Introduction

Nicotinamide adenine dinucleotide (NAD) is a indispensable cofactor involved in several redox reactions in all forms of cellular life. It exists in two forms: an oxidized and reduced form abbreviated as NAD+ and NADH respectively.NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can then be used as a reducing agent to donate electrons.Both of these two stabilized form of NAD are marketed as a anti-age nutritional supplement, which is not under FDA regulation at the moment.

How NAD+/NADH works?

NAD+/NADH plays a significant role in the reactions associated with glycolysis, oxidative phosphorylation, and fermentation. Nicotinamide adenine dinucleotide(NAD) effects include the stimulation of dopamine, noradrenaline, and serotonin receptors, by which mechanism it is thought to increase mental alertness and clarity and improve concentration.

In the jet lag study, subjects who received NADH had significantly better cognitive performance and a trend toward reduced sleepiness on the first post-flight day than controls, and a smaller pilot study showed similar trends lasting through the second day. 

In 2000, Guarente's lab reported that NAD fuels the activity of sirtuins, including SIRT1—the more NAD there is in cells, the more SIRT1 does beneficial things. One of those things is to induce formation of new mitochondria. NAD can also activate another sirtuin, SIRT3, which is thought to keep mitochondria (Mitochondria are our cells' energy dynamos. Descended from bacteria that colonized other cells about 2 billion years, they get flaky as we age) running smoothly.

Side effects and Safety

Currently there are not enough human clinical study about Nicotinamide adenine dinucleotide(NAD) in both form NAD+ and NADH.But considering they are naturally exist in all living cell, NADH seems safe for most people when used appropriately and short-term, up to 12 weeks. Most people do not experience any side effects when taking the recommended amount each day, which is 10 mg. 

References:

https://www.webmd.com/vitamins/ai/ingredientmono-1016/nadh

https://en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleotide

https://blogs.scientificamerican.com/guest-blog/beyond-resveratrol-the-anti-aging-nad-fad/

Leonardo Sorci, ... Andrei L. Osterman, in Comprehensive Natural Products II, 2010

Susan L.F. McLellan, in Travel Medicine (Third Edition), 2013

A. Hazra, ... M.J. Snider, in Encyclopedia of Microbiology (Third Edition), 2009