Vitamin B7 requement
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Vitamin B7 biotin daily requirement recommended dietary allowance 2024
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Vitamin B7 (Biotin) - Requirements
What is Biotin?
Biotin (Vitamin B7, also called Vitamin H) is a water-soluble vitamin that acts as a coenzyme for carboxylation reactions involved in:
- Gluconeogenesis
- Lipogenesis
- Catabolism of branched-chain amino acids
- Cell signaling and epigenetic gene regulation
- Chromatin structure maintenance
The key enzymes it supports include carboxylases for pyruvate, acetyl-CoA, propionyl-CoA, and β-methylcrotonyl-CoA.
Daily Requirement (Adequate Intake - AI)
No RDA (Recommended Dietary Allowance) has been established for biotin because there is insufficient evidence to determine the precise amount needed by most healthy people. Instead, an Adequate Intake (AI) is used.
| Life Stage | AI (mcg/day) |
|---|---|
| Infants 0-6 months | 5 mcg |
| Infants 7-12 months | 6 mcg |
| Children 1-3 years | 8 mcg |
| Children 4-8 years | 12 mcg |
| Children 9-13 years | 20 mcg |
| Adolescents 14-18 years | 25 mcg |
| Adults (19+ years) | 30 mcg |
| Pregnant women | 30 mcg |
| Breastfeeding women | 35 mcg |
- Healthy adults typically consume 40-60 mcg/day from their diet, which exceeds the AI.
- No Tolerable Upper Intake Level (UL) has been set - toxicity from dietary or supplemental biotin has not been reported.
(Yamada's Textbook of Gastroenterology, 7th ed; Tietz Textbook of Laboratory Medicine, 7th ed)
Dietary Sources
| Rich Sources | Poor Sources |
|---|---|
| Eggs (especially egg yolk) | Cereal grains |
| Liver, kidney, pancreas | Fruits |
| Yeast | Most vegetables |
| Milk | Lean meat |
| Nuts (peanuts, hazelnuts) | |
| Mushrooms, chocolate |
- Dietary biotin exists in free and protein-bound forms - the protein-bound form must be digested first.
- Intestinal microflora (colon) also synthesize and release biotin, contributing to supply.
Absorption
- Protein-bound biotin is hydrolyzed by intestinal proteases/peptidases to biocytin (ε-N-biotinyl lysine), then cleaved by intestinal biotinidase to free biotin.
- Absorbed via the sodium-dependent multivitamin transporter (SMVT) in the small and large intestine.
- Raw egg white contains avidin, a protein that binds biotin tightly and blocks absorption - prolonged raw egg consumption can cause deficiency.
Deficiency
Biotin deficiency is rare in healthy people. Causes include:
- Prolonged parenteral nutrition without biotin supplementation
- Chronic raw egg white ingestion (avidin)
- Biotinidase deficiency (genetic)
- Holocarboxylase synthetase deficiency (genetic)
Symptoms:
- Scaly, red rash around body orifices (eyes, nose, mouth)
- Hair loss (alopecia)
- Neurological: lethargy, depression, paresthesias, seizures
Important Clinical Note
High-dose biotin supplements (>=10 mg/day) can interfere with many laboratory tests (thyroid function, troponin, hormones), potentially causing misdiagnosis. Patients taking high-dose biotin should stop 3-7 days before blood tests. This is a well-recognized diagnostic pitfall.
(Tietz Textbook of Laboratory Medicine, 7th ed; Harvard Nutrition Source)
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