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 stud-
ies 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 val-
ues calledDietary Reference Intakes(DRIs) for vita-
mins andminerals. 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 an RDA. The Tolerable Upper Intake Level
(UL) is the average maximum amount that can betaken daily without risking negative side effects. The
DRIs are calculated for children, adult men, adult
women, pregnant women, andbreastfeedingwomen.
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 mcgBiotinRecommended
dietary allowance
Age (mcg/day)
Children 0–6 mos. 5
Children 7–12 mos. 6
Children 1–3 yrs. 8
Children 4–8 yrs. 12
Children 9–13 yrs. 20
Children 14–-18 yrs. 25
Adults 19 yrs. 30
Pregnant women 30
Breastfeeding women 35
Food Biotin (mcg)
Liver, cooked, 3 oz. 27
Egg, 1 cooked 25
Bread, whole wheat, 1 slice 6
Swiss chard, cooked, ½ cup 5.2
Salmon, cooked, 3 oz. 4
Chicken, cooked, 3 oz. 3
Cauliflower, raw, ½ cup 2
Pork, cooked, 3 oz. 2
mcg microgram(Illustration by GGS Information Services/Thomson Gale.)KEY TERMS
B-complex vitamins—A group of water-soluble
vitamins that often work together in the body.
These include thiamine (B 1 ), riboflavin (B 2 ), niacin
(B 3 ), pantothenic acid (B 5 ), pyridoxine (B 6 ), biotin
(B 7 or vitamin H), folate/folic acid (B 9 ), and coba-
lamin (B 12 ).
Coenzyme—Also called a cofactor; a small non-pro-
tein molecule that binds to an enzyme and catalyzes
(stimulates) enzyme-mediated reactions.
Dietary supplement—A product, such as a vitamin,
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 them-
selves 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 break-
down 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.Biotin