As the history of thiamine (B1) is related to beriberi, history of niacin (B3) does with pellagra. Beriberi is associated with the East and a diet of rice, and pellagra in the West and a corn-based diet. Over 200 years ago, the Spanish doctor Gaspar Casal, first pellagra attributed to poor nutrition. At first, it was believed that pellagra could lead to a lack of protein, because the disease improved with some high-protein diets. Later it was demonstrated that the yeast extract containing a non-protein substance that prevented pellagra (PP). In 1937, was isolated niacin or niacinamide or nicotinamide (nicotinic acid amide) or vitamin PP and found that in dogs cure a disease like pellagra, known as black tongue.
Because pellagra is found mostly in people whose staple diet was corn, it was assumed that this cereal was very poor in niacin. Since then, white bread showed that niacin contains much less than maize.
The discovery that the amino acid tryptophan prevents pellagra in laboratory animals such as niacin makes complicated the picture even when it was shown that tryptophan is converted to niacin in the organism. This work justified and explained that the first theories of proteins (composed of amino acids) could prevent pellagra. The fact that zein, the major protein in maize, is very low in the amino acid tryptophan, further explains the relationship between maize and pellagra. It was also found that a high intake of leucine, and in the diets based sorghum, interferes with the metabolism of tryptophan and niacin and can also produce pellagra.
Niacin, a pyridine derivative is a white crystalline substance, water soluble, highly stable, which has been synthesized artificially. Its main function in the body is the oxidation holder. Niacin can be in the form of nicotinic acid and nicotinamide are obtained directly from food. But can also be obtained from tryptophan, an amino acid which the body obtained by the aid of B vitamins from food proteins. For this, they are essential vitamins B1, B2, B6, vitamin C and iron. Otherwise, the tryptophan can not be converted to niacin (B3).
As part of the vitamin B complex, niacin participates in the conversion of carbohydrates into energy. Along with riboflavin and pyridoxine, helps to keep the nervous system healthy. Improves circulation by relaxing (dilating) blood vessels. Work together with other B vitamins in the maintenance of the skin and the digestive mucosa are in good condition. Participates in the formation of DNA (genetic material). It also helps stabilize blood sugar and blood cholesterol.
Niacin is widely distributed in foods of animal and plant origin. Particularly good sources are peanuts, nuts, cereal bran and wheat germ, eggs and liver. Like other B vitamins, the main sources of supply tend to be whole foods. The soy beans in general, peas and other seeds (almonds) contain amounts similar to those found in most cereals. Plant sources rich in tryptophan (which can be converted to niacin) are: avocado, oats and dates.
The suitable amount is 20 mg per day. It takes at least about 13 mg. in women and 18 mg. in men. Niacin needs are affected by the amount of tryptophan in protein consumed. The FAO / WHO suggests 6.6 mg per 1000 kcal. in the diet.
Niacin deficiency leads to pellagra, the disease three Ds: dermatitis, diarrhea and dementia. At first manifests as skin problem, but if left untreated, can continue for many years, worsening steadily and progressively.
Lack of this vitamin is evidenced by the following symptoms: muscle weakness, generalized fatigue, loss of appetite and headaches. Pellagra is manifested: skin sensitivity and increased pigmentation (red end), scaly skin, eczema, nausea, redness and swelling of the tongue, vomiting, diarrhea, irritability, sleeplessness, tremors, depression and dementia.
No toxic effects have been reported with large doses. However, people taking medications for hypertension, those with ulcers, gout or diabetes should consult their doctor before deciding to take vitamin supplements.