Niacin deficiency

A deficiency in niacin results in pellagra, which is a
nutritional disease endemic among poor communities
who subsist chiefl y on maize. The classical features
of endemic pellagra are dermatitis, infl ammation of
the mucous membranes, diarrhoea and psychiatric
disturbances. The dermatitis often appears after exposure
to sunlight and resembles sunburn. The skin
becomes red and blistered and frequently peels off in
large areas. In chronic cases the skin becomes rough
and thickened with a brown pigmentation. In acute
pellagra, the mucous membranes of the gastrointestinal
and genitourinary tracts are severely infl amed.
The mouth becomes extremely sore and the tongue
is swollen and scarlet in colour. Chewing and swallowing
are painful and even liquids may be refused.
Infl ammation of the small and large intestine is manifested
by diarrhoea, abdominal pain and soreness of
the rectum. Hypermotility of the gastrointestinal
tract and the loss of appetite lead to profound loss of
weight. Infl ammation of the lower urinary tract causes
urethritis with increased micturition accompanied
by a burning sensation. In the female, severe vaginitis
is observed and amenorrhoea is common. Bender
(1984) vividly described neurological and neuropsychiatric
signs. Early signs include tremor, irritability,
anxiety and depression, with delirium and dementia
sometimes occurring in severe and chronic cases.
Unless the disease is treated, the inevitable outcome
is death. Fortunately, the response to nicotinamide
therapy is rapid and dramatic.
The prognosis is complicated by signs of proteinenergy
malnutrition and by an imbalance of amino
acid intake, particularly low levels of tryptophan and
high levels of leucine. Because most proteins contain
at least 1.0% tryptophan, it is theoretically possible
to maintain adequate niacin status on a diet devoid
of niacin but containing >100 g of protein. Primary
defi ciencies are rare (at least in industrialized countries),
but secondary defi ciencies may arise from
gastro intestinal disorders or alcoholism.