Niacin - what is it?
Niacin, New RDA* 16 mg NE
There are two forms of niacin: nicotinic acid and nicotinamide, and both are found in food.
Niacin is a water-soluble vitamin, which means you need it in your diet every day because it can't be stored in the body.
Free nicotinic acid and nicotinamide are present in nature in only small amounts. Nicotinic acid is mainly bound to macromolecules in plants, while nicotinamide is usually a component of NADP in the animal world.
Nicotinic acid can be formed in humans from the metabolism of dietary tryptophan, and so niacin is not really a vitamin providing adequate tryptophan is available.
*Sourced from EFSA WEBSITE
Niacin - what does it do?
Releases energy from food, and is important for the normal structure of the skin and body linings.
It also keeps the digestive and nervous systems healthy.
Niacin is the functional factor of two important coenzymes, NAD and NADP, which activate over 200 dehydrogenases essential to electron transport and other cellular respiratory reactions. Despite their structural similarity, NAD and NADP have quite different metabolic roles.
NAD functions as an electron carrier for intracellular respiration as well as a co-factor for enzymes involved in the oxidation of fats and carbohydrates, such as glyceraldehyde 3-phosphate, lactate, pyruvate and α-ketoglutarate dehydrogenases.
NADP functions as a hydrogen donor in reductive biosynthesis, such as in fatty acid and steroid synthesis and like NAD as a cofactor for enzymes, such as in the oxidation of glucose-6- phosphate to ribose 5-phosphate in the pentose phosphate pathway.
Deficiency
The most common symptoms of niacin deficiency are changes in the skin, mucosa of the mouth, stomach and intestinal tract and the nervous system. The changes in the skin are among the most characteristic in human beings. They are called ‘Pellagra’, which means ‘raw skin’ and are most pronounced in the parts of skin exposed to sunlight.
Other signs and symptoms include dizziness, vomiting, constipation or diarrhoea, and inflammation of the tongue and gastric mucosa. The neurological symptoms can include fatigue, sleeplessness, depression, memory loss and visual impairment.
Niacin - Sources
Meat, wheat and maize flour, eggs, dairy products and yeast.
