Vitamin B7 (Biotin)

Your intake

What each level of vitamin b7 (biotin) does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

1. Severely lowYOU ARE HERE

   0 mcg – 9.9 mcg

   Well below target. Risk of deficiency symptoms tied to hair · skin · nails.

2. Insufficient

   9.9 mcg – 30 mcg

   Below the recommended daily target. Long-term adequacy not assured.

3. Adequate

   30 mcg – 45 mcg

   Daily target met. Standard nutritional support for hair · skin · nails.

4. Therapeutic

   45 mcg – 60 mcg

   Common for specific health goals. Check the evidence for your situation before sustaining this level.

5. Diminishing returns

   60 mcg – +

   Past the point where extra intake typically helps. Evidence for further benefit is thin.

Overview

Biotin is a water-soluble B vitamin and cofactor for five carboxylases involved in glucose, fatty acid, and amino acid metabolism. Famous for hair/skin/nail marketing claims (largely unsupported in non-deficient adults) and infamous for interfering with lab immunoassays at common supplement doses.

Functions

• ●Cofactor for pyruvate, acetyl-CoA, propionyl-CoA, and methylcrotonyl-CoA carboxylases
• ●Required for fatty acid synthesis and gluconeogenesis
• ●Modulates gene expression via histone biotinylation
• ●Supports keratin infrastructure in true deficiency

Mechanism

Biotin is covalently attached to apo-carboxylase enzymes by holocarboxylase synthetase, then carries a CO2 group during carboxylation reactions. Recycling is performed by biotinidase — congenital biotinidase deficiency presents in infancy and is screened for in most newborn programs.

Benefits

• ●Treats biotinidase deficiency and biotin-responsive basal ganglia disease
• ●Improves brittle nails in clinically deficient individuals (older small trials)
• ●Standard dietary intake meets requirements for healthy adults
• ●Routine 5–10 mg/day for hair/skin in healthy adults has no controlled-trial support

Deficiency

Rare in adults outside of long-term raw-egg-white consumption (avidin binds biotin), prolonged TPN without biotin, or anticonvulsant therapy.

Excess

No UL established and no acute toxicity, but high-dose biotin (≥10 mg/day) interferes with biotin-streptavidin immunoassays — causing falsely low TSH, falsely high troponin (missed heart attacks), and other clinical errors.

Forms

• D-biotin
  The biologically active stereoisomer; standard supplement form
• Biotinidase
  Replacement enzyme for inborn errors; not used as supplement

Food sources

• Beef liver (cooked) · 3 oz31 mcg
• Egg (whole, cooked) · 1 large10 mcg
• Cooked salmon · 3 oz5 mcg
• Sunflower seeds · 1 oz2.5 mcg
• Almonds · 1 oz1.5 mcg
• Sweet potato (cooked) · 1/2 cup2.5 mcg

Supplement forms

If you take biotin, stop it at least 72 hours before lab work — high-dose biotin has caused missed heart attacks and incorrect thyroid diagnoses through assay interference. For hair/nail goals, 30–100 mcg is far above population AI; the 5–10 mg ('high-potency') doses are marketing, not evidence.

Bioavailability

Cooked-egg biotin is well-absorbed; raw egg white avidin binds biotin into an unabsorbable complex (cooking denatures avidin). Gut bacteria synthesise some biotin but contribution to host needs is uncertain.

Longevity relevance

Adequacy is essential for energy metabolism; supplementation above adequacy has no longevity signal. The clinical-assay interference is the more practical concern.

Relationships

References

• NIH ODS — Biotinguideline
• Linus Pauling Institute — Biotinreview
• FDA — biotin lab assay interference safety communication (2017)guideline

About Vitamin B7 (Biotin)

Carboxylase cofactor; fatty acid synthesis and gluconeogenesis.

Role

Hair · skin · nails

Daily target

30 mcg (DV)

Also called

biotin, vitamin b7, vitamin b-7, vitamin h, d-biotin