Biotin (Vitamin B7) – Functions, Deficiency & Intake
Biotin, also known as Vitamin B7 or Vitamin H, is a water-soluble B vitamin essential for metabolism, as well as the health of skin, hair, and nails.
Things worth knowing about "Biotin"
Biotin, also known as Vitamin B7 or Vitamin H, is a water-soluble B vitamin essential for metabolism, as well as the health of skin, hair, and nails.
What is Biotin?
Biotin (also referred to as Vitamin B7, Vitamin H, or Coenzyme R) is a water-soluble vitamin belonging to the B-vitamin family. It plays a central role in human metabolism and acts as a cofactor for several key enzymatic reactions. The name Vitamin H originates from the German words Haut (skin) and Haar (hair), reflecting its importance for these tissues.
Biological Functions
Biotin serves as a coenzyme for several important carboxylase enzymes in the body. It is essential for:
- Carbohydrate metabolism: Conversion of pyruvate to oxaloacetate (gluconeogenesis)
- Fat metabolism: Fatty acid synthesis via acetyl-CoA carboxylase
- Amino acid metabolism: Breakdown of branched-chain amino acids
- Gene expression: Biotin influences the regulation of certain genes
- Cell growth and division: Plays an important role in DNA replication and cell proliferation
Dietary Sources
Biotin is found in a wide variety of foods. Particularly rich sources include:
- Liver and organ meats (e.g., beef liver)
- Eggs (especially egg yolk)
- Nuts and seeds (e.g., sunflower seeds, almonds)
- Legumes (e.g., soybeans, lentils)
- Whole grains
- Dairy products (e.g., cheese, yogurt)
- Vegetables (e.g., sweet potatoes, cauliflower, spinach)
Biotin is also partially synthesized by the gut microbiota, although the contribution to total human biotin status is considered minimal.
Recommended Daily Intake
According to the European Food Safety Authority (EFSA) and the National Institutes of Health (NIH), the following adequate intake values are recommended:
- Adults: 30–40 µg per day
- Pregnant women: 30–35 µg per day
- Breastfeeding women: 35–45 µg per day
- Children (depending on age): 5–25 µg per day
Biotin Deficiency
Causes
Biotin deficiency is uncommon in developed countries but can occur under certain circumstances:
- Excessive consumption of raw egg whites (which contain avidin, a protein that binds biotin and prevents its absorption)
- Long-term parenteral nutrition without biotin supplementation
- Chronic alcohol abuse
- Genetic disorders such as biotinidase deficiency
- Long-term use of antiepileptic drugs (e.g., carbamazepine, phenytoin)
Deficiency Symptoms
Common symptoms of biotin deficiency include:
- Hair loss (alopecia) and brittle nails
- Skin changes: scaly, red rashes, especially around the mouth, nose, and eyes
- Neurological symptoms: numbness, tingling, fatigue, and depression
- Conjunctivitis (inflammation of the eye)
Biotin Toxicity
Because biotin is water-soluble, excess amounts are generally excreted through the kidneys. No toxic effects from high biotin intake have been reported in humans. However, very high doses (approximately 10 mg per day or more) can interfere with certain laboratory tests, including immunoassays for thyroid hormones, troponin, and vitamin D, since biotin is used as a signal molecule in many diagnostic assay systems.
Biotin in Medicine and as a Dietary Supplement
Biotin is widely marketed as a dietary supplement for promoting hair growth, nail strength, and skin health. However, scientific evidence for these effects in individuals without a deficiency remains limited. In cases of confirmed deficiency or genetic biotinidase deficiency, therapeutic supplementation is medically indicated and effective. High-dose biotin (100–300 mg daily) is currently being investigated in clinical trials for the treatment of multiple sclerosis.
Interactions
The following substances may affect biotin metabolism:
- Avidin (found in raw egg whites): inhibits biotin absorption in the intestine
- Antiepileptic drugs (carbamazepine, phenytoin, primidone): may impair biotin metabolism
- Antibiotics: can alter gut flora and thereby affect microbial biotin synthesis
- Alpha-lipoic acid: at very high doses, may compete with biotin for the same transport proteins
References
- European Food Safety Authority (EFSA) - Dietary Reference Values for Biotin. EFSA Journal. 2014;12(2):3580.
- Zempleni J, Hassan YI, Wijeratne SS. Biotin and biotinidase deficiency. Expert Rev Endocrinol Metab. 2008;3(6):715-724.
- National Institutes of Health (NIH), Office of Dietary Supplements - Biotin Fact Sheet for Health Professionals (2023). Available at: ods.od.nih.gov
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