Biotiinin

Biotin, also known as vitamin B7, is a water-soluble vitamin that acts as a coenzyme for carboxylases involved in the metabolism of fats, carbohydrates, and proteins. It plays a central role in gluconeogenesis, fatty acid synthesis, and the breakdown of certain amino acids. The enzymes biotin activates include pyruvate carboxylase, acetyl-CoA carboxylase, and propionyl-CoA carboxylase.

Dietary sources include egg yolks, liver, nuts, seeds, dairy products, and fortified cereals. Biotin is also produced in small amounts by gut bacteria. Most people obtain sufficient amounts from a typical mixed diet, but needs can increase during pregnancy and lactation or in cases of malabsorption or certain genetic disorders.

Deficiency is rare in healthy individuals but can occur with prolonged consumption of raw egg whites (avidin), genetic biotinidase deficiency, holocarboxylase synthetase deficiency, chronic alcohol use, or the use of certain medications. Symptoms include thinning hair, scaly dermatitis around the face and genital area, mood changes, depression, and in severe cases lethargy or seizures.

Recommended intake for adults is about 30 micrograms per day; no universal upper intake level has been established due to low toxicity. High-dose biotin supplements are used by some for cosmetic reasons, though evidence for efficacy on hair and nails is limited. Very high intakes can interfere with certain laboratory tests, potentially causing inaccurate results.