Vitamin Bi
181
accompaniment of pellagra and sprue, and it is undoubtedly
involved as a complication in many diseases which affect the
alimentary canal or liver. The neuritis and insomnia which
frequently develop in dysentery, typhoid, typhus fever,
malaria, metal poisoning, alcoholism, etc., is undoubtedly
traceable to interference with the proper absorption and
utilization of thiamin or other members of the “B” family.
Human requirements of thiamin vary with the weight and
the number of calories consumed. For normal adults the
amount required has generally been thought to be between
300 and 600 international units per day, or 1 to 2 mil-
ligrams, but some recent workers have reckoned it at twice
this amount. Infants and growing children, whose calorie
intake is relatively high, need more in proportion to their
size. In some children it has been found that as high as 3.5
milligrams (1000 units) per day may be retained. There
are a number of conditions in adult life also in which extra
thiamin is needed, and in which a border-line diet may
prove insufficient. People whose metabolism is accelerated
by an over-enthusiastic thyroid gland, by pregnancy, or by
such febrile diseases as malaria or typhoid, need more than
normal individuals. Pregnant women very often develop
symptoms of neuritis which indicate lack of sufficient thia-
min, probably because of the heavy demands made by the
fetus. Often the neuritis is accompanied by pernicious
vomiting, low stomach acidity, and other gastro-intestinal
troubles. It is difficult in this case to say which is the cart
and which is the horse, but the vomiting and dyspepsia on
the one hand and low thiamin on the other probably each
aggravate the other, to the increasing distress of the patient.
Nursing mothers also require extra thiamin, for if they
do not suffer themselves their offspring are liable to—as in
the case of the people on the mandated Polynesian island