Vitamin B7, more commonly known as biotin, is a B vitamin. Like all B vitamins, biotin aids the body in breaking down carbohydrates, fats, and proteins for energy production. It also has roles in maintaining healthy skin, hair, and nervous system function.
Read this post to learn more about the many health benefits of biotin.
What is Biotin (Vitamin B7)?
Biotin, also known as vitamin B7, is a water-soluble B-complex vitamin essential for the growth and development of all organisms .
As a coenzyme of carboxylase enzymes, vitamin B7 is involved in the metabolism of fatty acids, amino acids, and carbohydrates .
The body cannot synthesize vitamin B7, so it needs to be obtained regularly from the diet and intestinal bacteria .
Biotin can be found in a wide variety of foods including animal liver, egg yolks, cow milk, and some fruits and vegetables .
Although vitamin B7 deficiency is rare, it can be dangerous if left untreated. Suboptimal levels or marginal deficiencies, which are a lot more common, have been linked to a variety of negative health effects including growth retardation, neurological dysfunction, hair loss, skin rash, muscle pain, and anemia .
Oral vitamin B7 supplements are completely absorbed even at high pharmacological doses (81.9 micromoles taken orally or 18.4 micromoles taken intravenously) .
Biotin is absorbed via a sodium-dependent multivitamin transporter (SMVT) in the small and large intestines .
After transport from the intestines into the systemic circulation, biotin is taken up by the liver and eventually crosses the blood-brain barrier into the central nervous system .
Soon after oral ingestion by humans, single high doses of biotin (600 micrograms and 900 micrograms) are eliminated from the circulation leading to a significant increase of urinary excretion. Therefore, for prolonged maintenance of blood biotin levels, lower doses (300 micrograms) each day for a week are recommended .
Roughly half of the absorbed vitamin B7 undergoes metabolism to bisnorbiotin and biotin sulfoxide prior to excretion. Vitamin B7, bisnorbiotin, and biotin sulfoxide are present in molar ratios of approximately 3:2:1 in human urine and blood .
The elimination half-life time of biotin is approximately 1 hour, 50 minutes .
Health Benefits of Biotin
1) Necessary for Energy Metabolism
Biotin is a coenzyme for carboxylases, the enzymes that assist in the metabolism of fats, proteins, and carbohydrates for energy production .
These enzymes are essential for the following processes:
- Gluconeogenesis, the metabolic pathway that produces glucose from non-carbohydrate sources including amino acids .
- Cellular energy production .
- The use of branched-chain amino acids (e.g., leucine, isoleucine, and valine) for neurotransmitter production and energy .
- Synthesis and breakdown of fatty acids for energy .
- Insulin release .
Inadequate vitamin B7 levels in the body can slow down metabolism, which leads to fatigue, digestive problems, and weight gain .
2) May Be Beneficial For Type 2 Diabetes
Biotin helps lower blood sugar levels by increasing insulin production, enhancing glucose uptake in muscle cells, and stimulating glucokinase, an enzyme in the liver that promotes glycogen synthesis [20, 21, 22].
Daily supplementation of vitamin B7 decreased fasting blood sugar concentrations by an average of approximately 45% in patients with type 2 diabetes .
Furthermore, high doses have been shown to improve symptoms of diabetic neuropathy, a nerve damage condition commonly exhibited in diabetic patients .
3) May Help Lower Risk of Heart Disease
In combination with chromium, vitamin B7 can help reduce heart disease risk factors by increasing high-density lipoprotein (HDL) levels and decreasing low-density lipoprotein (LDL) levels, especially in diabetic patients with heart disease [28, 29].
Pharmacological doses of biotin (15,000 mcg/day) are also effective in lowering blood triglyceride concentrations in patients with elevated triglyceride levels .
4) Promotes Brain Function and Prevents Cognitive Decline
Biotin is required for myelin sheath formation, a fatty substance that surrounds nerves and facilitates nerve impulse conduction. As such, biotin deficiency can delay myelination .
Multiple sclerosis is an autoimmune disorder characterized by myelin damage and loss. Given its role in the fatty acid synthesis and energy production (both are needed for myelin repair and axonal survival), it has been proposed that biotin may be effective in limiting or reversing multiple sclerosis-related impairments .
However, although these results are promising, research is currently limited and more large-scale clinical trials are required to fully assess the potential disease-modifying mechanism of high-dose vitamin B7 .
Biotin deficiency can also lead to a number of other neurological symptoms, including seizures, lack of muscle coordination, learning disabilities, hallucinations, depression, and lethargy. Most of these conditions can be resolved with biotin supplementation [35, 36, 31].
High-dose biotin supplementation (5-10 mg/kg/day) is also effective in treating biotin-responsive basal ganglia disease, a rare brain metabolic condition characterized by seizures, confusion, and abnormal coordination .
5) Needed for a Healthy Immune System
It increases the production of Th1 cytokines like IL-1β and IFN-γ, which are essential for eliciting an immune response to fight bacterial and viral infections .
Decreased rates of cellular proliferation during biotin deficiency may account for some of these adverse effects on immune function .
A deficiency of biotinidase, an enzyme that helps recycle biotin, is associated with chronic vaginal candidiasis and is treatable with biotin supplementation. Since 1 in every 123 people is believed to be biotinidase deficient, women with chronic vaginal candidiasis may be responsive to biotin treatment .
6) Suppresses Inflammation and May Alleviate Allergic Disorders
In biotin-deficient mice with nickel allergies, biotin supplementation decreased the production of pro-inflammatory cytokines and improved allergic inflammation, suggesting a potential therapeutic effect of biotin against inflammatory and allergic diseases in humans .
7) Promotes Skin, Hair, and Nail Health
This may be related to biotin’s roles in fatty acid synthesis and metabolism, which is critical for skin health .
Skin cells are particularly dependent on fat production since they require extra protection against damage and water loss from constant outdoor exposure .
Inadequate levels of vitamin B7 can also lead to hair loss, which is reversible with supplementation. Although some studies have found that vitamin B7 promotes hair growth in women with thinning hair, there is minimal evidence to support that it promotes hair growth in otherwise healthy individuals [17, 52, 53, 54].
8) May Prevent Birth Defects
Marginal biotin deficiency is common during pregnancy due to the increased biotin demands from the growing fetus .
In animals, even a subclinical level of biotin deficiency can result in cleft palate and limb abnormalities .
It is hypothesized that a low biotin status during pregnancy may increase the risk of birth defects in humans by altering fat metabolism and increasing genomic instability, both of which can lead to the development of chromosomal abnormalities and fetal malformations [60, 61].
In human embryonic palatal (roof of the mouth) stem cells, vitamin B7 depletion was found to suppress carboxylase production and cellular proliferation, indicating that lower levels of vitamin B7 may delay or halt the growth of the embryonic palate, resulting in cleft palate development .
However, definitive evidence establishing the connection between biotin deficiency in humans and the development of birth defects is currently lacking and thus, more research is required .
9) May Protect Against Cancer
Biotin covalently binds to histones, DNA binding proteins that help fold and package DNA into chromatin . The addition of biotin to histones plays a significant role in cellular proliferation, gene silencing, and DNA repair and stability [17, 1].
Low levels of biotin can lead to inadequate histone biotinylation, which can result in genomic instability and abnormal gene expression (cellular production) and thus increases the risks of cancer. These effects have been shown to increase cancer risk in fruit flies and human cancer cell studies [64, 65, 66].
However, in 1 study, higher levels of biotin (up to 600 micrograms) were actually found to increase genomic instability and damage, indicating that biotin’s DNA stabilizing effects may be dose-dependent .
Interestingly, the causal link between histone biotinylation and cancer risk in humans remains to be investigated .
Genetics of Biotin
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BTD Gene – The Enzyme that Recycles Biotin
The BTD gene encodes biotinidase, an enzyme that recycles biotin. Biotinidase transports free biotin through the bloodstream and attaches biotin to other proteins . Single nucleotide polymorphisms (SNPs) in the BTD genome include the following:
- RS2455826 – This gene variant is associated with an increased risk of psoriasis .
- RS7651039 – The “C” allele is associated with a higher risk of coronary heart disease .
SLC5A6 Gene – The Transporter that Transport Biotin Into the Cells
HLCS Gene – The Enzyme that Attaches Biotin to Other Proteins
This gene encodes holocarboxylase synthetase (HLCS), an enzyme that attaches biotin molecules to histones and carboxylase enzymes. Mutations in this gene can reduce biotin binding to molecules and suppress carboxylase activity, resulting in impaired protein, fat, and carbohydrate metabolism. They can also affect the production of genes that are important for normal development [73, 74].
Biotin covalently binds to histones using the enzyme HLCS and is involved in gene silencing, DNA repair, chromatin structure, and transposon repression .
Side Effects & Precautions
Since it is a water-soluble vitamin, vitamin B7 overdose is unlikely as excess amounts are excreted in the urine .
High-dose vitamin B7 supplementation may skew thyroid test results and mimic the laboratory pattern of Grave’s disease .
Lipoic acid competes with vitamin B7 for binding to the sodium-dependent multivitamin transporter (SMVT) in the intestine, so long-term use of lipoic acid could result in depleted vitamin B7 levels .
Prolonged use of antibiotics like tetracycline and sulfonamides can reduce biotin levels because they kill biotin-producing bacteria in the intestines .
Furthermore, some anticonvulsants like primidone and carbamazepine inhibit vitamin B7 absorption. Chronic anticonvulsant use can also increase vitamin B7 breakdown .
Raw egg whites contain the protein avidin, which binds biotin tightly and inhibits its absorption .
Smoking accelerates biotin breakdown, especially in women, resulting in marginal biotin deficiency .
Chronic alcohol consumption can inhibit intestinal biotin absorption .
There is no recommended dietary allowance (RDA) established for vitamin B7 because of limited data on bioavailability .
Adequate intakes for vitamin B7 established by the Food and Nutrition Board (FNB) of the Institute of Medicine (IOM) are listed in the table below:
|Age||Males (μg biotin/day)||Females (μg biotin/day)|
|19 years and older||30||30|
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