Vitamin 32 or niacin is a water soluble vitamin. Vitamin B3 is actually a generic term for nicotinic acid and nicotinamide, which are the compounds of coenzymes NAD and NADP.
The term vitamin PP may also be used, where PP stands for preventive pellagra. It is a strong acid which is relatively persistent to heating, light, air, acids and alkali.
Which foods contain the vitamin?
- Wheat bran
Biological functions of the vitamin
Niacin participates in the decomposition of carbohydrates, lipides and amino acids. It also has an important role in the functioning of the enzymes of the breathing circuit and the functioning of nervous tissue and skin.
Absorption, storage and excretion
NAD and NADP obtained with food are turned into nicotinic acid and nicotinamide which are absorbed from the stomach and small intestine. However, the absorption is inhibited by alcohol, coffee, sugar and antibiotics.
The vitamin is stored in liver and the reserves last for 2–5 weeks.
Excessive niacin is excreted with urine.
Niacin deficiency does not usually occur since the organism can synthesise niacin from tryptophan (essential amino acid). It takes 60 mg of tryptophan to synthesise 1 mg of niacin. Besides tryptophan, the synthesis process also needs other vitamins (thiamine, riboflavin and pyridoxine).
It must be kept in mind, however, that pregnant women or women taking oral contraceptives can synthesise niacin more effectively, which is why additional intake of niacin is not necessary during the first two months of pregnancy
If the deficiency still occurs, the symptoms are the following:
- muscle weakness
- loss of appetite
- symptoms of depression, irritability
- skin inflammations
- sellagra — dermatitis, diarrhoea, dementia
Risk groups for developing the deficiency
- Persons consuming excessive alcohol
- Persons with chronic gastrointestinal diseases
- Persons whose diet contains mainly fibre-rich foods
Doses over 100 mg of nicotinic acid may cause certain side effects for some people, such as heat sensation, redness in face, itching, weakness, weak headache and hypotonia. This is mainly due to the vasodilatory (vascular enlargement) effect of nicotinic acid.
Continuous administration of large doses may cause arrhytmia, hypotension, hyperuricemia, hyperglycemia, baldness and the formation of peptic ulcer in the gastrointestinal tract. Seldom also the impairment of liver functions and skin flaking.
Use of vitamin preparations
Additional intake is reasonable in case of chronic inflammatory diseases of the gastrointestinal tract, continuous and overwhelming use of cereals and for athletes.
As an additional treatment component, niacin is used for treating alcoholism, stress, indigestion, dermatitis, acne, tuberculosis, arthritis, hyperlipidemia, hypertonia, atherosclerosis, conjunctivitis, multiple sclerosis, neuritis, headache, dizziness, Parkinsonism, epilepsy and hypoglycemia.
The vitamin should be taken together with thiamine and riboflavin.
Figure 1. Vitamin B3: niacin
Vitamin B3 content in food
Quantities of food products which should be consumed daily to obtain the recommended daily amount of vitamin B3.
|Liver||37 g||53 g||84 g||79 g||79 g||89 g||105 g|
|Milk, 3,5%||875 g||1250 g||2000 g||1875 g||1875 g||2125 g||2500 g|
|Chicken||64 g||91 g||145 g||136 g||136 g||155 g||182 g|
|Whear bran||26 g||37 g||59 g||56 g||56 g||63 g||74 g|
|Beans||636 g||909 g||1455 g||1364 g||1364 g||1545 g||1818 g|
|Liver||89 g||95 g||95 g|
|Milk, 3,5%||2125 g||2250 g||2250 g|
|Chicken||155 g||164 g||164 g|
|Whear bran||63 g||67 g||67 g|
|Beans||1545 g||1636 g||1636 g|