Livro DRI 2006 (Micronutrientes)

Livro DRI 2006 (Micronutrientes)


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intake does not appear
may lead to an to provide the
increased cholesterol-
production of lowering effects of
short-chain viscous fiber, but
fatty acids. rather acts more
like nonviscous
fiber.
TABLE 2 Continued
Potential Effect on
Attenuation
Normalization of Blood Other
of Blood Lipid Glucose Physiological
Laxation Levels Responses Effects
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Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
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118 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
cause fiber is not absorbed. Therefore, the potential health benefits of fiber
consumption have been considered in determining DRIs.
Since information was insufficient to determine an EAR and thus calculate
an RDA, an AI was instead developed. The AIs for Total Fiber are based on the
intake level observed to protect against CHD based on epidemiological, clini-
cal, and mechanistic data. The reduction of risk of diabetes can be used as a
secondary endpoint to support the recommended intake level. The relationship
of fiber intake to colon cancer is the subject of ongoing investigation and is
currently unresolved. Recommended intakes of Total Fiber may also help ame-
liorate constipation and diverticular disease, provide fuel for colonic cells, re-
duce blood glucose and lipid levels, and provide a source of nutrient-rich, low
energy-dense foods that could contribute to satiety, although these benefits were
not used as the basis for the AI.
There is no AI for fiber for healthy infants aged 0 to 6 months who are fed
human milk because human milk does not contain Dietary Fiber. During the 7-
to 12-month age period, solid food intake becomes more significant, and so
Dietary Fiber intake may increase. However, there are no data on Dietary Fiber
intake in this age group and no theoretical reason to establish an AI. There is
also no information to indicate that fiber intake as a function of energy intake
differs during the life cycle.
Criteria for Determining Fiber Requirements,
by Life Stage Group
Life stage group Criterion
0 through 6 mo NDa
7 through 12 mo ND
1 through 70 y Intake level shown to provide the greatest protection against
coronary heart disease (14 g/1,000 kcal) ¥ median energy
intake level from CSFII (1994-1996, 1998)
(kcal/1,000 kcal/day)
Pregnancy and Intake level shown to provide the greatest protection against
Lactation coronary heart disease (14 g/1,000 kcal) ¥ median energy
intake level from CSFII (1994\u20131996, 1998)
(kcal/1,000 kcal/day)
a Not determined.
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
PART II: FIBER 119
The UL
The Tolerable Upper Intake Level (UL) is the highest daily nutrient intake that
is likely to pose no risk of adverse effects for almost all people. Although occa-
sional adverse gastrointestinal symptoms are observed when consuming some
of the isolated or synthetic fibers, serious chronic adverse effects have not been
observed. A UL was not set for Dietary Fiber or Functional Fiber. Due to the
bulky nature of fibers, excess consumption is likely to be self-limited.
DIETARY SOURCES
Dietary Fiber is found in most fruits, vegetables, legumes, and grains. Nuts,
legumes, and high-fiber grains typically contain fiber concentrations of more
than 3 percent Dietary Fiber, or greater than 3 g/100 g of fresh weight. Dietary
Fiber is present in the majority of fruits, vegetables, refined grains, and miscel-
laneous foods such as ketchup, olives, and soups, at concentrations of 1 to 3
percent or 1 g/100 g to 3 g/100 g of fresh weight.
Dietary Supplements
This information was not provided at the time the DRI values for fiber were set.
Bioavailability
Fiber is not absorbed by the body.
Dietary Interactions
Foods or diets that are rich in fiber may alter mineral metabolism, especially
when phytate is present. Most studies that assess the effect of fiber intake on
mineral status have looked at calcium, magnesium, iron, or zinc (see Table 3).
INADEQUATE INTAKE AND DEFICIENCY
Dietary and Functional Fibers are not essential nutrients, so inadequate intakes
do not result in biochemical or clinical symptoms of a deficiency. A lack of these
fibers in the diet, however, can cause inadequate fecal bulk and may detract
from optimal health in a variety of ways depending on other factors, such as the
rest of the diet and the stage of the life cycle.
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
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120 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
ADVERSE EFFECTS OF CONSUMPTION
Although occasional adverse gastrointestinal symptoms were observed with the
consumption of Dietary and Functional Fibers, serious chronic adverse effects
have not been observed. The most potentially deleterious effects may arise from
the interaction of fiber with other nutrients in the gastrointestinal tract. Addi-
tionally, the composition of Dietary Fiber varies, making it difficult to link a
specific fiber with a particular adverse effect, especially when phytate is also
present. It has been concluded that as part of an overall healthy diet, a high
intake of Dietary Fiber will not cause adverse effects in healthy people. In addi-
tion, the bulky nature of fiber tends to make excess consumption self-limiting.
TABLE 3 Potential Interactions of Dietary Fiber with Other Dietary
Substances
Substance Potential Interaction Notes
FIBER AFFECTING OTHER SUBSTANCES
Calcium Decreased calcium absorption Some types of fiber have been shown to significantly
when ingested with Dietary increase fecal excretion of calcium. However, most
Fiber human studies have reported no effect.
Magnesium Decreased magnesium Studies report no effect on magnesium balance or
absorption when ingested absorption.
with Dietary Fiber
Iron Reduced iron absorption In one study, the addition of 12 g/day of bran to a meal
when ingested with Dietary decreased iron absorption by 51\u201374 percent, which
Fiber was not explained by the presence of phytate. Other
studies suggest that the effect of bran on iron
absorption is due to phytate content rather than fiber.
Zinc Reduced zinc absorption Most studies also include levels of phytate that are
when ingested with Dietary high enough to affect zinc absorption. Metabolic
Fiber balance studies in adult males consuming 4 oat bran
muffins daily show no changes in zinc balance.
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
PART II: FIBER 121
KEY POINTS FOR FIBER
3 A new set of definitions for fiber has been developed for
Dietary Fiber, Functional Fiber, and Total Fiber. The term Dietary
Fiber describes the nondigestible carbohydrates and lignin that
are intrinsic and intact in plants. Functional Fiber consists of
the isolated nondigestible carbohydrates that have beneficial
physiological effects in humans. Total Fiber is the sum of
Dietary Fiber and Functional Fiber. Nondigestible means not
digested and absorbed in the human small intestine.
3 There is no biochemical assay that reflects Dietary Fiber or
Functional Fiber nutritional status. Blood fiber levels cannot be
measured because fiber is not absorbed.
3 Since data were inadequate to determine an EAR and thus
calculate an RDA for Total Fiber, an AI was instead developed.
3 The AI for fiber is based on the median fiber intake level
observed to achieve the lowest risk of CHD.
3 A UL was not set for Dietary Fiber or Functional Fiber.
3