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6
Special Con si cleration s an c!
Act justments
SUMMARY
This chapter provides a discussion of the process and criteria used
to establish the Dietary Reference Intakes (DRIB) in order to help
users make informed judgments cluring the clietary planning
process.
The limitations in the ciata used to develop the DRIs and the
relationship between clietary nutrient inacloquacy and inacloquate
nutritional status are important considerations when planning diets.
This chapter also aciciresses factors such as nutrient bioavailability
and physiological, lifestyle, and health factors that may alter nutri-
ent requirements and leaci to adjustments in the DRI values when
planning clietary intakes for individuals and Croons
INTRODUCTION
- a-~--r-
It is well established that biological variability exists among indi-
vicluals with regard to both nutrient requirements and susceptibility
to adverse effects from excessive nutrient intakes. These individual
differences, when known, in the normal, apparently healthy popula-
tion have already been considered in establishing the Dietary Refer-
ence Intakes (DRIs). Specifically, variability in incliviclual requirements
around the Estimated Average Requirement (EAR) is consiclereci in
setting the Recommencleci Dietary Allowance (RDA), the intake
recommendation for inclivicluals. The Acloquate Intake (AI) is set at
a level thought to meet or exceed the neecis of almost all inclivicluals
133
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134
DIETARY REFERENCE INTAKES
of a given life stage and gender group. The Tolerable Upper Intake
Level (UL) is set at an intake at which all but the most sensitive
members of a population would not be expected to experience
adverse effects. Thus, most normal sources of variability have already
been considered in setting the DRI values, as they apply to the
typical diets of apparently healthy people in the United States and
Canada. However, there are other identifiable factors that may alter
nutrient requirements systematically such that the DRI values may
need to be adjusted when planning nutrient intakes for certain indi-
viduals or groups. These factors, discussed below, include charac-
teristics of the nutrient source that influence nutrient bioavailability,
as well as physiological, health, or lifestyle characteristics of indi-
viduals that may require tailoring of requirement estimates.
INFLUENCE OF THE NUTRIENT SOURCES
Bioavailability
Information on the bioavailability of nutrients from foods, forti-
fied foods, and supplemental nutrient sources has been used in
developing the Dietary Reference Intakes (DRIB) and must also be
considered in applying the DRIs to dietary planning. Issues regard-
ing bioavailability for each nutrient are discussed briefly below and
in greater detail in the individual DRI nutrient reports (IOM, 1997,
1998a, 2000b, 2001, 2002a).
Different sources of a nutrient can vary in chemical or physical
form, which can affect bioavailability. Thus, in planning diets for
individuals or groups, consideration may need to be given to whether
the nutrient is supplied in its natural food matrix, as a fortificant to
a food source, or in a supplemental form not associated with food.
For example, U.S. Department of Agriculture food composition data
have only recently been modified to reflect the different bioavail-
ability between natural food sources of folate (1 dietary folate equiv-
alent tDFE] = 1 ,ug of folate found naturally in food) and folate
added as a fortificant to foods (1 DEE = 0.6 fig). Accordingly, in
planning to increase an individual's folate intake by about 100 DFEs
to meet the Recommended Dietary Allowance (RDA), it would be
necessary to consider whether to increase the intake of fruits and
vegetables or fortified grain products (or both). An increase of 100
DFEs would require 100,ug of folate from fruits and vegetables, but
only 60,ug from fortified grain products. However, if the food com-
position data were reported in DEE units, differences in bioavail-
ability would already have been taken into account.
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SPECIAL CONSIDE~TIONS AND ADJUSTMENTS 1 35
The source of a nutrient can also affect the potential risk of nutri-
ent intakes that exceed the Tolerable Upper Intake Level (UL). For
several nutrients, there is no known risk of excessive intake from
natural foocis. Accordingly, the UL for nutrients such as magne-
sium, folate, niacin, and vitamin E are baseci only on chemical or
synthetic forms obtained from supplements or acicleci to foocis (IOM
1997, 1998a, 2000b). Excessive intakes for other nutrients such as
calcium, selenium, iron, and vitamins C and D are baseci on the
combination of intakes from food and supplements (IOM 1997,
2000b, 2001~.
For some nutrients, the chemical form varies within natural foocis,
as well as between natural and synthetic sources. For instance, heme
iron, the form of approximately 40 percent of the iron in meat,
poultry, and fish (Monsen et al., 1978), is generally better absorbed
than the remaining (nonheme) form of iron in foocis. This cliffer-
ence between heme and nonheme iron absorption, which is one
factor that can contribute to the lower iron absorption seen in plant-
baseci cliets, has been aciciresseci by recommencling intakes for vege-
tarians that reflect the lower average absorption.
These differences between sources of a nutrient can be of such
importance that, in some cases, it is specified which source should
be used to meet nutrient intake recommendations. For example,
because about 10 to 30 percent of older adults have recluceci gastric
acidity, they may not readily absorb the protein-bounci form of vita-
min BE that is found naturally in food sources. To ensure that
adequate vitamin BE is absorbed when planning for individuals or
groups where the average age is over 50, planners are encouraged
to include foods fortified with vitamin BE or a supplement contain-
ing vitamin BE since the synthetic form of the vitamin is absorbed
effectively even in those with low gastric acid secretion. Another
example relates to planning for inclivicluals or groups where women
are in their childbearing years. In this case, the diet plan should
include 400 ,ug of folate from fortified foocis or supplements in
aciclition to the food folate contained in a varied cliet since studies
that showed reduced risk of neural tube defects were conducted
with 400,ug of folate as supplements.
Interactions with Other Nutrients, Food Components, and Properties
of the Dietary Matrix
In aciclition to the bioavailability factors cliscusseci above, nutrient
utilization can be influenced by interactions with other nutrients or
food constituents. Examples include enhancement of nonheme iron
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DIETARY REFERENCE INTAKES
absorption by ascorbic acid; inhibition of calcium, iron, and zinc
absorption by physic acid from whole grains, nuts, and legumes;
enhancement of the absorption of the fat-soluble vitamins A, D, E,
and K by clietary fat; improved absorption of ,3-carotene in some
vegetables after cooking and blencling; and competitive imbalances
of minerals such as calcium, iron, zinc, and copper (Mertz et al.,
1994~. Excessive intake of one nutrient may interfere with absorp-
tion. excretion. transport, storage, function, or metabolism of
another.
Specific nutrient interactions with food components and drugs
have also been iclentifieci (IOM, 1997, 1998a, 2000b, 2001, 2002a).
Because of quantitative and bioavailability differences, nutrient-
nutrient interactions are of particular concern in cliet planning
when nutrients are provicleci by supplementation or fortification
rather than by food sources. Such interactions have been consici-
ereci in setting the DRIB, including the establishment of ULs that
may be specific for nutrients used in fortification or taken as sup-
plements. Accordingly, in most cases planners do not need to make
adjustments to DRIs baseci on nutrient-nutrient interactions.
Special Considerations for Vegetarian Diets
Well-planneci vegetarian cliets are associated with good health
(Messina and Burke, 1997~. However, not all vegetarian cliets are
the same. Depending on the foocis inclucleci or exclucleci from the
cliet, careful planning may be required to meet recommendations
for various nutrients.
For example, vitamin BE is found only in foocis cleriveci from
animal sources or in those foocis to which it is acicleci cluring fortifi-
cation. Inclivicluals following vegan cliets (exclusively composed of
plant foocis) will neeci to either use a vitamin BE supplement or
consume fortified foocis containing sufficient amounts of synthetic
vitamin Bit. Vegetarians who do not use fluici milk are likely to have
low vitamin D intakes, especially those living in northern latitudes
where exposure to ultraviolet light floes not occur cluring winter
months (Laclizesky et al., 1995; Webb et al., 1988~. Populations who
do not use milk and milk products are likely to neeci aciclitional
sources of calcium in their cliets. This can be achieved with the
judicious selection of plant sources or the use of calcium-fortifieci
foods and beverages.
Inclivicluals or groups who follow vegetarian cliet plans that omit
all animal products are likely to be at risk for inacloquate intakes of
iron and zinc, which also neecis to be taken into account when
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SPECIAL CONSIDERATIONS AND ADJUSTMENTS 1 37
planning cliets. Hunt and Rougheaci (1999) clemonstrateci that iron
absorption from vegetarian cliets was recluceci compared with an
omnivorous cliet. In similar studies, zinc absorption was approxi-
mately 35 percent less from a lactoovovegetarian cliet as compared
with an omnivorous cliet (Hunt et al., 1998~. The description of the
recommencleci intakes for iron and zinc further reviews the evidence
of lower bioavailability of these nutrients from plant sources and
recommencis iron intakes for vegetarians that are higher than the
RDAs for the general population (IOM, 2001~.
Another nutrient of potential concern for vegetarians is protein.
Because protein intakes of vegetarians are typically lower than intakes
of those following omnivorous cliets, the issue of protein quality
becomes particularly important. In the past there were no recom-
mencleci intakes for indispensable amino acids, and it was assumed
that inclivicluals consuming a mixed cliet (animal and vegetable pro-
teins with a biological value of 75 percent) with the recommencleci
amounts of protein would obtain the neecleci amounts of inclispens-
able amino acids. Now that both Estimated Average Requirements
(EARs) and RDAs have been provicleci for indispensable amino
acids, it is important to reexamine this issue.
. .
It appears that cliets acloquate in total protein may not be neces-
sarily acloquate in all the indispensable amino acids, at least for
lysine. Data in Table 6-1 compare the amino acid composition of
various protein sources to the Food and Nutrition Boarci/Institute
of Medicine amino acid scoring pattern (IOM, 2002a). The scoring
pattern indicates the amounts of each indispensable amino acid per
gram of protein neecleci to meet the EAR for the indispensable
amino acid when total protein intake equals the EAR. A single
scoring pattern has been aclopteci because there are relatively small
differences between the amino acid requirements of children and
adults when the requirements are expressed relative to total protein
requirements. The ciata suggest that although most protein sources
provide recommended amounts of threonine, tryptophan, and sulfur-
containing amino acids, this may not be true for lysine. Animal
protein sources provide relatively high amounts of lysine, so incli-
vicluals who do not consume animal protein sources (or who con-
sume limited amounts) may be unlikely to obtain the recommencleci
amounts of lysine when total protein intake is limited to the RDA,
unless beans are the primary protein source in their cliet. Even then,
cliets may be marginal, as the ciata in the table are not acljusteci for
the lower digestibility often seen in plant protein sources. There-
fore, in addition to planning total protein intakes, it may be neces-
sary to plan for intakes of lysine in vegan diets.
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DIETARY REFERENCE INTAKES
TABLE 6-l Selected Indispensable Amino Acici Content of
Protein Sourcesa Compared to Recommencleci Levels
Indispensable Amino Acid (mg/g protein)
Methionine
Lysine Threonine Tryptophan + Cysteine
FNB/IOM scoring patterns 51 27 7 25
Beef, lean 83 44 11 37
Cheddar cheese 76 33 12 29
Egg 70 49 16 56
Tofu 66 41 16 27
Soymilk 65 41 16 32
Garbanzo beans 67 37 10 26
Almonds 29c 32 15 25
Peanut butter 36c 34 10 33
Brown rice 38c 37 13 35
Cornmeal 28C 38 7 39
Wheat bread 28C 30 13 39
a USDA Nutrient Database for Standard Reference, Release 15, August 2002.
b From IOM (2002). The scoring patterns indicate the amounts of essential amino acids
per gram of protein needed to meet the Estimated Average Requirement (EAR) for the
essential amino acid when total protein intake equals the EAR for protein.
c The protein source would not provide recommended amounts of the indispensable
amino acid if it were the only source of protein in the diet.
The neeci to plan intakes of lysine is likely of greatest importance
for individuals whose diets emphasize plant foods and are relatively
low in total protein. For example, the RDA for total protein for the
reference 57-kg woman is 46 g/ciay. If she followoci a plant-baseci
cliet and ate no more than the RDA of 46 g of protein tinily, she
would be unlikely to meet her RDA for lysine (2.2 g/ciay) unless 50
percent or more of her clietary protein was provicleci from beans or
tofu (rich sources of lysine). To be specific, 23 g of protein from
beans and tofu would provide about 1.5 g of lysine, and 23 g of
protein from other sources, such as wheat, rice, and nuts, would
provide about 0.7 g of lysine. However, if her total protein intake
was greater (e.g., about 63 g/ciay, or similar to the meclian protein
intake reported by women in the 1994-1996 Continuing Survey of
Food Intakes by Inclivicluals tUSDA/ARS, 19974), she could meet
her RDA for lysine with much smaller amounts of beans and tofu
(providing about 10 percent of her total dietary protein). Thus,
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SPECIAL CONSIDE~TIONS AND ADJUSTMENTS 1 39
planning for inclivicluals who consume only plant sources of protein
should involve careful review of lysine intakes. If their total protein
intake is limited to the RDA for protein, beans and legumes should
be emphasized as the major source of clietary protein.
INDIVIDUAL CHARACTERISTICS THAT INFLUENCE
DIETARY REQUIREMENTS
Recommencleci Dietary Allowances (RDAs) and Acloquate Intakes
(AIs) are used as goals for nutrient intakes to meet the known nutri-
ent requirements of almost all healthy inclivicluals in various life
stage and gentler groups. As cliscusseci below, the Dietary Reference
Intake (DRI) process has already accounted for normal incliviclual
variability, and incliviclual adjustments for factors such as age, nutri-
ent status, genetic variation, or body size are generally not required.
In other instances, adjustments may be warranted for inclivicluals
with lifestyle differences or who are ill.
Nutrient Status
Nutrient absorption, excretion, and utilization can all be substan-
tially affected by the nutrient status of the incliviclual (e.g., low,
moderate, or high tissue concentrations). Inclivicluals with lower
body stores or who have aciapteci to lower intakes of a nutrient are
likely to have greater rates of absorption and lower rates of excre-
tion. These relationships have probably been best characterized in
humans for iron. However, the Estimated Average Requirement
(EAR) and resulting RDA are baseci on 18 percent iron absorption
by people with minimal iron stores (defined as a serum ferritin level
of 15 ,ug/L) and have already been acljusteci for incliviclual variation
in iron status; thus, no further adjustments are required.
Genetic Variation
Rapidly expanding information on the human genome indicates
many possible interactions between incliviclual genetic traits and
nutrient requirements. Examples of genetic clisorclers requiring
nutritional treatment include classical inborn errors of metabolism
such as phenylketonuria, lipoprotein lipase deficiency, and vitamin
D-clepenclent rickets. More subtle genetic differences may contribute
to variability in requirements within populations generally regarded
as normal and healthy. For example, a genetic polymorphism under
current investigation adversely affects homocysteine concentrations
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DIETARY REFERENCE INTAKES
(and thus potential heart disease risk) in subjects with relatively
poor folate status Jacques et al., 1996~. The continuing discovery
and evaluation of genetic influences on nutritional requirements
may lead to more specific recommendations for subgroups of the
population. In the meantime, however, the RDAs are expected to
meet the needs of almost all individuals, which should include many
who may have higher than average requirements.
Unusual Body Size or Composition, Energy Expenditure, or
Physical Activity
By establishing EARs and using the estimated variability of the
requirement distribution to set RDAs to include 97 to 98 percent of
all individuals in a life stage and gender group, these recommended
intakes already account for typical variation in body size or energy
expenditure in a specific group. Depending on the function and
tissue distribution of the nutrient, such variation may be associated
with skeletal mass, lean body mass, body water, or total body mass
(IOM, 1997, 2000b). Larger individuals would be expected to have
greater requirements based on larger body nutrient pools or func-
tional compartments. Although reference body sizes (IOM, 1997)
have been considered in deriving recommended intakes for specific
life stage and gender subgroups, information on most nutrients is
inadequate to precisely set recommendations in relation to an indi-
vidual's body size or energy expenditure.
While there was insufficient evidence to define a relationship
between energy requirements or body size and the requirements
for thiamin, riboflavin, and niacin (IOM, 1998a), the functions of
these nutrients are known to be directly related to energy metabo-
lism. If, when planning diets, professionals choose to make an
upward adjustment of B vitamin recommendations for individuals
with unusually high energy requirements, the conservative approach
(in terms of making recommendations to minimize the possibility
of dietary inadequacy) would be to assume that vitamin require-
ments increase in direct proportion to energy requirements. An
example of how these adjustments should be made has been oro-
vided in the DRI assessment report (IOM, 2000a).
. .
Research on the impact of physical activity on nutrient require-
ments was evaluated as part of the DRI process, especially in rela-
tion to the requirements for B vitamins, vitamins with antioxidant
properties such as vitamins C and E, and protein. For most nutri-
ents, the data were considered insufficient to recommend specific
alterations in the EARs or RDAs related to physical activity or athletic
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SPECIAL CONSIDERATIONS AND ADJUSTMENTS 141
performance. An exception is iron. Body iron losses appear to increase
with vigorous exercise, perhaps because of increased gastrointestinal
blood losses or because of erythrocyte rupture within the foot clur-
ing running (IOM, 2001~. Consequently, athletes engaged in regu-
lar intense exercise may have average requirements for iron that
range from 30 to 70 percent above those of normally active incli-
vicluals. Aciclitionally, athletes with extremely high energy intakes
Exceeding 6,000 kcal/ciay) may have clietary phosphorus intakes
that exceed the Tolerable Upper Intake Level (UL), but this is not
thought to be harmful (IOM, 1997~.
Age and Physio11og~ca11 Stage
Children
Recommencleci intakes change considerably across some age
boundaries in children. For example, the RDA for magnesium for
children ages 4 to 8 years is 130 mg/ciay, whereas the RDA for
children ages 9 to 13 years is 240 mg/day. Clearly, magnesium needs
do not change abruptly on a child's ninth birthday. Although it
might appear reasonable to speculate that those at the higher end
of an age range would have higher requirements than those at the
lower end of the age range, in most cases knowledge of exactly how
a chilcl's nutrient requirements change with age is imprecise. For
this reason, adjustment of recommencleci intakes within an age range
is not recommencleci.
Adjustments in recommencleci intakes may be appropriate when
relevant physiological changes can be iclentifieci for inclivicluals. An
example is the onset of menarche in girls. The RDA for iron for
girls 14 to 18 years of age allows for iron losses in menses. If
menarche occurs prior to age 14, an aciclitional amount, about
2.5 mg of iron/clay, would be neecleci to cover menstrual blood
losses. Conversely, girls ages 14 and above who have not reached
menarche can subtract 2.5 mg from the RDA for this age group.
When boys or girls can be iclentifieci as undergoing the growth spurt
of adolescence, the RDA for iron can be further adjusted by increas-
ing daily intakes by 2.9 and 1.1 ma, respectively (IOM, 2001~.
Women of Reproductive Age
To reduce the risk of neural tube defects it is recommended that
all women capable of becoming pregnant obtain 400 ,ug of folate
from fortified foocis or supplements on a ciaily basis in aciclition to
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DIETARY REFERENCE INTAKES
folate from a varied cliet. For most women, a straightforward way to
do this is to use a multivitamin supplement containing 400 ,ug of
folate. Folate is also acicleci to grains and cereals, but unless a highly
fortified breakfast cereal is consumed, it would take unusually large
amounts of some of these foocis to obtain 400 ,ug. For example, a
slice of breaci contains 20 ,ug of acicleci folate (the required level of
folate fortification of breaci).
Major differences in menstrual iron losses are an example of iclen-
tifiable incliviclual characteristics that mollify nutrient requirements.
These losses can be substantially moclifieci by physiological changes
such as menopause or hormonal therapy. The RDA for women ages
31 to 50 is intencleci to cover losses associated with menstruation,
while the RDA for women over age 50 assumes that menopause has
occurred. Menopause, then, rather than turning 50, is the physio-
logically significant event related to iron requirements. A woman
who experiences menopause before age 50 (anci who floes not com-
mence cyclic hormone treatment that results in the partial return
of menstrual blood losses) could safely aim for an iron intake of
8 ma, the RDA for women over age 50. Conversely, a bl-year-olci
woman who is still menstruating regularly should aim for an iron
intake of 18 ma, the RDA for women ages 31 to 50.
Dietary iron neecis are lower for women using oral contraceptives
clue to recluceci menstrual blood loss. Accordingly, the recommencleci
intake for iron is adjusted down to 11.4 mg/day for adolescent girls
and clown to 10.9 mg/ciay for premenopausal women using oral
contraceptives (IOM, 2001~. Although a number of reports suggest
some changes in riboflavin, B6, or folate status for women using
oral contraceptives, the available evidence floes not indicate any
neeci for adjustment in the RDAs for these nutrients.
Gestation of Mu;ttip;te Fetuses
The RDAs and AIs for pregnancy and lactation have been clevel-
oped for singleton pregnancies and the production of sufficient
breast milk to nourish one infant. During pregnancy and lactation
of multiple births, the intakes recommencleci for singletons may not
be appropriate.
To experience good pregnancy outcomes, women who are preg-
nant with two or more fetuses neeci to gain more weight than has
been associated with good outcomes for singleton pregnancies, and
guidelines for weight gain during multiple pregnancies have been
clevelopeci (IOM, 1990~. At this point, however, average nutrient
requirements for women pregnant with multiple fetuses are not
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SPECIAL CONSIDERATIONS AND ADJUSTMENTS 143
known and specific recommencleci intakes have therefore not been
cleriveci. It has been noted, though, that intakes of some nutrients,
such as protein, should be higher for women pregnant with two or
more fetuses than for women pregnant with one (IOM, 2002a).
For lactating women, recommencleci intakes for many nutrients
are clevelopeci, at least in part, on the basis of the amount of the
nutrient secreted in breast milk. Women nursing two or more
infants secrete greater volumes of breast milk (Saint et al., 1986~;
thus, it is reasonable to assume that their nutrient neecis are also
higher. The increased amount of energy required to nurse multiple
infants will likely be met by natural appetite adjustments, and energy
balance can be evaluated by monitoring body weight for mother
and infants. If this increase in maternal energy intake emphasizes
nutrient-clense food selections, then consumption of a variety of
nutrients will be proportionally increased. Similar to pregnancy,
however, specific recommendations for women nursing more than
one infant have not been established.
Adu;tts Over Age 50
For some nutrients, requirements (anci thus recommenciations)
change in association with physiological changes that are expected
to occur with aging. For example, the AI for vitamin D is higher for
adults over age 50 years than for those uncler age 50 years.
The AI for vitamin D increases from ~ ,ug for inclivicluals through
age 50 years to 10 ,ug for those ages 51 to 70 years, and to 15 ,ug for
those over age 70 years (IOM, 1997~. Because vitamin D is not wicle-
ly clistributeci in the food supply (it occurs naturally in liver, fatty
fish, and egg yolk, and is routinely acicleci to fluici milk, cirieci skim
milk powder, and margarine), it is easy to envision cliets that would
not provide vitamin D in amounts recommencleci for older adults.
Special attention to intakes of this vitamin is thus warranted for
individuals in this category, particularly because endogenous syn-
thesis is less efficient with advancing age (MacLaughlin and Holick,
1985~. Use of a supplement containing vitamin D could be consid-
ered, particularly by those living in northern latitudes or who rarely
receive sun exposure and do not regularly drink milk.
It has been estimated that from 10 to 30 percent of inclivicluals
over the age of 50 have low levels of gastric acidity, resulting in
insufficient release of vitamin BE from the protein to which it is
bounci in foocis, and thereby resulting in recluceci absorption of the
vitamin. For this reason it is recommencleci that adults over the age
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DIETARY REFERENCE INTAKES
of 50 obtain most of their RDA for vitamin BE from synthetic
sources (either in a supplement or in fortified foods) (IOM, 1998a).
LIFESTYLE FACTORS THAT AFFECT REQUIREMENTS
Alcohol Abuse
Alcoholism or alcohol abuse is associated with reduced food and
nutrient intakes and a greater frequency of nutrient deficiencies,
especially thiamin, niacin, vitamin Be and folate (IOM, 1998a).
Chronic, excessive alcohol intake results in damaging physiological
effects that may affect absorption, plasma concentrations, metabolism,
and excretion of nutrients such as vitamin B6 and folate. Specific
nutrient requirements have not been established in relation to levels
of alcohol consumption.
The importance of assuring adequate intakes of micronutrients in
situations of alcohol abuse is emphasized by the greater frequency
of nutrient deficiencies in alcoholics, an example of which is the
irreversible consequences of the Wernicke-Korsakoff syndrome of
severe thiamin deficiency. For uncontrolled alcoholics who are unable
to correct their poor food intake habits, a nutrient supplement may
be helpful in meeting their requirements for micronutrients.
Cigarette Smoking
Although blood folate concentrations have been reported to be
lower in smokers than in nonsmokers (IOM, 1998a), data suggest
that a low intake (Subar et al., 1990) rather than an increased
requirement may account for the poorer folate status of smokers.
In contrast, there is substantial evidence that smoking increases
oxidative stress and metabolic turnover of vitamin C, thus recom-
mended intakes of vitamin C are increased by 35 mg/day for
smokers (IOM, 2000b).
DIETARY PLANNING FOR PEOPLE WHO ARE ILL
Just as is the case with healthy persons, planning diets for those
who are ill first involves setting nutrient goals that are appropriate
for their health status and nutrient needs. The Recommended
Dietary Allowance (RDA), the Adequate Intake (AI), and the Toler-
able Upper Intake Level (UL) are appropriate Dietary Reference
Intakes (DRIB) for dietary planning for healthy individuals. How-
ever, some individuals who are ill have conditions that affect the
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SPECIAL CONSIDERATIONS AND ADJUSTMENTS 145
absorption, storage, metabolism, or excretion of one or more nutri-
ents and, as a result, the DRIs for these nutrients must be moclifieci
to take these clisease-relateci factors into account. This section
describes a general approach for using the DRIs in these situations.
Once appropriate therapeutic goals are cletermineci, they too must
be converted into a cliet that the incliviclual can acquire, afford, and
will eat.
Most diseases and conditions alter neecis for only a few nutrients,
with other nutrient neecis remaining similar to those of healthy
persons. In clinical practice it is usually assumed that unless there is
a specific deviation of a nutrient known to be associated with the
disease or condition, the incliviclual is "healthy" with regard to that
nutrient and the RDAs or AIs are reasonable goals for incliviclual
planning. Thus, the intake recommendation that is appropriate for
the incliviclual's gentler, age, level of physical activity, and physio-
logical state (e.g., pregnancy, lactation) would apply.
Government agencies or other organizations frequently specify
that cliets feci to patients or to institutionalized populations meet
previously established RDA or Recommencleci Nutrient Intake
(RNI) levels. The approaches clescribeci in this report to plan cliets
for a low risk of inacloquate nutrient intakes for groups and inclivici-
uals would apply in these situations. For example, patients who are
not at nutritional risk, who do not require a nutrition intervention,
or who receive a regular cliet, can be treated as a group unless their
nutritional status changes. Individual patients with specific nutri-
tion therapy plans can have their dietary intakes planned initially
using the RDAs or AIs with appropriate mollifications macle for
their specific conditions by a trained health care professional or
dietitian.
After the appropriate nutrient goals for the individual who is ill
have been cletermineci, these goals must then be converted into a
clietary pattern that the incliviclual will consume. Therapeutic clietary
planning relies upon specialized food guidance and menu planning
systems specific to the various disease states that affect nutrient
needs. The DRIs will be useful in the development of diet manuals
for people with special health care needs. Parenterally-fed patients
require special forms of nutrients, and needs must be adjusted since
bioavailability factors are not applicable and absorptive losses do
not occur. Thus, the DRIs cannot be used directly to plan parenteral
intakes.
As an example, a uremic patient who has end-stage renal disease
might be placed on a very low protein diet to decrease blood urea
nitrogen and other biochemical indices of uremia and to provide
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DIETARY REFERENCE INTAKES
symptomatic relief. The cliet might also be moclifieci to restrict
sodium and phosphorus. However, the RDA or AI would be used
for other nutrients not known to be affected by the disease process.
The DRIs are formulated to meet the neecis of the vast majority of
the healthy population within specified life stage and gentler
groups. However, when the absorption, metabolism, or excretion of
a nutrient is known to be altered by a specific illness or disease
process, the DRIs can also be used as the base for developing thera-
peutic flints.
Representative terms from entire chapter:
reference intakes
