From Nutrient Journal
NADH stands for nicotinamide adenine dinucleotide (NAD) + hydrogen (H) and is a naturally‐occurring and vital compound found in all living cells of plants, animals, and humans. NADH plays an important role in the chemical process that generates energy. It is the metabolically active form of Vitamin B-3, also known as Niacin. NADH is used as medicine as well as for improving mental clarity, memory, improving athletic endurance, and treating chronic fatigue syndrome.
Effects of NADH on Physical Performance
Theoretically, NADH could have many beneficial effects for athletes such as increased ATP production by muscle cells [1,2], antioxidant activity, enhanced body’s immune system, repairing damaged and wounded cells, repairing cellular DNA, etc.
… in Patients With Chronic Fatigue Syndrome
A few short studies in patients with chronic fatigue syndrome reported minor effects. A study by Santaella and others  compared oral nicotinamide adenine dinucleotide to conventional therapy for chronic fatigue syndrome. Twelve patients that received 5-10 mg/day NADH exhibited dramatic reduction of the mean symptom score in the first trimester, however the difference did not reach statistical significance in the subsequent trimester. Forsyth et al.  reported that 31% of patients receiving 10 mg/day NADH responded favorably in contrast to 8% of patients from placebo group. A bit larger study in 77 patients reported that 20 mg/day of oral NADH is able to decrease anxiety and maximum heart rate, after a stress test in patients with chronic fatigue syndrome but the treatment did not modify fatigue or functional performance .
… in Healthy Population
A well-designed, small-scale study examined the effects of 30 mg NADH as tablets per day in eight men for 4 weeks . Researchers concluded that NADH supplementation for 4 weeks had no effects on VO2max or maximal anaerobic running time. However, counter-movement jump performed at rest and 2 min after the aerobic test was higher in NADH group. A small, open label trial conducted by Birkmayer Institute concluded that 5 mg/day NADH for 4 weeks improved maximum performance .
More unbiased, large-scale and long-term clinical studies should be conducted in order to further asses the usage of NADH for physical performance as Birkmayer Laboratories of Vienna, Austria funded majority of these studies which also sells and promotes their NADH products.
Effects on Cognition
Although sold as memory enhancer, Rainer and co-workers  concluded that 10 mg/day NADH in 25 patients with mild to moderate dementia is unlikely to achieve cognitive improvements as defined by established psy-chometric tests. No improvement in mental performance was also reported by Mero et al. .
NADH is unstable in acidic conditions, contrary to NAD+ which is stable . NADH appears to be equivalent to NAD+ and Nicotinamide when given intraperitoneally but at acidic pH (such as gastric juice) NADH was reported to be rapidly converted into an unknown compound . It seems that very high doses of NADH (50 mg/kg and higher) increase the concentration of NADH in the rat cortex [10,11]. Since NADH is used as therapeutic and supplement, better understanding of its fate is needed.
Side Effects of NADH
NADH appears to be safe for most people when taken in small amounts for up to 12 weeks as no serious adverse events have been reported.
(Other common names: B-DPNH, BNADH, Coenzyme 1, Reduced Coenzyme 1, Enada, NAD, Nicotinamide Adénine Dinucléotide, Nicotinamide Adenine Dinucleotide Hydrate, Reduced DPN, Reduced Nicotinamide Adenine Dinucleotide)
- Pelzmann, Brigitte, et al. “NADH supplementation decreases pinacidil‐primed IK (ATP) in ventricular cardiomyocytes by increasing intracellular ATP.” British journal of pharmacology 139.4 (2003): 749-754.
- Birkmayer, J. G. D., and W. Birkmayer. “The coenzyme nicotinamide adenine dinucleotide (NADH) as biological antidepressive agent: experience with 205 patients.” New Trends Clin Neuropharmacol 5.3-4 (1991): 75-86.
- Santaella, María L., Ivonne Font, and Orville M. Disdier. “Comparison of oral nicotinamide adenine dinucleotide (NADH) versus conventional therapy for chronic fatigue syndrome.” Puerto Rico health sciences journal 23.2 (2004).
- Forsyth, Linda M., et al. “Therapeutic effects of oral NADH on the symptoms of patients with chronic fatigue syndrome.” Annals of Allergy, Asthma & Immunology 82.2 (1999): 185-191.
- Alegre, J., et al. “[Nicotinamide adenine dinucleotide (NADH) in patients with chronic fatigue syndrome].” Revista clinica espanola 210.6 (2010): 284-288.
- Mero, Antti, et al. “Effects of nicotinamide adenine dinucleotide hydride on physical and mental performance.” Journal of sports sciences 26.3 (2008): 311-319.
- Birkmeyer, J. G. D., and P. Vank. “Reduced coenzyme 1 (NADH) improves psychomotoric and physical performance in athletes.” New York: Menuco Corp (1996).
- Rainer, M., et al. “No evidence for cognitive improvement from oral nicotinamide adenine dinucleotide (NADH) in dementia.” Journal of neural transmission 107.12 (2000): 1475-1481.
- Kimura, Naoko, et al. “Comparison of metabolic fates of nicotinamide, NAD+ and NADH administered orally and intraperitoneally; characterization of oral NADH.” Journal of nutritional science and vitaminology 52.2 (2006): 142-148.
- Rex, André, Mike‐Percy Hentschke, and Heidrun Fink. “Bioavailability of Reduced Nicotinamide‐adenin‐dinucleoti de (NADH) in the Central Nervous System of the Anaesthetized Rat Measured by Laser‐Induced Fluorescence Spectroscopy.” Pharmacology & toxicology 90.4 (2002): 220-225.