Niacin is a member of the B-vitamin complex group vital to oxidation of all living cells. It also has a pharmacological role in the management of dyslipidemic conditions and in the reduction of cardiovascular events. As a consequence, this vitamin does not only have a historical meaning as the treatment for pellagra, but also represents a compound with a possible relevance to contemporary therapeutics.
Today, niacin deficiency is a rare event in developed countries, usually discernible only in circumstances of poverty, chronic alcoholism and malnutrition. Nevertheless, classic pellagra continues to be a health issue in certain countries where people eat maize as a staple food, and especially during food emergency and refugee programs.
Pellagra is a deficiency disease associated with a nutrition that provides low levels of niacin and/or tryptophan, resulting in changes in the skin, gastrointestinal tract and nervous system. The classical triad of symptoms encompasses dermatitis, diarrhea and dementia (“the three Ds”) and can lead to death (the fourth D).
Among those leading symptoms, changes on the skin often represent the most prominent sign of the disease. Initial erythema resembles sunburn, and is usually symmetrically distributed on the body parts exposed to direct sunlight. Such erythema is accompanied by burning and itching, as well as scaling and exfoliation of the skin. There is a clear zone of demarcation between the affected and normal skin.
Changes in the gastrointestinal tract usually lead to excessive salivation, nausea, a burning sensation in the epigastrium and diarrhea. The mouth is sore and the tongue swollen and beef red in color. Gastrointestinal symptoms always precede dermatitis, thus it is often said that pellagra begins in the stomach. Bacterial infections may worsen the diarrhea and cause the anemia.
Early neurological symptoms of pellagra include anxiety, depression and fatigue, while headaches, dizziness, irritability and tremors can occur later. Although manifestations are psychoneurotic at the start of the disease, lesions can also affect the nerves. Mental aberrations may result with dementia in approximately 4-10% of chronic pellagra patients.
The clinical diagnosis of pellagra is usually straightforward in people with dermatitis. However, if the skin has not been exposed to sunlight, skin lesions may be minimal or even absent. In addition, the classical triad of pellagra symptoms is usually seen only in adults and is generally not so explicit in infants and children.
Oral therapy with niacin is usually effective in reversing the clinical manifestations of pellagra. The prevention is best achieved by providing grain legumes (particularly groundnuts) and meat or fish in sufficient quantities in all rations where maize represents the principal cereal.
Recommended daily allowance of niacin
In order to avoid the deficiency, recent studies confirmed that the recommended daily allowance of niacin in adults is 6.6 niacin equivalents per 1000 kcal daily and not less than 13 niacin equivalents when there is an intake of less than 2000 kcal. On the basis of those numbers, the “reference man” (3200 kcal) would need an intake of 21.1 niacin equivalents, and the “reference women” (2300 kcal) an intake of 15.2 niacin equivalents per day.
For children of 6 months or older, the same recommended intake of 6.6 niacin equivalents per 1000 kcal daily is accepted. Younger infants necessitate 8 niacin equivalents per 1000 kcal, which can be fulfilled via breastfeeding by well-nourished mothers.
There is no evidence that pregnancy or lactation increase the requirement for niacin above the recommended intake. Still, the United States National Research Council issued a recommendation for an additional 5.0 niacin equivalents daily for lactating women, based on the loss of 1.5 mg niacin per 850 ml of breast milk and the additional energy invested to support lactation.
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