is an energetically demanding process that requires robust mitochondrial function. NAD+ is essential for the electron transport chain that powers mitochondrial ATP production. As NAD+ levels decline with age, Leydig cell mitochondrial function deteriorates, contributing to the age-related decline in testosterone production (approximately 1-2% per year after age 30).
SIRT1 and Androgen Receptor Sensitivity
SIRT1 — the longevity-associated deacetylase that requires NAD+ as its substrate — directly modulates androgen receptor sensitivity. Higher SIRT1 activity (driven by higher NAD+ levels) is associated with improved androgen receptor function, meaning that NAD+ restoration may improve the cellular response to testosterone even at the same circulating levels.
Muscle Mitochondria and Performance
Male skeletal muscle has a higher mitochondrial density than female muscle, making it particularly sensitive to NAD+ levels. NAD+ activates SIRT3 in muscle mitochondria, which deacetylates and activates key enzymes of oxidative metabolism. The result is improved mitochondrial efficiency, reduced fatigue, and better exercise performance and recovery.