Livro DRI 2006 (Micronutrientes)

Livro DRI 2006 (Micronutrientes)


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indicates a positive linear trend between cholesterol intake and LDL
cholesterol concentration, and therefore an increased risk of CHD.
A UL was not set for cholesterol because any incremental increase in cho-
lesterol intake increases CHD risk. Because cholesterol is unavoidable in ordi-
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
142 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
nary non-vegan diets, eliminating cholesterol in the diet would require signifi-
cant dietary changes. These changes require careful planning to ensure adequate
intakes of proteins and certain micronutrients. Still, it is possible to eat a low-
cholesterol, yet nutritionally adequate, diet.
DIETARY SOURCES
Foods
Foods of animal origin contain cholesterol. High amounts are found in liver
and egg yolk. Moderate amounts are found in meats, some types of seafood,
including shrimp, lobster, certain fish (such as salmon and sardines), and full-
fat dairy products.
ADVERSE EFFECTS OF CONSUMPTION
The main adverse effect of dietary cholesterol is increased LDL cholesterol con-
centration, which could result in an increased risk for CHD. Serum HDL con-
centration also increases, although to a lesser extent, but the impact of such a
diet-induced change in CHD risk is uncertain. Studies have shown that serum
cholesterol concentrations increase with increased dietary cholesterol and that
the relationship of blood cholesterol to the risk of CHD progressively increases.
On average, an increase of 100 mg/day of dietary cholesterol is predicted to
result in a 0.05\u20130.1 mmol/L increase in total serum cholesterol, of which ap-
proximately 80 percent is in the LDL fraction.
There is also increasing evidence that genetic factors underlie a substantial
portion of the variation among individuals in response to dietary cholesterol.
Although mixed, there is evidence that increases in serum cholesterol concen-
tration due to dietary cholesterol are blunted by diets low in saturated fat, high
in polyunsaturated fat, or both.
No consistent significant associations have been established between di-
etary cholesterol intake and cancer, including lung, breast, colon, and prostate
cancers.
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: CHOLESTEROL 143
KEY POINTS FOR CHOLESTEROL
3 Cholesterol plays an important role in steroid hormone and bile
acid biosynthesis and serves as an integral component of cell
membranes.
3 Because all tissues are capable of synthesizing enough
cholesterol to meet their metabolic and structural needs, there
is no evidence for a biological requirement for dietary
cholesterol.
3 Neither an EAR, RDA, nor AI was set for cholesterol.
3 Much evidence indicates a positive linear trend between
cholesterol intake and LDL cholesterol concentration, and
therefore increased risk of CHD.
3 It is recommended that people maintain their dietary
cholesterol intake as low as possible, while consuming a diet
nutritionally adequate in all required nutrients.
3 A UL was not set for cholesterol because any incremental
increase in cholesterol intake increases CHD risk.
3 High amounts of cholesterol are found in liver and egg yolk.
Meats, some types of seafood, including shrimp, lobster, and
certain fish, as well as full-fat dairy products contain moderate
amounts of cholesterol.
3 The main adverse effect of dietary cholesterol is increased LDL
cholesterol concentration, which could result in an increased
risk of CHD.
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
TABLE 1 Dietary Reference Intakes for Total Protein by
Life Stage Groupa
DRI values (g/kg/day)
EARb RDAc AId
males females males females
Life stage group
0 through 6 mo 1.52 (9.1)
7 through 12 mo 1.0 1.0 1.2 (11)e 1.2 (11)
1 through 3 y 0.87 0.87 1.05 (13) 1.05 (13)
4 through 8 y 0.76 0.76 0.95 (19) 0.95 (19)
9 through 13 y 0.76 0.76 0.95 (34) 0.95 (34)
14 through 18 y 0.73 0.71 0.85 (52) 0.85 (46)
19 through 30 y 0.66 0.66 0.80 (56) 0.80 (46)
31 through 50 y 0.66 0.66 0.80 (56) 0.80 (46)
51 through 70 y 0.66 0.66 0.80 (56) 0.80 (46)
> 70 y 0.66 0.66 0.80 (56) 0.80 (46)
Pregnancy 0.88 f 1.1 (71)f
Lactation 1.05 1.3 (71)
a Dietary Reference Intakes for individual amino acids are shown in Appendix E.
b EAR = Estimated Average Requirement. An EAR is the average daily nutrient
intake level estimated to meet the requirements of half of the healthy individuals in a
group.
c RDA = Recommended Dietary Allowance. An RDA is the average daily dietary
intake level sufficient to meet the nutrient requirements of nearly all (97\u201398 percent)
healthy individuals in a group.
d AI = Adequate Intake. If sufficient scientific evidence is not available to establish
an EAR, and thus calculate an RDA, an AI is usually developed. For healthy breast-fed
infants, the AI is the mean intake. The AI for other life stage and gender groups is
believed to cover the needs of all healthy individuals in the group, but a lack of data or
uncertainty in the data prevents being able to specify with confidence the percentage
of individuals covered by this intake.
e Values in parentheses ( ) are examples of the total g/day of protein calculated
from g/kg/day times the reference weights in Part I, \u201cIntroduction to the Dietary
Reference Intakes,\u201d Table 1.
f The EAR and RDA for pregnancy are only for the second half of pregnancy. For
the first half of pregnancy, the protein requirements are the same as those of
nonpregnant women.
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: PROTEIN AND AMINO ACIDS 145
PROTEIN AND AMINO ACIDS
Proteins form the major structural components of all the cells of the body.Proteins also function as enzymes, in membranes, as transport carriers,and as hormones. Amino acids are constituents of protein and act as
precursors for nucleic acids, hormones, vitamins, and other important mol-
ecules. Thus, an adequate supply of dietary protein is essential to maintain
cellular integrity and function, and for health and reproduction.
The requirements for protein are based on careful analyses of available
nitrogen balance studies. Data were insufficient to set a Tolerable Upper Intake
Level (UL). DRI values are listed by life stage group in Table 1. The Acceptable
Macronutrient Distribution Range (AMDR) for protein is 5\u201320 percent of total
calories for children 1 through 3 years of age, 10\u201330 percent of total calories for
children 4 to 18 years of age, and 10\u201335 percent of total calories for adults
older than 18 years of age.
For amino acids, isotopic tracer methods and linear regression analysis
were used whenever possible to determine requirements. The estimated aver-
age requirements (EARs) for amino acids were used to develop amino acid scor-
ing patterns for various age groups based on the recommended intake of di-
etary protein. Data were insufficient to set a Tolerable Upper Intake Level (UL)
for any of the amino acids. However, the absence of a UL means that caution is
warranted in using any single amino acid at levels significantly above those
normally found in food.
Proteins found in animal sources such as meat, poultry, fish, eggs, milk,
cheese, and yogurt provide all nine indispensable amino acids and are referred
to as \u201ccomplete proteins.\u201d Proteins found in plants, legumes, grains, nuts, seeds,
and vegetables tend to be deficient