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B-

Vitamin B7 (Biotin)

water-soluble

Vitamin
(0 studies)

Key Takeaways

  • Biotin is a cofactor for five carboxylase enzymes critical to fatty acid, glucose, and amino acid metabolism
  • FDA daily value is 30 mcg for adults
  • Deficiency is uncommon but can occur during pregnancy and with certain genetic conditions
  • Widely marketed for hair, skin, and nails, but clinical evidence for these claims is limited in healthy individuals
  • High-dose biotin supplements can interfere with certain laboratory test results

Evidence Spectrum

0 studies reviewed →
Insufficient (1)

Metabolic cofactor function

Biotin is biochemically essential as a carboxylase cofactor, but no PubMed studies were available in the rawData to evaluate clinical supplementation outcomes.

30 mcg

RDA (Adults (FDA Daily Value))

water-soluble

Solubility

Role in the Body

Biotin (vitamin B7) is a water-soluble vitamin that serves as an essential cofactor for five carboxylase enzymes in humans. These enzymes are involved in critical metabolic pathways including fatty acid synthesis (acetyl-CoA carboxylase), gluconeogenesis (pyruvate carboxylase and propionyl-CoA carboxylase), and amino acid catabolism (3-methylcrotonyl-CoA carboxylase and propionyl-CoA carboxylase). Biotin also plays a role in gene regulation and cell signaling. It can be covalently attached to histones, which may influence gene expression and chromatin structure, though the physiological significance of histone biotinylation remains an area of active research. The vitamin is found in a variety of foods and is also produced by intestinal bacteria, though the extent to which bacterially synthesized biotin contributes to human requirements is not well established.

  • Cofactor for five carboxylase enzymes
  • Fatty acid synthesis via acetyl-CoA carboxylase
  • Gluconeogenesis via pyruvate carboxylase
  • Amino acid catabolism
  • Potential role in gene regulation via histone biotinylation
  • Cell signaling processes

Supplement Forms

D-biotin (free biotin)

Recommended

Bioavailability: 0%

The naturally occurring and biologically active form. Specific bioavailability data not available in rawData.

Biocytin (biotinyl-L-lysine)

Bioavailability: 0%

Protein-bound form found in foods; must be cleaved by biotinidase before absorption. Bioavailability data not available in rawData.

Food Sources

Organ meats (liver, kidney)

Eggs (cooked)

Salmon and other fish

Pork

Beef

Sweet potatoes

Nuts and seeds (almonds, sunflower seeds)

Legumes (soybeans, peanuts)

Whole grains

Deficiency

Prevalence: Uncommon in the general population; marginal deficiency may occur during pregnancy

Symptoms:

  • Thinning hair and hair loss (alopecia)
  • Scaly, red rash around eyes, nose, and mouth (periorificial dermatitis)
  • Brittle nails
  • Neurological symptoms including depression, lethargy, and paresthesias
  • Conjunctivitis
  • Skin infections

Risk Factors:

  • Biotinidase deficiency (genetic disorder)
  • Pregnancy and lactation
  • Prolonged consumption of raw egg whites (avidin binds biotin)
  • Chronic alcohol use
  • Certain anticonvulsant medications

Safety & Interactions

Possible Side Effects:

  • • No known toxicity; no tolerable upper intake level has been established

Drug Interactions:

  • • High-dose biotin supplements (e.g., 5-10 mg) can interfere with streptavidin-biotin immunoassays used in clinical laboratory tests, potentially causing falsely high or low results for thyroid hormones, troponin, and other analytes
  • • Raw egg whites contain avidin, which binds biotin and reduces absorption
  • • Certain anticonvulsants (carbamazepine, phenytoin, phenobarbital) may reduce biotin levels

Contraindications:

  • • Inform healthcare providers of high-dose biotin use before laboratory testing

Frequently Asked Questions

Does biotin really help hair growth?

Biotin deficiency can cause hair loss, and supplementation may help in deficient individuals. However, evidence for hair growth benefits in people with adequate biotin levels is limited.

How much biotin should I take daily?

The FDA daily value is 30 mcg per day for adults. There is no established tolerable upper intake level.

Can biotin supplements affect blood test results?

Yes. High-dose biotin supplements can interfere with certain laboratory immunoassays, potentially producing inaccurate results for thyroid hormones, troponin, and other tests.

What foods are high in biotin?

Organ meats, cooked eggs, salmon, nuts, seeds, sweet potatoes, and legumes are good food sources of biotin.