Biotin in human milk: methods, location, and chemical form

Area of Science:

• Nutritional Biochemistry
• Human Milk Composition
• Infant Nutrition

Background:

• No established Recommended Dietary Allowance (RDA) for biotin in infants exists.
• Estimated safe and adequate intake relies on human milk biotin measurements.
• Significant discrepancies in published human milk biotin content data are noted.

Purpose of the Study:

• To identify and address sources of disagreement in human milk biotin content measurements.
• To define optimal conditions for collecting and storing human milk for biotin analysis.
• To determine the subcompartment distribution of biotin within human milk.

Main Methods:

• Utilized the [125I]avidin assay for biotin quantification.
• Investigated the effect of collection vessel material (glass vs. plastic) on biotin content.
• Assessed biotin stability under various storage conditions (temperature and duration).
• Determined biotin distribution across milk fractions (skim, fat, cell pellet).

Main Results:

• Collection vessel material did not impact milk biotin levels.
• Biotin content remained stable during extended storage at room temperature, 5°C, -20°C, and -70°C.
• Biotin is predominantly found in the skim fraction (<5% in cell pellet and fat).
• Minimal biotin was found to be reversibly or covalently bound to macromolecules in the skim fraction.

Conclusions:

• Standardized collection and storage protocols are less critical than previously thought for biotin analysis.
• The [125I]avidin assay effectively measures almost all free biotin in mature human milk.
• Findings simplify accurate biotin assessment in human milk, aiding infant nutritional recommendations.