Also said vitamin B3 constitutes, in truth, a complex of three elements; respectively:
- Niacin (chemical formula C6H5NO2) or nicotinic acid - pyridincarboxylic acid group;
- Nicotinamide (NAM) or niacinamide - nicotinic acid amide (niacin + amide).
- Nicotinamide riboside (NR) - pyridine nucleoside, recognized as a vitamin B3 factor only in 2004.
Vitamin PP is in fact a precursor of nicotinamide adenine dinucleotide (NAD), a vital cellular metabolic cofactor. Without vitamin B3 or tryptophan (from which it can be synthesized), the body is unable to produce NAD.
Vitamin PP is found in a wide range of foods, both plant and animal. The requirement for this essential nutrient can be met by taking about 6.6 mg of it for every 1000 kcal introduced in the diet - for example, in a 2000 kcal diet, 13.2 mg of vitamin B3 is required.
Any deficiency, rare in the West, manifests itself with numerous symptoms and, in the most severe form, leads to the clinical picture of pellagra. Vitamin B3 hypo- and avitaminosis are treated with supplements and drugs based on the nutrient itself, in the form of niacin or nicotinamide. The three chemical forms, however, seem to show different pharmacological actions. Niacin, for example, is used in cholesterol-lowering treatment without drugs, while niacinamide is a typical ingredient in acne ointments.
An excess of vitamin PP (hypervitaminosis) induces toxicity which, if neglected, can be very serious.
(NADP) - are involved in DNA repair transfer reactions and calcium mobilization.
NAD has several essential roles in metabolism; acts as:
- coenzyme in redox reactions;
- donor of portions of ADP-ribose in the ADP ribosylation reactions;
- precursor of the second messenger molecule-ADP-ribose;
- substrate for bacterial DNA alloys and a group of enzymes called sirtuins that use NAD + to remove acetyl groups from proteins.
In addition to these metabolic functions, NAD + represents an adenine nucleotide that can be released from cells spontaneously or by regulated mechanisms; it can therefore have important extracellular roles.
