Biotin – Vitamin B7

Biotin, also referred to as Vitamin B7 or Vitamin H, is a water-soluble vitamin that is primarily classified as a B-complex vitamin.

It is required by all forms of life yet only yeasts, bacteria, algae, and some plant species have the ability to synthesize it.

All B vitamins are needed by the body in order to have healthy liver, eyes, skin, and hair. They are also essential in the proper functioning of the nervous system.

B vitamins are not stored in the body and excess amounts are eliminated through waste products such as urine and sweat.

Bacteria found in the intestine can produce biotin and this nutrient is also found in trace amounts in several foods. Biotin is also vital for normal embryonic growth thus; it is a highly needed nutrient during pregnancy.

Biological Role of Vitamin B7, Biotin, in the Body

Vitamin B7 is attached at the active site of carboxylases, which are a group of five mammalian enzymes. The attachment of this vitamin nutrient to another molecule like protein is referred to as biotinylation. The biotinylation of apocarboxylases, such as the enzyme’s catalytically inactive form, are catalyzed by Holocarboxylase synthetase (HCS).

Biotinidase catalyzes the release of the biotin from the peptide products of carboxylase breakdown as well as from histones.

Histones are proteins that are bound to deoxyribonucleic acid (DNA) and package it into compact structures, thus forming nucleosomes, which are the integral structural components of chromosomes.

Biotin is not known to be a toxic nutrient, as the body can eliminate excess amounts that are not required since it is a water-soluble vitamin. Oral supplementation of biotin has been well-tolerated in doses that are up to 200,000 mcg/day for individuals with hereditary disorders of biotin metabolism. It has been reported that a person can have doses of up to 5,000 mcg/day for two years if there are diagnosis of disorders of biotin metabolism.

Biotin Deficiency

Although overt deficit of vitamin B7 is very rare, the requirement for biotin of humans has been seen in two different conditions: the consumption of raw egg white for several weeks to years (prolonged usage) and prolonged intravenous feeding, or parenteral, without proper supplementation of biotin.

The antimicrobial protein found in egg white, known as avidin, binds biotin and prevents its absorption. Avidin is denatured when egg white is cooked, making it susceptible to digestion and making the absorption of biotin possible.

The reduced urinary excretion of biotin; propionyl-CoA carboxylase activity in peripheral blood lymphocytes; and the  high excretion of  3-hydroxyisovaleric acid (organic acid) that reflects decreased activity of the  methylcrotonyl-CoA carboxylase (a biotin-dependent enzyme), are the three measures of the status of biotin, which are validated as indicators of vitamin B7 status.

Biotin deficiencies have signs and symptoms that include hair loss, and a scaly red rash around the mouth, nose, eyes, and in the genital area. Neurologic symptoms of vitamin B7 deficit in adults are tingling and numbness of the extremities; lethargy; depression; and hallucination.

Persons with hereditary disorders of biotin metabolism that result to functional biotin deficiency normally have similar physical findings and signs of having an increased susceptibility to fungal and bacterial infections, as well as having an impaired function of the immune system.

Vitamin B7 deficiency is very rare. Patients with parenteral nutrition, which is a nutrition provided via an IV, for a long period of time; with conditions such as Crohn’s disease that make it difficult for nutrients to be absorbed; and those taking antibiotics or antiseizure medication on a long term basis, are more likely to develop biotin deficiency.

Biotin RDA

The Food and Nutrition Board of the Institute of Medicine set an Adequate Intake level (AI) for biotin in 1998 since there is an insufficient scientific evidence to calculate the recommended dietary allowance (RDA) for vitamin B7. The AI for this nutrient assumes that the recent average intake can meet the proper dietary requirement.

Adequate Intake (AI) for Vitamin 7 – Biotin

AGE FEMALES (µg/day) MALES (µg/day)
0 to 6 months 5 5
7 to 12 months 6 6
1 to 3 years 8 8
4 to 8 years 12 12
9 to 13 years 20 20
14 to 18 years 25 25
19 years and older 30 30
Pregnant 30
Lactating 35

 Dietary Sources of Biotin

This essential nutrient is found in several foods but in lower amounts compared to other water-soluble vitamins. Some good vitamin B7 rich foods include whole wheat bread, yeast, cheddar cheese, egg, salmon, liver, pork, cauliflower, avocado, raspberry, and legumes such as beans and black-eyed peas.


UMM; LPI; Hoffman; Colorado State University; Wikipedia.