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By Hamid
M. Said
Biotin is an essential micronutrient
for all mammals and is a member of the B complex group of vitamins. Biotin
was discovered in nutritional experiments that revealed a factor in many
foodstuffs that was capable of curing the scaly dermatitis, hair loss,
and neurologic signs induced in rats fed dried egg whites.
Avidin is a glycoprotein found
in egg whites and binds biotin very specifically and tightly. From an
evolutionary standpoint, avidin probably serves as a antibacterial in
egg whites because it is resistant to a broad range of bacterial proteases
in both the free and biotin-bound forms.
Because it is resistant to
digestive enzymes from the pancreas dietary avidin binds to dietary biotin
and prevents its absorption. The normal bacteria of the large intestine
synthesize biotin. Cooking changes avidin and makes it susceptible to
digestion and unable to interfere with the intestinal absorption of biotin.
The fact that we have a requirement
for biotin has been most clearly shown in 2 situations that result in
biotin deficiency:
- Prolonged consumption of
raw egg whites and
- IV nutrition without biotin
supplementation in patients with short-gut syndrome
Interestingly, the biotin requirements
for normal persons and for persons in special clinical circumstances are
not known. Safe and adequate doses have been suggested.
American
Journal Clinical Nutrition February 2002;75(2):179-80
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