Biotin

• Method of Action
• Consequences of Deficiency
• Deficiency Symptoms
• Recommended Dietary Allowances

• Properties and Uses
• Toxicity Levels
• Food Sources

Description

Biotin is one of the vitamin B-complex vitamins. It is a cofactor for many enzymatic reactions occurring in mammalian cells. Biotin is needed for growth, maintenance of skin, nerves, sex glands, bone marrow, and sebaceous glands.

Until recently, biotin was not recognized as being clinically significant because it was believed that the gastrointestinal bacteria produced a sufficient amount of biotin for the body’s needs. In the early 1970’s however, an inborn error of biotin metabolism was reported and, shortly thereafter, other biotin deficient individuals were recognized.

Biotin is stable when food is stored or processed.

Method of Action

Biotin is involved with the metabolism of fatty acids, amino acids, and carbohydrates. It is used as a coenzyme for the removal of carbon dioxide from oxaloacetate, succinate, malate, and aspartate; it is also used in biosynthesis of citrulline, aspartate, and unsaturated fatty acids, and in other reactions involving the transfer of carbon dioxide.

Biotin in enzymes is usually connected to a lysine residue. There are nine known enzymes which require biotin to function, but only four of the nine exist in mammalian cells; the other enzymes are found in microoganisms.

Properties and Uses

Biotin has been used successfully to treat seborrheic dermatitis in infants in the United States and Europe. Inconclusive results have been achieved in the treatment of other skin and scalp disorders, such as baldness.

Consequences of Deficiency

Biotin deficiencies are not frequently found in humans. The small amount of biotin required is usually supplied by the diet and by microorganisms in the gastrointestinal tract. One possible cause of biotin deficiency is the eating of raw egg white. Raw egg white contains avidin which complexes to biotin and prevents its absorption into the body. However, for the avidin to produce this negative effect, four or five raw eggs would have to be consumed per day. Other causes of biotin deficiency include other antagonists to biotin as well as inborn metabolic errors.

The symptoms of biotin deficiency are: dermatitis, nausea, depression, vomiting, and anorexia. These symptoms occur only under highly abnormal, or experimental, conditions.

Toxicity Levels

Biotin is essentially nontoxic to humans.

Recommended Dietary Allowances

RDA for adults: 150 to 300 mcg

RDA for children: unknown

Biotin is taken orally for biotin deficiency.

Food Sources

Summary Deficiency Symptoms