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OCR for page 196
TABLE 1 Dietary Reference Intakes for Biotin by
Life Stage Group
DRI values (mg/day)
AIa ULb
Life stage groupc
0 through 6 mo 5
7 through 12 mo 6
1 through 3 y 8
4 through 8 y 12
9 through 13 y 20
14 through 18 y 25
19 through 30 y 30
31 through 50 y 30
51 through 70 y 30
> 70 y 30
Pregnancy
£ 18 y 30
19 through 50 y 30
Lactation
£ 18 y 35
19 through 50 y 35
a AI = Adequate Intake.
b UL = Tolerable Upper Intake Level. Data were insufficent to set a UL. In the
absence of a UL, extra caution may be warranted in consuming levels above the
recommended intake.
c All groups except Pregnancy and Lactation represent males and females.
OCR for page 197
PART III: BIOTIN 197
BIOTIN
B
iotin functions as a coenzyme in bicarbonate-dependent carboxylation
reactions. It exists both as free biotin and in protein-bound forms in
foods. Little is known about how protein-bound biotin is digested.
Since data were insufficient to set an Estimated Average Requirement (EAR)
and thus calculate a Recommended Dietary Allowance (RDA) for biotin, an
Adequate Intake (AI) was instead developed. The AIs for biotin are based on
data extrapolation from the amount of biotin in human milk. Data were insuf-
ficient to set a Tolerable Upper Intake Level (UL). DRI values are listed by life
stage group in Table 1.
The biotin content of foods is generally not documented. It is widely dis-
tributed in natural foods, but its concentration varies. Signs of biotin deficiency
have been conclusively demonstrated in individuals consuming raw egg whites
over long periods and in patients receiving total parenteral nutrition (TPN)
solutions that do not contain biotin. No adverse effects have been documented
for biotin at any intake tested.
BIOTIN AND THE BODY
Function
Biotin functions as a coenzyme in bicarbonate-dependent carboxylation
reactions.
Absorption, Metabolism, Storage, and Excretion
Biotin exists both as free biotin and in protein-bound forms in foods. Little is
known about how protein-bound biotin is digested. It appears to be absorbed
in both the small intestine and the colon. The mechanism of biotin transport to
the liver and other tissues after absorption has not been well established. Avi-
din, a protein found in raw egg white, has been shown to bind to biotin in the
small intestine and prevent its absorption. The mechanism of biotin transport
to the liver and other tissues after absorption has not been well established.
Biotin is excreted in the urine.
OCR for page 198
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
198
DETERMINING DRIS
Determining Requirements
Since data were insufficient to establish an EAR and thus calculate an RDA, an
AI was instead developed. The AIs for biotin are based on extrapolation from
the amount of biotin in human milk. Most major nutrition surveys do not re-
port biotin intake.
Special Considerations
Individuals with increased needs: People who receive hemodialysis or perito-
neal dialysis may have an increased requirement for biotin, as do those with
genetic biotinidase deficiency.
Criteria for Determining Biotin Requirements,
by Life Stage Group
Life stage group Criterion
0 through 6 mo Human milk content
7 through 12 mo Extrapolation from infants
1 through > 70 y Extrapolation from infants
Pregnancy
£ 18 through 50 y Extrapolation from infants
Lactation
£ 18 through 50 y To cover the amount of biotin secreted in milk, the AI is
increased by 5 mg/day
The UL
The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient
intake that is likely to pose no risk of adverse effects for almost all people. Due
to insufficient data on the adverse effects of excess biotin consumption, a UL for
biotin could not be determined.
DIETARY SOURCES
Foods
Biotin content has been documented for relatively few foods, and so it is gener-
ally not included in food composition tables. Thus, intake tends to be underes-
OCR for page 199
PART III: BIOTIN 199
timated in diets. Although biotin is widely distributed in natural foods, its con-
centration significantly varies. For example, liver contains biotin at about 100
mg/100 g, whereas fruits and most meats contain only about 1 mg/100 g.
Dietary Supplements
According to the 1986 National Health Interview Survey (NHIS), approximately
17 percent of U.S. adults reported taking a supplement that contained biotin.
Specific data on intake from supplements were not available.
Bioavailability
This information was not provided at the time the DRI values for this nutrient
were set.
Dietary Interactions
This information was not provided at the time the DRI values for this nutrient
were set.
INADEQUATE INTAKE AND DEFICIENCY
Signs of biotin deficiency have been conclusively demonstrated in individuals
consuming raw egg whites over long periods and in patients receiving total
parenteral nutrition (TPN) solutions that do not contain biotin. The effects of
biotin deficiency include the following:
• Dermatitis (often appearing as a red scaly rash around the eyes, nose,
and mouth)
• Conjunctivitis
• Alopecia
• Central nervous system abnormalities, such as depression, lethargy, hal-
lucinations, and paresthesia of the extremities
Symptoms of deficiency in infants on biotin-free TPN appear much earlier after
the initiation of the TPN regimen than in adults. In biotin-deficient infants,
hypotonia, lethargy, and developmental delays, along with a peculiar withdrawn
behavior, are all characteristic of a neurological disorder resulting from a lack of
biotin.
OCR for page 200
DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
200
EXCESS INTAKE
There have been no reported adverse effects of biotin in humans or animals.
Toxicity has not been reported in patients given daily doses of biotin up to 200
mg orally and up to 20 mg intravenously to treat biotin-responsive inborn er-
rors of metabolism and acquired biotin deficiency.
OCR for page 201
KEY POINTS FOR BIOTIN
Biotin functions as a coenzyme in bicarbonate-dependent
3
carboxylation reactions.
Since data were insufficient to establish an EAR and thus
3
calculate an RDA, an AI was instead developed.
The AIs for biotin are based on extrapolation from the amount
3
of biotin in human milk.
People who receive hemodialysis or peritoneal dialysis may
3
have an increased requirement for biotin, as may those with
genetic biotinidase deficiency.
Data were insufficient to set a UL.
3
The biotin content of foods is generally not documented. It is
3
widely distributed in natural foods, but its concentration varies.
Signs of biotin deficiency have been conclusively
3
demonstrated in individuals consuming raw egg whites over
long periods and in patients receiving total parenteral nutrition
(TPN) solutions that do not contain biotin.
The effects of biotin deficiency include dermatitis, alopecia,
3
conjunctivitis, and abnormalities of the central nervous system.
No adverse effects have been associated with high intakes of
3
biotin.
