NADH

NADH and its oxidized counterpart NAD+ form a redox pair built from two nucleotides joined through their phosphate groups ^[4]. During metabolism, energy-rich molecules such as glucose and fatty acids are oxidized, and the electrons released are captured by NAD+ as it is reduced to NADH in pathways including glycolysis and the citric acid cycle ^[4]. Within mitochondria, NADH is then re-oxidized by the electron transport chain, driving proton pumping and the synthesis of ATP through oxidative phosphorylation ^[4]. The same coenzyme also participates in DNA repair and cellular signaling, and NAD+ levels are known to decline with age ^[4].

As a supplement, NADH has been studied mainly for fatigue and neurodegenerative disease. In chronic fatigue syndrome, a condition linked to mitochondrial and oxidative disturbances, a randomized trial combining oral NADH with coenzyme Q10 reported reductions in fatigue scores alongside improvements in energy-related biochemical markers ^[1]. Results for NADH on its own have been weaker; another controlled trial found that oral NADH did not improve most measures of fatigue or function, with only modest effects on anxiety and exercise heart rate ^[2]. In Parkinson's disease, early open-label work by Birkmayer described clinical improvement in a majority of patients ^[3], but that work was uncontrolled, and later placebo-controlled testing of NADH did not confirm a meaningful benefit.

NADH is marketed as an over-the-counter supplement, typically in stabilized oral tablets, sometimes with the claim that it boosts cellular energy. A practical uncertainty is bioavailability, since NADH is a large, charged molecule that may be degraded in the digestive tract, and it is unclear how much intact coenzyme reaches tissues after oral intake. Overall the human evidence is modest and inconsistent, and NADH supplements are not approved treatments for any disease.

NADH appears well tolerated, with occasional mild GI upset or jitteriness at higher doses. It has a good short-term safety record. Long-term effects and true tissue delivery remain poorly characterized.