Cover Image

PAPERBACK
$49.95



View/Hide Left Panel
Click for next page ( 197


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

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 196
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 196
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 196
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 196
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 196
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.