Nicotinamide (NA) and nicotinamide riboside (NR) are two distinct forms of vitamin B3, also known as niacin. Both compounds serve as precursors to nicotinamide adenine dinucleotide (NAD+), a coenzyme present in every living cell. NAD+ plays a broad role in cellular metabolism and energy production, influencing numerous biochemical reactions within the body. While both NA and NR contribute to maintaining NAD+ levels, they possess different properties and are utilized through distinct metabolic pathways.
Nicotinamide Explained
Nicotinamide, often referred to as niacinamide, is a common form of vitamin B3 found in various foods and widely used in supplements. It is present in dietary sources such as meat, poultry, fish, nuts, seeds, grains, mushrooms, and leafy green vegetables. Nicotinamide acts as a precursor in the salvage pathway for NAD+ synthesis, which is a major route for NAD+ production in mammalian tissues.
Within this pathway, nicotinamide is converted to nicotinamide mononucleotide (NMN) by the enzyme nicotinamide phosphoribosyltransferase (NAMPT). NAMPT is considered a rate-limiting enzyme in this conversion process. Subsequently, NMN is converted into NAD+ by nicotinamide mononucleotide adenylyltransferases (NMNATs).
Nicotinamide Riboside Explained
Nicotinamide riboside (NR) is a more recently identified form of vitamin B3 that has garnered interest due to its potential to increase NAD+ levels. NR is found naturally in small amounts in certain foods like milk. It is also available as a dietary supplement.
NR follows a unique metabolic pathway to convert into NAD+. It is first phosphorylated by nicotinamide riboside kinases (NRK1 and NRK2) to form NMN. This NMN is then converted to NAD+ by NMNATs, similar to the final step in the nicotinamide pathway.
Comparing Their Mechanisms and Benefits
The primary difference between nicotinamide and nicotinamide riboside lies in their initial steps of conversion to NAD+. Nicotinamide enters the salvage pathway by being converted to NMN through the NAMPT enzyme, which can be a rate-limiting step. Nicotinamide riboside, on the other hand, bypasses this NAMPT-mediated step by being directly phosphorylated by NRK enzymes to form NMN. This distinct entry point for NR is thought to influence its efficiency in raising NAD+ levels.
Both compounds ultimately aim to increase NAD+ levels, which offers shared benefits. Increased NAD+ supports cellular energy production by playing a role in mitochondrial function and the conversion of food into ATP, the cell’s energy currency. NAD+ also participates in DNA repair mechanisms, helping to maintain genomic stability and cellular health. Enhanced NAD+ levels are associated with metabolic support, including improved glucose regulation and insulin sensitivity, and are being explored for their role in healthy aging processes.
Choosing Between Nicotinamide and Nicotinamide Riboside
Nicotinamide has a longer history of use and is more widely available and often less expensive than nicotinamide riboside. Nicotinamide also has established uses, particularly in dermatology for skin health due to its anti-inflammatory properties.
Nicotinamide riboside, while newer to the market, has been the subject of increasing research interest regarding its potential to efficiently boost NAD+ levels and its emerging role in metabolic and anti-aging research. While both are generally considered safe, some studies suggest NR is well-tolerated at doses up to 1000-2000 mg per day, with mild side effects like nausea or bloating possible. It is always advisable to consult with a healthcare professional before beginning any new supplement regimen to determine the most suitable option for individual needs and health goals.