What does biotin do?: A comprehensive guide to vitamin B7's role in nutrition

October 4, 2025 •

4 min read

As a crucial B-complex vitamin, biotin (also known as B7) assists the body in converting food into energy. So, what does biotin do beyond this fundamental metabolic function? It also plays a significant role in maintaining the health of hair, skin, and nails, though its benefits for healthy individuals are often debated.

Quick Summary

Biotin, or vitamin B7, acts as a vital coenzyme for metabolism, helping break down fats, carbs, and proteins. It is crucial for cellular health and supports the body's energy production.

Key Points

Metabolic Coenzyme: Biotin is an essential coenzyme for carboxylase enzymes that are vital for metabolizing fats, carbohydrates, and proteins into energy.
Supports Keratin Production: It plays a role in the synthesis of keratin, the protein that forms hair, skin, and nails, supporting their health.
Benefit for Deficiency: Biotin supplements show clear benefits for individuals with a true deficiency, but scientific evidence is lacking for healthy people.
Found in Whole Foods: You can get sufficient biotin from a balanced diet, with rich sources including eggs, nuts, organ meats, and legumes.
Can Interfere with Lab Tests: High-dose biotin supplements can lead to inaccurate results in important lab tests, including those for heart and thyroid function.
Deficiency is Rare: Overt biotin deficiency in healthy people is uncommon due to its presence in various foods and gut bacteria synthesis.

Biotin's Core Role in Metabolic Processes

Biotin's primary function in the body is as a vital coenzyme for several key enzymes known as carboxylases. These enzymes are essential for a wide range of metabolic processes that convert the food we eat into usable energy. Biotin plays a crucial role in:

Fatty Acid Synthesis: Biotin assists in the irreversible carboxylation of acetyl-CoA to malonyl-CoA, a critical step in producing fatty acids. These fatty acids are essential building blocks for healthy cells and energy storage.
Gluconeogenesis: As a cofactor for pyruvate carboxylase, biotin enables the conversion of pyruvate to oxaloacetate, a process that helps produce glucose from non-carbohydrate sources like amino acids. This is vital for maintaining blood sugar levels, especially during fasting.
Amino Acid Metabolism: Biotin-dependent enzymes also participate in the catabolism of certain amino acids, which helps the body process protein and reuse its components.

Because of its central role in these biochemical pathways, biotin is fundamental for keeping your body's energy systems functioning efficiently.

Biotin for Hair, Skin, and Nails: The Reality

Biotin's most famous, and often misunderstood, benefit is its supposed effect on hair, skin, and nail health. While biotin is involved in the synthesis of keratin, the protein that forms hair, skin, and nails, the evidence is not as clear-cut as many advertisements suggest.

For healthy individuals who consume a balanced diet, there is a lack of scientific evidence to support the claim that biotin supplementation will improve hair quality or quantity, or promote nail growth. This is because dietary deficiency is extremely rare in the general population. The most dramatic positive results from biotin supplementation are seen in individuals with a true biotin deficiency, often caused by rare inherited conditions like biotinidase deficiency. These individuals often experience significant improvement in symptoms like hair loss and skin issues after supplementation.

Causes and Symptoms of Biotin Deficiency

Although rare, biotin deficiency can occur in certain populations or under specific conditions. Risk factors include:

Genetic disorders: Biotinidase deficiency is a rare inherited condition that prevents the body from recycling or releasing biotin from food, leading to a functional deficiency.
Prolonged medication use: Long-term use of certain anticonvulsant drugs can increase the body's metabolism of biotin, leading to lower levels.
Chronic alcohol exposure: Excessive alcohol consumption inhibits the absorption of biotin.
Excessive raw egg white consumption: Raw egg whites contain a protein called avidin, which binds to biotin and prevents its absorption. Cooking eggs denatures avidin, rendering it harmless.
Pregnancy: Marginal biotin deficiency is common during pregnancy, with increased requirements for fetal development.

Symptoms of biotin deficiency appear gradually and may include:

Thinning hair (alopecia) and loss of body hair.
A red, scaly rash around the eyes, nose, mouth, and genital area.
Brittle nails.
Lethargy, depression, and hallucinations.
Numbness or tingling in the extremities.

Best Food Sources of Biotin

For most people, a healthy, varied diet provides all the biotin needed. Since it is water-soluble, it needs to be replenished daily through food intake. Here are some of the best dietary sources of biotin:

Cooked Eggs: Especially the egg yolk, which is a very rich source.
Organ Meats: Beef liver is particularly high in biotin.
Nuts and Seeds: Almonds, peanuts, walnuts, and sunflower seeds are great options.
Legumes: Soybeans, lentils, and black-eyed peas.
Sweet Potatoes: A good source of both biotin and beta-carotene.
Mushrooms: Contain a moderate amount of the vitamin.
Avocados and Bananas: These fruits offer some biotin alongside other nutrients.

Biotin from Food vs. Supplements


Feature	Biotin from Food	Biotin from Supplements
Absorption	Typically highly bioavailable when cooked, alongside other synergistic nutrients.	Oral absorption is high, but supplements often contain very high doses.
Dosage Control	Naturally regulated and balanced by the diet, making overdose virtually impossible.	High doses are common, which are unnecessary for most people and can interfere with lab tests.
Nutrient Profile	Comes with a host of other beneficial vitamins, minerals, fiber, and healthy fats.	Isolated nutrient, lacking the comprehensive nutrition of whole foods.
Target Audience	Suitable for most healthy individuals to meet daily nutritional needs.	Best for individuals with diagnosed deficiencies or certain medical conditions, as prescribed by a healthcare provider.

Risks of High-Dose Biotin Supplementation

While biotin is generally safe and excess amounts are excreted in urine due to its water-solubility, consuming very high doses carries specific risks. The most significant concern is the interference with laboratory test results. The U.S. Food and Drug Administration (FDA) has issued warnings that high levels of biotin can cause falsely high or low results in various tests, including:

Troponin tests for heart attacks.
Thyroid hormone level tests.
Some reproductive hormone tests.

Incorrect test results can lead to misdiagnosis and inappropriate treatment. For this reason, it is crucial to inform your doctor about any biotin supplements you are taking before any laboratory testing is performed. For more information, the National Institutes of Health provides a comprehensive fact sheet on biotin for health professionals and consumers.

Conclusion

So, what does biotin do in summary? It's an indispensable coenzyme for crucial metabolic processes that convert food into energy, and it supports the synthesis of keratin for healthy hair, skin, and nails. However, the popular belief that supplementation is a magic bullet for beauty is largely unsubstantiated for healthy people with no deficiency. A balanced diet rich in biotin from whole foods like eggs, nuts, and legumes is the best and safest approach for most individuals to meet their needs. If you suspect a deficiency or are considering high-dose supplements, always consult with a healthcare provider to understand your specific needs and avoid potential risks, especially related to lab testing.

Frequently Asked Questions

The best food sources of biotin include cooked eggs (especially the yolk), organ meats like beef liver, nuts and seeds (such as almonds and sunflower seeds), legumes, and sweet potatoes.

For most healthy people, obtaining biotin from food is ideal. Food sources provide a balanced nutritional profile, while supplements offer a concentrated, and often excessive, dose that is typically only necessary for those with a confirmed deficiency.

Biotin supplements are generally considered safe at recommended doses, as the body excretes excess amounts. However, high doses can interfere with certain laboratory tests and should be disclosed to a doctor before testing.

Biotin supplementation is most effective for hair loss caused by a biotin deficiency. For hair loss due to other factors, such as genetics or hormonal changes, there is limited evidence that biotin provides a significant benefit.

Overdosing on biotin is very difficult because it is a water-soluble vitamin and any excess is passed out in urine. The main risk of excessive intake is interference with lab test results, not toxicity.

If you have a diagnosed biotin deficiency, noticeable improvements in hair or skin can occur within a few months of supplementation. In healthy individuals, evidence of noticeable results from supplementation is limited.

While biotin is involved in the metabolism of fats and carbohydrates for energy, there is no conclusive evidence to suggest that biotin supplementation directly promotes weight loss in humans.