Thiamine, a coenzyme, was
originally named vitamin B1. It is partially de-stroyed by heat and
alkalies, and it is lost in cooking water.
Functions.Thiamine is essential for the metabolism of
carbohydrates andsome amino acids. It is also essential to nerve and muscle
action. It is absorbed in the small intestine.
Sources.Thiamine is found in many foods, but generally
in small quantities.(See Appendix D.) Some of the best natural food sources of
thiamine are unrefined and enriched cereals, whole grains, lean pork, liver,
seeds, nuts, and legumes.
Requirements.Thiamine is measured in milligrams. The daily
thia-mine requirement for the average adult female is 1.1 mg a day, and for the
average adult male it is 1.2 mg a day. The requirement is not thought to
increase with age. In general, however, an increase in calories increases the
need for thiamine.
Most breads and
cereals in the United States are enriched with thiamine, so that the majority
of people can and do easily fulfill their recommended intake.
Deficiency.Symptoms of thiamine deficiency include loss
of appetite,fatigue, nervous irritability, and constipation. An extreme
deficiency causes beriberi. Its deficiency is rare, however, occurring mainly
among alcoholics whose diets include reduced amounts of thiamine while their
requirements are increased and their absorption is decreased. Others at risk include
renal clients undergoing long-term dialysis, clients undergoing bypass surgery
for weight loss, and those who eat primarily rice.
Because some raw fish
contain thiaminase, an enzyme that inhibits the normal action of thiamine,
frequent consumption of large amounts of raw fish could cause thiamine
deficiency. Eating raw fish is not recommended. Cooking inactivates this
There are no known ill
effects from excessive oral intake of thiamine, but it may be toxic if
excessive amounts are given intravenously.