Vitamin B3 - niacin

The essential vitamin B3 or niacin is a part of the coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which are important in the metabolism of carbohydrate, fat and protein.

Furthermore vitamin B3 can expand the blood vessels, reduce cholesterol concentration in the blood, protect the nervous system, prevent the development of pellagra and promote the production of hydrochloric acid in the stomach.

Niacin is involved in DNA repair, production of steroid hormones in the adrenal gland and in building the fat-containing structures in the cell membranes.

Niacin also helps synthesize glycogen that can be stored in the body's muscles and liver as an energy source.

Sources

Niacin is found in variety of foods, including liver, chicken, beef, fish, whole grain, peanuts and legumes, and is also synthesized from the amino acid tryptophan, which is found in meat, dairy products and eggs. Here is a list of foods with the highest content of niaci n.

Daily intake

The recommended daily intake is 14 mg for women, 16 mg for men, and 18 mg for pregnant or breastfeeding women.

The upper limit for adult men and women is 35 mg/day. Higher intakes provoke flushing of the skin as an adverse effect.

Deficiency

Mild niacin deficiency has been shown to slow metabolism, causing decreased tolerance to cold.

Severe deficiency of niacin in the diet causes the disease pellagra, which is characterized by diarrhea, dermatitis, and dementia, as well as “necklace” lesions on the lower neck, hyperpigmentation, thickening of the skin, inflammation of the mouth and tongue, digestive disturbances, amnesia, and delirium.

Psychiatric symptoms of niacin deficiency include irritability, poor concentration, anxiety, fatigue, restlessness, apathy, and depression.

Excess

In the amounts provided by food, no symptoms of toxicity have been reported.

Large doses of niacin (1.5 - 6 g per day) may lead to skin flushing and itching, dry skin, and skin rashes like eczema. Gastrointestinal complaints, such as dyspepsia (indigestion), nausea and liver toxicity have been reported. High blood sugar, cardiac arrhythmias, and aggravation of gout may also be seen.

References: 1 , 2 , 3