NAD (nicotinamide adenine dinucleotide) is a key coenzyme in energy metabolism, it is widely present in all kinds of life, it has two forms, respectively, NAD+ and NADH (hereinafter collectively referred to as NAD). NAD plays the role of accepting and providing protons and electrons in material metabolism. Without NAD, electron transfer cannot be carried out, and the metabolism of all energy substrates will be stalled. Below is a picture of the electron transport chain process in which NAD is involved in glycolysis. When the aldehyde group of glyceraldehyde 3-phosphate is oxidized to the carboxyl group, the energy of the oxidation process is stored in the molecule of ATP. NAD+ must be involved in this process.

One of the key characteristics of skeletal muscle is its high adaptability. From the perspective of energy, muscles can quickly start the catabolic mode and mobilize substrates to promote energy production when they exercise or contract, and immediately switch to the anabolic mode after the end of exercise, up-regulate the anabolic signal through various pathways, promote the synthesis of substances to supplement the consumption of substrates, and gradually return to the resting state after the supplementation of substrates.

Given that skeletal muscle is a major consumer of energy, the consumption of NAD in order to meet the energy requirements of skeletal muscle is also huge. NAD can be synthesized in the body from raw materials such as tryptophan, niacin (also known as vitamin B3), and niacinamide in the liver, kidneys, skeletal muscle, and certain immune cells. For skeletal muscle, the synthesis of NAD is more dependent on the metabolic pathway of niacinamide, because the synthesis of NAD through niacinamide is faster and shorter, and essentially can better meet the energy needs of skeletal muscle.

With the increase of age, the amount of NAD+ in human skeletal muscle that can accept electrons is gradually decreasing. Data show that the content of NAD+ is significantly lower in the muscles of elderly people aged 65-80 years, and the muscle strength and physical function of elderly people in this age group are also significantly weaker than that of younger subjects. In animal studies, 15-month-old mice had significantly less NAD+ in their gastrocnemius muscles than 7-month-old controls, and in another study, 25-month-old mice had 13% less NAD+ in their soleus, quadriceps, and gastrocnemius muscles than 3-month-old controls. Many experiments have shown the fact that increasing age leads to increased consumption of NAD+.

For athletes, skeletal muscle growth, repair and energy supply are two of the most critical factors in determining athletic performance, and NAD+ has a profound impact on both aspects. Therefore, logically, supplementing NAD+ or supplementing raw materials to increase the synthesis of NAD+ is a reasonable nutritional strategy. In fact, as early as 1995, there were studies on endurance athletes supplementing with NAD (in the form of NADH), and the results found that the supplementation of athletes during training decreased oxygen consumption, increased respiration, decreased carbon dioxide exhalation, and decreased lactate levels. The reason for such a significant change may be that the energy supply level of ATP is increased due to the supplementation of NAD-related supplements. These changes suggest that athletes can oxidize carbohydrates more efficiently to fuel performance, and can continue to exercise for longer.

In addition to supplementing NAD through supplements, it can also be carried out through dietary nutrition. As we said earlier, in addition to niacinamide, the precursors of NAD include tryptophan and niacin, so supplementing foods rich in tryptophan and niacin can also effectively increase the content of NAD in the body. Foods rich in tryptophan include dairy products, tuna, poultry, oats, nuts, whole wheat bread, chocolate, etc. Foods rich in niacin include red meat, poultry, fish, brown rice, nuts, beans, and bananas. In addition, exercise itself also stimulates the body to increase the level of the total NAD pool.