Niacin (pyridine-3-formic acid) an organic vitamin, is also known as Vitamin B₃ , (a generic name that also includes vitamin PP, niacinamide, nicotinamide, nicotinic acid and derivatives) is one of the 8 water-soluble B-complex vitamins. 

It is found in :

• muscle tissue
• fish
• meat
• chickens
• peanuts
• yeasts
• and other  

Industrially it appears in the form of a white powder.

What it is used for and where

Medical

It is important for the conversion of proteins, carbohydrates and fats into energy and an essential nutrient that has several important functions in the body, including helping the body convert food into energy, contributing to the health of the skin and nervous system, and supporting cell function.

It can reduce harmful LDL-cholesterol (which thickens and clogs the arteries), improve HDL-cholesterol values and thus reduce the risks for the cardiovascular system (1).

It also has positive indications for diabetes mellitus by bringing glycaemic values back to normal (2).

As for eye health, there isn't much research specifically linking niacin to eye health. However, some research suggests that niacin may help prevent glaucoma, a condition that can damage the optic nerve and lead to vision loss. It's important to note that further research is needed to confirm this.

Food

Its deficiency can develop pellagra-like symptoms and is linked to a state of malnutrition. Ingredient included in the list of European food additives as E375 under the name nicotinic acid, acting as a stabiliser.

It is used in dairy products, in pasta making and in the production of maize flour.

Animal feed

Feed additive, which can improve milk production, poultry and meat quality.

Cosmetics

Skin conditioning agent - Mixed. This ingredient is responsible for modifying the condition of the skin when it is damaged or dry by reducing flaking and restoring elasticity.

Antistatic agent. Static electricity build-up has a direct influence on products and causes electrostatic adsorption. The antistatic ingredient reduces static build-up and surface resistivity on the surface of the skin and hair.

The most relevant studies on this vitamin have been selected with a summary of the contents:

Vitamin B₃ studies

• Molecular Formula    C₆H₅NO₂    C₅H₄NCOOH   HOOC₅H₄N 
• Molecular Weight   123.111 g/mol
• CAS   59-67-6
• EC Number   200-441-0
• UNII   2679MF687A
• PubChem Substance ID 329823272
• MDL number   MFCD00006391
• Beilstein Registry Number   109591

Synonyms: 

• Nicotinic Acid
• niacin
• Pyridine-3-carboxylic acid
• Pellagrin
• 3-pyridinecarboxylic acid
• Akotin
• vitamin B3
• Daskil
• 3-Carboxypyridine
• Efacin
• Enduracin
• Pelonin
• Nicodelmine
• Linic
• Niconacid
• nicamin
• Pellagramin
• nicobid
• Direktan
• nicocap
• Niaspan
• nicolar
• Nicacid
• Bionic
• Nicangin
• Diacin
• Peviton                  

References____________________________________________________________________

(1) Landray MJ, Haynes R, Armitage J. Niacin for reduction of cardiovascular risk.   N Engl J Med. 2014 Nov 13;371(20):1943-4. doi: 10.1056/NEJMc1411240.

Niacin for reduction of cardiovascular risk.
Mayer L.
N Engl J Med. 2014 Nov 13;371(20):1943. doi: 10.1056/NEJMc1411240#SA6.

Niacin for reduction of cardiovascular risk.
Santos-Gallego CG, Badimon J.
N Engl J Med. 2014 Nov 13;371(20):1943. doi: 10.1056/NEJMc1411240#SA5.

Niacin for reduction of cardiovascular risk.
van den Oever IA, Nurmohamed MT, Lems WF.
N Engl J Med. 2014 Nov 13;371(20):1942. doi: 10.1056/NEJMc1411240#SA4.

(2) Ding Y, Li Y, Wen A. Effect of niacin on lipids and glucose in patients with type 2 diabetes: A meta-analysis of randomized, controlled clinical trials.  Clin Nutr. 2014 Sep 28. pii: S0261-5614(14)00247-7. doi: 10.1016/j.clnu.2014.09.019. 

Wu L, Parhofer KG.  Diabetic dyslipidemia.  Metabolism. 2014 Aug 29. pii: S0026-0495(14)00258-3. doi: 10.1016/j.metabol.2014.08.010.