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Biotin for hair and nails: what is it for?

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Biotin for hair and nails: what is it for?

What is Biotin?

Biotin is an essential molecule, i.e. a substance that the human body must necessarily introduce with the diet because it is unable to produce it autonomously.

It was discovered in the first decades of the 20th century under curious circumstances: yes, in 1916 he observed such as a diet excessively rich in egg whitesraw egg quickly became a cause of toxicity in many animals, as well as in humans; when the only source of protein consisted of this food, neurological dysfunction, hair loss, dermatitis and finally death appeared. However, we have to wait many years for biotin to be isolated and linked to the unanswered experiments related to egg white.

Several research groups, including the Hungarian scientist Paul Gyorgy, dealt with the question by discovering biotin in the 1930s, but it was only in 1941 that the mystery was finally revealed: the toxicity of egg white was caused by the of biotin with avidin, a antinutritional factor present in the albumen, which prevented the correct absorption of the molecule, making the animals rapidly deficient in a clearly vitamin essential.

Biotin is water soluble and is actively involved in a wide range of metabolic processes, mainly related to the utilization of grassi, carbohydrates and amino acids; its deficiency can manifest itself in the form of skin, nerve and eye disorders.

Also referred to as vitamin H, commercially it is typically included in supplements against the hair loss and for the brittle nails.

How much do you need?

According to the Italian guidelines, it is currently not possible to define the average biotin requirementborn the maximum tolerable dosewhile the daily amount considered appropriate predicts (doses in μg, or micrograms):

  • 6-12 months: 7
  • 1-3 years: 10
  • 4-6 years: 15
  • 7-10 years: 20
  • 11-14 years: 25
  • 15-17 years: 30
  • Adults: 30
  • Pregnancy and feeding time: 35
See also  Favism, what it is, symptoms and drugs to avoid

Where is it?

It is possible to introduce biotin through numerous foods; Among the richest sources are:

  • offal,
  • egg,
  • pesce,
  • carne,
  • semi,
  • nights
  • and some vegetables (such as sweet potatoes).

Shutterstock/Yulia Furman

However, the content actually present can vary considerably, due to factors such as, for example, the variety of the vegetable and the season in which the food is harvested and processed; it should also be remembered that avidin, a glycoprotein contained in raw egg whites (cooking deactivates it), binds tightly to food biotin and prevents its correct absorption.

A lower bioavailability is observed in plants, but it is useful to remember that it can also be produced by intestinal bacteria (and yes believes that not even one strictly vegan diet could constitute a risk of shortage), overall it is therefore not believed that there is an effective diffusion of shortage states in Western populations.

Biotin is absorbed in the small intestine and, for the most part, then stored in the liver.

What is it for? For hair and nails?

Physiologically, biotin is used by the body in numerous metabolic processes and in the regulation of gene expression, but since the most characteristic symptoms of its deficiency include skin rashes, hair loss and brittle nails, it should come as no surprise that supplements based on this vitamin are often promoted to promote the health of skin appendages. At best, however, these claims are supported by only a few case reports and small studies.

Although there are therefore no particular contraindications to trying an integration of a few weeks (biotin is very well tolerated even at high doses), there is no clear evidence of efficacy to date in the general population.


Biotin deficiency is rare and has never been reported in severe form in healthy subjects following a normal mixed diet.

Signs and symptoms of deficiency appear gradually and may include:

  • thinning hair with progression to loss of all body hair
  • red, scaly rash around body openings (eyes, nose, mouth, and perineum)
  • conjunctivitis (inflammation of the conjunctiva, with Red eyes)
  • lactic acidosis (which occurs when the production of lactate exceeds disposal capacity) and aciduria (excessive amounts of acid in the urine)
  • convulsions
  • skin infections
  • brittle nails
  • neurological impairment in adults:
  • hypotonia (loss of muscle tone) lethargy (inability to stay awake) and developmental delay in infants.

I am at risk of shortage

  • patients with genetic biotinidase deficiency (a rare autosomal recessive disorder)
  • alcoholics
  • pregnant and breastfeeding women.

Finally, note that taking antiepileptic drugs could be reduce the absorption capacity of the vitamin.

Side effects

Biotin is considered reasonably safe even in high doses; several studies have found no adverse effects up to very high doses (also because the excess is rapidly excreted in the urine). According to some sources a dramatic excess of biotin could cause insomnia, excessive thirst e increased urinationbut this is more of a theoretical risk than a practical one.

However, it should be borne in mind that taking biotin-containing supplements could alter the results of some common blood tests, leading to inappropriate patient management or even the formulation of an erroneous diagnosis. Tests that have found possible interference include:

Biotin interference can produce both falsely normal and falsely abnormal results, thus in an unpredictable manner.

And recommend the interruption of the intake of the supplement at least 48 hours before the sampling, even more in the case of high doses.


There are no specific contraindications to taking biotin-based supplements, with the important warning of the previous paragraph, relating to the risk of alteration of blood tests.

Biotin and thyroid

Biotin does NOT interfere with the functioning of the thyroid gland, but it is known for the possible interference in the blood tests used for its evaluation; the Italian Medicines Agency Report That:

  • erroneously high or erroneously low results may occur in patients taking biotin [… e] such unreliable results may lead to inappropriate patient management or misdiagnosis.
  • [Ad esempio] Biotin may cause thyroid test results to mimic the Graves’ diseaseand thus lead to unnecessary treatment with antithyroid drugs.

Sources and bibliography

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