Biotin is absorbed in the small intestines
RDA - 100-200 mcg
Optimal - 300 mcg
Raw eggs contain avadin, which inhibits biotin absorption.
Biotin is essential for carboxylation:
Acetyl CoA carboxylase, which is involved in synthesis and oxidation of fatty acids
Pyruvate carboxylase is a critical enzyme for gluconeogenesis
Methylcrotonyl-CoA carboxylase is needed to form leucene, an essential amino acid
Propionyl-CoA carboxylase is involved in the deamination of amino acids
Biotin is required for the synthesis of pancreatic amylase and niacin
Biotin may be involved in the synthesis and release of insulin
Biotin may play a role in DNA replication and transcription
propionyl CoA -> methyl malonyl CoA (forms Succinyl CoA)
pyruvate -> oxaloacetate
acetyl CoA -> malonyl CoA
Common manifestations resemble those of essential fatty acid deficiency. Avidin, a protein found in egg whites, binds to biotin and prevents absorption. Biotinase and holocarboxylase synthetase deficiency are hereditary disorders.
dermatitis with scales and hardening often starting near the eyes
perioral dermatitis, conjunctivitis, alopecia, hair loss
anorexia, lassitude, nausea
muscle atrophy, ataxia
Long-term anti-convulsant (anti-seizure) therapy reduces biotin levels.
Primidone and carbamazepine inhibit biotin absorption in the small intestine.
Phenobarbital, phentyoin, and carbamazepine increase urinary excretion of biotin.
diabetes mellitus - stimulates glucokinase, stimulates insulin secretion
one study showed that 9 mg/day lowered glucose levels by 45%
seborrheic dermatitis in infancy (cradle cap)
brittle fingernails - 2.5 mg/day increases nail thickness by 25%
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