Vitamin B3 – Niacin

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Occurrence and structure

Niacin is mainly found in fish and coffee beans. It is interesting that a modified form of niacin can be produced from the essential amino acid tryptophan (essential means that the body cannot produce it itself and must therefore absorb it with food), but in too small amounts, so that an external supply is necessary. Niacin is a synonym for nicotinic acid. It contains a pyridine ring (contains a nitrogen atom) to which a short side chain is attached. Vitamin B3 is also contained in: poultry, fish, mushrooms, eggs, liver, wholemeal products, peanuts, dates, wheat bran

Function

Niacin could be described as a relative of riboflavin. Like riboflavin, it is also a component of electron carriers, but different. Namely NAD+ and NADP+.

Again, these can accept electrons. In this case, however, only 1 proton (H+) and two electrons (e-), which corresponds to a hydride ion (H-). Thus, analogous to FAD, the following applies: NAD+ à NADH. This means that NAD and NADP are also involved in a large number of dehydrogenation reactions (oxidations), whereby NAD is a cofactor of catabolic (i.e. degrading) reactions, such as beta-oxidation (fatty acid degradation), while NADP is a cofactor of anabolic (constructive) reactions. The best known metabolic pathway in which NADP participates and is reduced to NADPH is the pentose phosphate pathway mentioned above.

Symptoms of deficiency

With a pronounced lack of niacin the clinical picture pellagra occurs. It is characterized by the symptom triad dermatitis (inflammation of the skin), diarrhea and dementia. A slight deficiency leads to symptoms such as insomnia, loss of appetite and dizziness. Water-soluble (hydrophilic) vitamins: Fat-soluble (hydrophobic) vitamins:

  • Vitamin B1 – thiamine
  • Vitamin B2 – Riboflavin
  • Vitamin B3 – Niacin
  • Vitamin B5 – pantothenic acid
  • Vitamin B6 – PyridoxalPyridoxinPyridoxamine
  • Vitamin B7 – biotin
  • Vitamin B9 – folic acid
  • Vitamin B12 – cobalamin
  • Vitamin A – Retinol
  • Vitamin C – Ascorbic acid
  • Vitamin D – Calcitriol
  • Vitamin E – tocopherol
  • Vitamin K – PhylloquinoneMenachinone