Vitamin B3 is also known as niacin (nicotinic acid).
The current estimated average requirements for niacin for women and men ages 14 and up are 11 mg/day and 12 mg/day, respectively, according to The Food and Nutrition Board of the U.S. Institute of Medicine.
It can be found in meat (turkey, tuna, pork, etc.), plant foods, spices, cereals (sesame seeds, ginger, potatoes etc.) and whole grain flours.
Niacin and its metabolites are the precursors of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). NAD plays role in the catabolism of fat, carbohydrate, protein, and alcohol, as well as cell signaling and DNA repair, NADP is involved in the anabolism reactions such as fatty acid and cholesterol synthesis.
The niacin deficiency leads to pellagra. Therefore the vitamin B3 is also called pellagra-preventing factor (PP).
Causes and risk factors
In the past, the development of pellagra was connected with the niacin-poor diet, although nowadays most people eat enough niacin-containing foods. Typically pellagra is caused by the impairment of niacin or tryptophan absorption in the gut, in most cases due to excessive intake of alcohol. Other possible causes include disorders of the digestive system (Chron’s disease, gastroenteritis, colitis, liver cirrosis), HIV/AIDS, anorexia, malignant carcinoid tumor and prolonged treatment of the tuberculosis with isoniazid.
Related: Vitamin B12 deficiency
Pellagra may develop primarily (primary pellagra) as the result of poor diet or secondary because of the inability of the gastrointestinal tract to absorb the vitamin (secondary podagra).
Usually pellagra is described as the combination of 4 D’s: photosensitive dermatitis, diarrhea, dementia, and death.
Symptoms of mild niacin deficiency include:
• canker sores;
Severe deficiency (pellagra) presents with a variety of symptoms. Early signs of pellagra include weakness, loss of appetite, mild digestive disturbances, and psychiatric or emotional distress. On the skin occur erythema (redness) and skin lesions called pellagrodermas. Acute pellagra skin lesions resemble sunburns. The skin is red with large blisters. The changes subside, leaving a dusky, brown-red coloration. The rash is symmetrical. In the late stages the skin appears hard, rough and cracked, usually described as the goose skin. The skin is darkly pigmented. The typical sites of the lesions are the dorsal surfaces of the hands, face, neck, arms, and feet.
Nails are soft and dull with transversal lines. Keratoconjunctivitis and keratomalacia may occur. The lips, tongue and mucous membranes of the mouth are also affected – they are inflamed and swollen. At the beginning the tongue is hypertrophic, later the atrophy develops. Cheilosis (fissuring and dry scaling of the vermilion surface of the lips and angles of the mouth) is also common The lips are inflamed and achy.
Diarrhea is also common. Affected person has a poor appetite experiences nausea, vomiting and abdominal pain.
In mild cases the psychiatric impairment may be even unnoticed. Affected individuals may be depressed or apathetic. They complain of headaches, inability to concentrate, insomnia, fatigue and depression. Other symptoms include aggression, delusions, hallucination, photophobia (sensitivity to sunlight), tremor, ataxia (inability to coordinate and keep the balance) and spastic paresis.
The development of encephalopathy manifests with confusion, memory loss and psychosis. Later the affected persons are disoriented, confused, stuporous or even comatose.
If not treated, pellagra can lead to death.
Low serum niacin, tryptophan, NAD, and NADP levels can reflect niacin deficiency and confirm the diagnosis of pellagra.
The urine test is performed to measure the excretion on niacin.
Other tests are performed, depending on the present symptoms.
The main treatment is an intake of niacin or nicotinamide orally. A long as pellagra is usually accompanied by the other deficiencies and malnutrition a high-protein diet and the administration of B-complex vitamins is recommended. To reduce the pain and discomfort in the areas of the affected skin the topical emollients are used. Sun protection is necessary during the recovery phase.