Nicotinic acid or niacin is known as pyridine-3- carboxylic. It occults in tissues principally as amide of nicotinic acid. In the body nicotinic acid is converted into the amide before it becomes active. In tissues, nicotinamide is present mainly as a dinucleotide.
Nicotinic acid is a white crystalline substance and is moderately soluble in water but quite soluble in alkali, alcohol and glycerine. It is heat stable and not lost during cooking and canning.
Sources of vitamin B 3
Vegetable sources include the husk of the cereals, green vegetables, peas, beans, tomatoes etc. whole wheat meal contains small amount of this vitamin.
Animal sources are meat, fish, liver, milk, yeast etc. it has also been produced synthetically. Body can synthesize this vitamin from tryptopahn.
Milk is a poor source of niacin but its proteins are rich in trptopahn, which is converted in the body into niacin.
In many cereals, especially maize, niacin occurs in “bound” form unavailable to the consumer.
Benefits of niacin:
It is essential for growth. It takes essential part in metabolism and tissue oxidation. Helps in the formation of fats from carbohydrates. Niacin may reduce the plasma lipid concentration in certain cases of hyperlipaemia, the process is not known.
It prevents pellagra. It has a stimulating effect on central nervous system.
In therapeutic doses, niacin produces the pronounced transient vasodilatation with flushing of the face. This is accompanied by an increase in peripheral blood flow and skin temperature.
Niacin also helps in the functions of the nervous and digestive system. It plays a role in food metabolism and in the formation of red blood cells and skin. NAD and NADP are coenzymes that are part of the energy production system of the body. This system works by means of oxidation and reduction (redox) reactions.
Niacin is suspected to decrease the susceptibility of certain type of cancer such as leukaemia, as a result of increase levels of DNA-repairing coenzymes (NAD).
It is a useful preparation for burn treatment.
Deficiency symptoms of vitamin B 3
Niacin deficiency results in pellagra. Three D’s – diarrhoea, dermatitis and dementia, characterize this disease.
In addition glossitis and stomatitis usually occur. The dermatitis is bilaterally symmetrical and is found only on those surfaces of the body exposed to sunlight, such as back of hands, lower legs, face and neck.
Mental changes may also occur which include depression, irritability and delirium.
Niacin deficiency may also result in many symptoms, such as fatigue, headaches, dry skin, loss of appetite, ulcers and emotional instability.
General effects are inadequate growth of children, loss of weight and strength and anaemia.
Who need more?
People who are taking antituberculaosis drugs such as isoniazid may result in niacin deficiencies. Therefore they need more niacin in diet as compare to others.
Women who take oestrogen contraceptives have a larger requirement for niacin resulting from increased niacin synthesis in their bodies.
People suffering from HIV may be given extra niacin to postpone symptoms and elongate their life.
Niacin can also be useful for alcohol addicts and people with high cholesterol, mental problems, and severe stress problems or hyperthyroid, for athletes and for elderly people.
The requirement for niacin increases in increased calorie intake or expenditure in acute illness, after severe infection, injury etc.
It is not recommended for
Pregnant or breastfeeding women should take niacin under medical supervision. Children under age 12 and people suffering from kidney disease are not recommended to take niacin. One should not take more than 150 mg of niacin, because this leads to facial flushing. Very large intakes (>3000 mg) may cause liver damage. People with liver disease or diabetes are more susceptible to problems caused by niacin over dose.
12-18 mgm for adult males and a little less in adult females. Requirement varies with the protein content of diet as amino acid tryptophan gives rise to niacin in the body.