Vitamin B7

Vitamin B7, commonly known as biotin, plays a vital role in energy metabolism by aiding the conversion of food into usable energy for the body.  Beyond its metabolic function, biotin is integral for the maintenance of healthy hair, skin, and nails. 

Given its water-soluble nature, the body does not retain biotin, necessitating regular dietary intake. Rich sources of biotin include egg yolks, nuts, whole grains, and certain fish varieties. 

Also, small amounts of biotin can also be synthesized by gut bacteria.

Vitamin B7 is indispensable for sustaining energy levels and promoting overall wellness in bodily appearance.

Furthermore, biotin is increasingly recognized for its potential benefits beyond basic nutrition. Studies suggest that biotin may play a role in supporting cognitive function and maintaining a healthy cardiovascular system. 

Additionally, biotin supplements have gained popularity for their purported effects on hair growth and nail strength, although further research is needed to confirm these claims conclusively. 

Understanding the importance of biotin in various bodily functions underscores the significance of ensuring adequate intake through diet or supplementation for overall health and well-being.

Overview of B Vitamin Family

The B vitamin family comprises a group of water-soluble vitamins that play critical roles in numerous physiological processes essential for human health. 

Comprising eight distinct vitamins, it includes riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), and cobalamin (B12), these vitamins are intricately related and often function as coenzymes in various metabolic pathways. 

VItamin B12 is the only B vitamin that can be stored in the body, in the liver.  All other B vitamins are quickly excreted through the urine, therefore they require daily repletion.  

Individually, the B vitamins contribute to energy production, DNA synthesis, nervous system function, and red blood cell formation, among other vital functions. Collectively, the B vitamins are indispensable for maintaining overall health and well-being, underscoring their importance in supporting various physiological systems within the human body.

Biotin (Vitamin B7)

What is Biotin? 

Biotin is a water soluble B vitamin.  It has a pivotal role in various metabolic processes within mammals, as it is a crucial coenzyme in bicarbonate-dependent carboxylation reactions. 

Biotin is a cofactor for four carboxylases, including pyruvate carboxylase, methylcrotonyl-CoA carboxylase, propionyl-CoA carboxylase, and acetyl-CoA carboxylase, each contributing to different biochemical pathways essential for cellular function. 

In addition to its enzymatic functions, biotin is involved in the breakdown of cellular proteins, where biotin-containing enzymes are degraded to biocytin or short oligopeptides, later released by biotinidase for reuse. 

Although the precise mechanisms of absorption and metabolism are not fully elucidated, biotin is found in both free and protein-bound forms in foods, with intestinal microflora contributing to its synthesis.  [9.]

Understanding the physiological importance of biotin underscores its significance as a vital nutrient for overall health and metabolic function.

Functions of Biotin: What Does Biotin Do in the Body?  [3., 9., 16.]

Vitamin B7 exerts a wide range of beneficial effects on human health.  

• Biotin is a necessary cofactor for four key carboxylases in mammals, supporting mitochondrial glucose, fatty acid, and amino acid metabolism.some text
  • Pyruvate carboxylase: Catalyzes the conversion of pyruvate to oxaloacetate, a crucial step in gluconeogenesis and the tricarboxylic acid (TCA) cycle.  Found in mitochondria.
  • Acetyl-CoA carboxylase (ACC): Converts acetyl-CoA to malonyl-CoA, essential for fatty acid synthesis.  Found in cellular mitochondria and cytosol.  
  • Propionyl-CoA carboxylase (PCC): Plays a role in the metabolism of amino acids and odd-chain fatty acids.  Found in mitochondria.  
  • β-Methylcrotonyl-CoA carboxylase: Involved in the catabolism of leucine.  Found in mitochondria.  
• It participates in histone biotinylation, influencing gene expression and chromatin structure, which affects approximately 2000 genes.  It also promotes gene stability.  
• Biotin regulates immunological and inflammatory functions, impacting B-cell and T-cell immunity, natural killer (NK) lymphocytes, and cytokine production.

Adequate Intake (AI) for Biotin

The AI for adult men and women is 30 mg/day; this is considered adequate to maintain levels of 3-hydroxyisovaleric acid excretion in the urine, although this evidence is limited.  [9.]

In pregnancy the AI remains 30 mg/day, and it rises to 35 mg/day in lactation.  [9.]  

Biotin intake is disrupted in the case of ingestion of large amounts of raw egg whites, which contain the substance avidin which blocks biotin absorption; a genetic defect causing biotinidase deficiency; the use of certain anticonvulsants that induce biotin catabolism in some individuals; and pregnancy.  [9.]

Sources of Biotin [6., 14.] 

Animal Sources of Biotin:

• Liver: Especially beef liver is a rich source of biotin.
• Eggs: Particularly egg yolks contain significant amounts of biotin.
• Meat: Various meats like pork, beef, and chicken provide biotin.
• Fish: Certain types of fish such as salmon and tuna contain biotin.
• Dairy Products: Milk and cheese are sources of biotin, though in smaller amounts compared to liver and eggs.

Plant Sources of Biotin:

• Nuts and Seeds: Almonds, peanuts, walnuts, and sunflower seeds are good sources of biotin.
• Legumes: Beans, lentils, and peas provide biotin.
• Whole Grains: Foods like oats, barley, and wheat germ contain biotin.
• Vegetables: Avocado, sweet potatoes, carrots, and spinach are vegetable sources of biotin.
• Fruits: Bananas, strawberries, and raspberries also contribute to biotin intake in the diet.

Biotin Forms and Supplementation Indications

Biotin Supplement Forms

Biotin is available as a single-vitamin supplement, or as part of a B vitamin complex.  It is commonly found in products marketed for skin, hair and nail support.  

Indications for Biotin Supplementation  [16.]

Vitamin B7 Deficiency

Supplementation may be necessary in cases of biotin deficiency, which can occur due to poor renal function, autoimmune diseases, increased alcohol intake, certain medications, or a diet lacking in biotin-rich foods.

‍Hair, Skin, and Nail Health 

Biotin supplementation is often sought to promote healthy hair, skin, and nails. It is commonly included in beauty supplements and products due to its role in keratin production.

Metabolic Support

Biotin is crucial for various metabolic processes including the metabolism of carbohydrates, fats, and proteins. Supplementation may be beneficial for individuals with metabolic disorders or those seeking to support their energy metabolism.

Blood Sugar Regulation 

Some studies suggest that biotin supplementation may help regulate blood sugar levels, particularly in individuals with diabetes or insulin resistance.

Neurological Health

Biotin plays a role in maintaining neurological function, and supplementation may be considered for conditions affecting the nervous system such as multiple sclerosis or neuropathy.

Pregnancy and Breastfeeding 

Pregnant and breastfeeding women may require higher levels of biotin to support fetal development and lactation.

Nail Disorders

Biotin supplementation has been studied for its potential benefits in improving nail strength and reducing brittleness in individuals with nail disorders like brittle nail syndrome.

Muscle Health 

Biotin is involved in muscle metabolism, and supplementation may support muscle growth, repair, and overall muscle health.

Wound Healing 

Biotin plays a role in the synthesis of fatty acids and cell proliferation, which are essential processes for wound healing. Supplementation may aid in wound healing, especially in individuals with chronic wounds or skin conditions.

Testing Options for Biotin Levels  [9.]

Blood Tests

Blood tests may be used to assess biotin levels in the body.  

‍Serum or Plasma Testing

Blood testing to assess serum or plasma levels of biotin may be used to assess biotin deficiency.  Results may be reported in ng/mL or pmol/L, so understanding the reference range of the laboratory used is essential for proper interpretation of results.  

Urine Tests

Urinary Excretion of Biotin and 3-Hydroxyisovaleric Acid: Validated indicators of biotin status include decreased urinary excretion of biotin and increased urinary excretion of 3-hydroxyisovaleric acid. 

Studies show a marked decrease in biotin excretion in subjects on a raw egg white diet, with abnormal values observed in most subjects by day 20. Conversely, increased excretion of 3-hydroxyisovaleric acid is indicative of early biotin deficiency.  [2., 9.]

Test Procedure and Preparation Guidelines

The procedure for testing biotin levels typically involves obtaining urine samples, which may be collected at home or in a lab setting.  

Before undergoing biotin testing, individuals may be instructed to fast for a certain period and avoid consuming biotin-rich foods or supplements to prevent interference with the results.

It's essential to follow any preparation guidelines provided by the healthcare team to ensure accurate test results and to discuss any medications or supplements being taken that could affect biotin levels.

Interpretation of Biotin Testing

While individual labs often report different reference ranges, the reference range for biotin  testing from one lab is:  [1.]

Serum or Plasma: 0.05−0.83 ng/mL.  It is important to contact the individual lab for their reference ranges.  

Urine: contact lab for reference ranges used.  Commonly accepted biotin levels in urine are between 18–127 nmol/24 hours.  [14.]

Additionally, the biotin marker b-Hydroxyisovalerate may also be measured in urine and is commonly assessed as part of an organic acids test such as the DUTCH Plus, DUTCH Complete, or DUTCH Organic Acids Test.  

Elevated levels of beta-hydroxyisovalerate occur in biotin or biotinidase (the enzyme that recycles biotin) deficiency.  [2.]

Clinical Significance of High Biotin Levels 

High biotin levels have not been associated with adverse effects in humans or animals, even with daily doses up to 200 mg orally and up to 20 mg intravenously used to treat biotin-responsive inborn errors of metabolism and acquired biotin deficiency. 

However, caution is warranted regarding acute doses, as studies in pregnant rats indicated that doses equivalent to extremely high human doses caused inhibition of fetal and placental growth and fetal and placental resorption.  [9.]

Nonetheless, these findings are not directly applicable to human intake recommendations due to the excessively high doses used in the study.

Clinical Significance of Low Biotin Levels 

Biotin deficiency, though rare, can lead to various symptoms and health complications.  Symptoms of biotin deficiency may include thinning hair, brittle nails, a scaly rash around the eyes, nose, and mouth, neurological symptoms such as depression, lethargy, hallucinations, and numbness and tingling in the extremities. 

In severe cases, deficiency can lead to neurological problems and developmental delays in infants. 

Specific populations at risk for biotin deficiency include:

‍Inherited Biotinidase Deficiency  [19.]

Biotinidase deficiency is a rare genetic disorder characterized by the body's inability to recycle biotin. This condition results in decreased levels of biotin in the body, leading to symptoms such as seizures, developmental delays, skin rash, and hair loss. 

However, early detection and treatment with biotin supplementation can effectively manage the symptoms and prevent complications in affected individuals.

Individuals with this genetic disorder are often diagnosed in childhood and infancy.

Chronic Alcohol Intake  [14., 16.]

Chronic alcohol intake can lead to biotin deficiency due to impaired absorption and increased urinary excretion of biotin. Symptoms of biotin deficiency in chronic alcoholics may include hair loss, skin rash, and neurological symptoms such as depression and hallucinations. 

Supplementing with biotin may help alleviate these symptoms and restore normal biotin levels in individuals with chronic alcohol intake.

Pregnancy and Breastfeeding  [16.]

Pregnancy and breastfeeding can increase the demand for biotin, potentially leading to deficiency if dietary intake is inadequate.

 Biotin deficiency during pregnancy may result in birth defects or pregnancy complications. Supplementation with biotin may ensure adequate levels for both the mother and the developing fetus or breastfeeding infant.  It is important to discuss supplementation with a healthcare provider in pregnancy and breastfeeding.  

Individuals Taking Certain Medications  [16.]

Antiepileptics such as carbamazepine, phenytoin, and phenobarbital, prolonged use of oral antibiotics, and isotretinoin have all been associated with low biotin levels.

Dietary Intake  [16.]

Individuals who consume raw egg whites regularly are at increased risk of biotin deficiency: egg whites contain avidin, a protein that binds biotin and prevents its absorption.  Chronic malnutrition and individuals on parenteral nutrition without biotin are also at risk of biotin deficiency.  

However, biotin deficiency is rare in healthy individuals with a balanced diet, as biotin is found in a variety of foods such as egg yolks, liver, nuts, seeds, and certain vegetables.

Natural Ways to Optimize B Vitamin Status

Dietary Sources of B Vitamins

Incorporate a variety of foods rich in B vitamins such as:

• Whole grains like brown rice, oats, quinoa, and barley
• Leafy greens such as spinach, kale, and Swiss chard
• Legumes including lentils, chickpeas, and black beans
• Nuts and seeds like almonds, sunflower seeds, and flaxseeds
• Lean meats such as chicken, turkey, and beef
• Dairy products like milk, yogurt, and cheese
• Eggs, particularly the yolk which contains B vitamins
• Seafood such as salmon, tuna, and mackerel which are rich in B12
• Include fortified foods like fortified cereals, bread, and plant-based milk alternatives to increase B vitamin intake.

Lifestyle Strategies to Optimize B Vitamin Status

• Consume a balanced diet rich in fruits, vegetables, whole grains, and lean proteins to ensure adequate B vitamin intake.
• Avoid excessive alcohol consumption as it can interfere with the absorption and utilization of B vitamins, particularly B1 (thiamine), folate and vitamin B6.  [8.] 
• Manage stress levels through relaxation techniques such as deep breathing exercises, meditation, yoga, or mindfulness practices, as chronic stress can deplete B vitamin stores.  [20.] 
• Get regular physical activity, which can help improve overall metabolism and enhance the body's utilization of B vitamins.  Increasing exercise increases vitamin B needs, so supplementing may be desirable in some individuals.  [11.] 

Medications That Lower Vitamin B Levels in the Body

Individuals taking the following medications may want to discuss their B vitamin needs with their healthcare provider:

• Metformin: Used to treat type 2 diabetes, metformin can reduce vitamin B12 absorption and increase the risk of deficiency over time.  [10., 12.]
• Proton pump inhibitors (PPIs): These medications, such as omeprazole and esomeprazole, are commonly used to treat acid reflux and peptic ulcers. Long-term use of PPIs can interfere with the absorption of vitamin B12.  [7., 12.]
• Histamine H2-receptor antagonists: Drugs like ranitidine and cimetidine, used to reduce stomach acid production, may also impair vitamin B12 absorption.  [12.]
• Anticonvulsants: Some antiepileptic drugs like phenytoin, phenobarbital, and primidone can lower levels of folate and vitamin B12 in the body.  [15.] 
• Chemotherapy drugs: Chemotherapy medications can affect the body's ability to absorb and utilize B vitamins, leading to deficiencies.  [5.] 
• Oral contraceptives: Some birth control pills can deplete levels of B vitamins, particularly folate and vitamin B6.  [18.] 
• Diuretics: Certain diuretic medications, including loop and thiazide diuretics, can increase urinary excretion of B vitamins, particularly vitamin B1 (thiamine) and folate.  [13., 17.]

It's important to consult with a healthcare professional if you're taking any of these medications to discuss potential nutrient deficiencies and appropriate supplementation, if needed.

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