Introduction
Our article is based on the work titled "Biotin," published in the prestigious journal Advances in Nutrition in issue 15 of 2024. The authors of this work are Cydne A. Perry from the Department of Applied Health Science at Indiana University School of Public Health and Tammy A. Butterick from the Minneapolis VA Health Care System and the University of Minnesota. This publication, an updated version of an earlier review on biotin, serves as an invaluable and up-to-date source of knowledge on this important nutrient, forming the foundation of our article.
Introduction to Biotin
Biotin is a water-soluble B-vitamin that plays a key role in many metabolic processes within the human body. It is an essential cofactor for several enzymes involved in carboxylation reactions, which are crucial for gluconeogenesis, lipid metabolism, and amino acid catabolism. The enzymes that require biotin include acetyl-CoA carboxylase (ACC) 1 and 2, methylcrotonyl-CoA carboxylase (MCC), propionyl-CoA carboxylase (PCC), and pyruvate carboxylase.
These enzymes serve important functions in a range of metabolic processes, including fatty acid synthesis, leucine catabolism, and gluconeogenesis – the process of generating glucose from non-carbohydrate precursors, which is especially critical during fasting or intense physical exertion. Biotin also plays a role in gene expression regulation, although research on this subject is still ongoing. Early evidence suggested that biotin might influence the epigenetic regulation of genes by binding to histones, but later studies showed that biotin’s binding to histones is minimal and likely has no significant effect on chromatin structures.
The Role of Biotin in Metabolism
Biotin acts as a cofactor for many vital enzymes involved in the metabolism of glucose, fats, and amino acids. These processes are essential for maintaining energy levels, especially during periods of food deprivation. Here are the key metabolic pathways where biotin plays a critical role:
- Gluconeogenesis: Biotin is involved in this process through pyruvate carboxylase, an enzyme that converts pyruvate into oxaloacetate, enabling the synthesis of glucose from non-carbohydrate substrates. Gluconeogenesis is crucial for maintaining blood glucose levels, especially during fasting periods.
- Fat Metabolism: Biotin is essential for both the synthesis and catabolism of fatty acids. Acetyl-CoA carboxylase 1 (ACC1) is involved in fatty acid synthesis, while ACC2 regulates their oxidation, which is vital for the body’s energy balance.
- Amino Acid Catabolism: Biotin is involved in the breakdown of leucine through the enzyme MCC, which is necessary for converting leucine into other metabolic compounds, allowing it to be further utilized in the body’s energy cycles.
Biotin Deficiency
Although rare, biotin deficiency can occur under certain conditions. The most at-risk groups include pregnant and breastfeeding women, who may experience increased biotin catabolism. Other risk factors include the consumption of large amounts of raw egg whites, which contain avidin – a protein that binds to biotin and prevents its absorption. People receiving parenteral nutrition without biotin supplementation, as well as those with chronic alcoholism, smoking habits, anticonvulsant use, or inflammatory bowel diseases, may also be at risk for functional biotin deficiencies.
Biotin deficiency can lead to a range of symptoms, including neurological issues (hallucinations, depression), skin problems (scaling, dermatitis), hair loss, muscle weakness, metabolic disorders, and immune system problems.
Indicators of Biotin Deficiency
Traditionally, biotin status has been assessed by analyzing blood and urine biotin levels. However, reduced biotin plasma levels are not always reliable indicators of biotin intake or nutritional status. A more sensitive early marker of biotin deficiency is increased urinary excretion of 3-hydroxyisovaleric acid (3-HIA), which reflects decreased activity of the MCC enzyme, dependent on biotin.
Recommended Biotin Intake
Biotin intake recommendations are established in the form of Adequate Intakes (AI) because there is not enough data to determine the Recommended Dietary Allowance (RDA). The U.S. National Academy of Sciences (Food and Nutrition Board) has set the following AI levels for biotin:
- Infants 0–6 months: 5 µg/day
- Infants 7–12 months: 6 µg/day
- Children 1–3 years: 8 µg/day
- Children 4–8 years: 12 µg/day
- Children 9–13 years: 20 µg/day
- Adolescents 14–18 years: 25 µg/day
- Adults 19 years and older: 30 µg/day
- Pregnant women: 30 µg/day
- Breastfeeding women: 35 µg/day
Food Sources of Biotin
Biotin is present in a wide range of foods, though its concentration can vary significantly. The richest sources of biotin are animal products, such as meat, fish, and eggs, while plant-based foods, including vegetables, fruits, dairy products, and grains, contain much smaller amounts. It is important to note that biotin found in animal products is often bound to proteins, which may reduce its bioavailability without proper enzymatic processes, such as the action of biotinidase, an enzyme that releases biotin from proteins.
Biotin in Clinical Context
Biotin has clinical applications for treating individuals with genetic mutations in holocarboxylase synthetase (HLCS) and biotinidase, leading to severe biotin deficiency. Increased biotin doses can be administered in such cases to prevent clinical symptoms, such as metabolic acidosis, developmental delays, or neurological disorders.
However, research on biotin's potential use in treating other conditions, such as multiple sclerosis (MS), is still in its early stages. While some studies suggest that high doses of biotin may offer clinical benefits in treating MS, recent phase 3 clinical trials have not confirmed significant improvements in neurological function or walking ability in patients with the disease. Further research is needed.
Biotin Toxicity
To date, no cases of biotin toxicity have been reported, even with very high doses taken in supplement form. For this reason, the Food and Nutrition Board has not established a tolerable upper intake level for biotin. Biotin is considered a safe nutrient that can be consumed in large amounts without health risks.
Recent Research on Biotin
Recent studies suggest that biotin may play a role in regulating gene expression by participating in protein complexes involved in histone methylation, DNA methylation, and histone deacetylation. Biotin may also contribute to defense against reactive oxygen species, as confirmed by studies on human kidney cells, where biotin was shown to reduce oxidative stress.
Conclusion
Biotin, though often overlooked compared to other vitamins, plays a crucial role in human metabolism and health. Its function as a cofactor for important carboxylase enzymes is essential for numerous metabolic processes, including fatty acid synthesis, amino acid catabolism, and gluconeogenesis. Although severe biotin deficiency is rare, adequate intake is essential for maintaining health, particularly for groups at risk of increased biotin catabolism, such as pregnant and breastfeeding women.
Authors Cydne A. Perry and Tammy A. Butterick present a detailed and clear account of the contemporary understanding of biotin’s role in the human body, making this publication a valuable resource for scientists, dietitians, and health-conscious individuals.
Source
Perry, C. A., & Butterick, T. A. (2024). Biotin. Advances in Nutrition, 15(7), 100251. doi: 10.1016/j.advnut.2024.100251
https://advances.nutrition.org/article/S2161-8313(24)00085-1/fulltext
