Vitamin B7 // Biotin

Vitamin B7 Deficiency

Overt biotin deficiency is very rare in humans. However, marginal biotin deficiency can be measured by several indicators such as reduced propionyl-CoA carboxylase (PCC) activity in peripheral blood lymphocytes and reduced urinary excretion of biotin  (4, 29, 30, 31, 41).

Causes/ Risk factors

Deficiency has been shown during prolonged intravenous (‘parenteral’) feeding without vitamin B7 supplementation and consumption of raw egg white for a prolonged period (many weeks to years), since an antimicrobial protein found in raw egg white (avidin) binds biotin and prevents its absorption (11). Cooking denatures avidin, making it digestible and hence stops its interference with the biotin absorption (11). Research suggests that a substantial number (at least one-third) of women develop marginal biotin deficiency during normal pregnancy (68, 9, 42), because the rapidly growing fetus requires biotin for the synthesis of essential biotin-dependent enzymes and proteins.

Additionally, some types of liver disease (cirrhosis) may increase the requirement for biotin due to decreased biotinidase activity (32), although not biotin deficiency was shown in this study.

Furthermore, anticonvulsant medications used to prevent seizures in individuals with epilepsy increase the risk of biotin depletion (1033) and smoking has been associated with increased biotin metabolism (43). Inborn metabolic disorders of the biotin metabolism are related to deficiencies in the enzymes biotinidase (release of biotin from protein) (44) and holocarboxylase synthetase (45).

 

Symptoms

Signs of overt biotin deficiency include hair loss and a characteristic scaly red rash in the face (around the eyes, nose, mouth), and in the genital area. Neurologic symptoms in adults have included depression, lethargy, hallucination, numbness and tingling of the extremities, and ataxia (11).

Individuals with inborn metabolic disorders of the biotin metabolism (functional biotin deficiency) show in addition impaired immune system function,  seizures, optical atrophy, and increased susceptibility to bacterial and fungal infections (34, 46). The prognosis of the two above mentioned disorders (enzyme deficiencies) is usually good if biotin supplementation is started early and continued for life (45).

Authored by Dr Peter Engel in 2010, reviewed and revised by Ines Warnke on 28.06.2017