Biotin, also known as vitamin H or B7, is a water-soluble vitamin that helps the body metabolize fats, carbohydrates, and protein. Water-soluble vitamins are not stored in the body so daily intake is necessary.
Vitamin B7 cannot be synthesized by human cells, but it is produced by bacteria in the body, and it is present in numerous foods.
Biotin therapy may help treat some medical conditions. Some people take supplements to strengthen their nails and hair, but there is a lack of evidence supporting this use.
This article looks at why we need biotin, the recommended intake, sources, and any possible health risks.
Fast facts on biotin:
- Biotin, or vitamin B7, is needed to metabolize fats, carbohydrates, and protein.
- Deficiency can lead to hair loss and skin problems, but it is rare.
- Dietary sources include red meat, eggs, seeds, and nuts.
- Supplements are unlikely to cause harm but they are not proven to help with hair, skin, and nail health.
The body needs biotin to metabolize fats, carbohydrates, and protein.
It is a coenzyme for carboxylase enzymes. These enzymes are involved in:
- synthesizing, or creating, fatty acids
- synthesizing the amino acids isoleucine and valine
- gluconeogenesis, or generating glucose
Biotin is important for a number of functions.
Maintaining a healthy pregnancy
Mild biotin deficiency is often seen during pregnancy. It can lead to abnormal development in the fetus.
Folic acid supplementation is recommended both the year before and during pregnancy. It is sensible to obtain a multivitamin that provides at least 30 mcg of biotin per day, in addition to folic acid, to decrease the risk of a deficiency.
Nails, hair, and skin
There is some evidence that biotin may improve the strength and durability of fingernails and enhance hair and skin health.
A study published in 1989 found that among 45 patients who took a supplement of 2.5 mg a day, 91 percent had "firmer and harder finger nails" after 5 months.
Other researchers have concluded that "brittle nail syndrome appears to abate with supplementation with a 2.5-mg dose of biotin daily or a 10-mg dose of silicon daily."
Research published in 2015 found that women with thinning hair experienced some reduction in shedding after taking an oral marine protein supplement (MPS) for 90 days. However, biotin was only one ingredient in this supplement, and the research was sponsored by a company that sells health and beauty products.
According to the Office of Dietary Supplements (ODS), there is little evidence that biotin supplements can strengthen nails and promote healthy hair.
Further studies are needed to support the use of biotin supplements for this purpose in healthy individuals.
Lowering blood glucose
Several studies have tested biotin's ability to lower blood glucose in people with type 1 and type 2 diabetes. Results have been promising.
More studies are needed before biotin's effects on blood sugar can be confirmed.
In 1990, scientists found that three patients who took a high dose of biotin for 1 to 2 years saw an improvement in symptoms.
Biotin is necessary for the activity of pyruvate carboxylase. Without this, high levels of pyruvate and aspartate may arise, and this can adversely affect the nerves.
However, more evidence is needed to confirm this.
Biotin-responsive basal ganglia disease
This is a rare, inherited disorder. It affects a part of the nervous system that controls movement. It can lead to involuntary tensing of muscles, muscle rigidity, muscle weakness, and other problems.
The condition appears to respond to treatment with thiamin and biotin.
Treating multiple sclerosis
Studies have suggested that high-dose biotin therapy might help improve symptoms in people with multiple sclerosis (MS), an autoimmune disease that affects the nervous system, leading to muscle weakness and a range of other problems.
Results published in 2016 suggested that biotin was a safe therapy. In some participants, a high dose, taken three times daily, reduced symptoms after 9 months of use.
Biotin deficiency is rare in humans, because biotin is widely available in foods, and the "good" gut bacteria can normally synthesize more biotin than the body needs.
Signs of deficiency include:
- hair loss, or alopecia
- a scaly, red rash around the eyes, nose, mouth, and genitals
- numbness and tingling in the hands and feet
- a loss of control of bodily movements, known as ataxia
- impaired immune function
- increased risk of bacterial and fungal infection
Biotin deficiency is most likely to arise in:
- women during pregnancy
- patients receiving prolonged intravenous nutrition
- infants who consume breastmilk with low amounts of biotin
- patients with impaired biotin absorption due to an inflammatory bowel disease (IBD) or other gastrointestinal (GI) tract disorder
- people who smoke
It may also affect:
- those who use medications for epilepsy, such as phenobarbital, phenytoin, or carbamazepine
- those with some kinds of liver disease
Biotinidase deficiency is another cause of biotin deficiency. This is an autosomal recessive metabolic disorder.
In people with this condition, the body does not produce enough of the enzyme needed to release biotin from proteins in the diet during digestion or from normal protein turnover in the cell.
Around 1 in 60,000 newborns have profound or partial biotinidase deficiency. In a profound deficiency, there is less than 10 percent of normal enzyme activity. In a partial deficiency, 10 to 30 percent of normal enzyme activity takes place.
There is no recommended daily allowance (RDA) for biotin, because there is insufficient evidence to establish one.
However, the Institute of Medicine (IOM) suggests an adequate intake (AI) 30 micrograms (mcg) a day for adults aged 19 years and over.
Food should be the first choice when looking for sources of biotin. Biotin in foods usually binds to protein.
Foods that are rich in biotin include:
- baker's yeast
- wheat bran
- organ meats
- cooked, whole eggs
Raw eggs contain a protein called avidin that inhibits the absorption of biotin. Eating two or more raw egg whites a day for several months has been linked to biotin deficiency.
Here are some specific foods and amounts of biotin:
- 3 ounces of cooked liver: 30.8 mcg
- 1 large, whole cooked egg: 10 mcg
- 3 ounces of canned pink salmon in water: 5 mcg
- 1 ounce of cheddar cheese: 0.4 to 2 mcg
- 1 cup of sweet potato: 4.8 mcg
- 3 ounces of cooked hamburger patty: 3.8 mcg
- 1 cup roasted sunflower seeds: 9.6 mcg
- 1 cup of roasted almonds: 6 mcg
Many foods, such as fruits and vegetables, contain a small amount of biotin.
Biotin supplements are available alone, combined in a supplement with B vitamins, or included in a multivitamin.
People take biotin supplements to prevent or treat:
- hair loss
- brittle nails
- seborrheic dermatitis, a skin condition that affects infants
- mild depression
Those with biotinidase deficiency usually start with a dose of 5 to 10 mg a day.
Those without this genetic condition should first try to get enough biotin from the diet, as dietary biotin also enhances the intake of other beneficial nutrients that work alongside it.
It is always best to get nutrients from dietary sources first, and then from supplements, if necessary, as a backup.
Always speak to a doctor before taking supplements, and choose brands carefully, as supplements are not monitored by the United States (U.S.) Food and Drug Administration (FDA).
Large doses of biotin have no known toxic effects, but some drugs, herbs, and supplements may interact.
If biotin is taken with alpha-lipoic acid, the body may not be able to absorb either of them effectively. The same is true of vitamin B5, or pantothenic acid.
Biotin supplements may also interact with some medications that are broken down by the liver, including clozapine (Clozaril), haloperidol (Haldol), olanzapine (Zyprexa), and others.
There is no evidence that most people need to take biotin supplements, and there have been no reports of a severe biotin deficiency in any healthy person consuming a balanced diet.
A well-balanced diet is likely to supply most people's needs, unless a doctor advises them otherwise.
Anyone who is considering taking biotin supplements should first check with a doctor.