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Vitamins, Water-Soluble
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...biotinidase, which is present in the small intest
Vitamins
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...biotin): joins with enzymes that regulate the bre
Digestion and Absorption
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...biotin by friendly bacteria; and (6) the excretio
Nutrients
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...biotin are both produced by bacteria that live wi
Niacin
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...biotin (B7 or vitamin H), niacin/folic acid (B9),
Pantothenic Acid
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...biotin (B7 or vitamin H), folate/folic acid (B9),
High-Protein Diet
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...biotin (B7 or vitamin H), folate/folic acid (B9),
Perricone Diet
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...biotin calcium, chromium, magnesium, selenium, zi
Choline
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...biotin (B7 or vitamin H), folate/folic acid (B9),
Folate
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...biotin (B7 or vitamin H), folate/folic acid (B9),


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Biotin

Definition

Biotin, also known as vitamin H or vitamin B7, belongs to the group of B-complex water-soluble vitamins. Humans make only a small amount of biotin, so most biotin must come from the foods they eat. Biotin is involved in conversion of carbohydrates, fats, and protein into usable energy in the body.

Purpose

Biotin joins with enzymes that regulate the breakdown of foods and their use in the body. Some researchers believe that biotin also plays a role in the duplication and “reading” (replication and transcription) of deoxyribonucleic acid (DNA—genetic material). Biotin is often promoted as a dietary supplement to help improve the strength of fingernails and prevent hair loss. These claims are unproven.

Description

Biotin is one of the less familiar B vitamins. It was discovered in the 1930s by researchers experimenting with different diets for chickens and rats, and later it was discovered to be essential to human health. Bacteria, yeasts, mold, algae, and some plants make biotin. The human large intestine (colon) contains some bacteria that synthesize biotin. Researchers believe that a portion of this biotin is absorbed into the bloodstream, but they are uncertain how much or how available it is to the body.

Biotin is essential to life because it combines with four different enzymes that control different metabolic reactions related to energy production and building new molecules from simple nutrients. These are:

  • Forming glucose from fats and amino acids (but not from carbohydrates)
  • Building fatty acids
  • Synthesizing leucine, an amino acid necessary for health
  • Metabolizing amino acids, cholesterol, and some fatty acids

Biotin

AgeRecommended dietary allowance (mcg/day)
Children 0–6 mos5
Children 7–12 mos6
Children 1–3 yrs8
Children 4–8 yrs12
Children 9–13 yrs20
Children 14–-18 yrs25
Adults 19> yrs30
Pregnant women30
Breastfeeding women35
FoodBiotin (mcg)
Liver, cooked, 3 oz27
Egg, 1 cooked25
Bread, whole wheat, 1 slice6
Swiss chard, cooked, ½ cup5.2
Salmon, cooked, 3 oz4
Chicken, cooked, 3 oz3
Cauliflower, raw, ½ cup2
Pork, cooked, 3 oz2
mcg =microgram 

(Illustration by GGS Information Services/Thomson Gale.)

Some researchers have found that biotin binds to proteins called histones that open up chromosomes so that their DNA becomes accessible and can be copied. If this is true, then biotin could play a role in gene expression.

Dietary supplement makers promote biotin to treat brittle fingernails, dry skin, and to prevent hair loss. It is sold as a dietary supplement in capsules or tablets, either alone, in a multivitamin, or combined with brewer’s yeast. Biotin is also added to cosmetics and skin creams. In animal studies, biotin improves the condition of horse hooves, but no controlled studies have shown the same effect on human fingernails. Biotin deficiency does cause hair loss, but there is no proof that supplemental biotin prevents hair loss.

Normal biotin requirements

The United States Institute of Medicine (IOM) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRIs) for vitamins and minerals The DRIs consist of three sets of numbers. The Recommended Dietary Allowance (RDA) defines the average daily amount of the nutrient needed to meet the health needs of 97–98% of the population. The Adequate Intake (AI) is an estimate set when there is not enough information to determine anRDA. The Tolerable Upper Intake Level (UL) is the average maximum amount that can be .

KEY TERMS

B-complex vitamins—A group of water-soluble vitamins that often work together in the body. These include thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7 or vitamin H), folate/folic acid (B9), and coba-lamin (B12)

Coenzyme—Also called a cofactor; a small non-protein molecule that binds to an enzyme and catalyzes (stimulates) enzyme-mediated reactions

Dietary supplement—A product, such as avitamin, mineral, herb, amino acid, or enzyme, intended to be consumed in addition to an individual’s diet with the expectation that it will improve health

Enzyme—A protein that changes the rate of a chemical reaction within the body without themselves being used up in the reaction.

Fatty acids—Complex molecules found in fats and oils. Essential fatty acids are fatty acids the body needs but cannot synthesize. They are made by plants and must be present in the diet to maintain health

Glucose—A simple sugar resulting from the breakdown of carbohydrates. Glucose circulates in the blood and is the main source of energy for the body

Vitamin—A nutrient the body needs in small amounts to remain healthy but that the body cannot manufacture for itself and must acquire through diet

Water-soluble vitamin—A vitamin that dissolves in water and can be removed from the body in urine.

taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.

The IOM has not set RDA values for biotin because of incomplete scientific information. Instead, it has set AI levels for all age groups. AI levels for biotin are measured by weight (micrograms or mcg). No UL levels have been set for biotin because large doses of biotin do not appear to cause any side effects.

The following are the AIs for biotin for healthy individuals:

  • Children birth-6 months: 5 mcg
  • Children 7-12 months: 6 mcg
  • Children 1-3 years: 8 mcg
  • Children 4-8 years: 12 mcg
  • Children 14-18 years: 25 mcg
  • Adults age 19 and older: 30 mcg
  • Pregnant women: 30 mcg
  • Breastfeeding women: 35 mcg

Sources of biotin

Biotin is found in small quantities in many foods. Bacteria in the large intestine also make biotin. Unlike some vitamins, biotin is recycled and reused by the body. Daily intake does not need to be high because only small amounts are lost in urine. Biotin is stable and little is lost when foods are exposed to heat, light, or air.

The approximate biotin content in common foods is:

  • Bread, whole wheat, 1 slice: 6 mcg
  • Egg, 1 cooked: 25 mcg
  • Liver, cooked, 3 ounces: 27 mcg
  • Chicken, cooked, 3 ounces: 3 mcg
  • Pork, cooked, 3 ounces: 2 mcg
  • Salmon, cooked, 3 ounces: 4 mcg
  • Swiss chard, cooked, 1/2 cup: 5.2 mcg
  • Cauliflower, raw, 1/2 cup: 2 mcg

Biotin deficiency

Biotin deficiency is very rare worldwide. Only a few conditions are known to cause biotin deficiency. Two rare inherited genetic disorders cause the body to need excessive amounts of biotin. These disorders are treated with high-dose biotin supplements. Prolonged (months or years) consumption of raw egg whitescan also cause a deficiency. A protein in raw egg whites binds biotin and makes it unavailable to the body. Cooking the egg releases the biotin. Receiving all nutrition through intravenous feeding (total parenteral nutrition or TPN) for an extended period may also lead to a shortage of biotin in the body.

Symptoms of biotin deficiency include skin and hair problems, such as a red scaly rash on the face, increased susceptibility to fungal infections, brittle hair, and hair loss. Individuals may also develop seizures, problems with coordination, and muscle cramps. Biotin deficiency has not been known to cause death. These symptoms have many other causes that should be considered first because biotin deficiency is so rare.

Precautions

In many species, pregnant animals who are biotin deficient give birth to offspring with birth defects at a higher rate than animals who have adequate levels of biotin. The same effect has not been seen in humans. However, blood levels of biotin tend to drop in pregnant women, causing concern among researchers that pregnant women may develop marginal biotin deficiency with no visible symptoms. Dietary supplements of biotin are not routinely recommended for women who are pregnant, but these women should make a special effort to get an adequate intake of 30 mcg biotin daily through diet. Pregnant and breastfeeding women should not take a biotin dietary supplement unless directed by their healthcare provider.

Interactions

Biotin is known to interact with a few drugs and dietary supplements

  • Antibiotics taken over a long period may reduce the amount of bacteria in the large intestine that synthesize biotin.
  • Long-term use of drugs used to prevent seizures such as phenytoin (Dilantin), primidone (Mysoline), car-bamazepine (Tegretol), phenobarbitol (Solfoton) and possibly valproic acid cause a reduction in the blood level of biotin.
  • High doses of pantothenic acid may decrease the amount of biotin absorbed from the large intestine.

Complications

No complications are expected from biotin. Even when large doses are taken for long periods, there are no reported side effects.

Parental concerns

Biotin deficiency is rare and biotin excess is so benign that parents should have almost no concern about their children’s biotin needs being met by diet.

BOOKS

Berkson, Burt, and Arthur J. Berkson. Basic Health Publications User’s Guide to the B-complex VitaminsLaguna Beach, CA: Basic Health Publications, 2006.

Gaby, Alan R., ed. A-Z Guide to Drug-Herb-Vitamin Interactions Revised and Expanded 2nd Edition: Improve Your Health and Avoid Side Effects When Using Common Medications and Natural Supplements TogetherNew York: Three Rivers Press, 2006.

Lieberman, Shari, and Nancy Bruning. The Real Vitamin and Mineral Book: The Definitive Guide to Designing Your Personal Supplement Program4th ed. New York: Avery, 2007.

Pressman, Alan H., and Sheila Buff. The Complete Idiot’s Guide to Vitamins and Minerals, 3rd edIndianapolis, IN: Alpha Books, 2007

Rucker, Robert B., ed. Handbook of Vitamins. Boca Raton, FL: Taylor & Francis, 2007.

ORGANIZATIONS

Linus Pauling Institute. Oregon State University, 571.

Weniger Hall, Corvallis, OR 97331-6512. Telephone: (541) 717-5075. Fax: (541) 737-5077. Website: <http://lpi.oregonstate.edu>.

OTHER

Higdon, Jane. “Biotin.’ Linus Pauling Institute-Oregon State University. June 1, 2004. [cited April 28, 2007] <http://lpi.oregonstate.edu/infocenter/vitamins/biotin>.

Scheinfeld, Noah S. and Stephanie B. Frelich. “Biotin.

Deficiency.” emedicine.com, June 22, 2006. [cited April 28, 2007]. <http://www.emedicine.com/ped/topic238>.

Tish Davidson, A.M.


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