Benefits
Supports Hair, Skin, and Nail Health
Biotin strengthens keratin, a protein in hair, skin, and nails, potentially reducing brittleness and promoting growth, though evidence is stronger for deficiency cases.
Aids Energy Metabolism
It helps convert carbohydrates, fats, and proteins into energy, supporting cellular function.
Regulates Blood Sugar
Biotin may improve glucose metabolism, potentially benefiting those with diabetes, though studies are mixed.
Supports Nervous System
It contributes to neurotransmitter activity and nerve health, aiding overall neurological function.
Pregnancy and Fetal Development
Adequate biotin is crucial during pregnancy to support embryonic growth and prevent developmental issues.
Mechanism of Action
Cofactor for Carboxylase Enzymes
Biotin is covalently bound to five key carboxylase enzymes: Pyruvate carboxylase, Propionyl-CoA carboxylase, Methylcrotonyl-CoA carboxylase, Acetyl-CoA carboxylase 1 and Acetyl-CoA carboxylase 2. These enzymes catalyze carboxylation reactions, transferring a carboxyl group (CO₂) to substrates, which is critical for metabolic pathways.
Activation via Holocarboxylase Synthetase
Biotin is attached to a lysine residue on these enzymes by the enzyme holocarboxylase synthetase (HCS), forming a biotinylated holoenzyme. This biotinylation is essential for the enzyme's catalytic activity. The biotin molecule acts as a swinging arm, facilitating the transfer of CO₂ from bicarbonate to the substrate.
Gluconeogenesis and Krebs Cycle
Pyruvate carboxylase converts pyruvate to oxaloacetate, a precursor for glucose synthesis and an intermediate in the citric acid cycle.
Fatty Acid Synthesis
Acetyl-CoA carboxylase (1 and 2) catalyzes the formation of malonyl-CoA, a key step in fatty acid biosynthesis and regulation of mitochondrial fatty acid oxidation.
Amino Acid Catabolism
Propionyl-CoA carboxylase and methylcrotonyl-CoA carboxylase are involved in the breakdown of branched-chain amino acids (e.g., leucine, isoleucine) and odd-chain fatty acids.
Energy Metabolism
These carboxylation reactions support energy production and biosynthetic processes by feeding intermediates into central metabolic pathways.
Biotin Cycle and Recycling
Biotin is recycled through the action of biotinidase, which cleaves biotin from biocytin (biotin-lysine complex) or biotinylated peptides during protein turnover, making it available for reuse by HCS. This recycling ensures a steady supply of biotin for carboxylase activity, even with low dietary intake.
Non-Enzymatic Roles (Emerging Evidence)
Biotin may influence gene expression by modifying histones through biotinylation, mediated by HCS or biotinidase, affecting chromatin structure and gene regulation. It may also play a role in cell signaling and immune function, though these mechanisms are less well-established.
Clinical Trials
A Double-blind, Placebo-controlled Study Evaluating the Efficacy of an Oral Supplement in Women with Self-perceived Thinning Hair
Study: A randomized, placebo-controlled, double-blind study conducted at one U.S. clinical site with healthy women aged 21–75 years with Fitzpatrick I–IV photo skin types and self-perceived thinning hair. Participants (N=15) were randomized to receive either a multi-ingredient oral supplement containing biotin, zinc, and other nutrients (N=10) or placebo (N=5) twice daily for 180 days. Hair counts were measured in a 4 cm² scalp area at baseline, 90 days, and 180 days. A self-assessment questionnaire evaluated perceived changes.
Findings: The supplement group showed a significant increase in terminal and vellus hair counts compared to the placebo group, which showed no significant change (baseline: 256.0 ± 24.1 hairs; 90 days: 245.0 ± 22.4; 180 days: 242.2 ± 26.9). Self-assessment reported improved hair volume, scalp coverage, and thickness. However, the study’s findings cannot be attributed to biotin alone due to multiple ingredients (e.g., zinc, iron) in the supplement, and the small sample size limits generalizability.
Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3509882/
A Review of the Use of Biotin for Hair Loss
Study: A systematic review of literature on biotin supplementation for hair and nail growth, conducted via PubMed search for case reports and randomized clinical trials (RCTs) using terms like “biotin and hair,” “biotin supplementation,” and “biotin and alopecia.” The review identified 18 case reports of biotin use for hair and nail changes, focusing on patients with underlying pathologies. No RCTs specifically evaluating biotin alone for hair growth in healthy individuals were found.
Findings: All 18 cases involved patients with underlying conditions (e.g., biotinidase deficiency, holocarboxylase synthetase deficiency, uncombable hair syndrome, or dietary-induced biotin deficiency). Biotin supplementation (doses ranging from 300–30,000 mcg/day) led to clinical improvement in hair and nail conditions in all cases. For inherited enzyme deficiencies, higher doses (10,000–30,000 mcg/day) were effective, while lower doses (300–3,000 mcg/day) helped with brittle nail syndrome and uncombable hair syndrome. One study of 541 women found 38% had low biotin levels, but 11% had risk factors for deficiency (e.g., antibiotics, antiepileptics), and 35% had co-existing seborrheic dermatitis, suggesting multifactorial causes. No evidence supports biotin’s efficacy in healthy individuals without deficiency.
Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5582478/
Familial Uncombable Hair Syndrome: Ultrastructural Hair Study and Response to Biotin
Study: A case study of three children with familial uncombable hair syndrome, a rare condition characterized by dry, frizzy, unmanageable hair. The study examined hair ultrastructure and assessed response to biotin supplementation (dose not specified but typically low, ~300–3,000 mcg/day).
Findings: All three cases showed improved hair quality (smoother, more manageable hair) after several months of biotin supplementation. Ultrastructural analysis suggested biotin may improve hair shaft structure, but the exact mechanism remains unclear. The study highlights biotin’s potential benefit in specific hair disorders but lacks a control group.
Link: https://pubmed.ncbi.nlm.nih.gov/17509110/
Biotin Deficiency in an Infant Fed with Amino Acid Formula
Study: A case report of an infant with dietary-induced biotin deficiency due to consumption of a biotin-free amino acid formula. The infant presented with perioral dermatitis and alopecia, with low serum and urine biotin levels. Biotin supplementation (dose not specified) was administered for 2 months.
Findings: Hair regrowth and resolution of perioral dermatitis occurred after 2 months of biotin supplementation, confirming the role of biotin in treating deficiency-related alopecia and skin issues. The study emphasizes the importance of ensuring adequate biotin in specialized diets.
Link: https://pubmed.ncbi.nlm.nih.gov/15863846/
High Doses of Biotin in Chronic Progressive Multiple Sclerosis: A Pilot Study
Study: A non-randomized, uncontrolled pilot study involving 23 patients with progressive multiple sclerosis (MS). Patients received high-dose biotin (100–600 mg/day) to assess its effect on disability, particularly visual loss and limb paralysis. Clinical improvements were evaluated after a mean of 3 months.
Findings: Of the 23 patients, 91.3% (21/23) showed clinical improvement, with 5/5 patients with progressive visual loss and 16/18 with partial limb paralysis experiencing reduced disability. The study suggested high-dose biotin might support myelin repair or energy metabolism in MS, but the lack of a control group and small sample size limit conclusions. Subsequent larger trials (e.g., SPI2) showed mixed results, with no significant benefits in a 326-patient cohort after 12 months.
Link: https://pubmed.ncbi.nlm.nih.gov/25787160/
Treatment of Brittle Fingernails and Onychoschizia with Biotin: Scanning Electron Microscopy
Study: An uncontrolled trial involving women with brittle fingernails, supplemented with biotin (2.5 mg/day) for 6–15 months. Nail quality was assessed subjectively and via scanning electron microscopy to evaluate nail plate thickness and splitting.
Findings: Subjective improvement was reported in 67–91% of participants, with reduced nail splitting and a 25% increase in nail plate thickness observed via microscopy. The study suggests biotin may strengthen brittle nails, but the uncontrolled design and subjective outcomes weaken the evidence.
Link: https://pubmed.ncbi.nlm.nih.gov/2273113/
Influence of Biotin Intervention on Glycemic Control and Lipid Profile in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis
Study: A systematic review and meta-analysis of studies evaluating biotin’s effects on glycemic control and lipid profiles in patients with type 2 diabetes mellitus. The review included randomized controlled trials and other studies assessing biotin supplementation (doses not specified in the abstract).
Findings: Preliminary evidence suggests biotin may improve glycemic control and reduce lipid levels (e.g., triglycerides, cholesterol) in type 2 diabetes, potentially via enhanced lipid metabolism or enzyme activity. However, the evidence is not conclusive, and further research is needed to establish efficacy and optimal dosing.
Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9659605/
Potential Side Effects
Skin Reactions
Acne or Rashes: High doses of biotin (e.g., 10 mg/day or more) have been associated with acne breakouts or skin rashes in some individuals. This may be due to altered sebum production or interactions with other B vitamins.
Gastrointestinal Issues
Nausea, Cramping, or Diarrhea: Some people report mild digestive upset, including nausea, abdominal cramping, or diarrhea, especially when taking high doses on an empty stomach.
Allergic Reactions
In very rare cases, individuals may experience allergic reactions, such as itching, swelling, or difficulty breathing. These require immediate medical attention.
Potential Imbalance of B Vitamins
High doses of biotin may compete with other B vitamins for absorption or metabolism, potentially leading to relative deficiencies if not balanced with a complete B-complex intake.