Biotin is a water-soluble B-complex vitamin that helps the body metabolize proteins and process glucose. It is also known as vitamin B7 or vitamin H.

The human body cannot synthesize biotin. Only bacteria, molds, yeasts, algae, and certain plants can make it, so the diet needs to supply it.

Unused biotin is eliminated in urine, so the body does not build up reserves. It must be consumed daily.

Biotin supplements are widely available in health food stores, but biotin deficiency is rare, and there is little evidence to suggest that most people need them.

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Biotin comes from a healthy diet.

Biotin is a coenzyme involved in the metabolism of:

  • Fatty acids, a type of molecule found in fats and oils
  • Leucine, an essential amino acid that humans cannot synthesize
  • Gluconeogenesis, the synthesis of glucose from molecules that are not carbohydrates, for example, amino and fatty acids

Coenzymes are substances that enhance an enzyme's action. Coenzymes cannot trigger or speed up a biological reaction, but they help enzymes do so.

The University of Maryland Medical Center (UMM) explain that biotin is important in helping the body to process glucose and to metabolize proteins, fats, and carbohydrates. It also helps to transfer carbon dioxide.

According to the European Food Safety Authority, biotin contributes to:

  • Metabolism of nutrients
  • Energy-producing metabolism
  • Maintaining hair, skin and mucous membranes
  • Nervous system function
  • Psychological function

Biotin contributes to healthy nails, skin and hair, so it features in many cosmetic and health products for the skin and hair. However, it cannot be absorbed through hair or skin.

Nails and hair loss

Biotin is sometimes called vitamin H. The "H" comes from the German words for hair and skin, "Haar" und "Haut."

Some small studies have suggested that taking a 2.5-milligram supplement of biotin for 6 months can increase fingernail strength and reduce the tendency of nails to split.

However, there is no evidence until now that biotin can prevent or treat hair loss in men or women.

A lack of biotin has been linked to cradle cap in infants, but there is no evidence that biotin supplements, for example, in formula milk, might help.

Biotin and diabetes

Since biotin aids metabolism, it could play a role in controlling diabetes. Research has suggested that B7 can improve the use of glucose in the body. People with diabetes have a problem using glucose, because of an insulin imbalance. Biotin appears to improve the synthesis of fatty acids, enhance the storage of glucose. In rats, it has been found to stimulate the secretion of insulin.

Some reports have suggested that biotin supplements can improve symptoms of neuropathy, for example, in people with diabetes. However, these have not been confirmed by research.

One study found that people with diabetes had lower levels of biotin than people without the condition.

In another, people who had lost their sense of taste reported improvements after taking an additional 10 to 20 micrograms a day of biotin.

However, research into the benefits of biotin has been too limited so far to draw any firm conclusions.

Little is known about how much biotin people need, but the United States Food and Nutrition Board suggest that infants of 0 to 6 months should have 6 micrograms a day, rising to 30 micrograms a day for adults of 19 years and older, and 35 micrograms for breastfeeding women.

In Europe, surveys have shown that on average, people consume 36 micrograms of biotin per day. There is no similar data for the U.S.

Biotin deficiency appears to be rare, but some groups may be more susceptible.

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Biotin supplements are widely available but rarely necessary.

A deficiency can lead to:

  • Hair loss
  • A scaly red rash around the eyes, nose, mouth, and genitals
  • Cracks in the corner of the mouth
  • Sore tongue that may be magenta in color
  • Dry eyes
  • Loss of appetite

Other symptoms may include:

  • Depression
  • Lethargy and fatigue
  • Hallucinations
  • Insomnia
  • Numbness and tingling in the hands and feet
  • Impaired immune function and increased susceptibility to infections

Pregnant women appear to break down biotin more quickly, and this may lead to a marginal deficiency. Symptoms have not been observed, but such a deficiency could lead to developmental problems for the fetus.

Just as women are advised to take additional folic acid, or B9, during pregnancy, it may be beneficial to add B7 to this supplement.

Other groups who may benefit from supplements include:

  • Those on anticonvulsant medications
  • People with some types of liver disease
  • People who are fed intravenously for a long time

Biotinidase deficiency is a rare, hereditary disorder that impairs biotin absorption, resulting in a deficiency of biotin. Biotin supplements can help people with this condition.

Those who have difficulty absorbing biotin and other nutrients due to chronic conditions such as Crohn's disease may benefit from biotin supplements.

A wide range of foods contain biotin. None of them have large amounts, as is the case with some other vitamins.

Foods that have slightly higher amounts include:

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Wholemeal bread is a source of vitamin B7.
  • Liver
  • Peanuts
  • Yeast
  • Whole-wheat bread
  • Cheddar cheese
  • Pork
  • Salmon
  • Sardines
  • Avocado
  • Raspberries
  • Bananas
  • Mushrooms
  • Cauliflower
  • Egg yolk

Processing food reduces levels of nutrients such as biotin, so raw cauliflower, for example, would provide more biotin than cooked cauliflower.

A study published in Advances in Nutrition estimates biotic intake in North America and Western Europe at between 35 to 70 μg per day, or 143 to 287 mmol per day.

Biotin is also available in supplements.

According to Oregon State University, biotin is not known to cause toxic effects.

People with hereditary disorders of biotin metabolism tolerate doses of up to 200,000 mcg per day without any problems. Individuals with no biotin metabolism disorder who took doses of 5,000 mcg per day for 24 months had no adverse effects.

However, it is important to speak to a physician or dietitian before making any change to nutritional intake or using supplements.