Key Concepts

  • Adequate Intake (AI) – 30 mcg/day
  • Deficiency is rare
  • No upper intake level (UL) is established – 10-50 mg/day has shown no adverse effects
  • Food Sources – beef liver, eggs, salmon, sunflower seeds, sweet potatoes, almonds
  • B Complex – $0.34/day

Adequate Intake (AI)

  • Adults – 30 mcg/day

Functions

Biotin (vitamin B7) is a water-soluble vitamin. It is a cofactor for five carboxylases (enzymes) that catalyze critical steps in the metabolism of fatty acids, glucose, and amino acids. Biotin also plays key roles in histone modifications, gene regulation, and cell signaling.

Deficiency

Biotin deficiency is rare. Thinning hair, a scaly red rash around body openings, conjunctivitis, ketolactic acidosis, aciduria (abnormal amounts of acid in urine), seizures, skin infection, brittle nails, neurological symptoms (e.g., depression, lethargy, hallucinations, and paresthesias of the extremities) in adults, hypotonia, facies, and developmental delay in infants are indicators of biotin deficiency.

Groups at risk for biotin deficiency are those with biotinidase deficiency, alcoholics, pregnant women, and breastfeeding women.

Toxicity

No upper intake level (UL) is established for biotin. Ten to 50 mg/day of biotin showed no adverse effects in several studies. Up to 200 mg/day of oral biotin or 20 mg/day intravenously in patients with biotinidase deficiency has not been shown to produce symptoms of toxicity.

Food Sources

  • Beef liver, cooked, 3 ounces – 30.8 mcg – 100% Daily Value (DV)
  • Egg, whole, cooked – 10 mcg – 33% DV
  • Salmon, pink, canned in water, 3 ounces – 5 mcg – 10% DV
  • Sunflower seeds, roasted, ¼ cup – 2.6 mcg – 5% DV
  • Sweet potato, cooked, ½ cup – 2.4 mcg – 5% DV
  • Almonds, roasted, ¼ cup – 1.5 mcg – 2.5% DV

Biotin cannot be absorbed in the gastrointestinal (GI) tract if eggs are eaten raw because avidin, a glycoprotein found in egg whites, binds tightly to biotin. Avidin is denatured by cooking and allows the biotin found in eggs to be absorbed.

Supplementation

The absorption rate of oral, free biotin is 100%, even when doses of up to 20 mg/day are consumed.

It does not appear that biotin can be readily absorbed through the skin and definitely not through the hair. Therefore, its use as a topical agent and in haircare products does not appear to be warranted. Additionally, biotin deficiency is rare, so the need to apply topical biotin, even if there is a biotin deficiency, does not appear warranted. A deficiency could be corrected through diet and would provide the promoted benefits related to hair and skin care.

Resources/References

  1. https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/
  2. http://lpi.oregonstate.edu/mic/vitamins/biotin#toxicity

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