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OCR for page 21
Nutritional Status of the U. S. Population:
Iron, Vitamin C, and Zinc
CATHERINE WOTEKI, CLIFFORD JOHNSON, Ad
ROBERT MURPHY
Conclusions can be drawn about the nutritional status of Americans by
relating data on selected indicators of nutritional status to data on food
consumption from two federal surveys: the second National Health and
Nutrition Examination Survey (NHANES II), conducted by the Depart-
ment of Health and Human Services (DHHS), and the Nationwide Food
Consumption Survey (NFCS), conducted by the U.S. Department of Ag-
riculture (USDA). In the first paper of this session, Dr. Welsh reviewed
the sufficiency of nutrition-related data from the two most recent of these
surveys. For some nutrients, a substantial quantity of data is available
from both surveys. For other nutrients, data on dietary intake, on nutri-
tional status, or on both may be of limited quantity or quality for a variety
of reasons. To illustrate how conclusions about the nutritional status of
Americans can be drawn from these surveys, three nutrients are discussed:
· iron, for which sufficient data are available to assess both nutritional
status and dietary intake;
· vitamin C, for which there is only one indicator of nutritional status
but sufficient dietary intake data; and
· zinc, for which there is one indicator of nutritional status and no data
on dietary intake.
DATA SOURCES
The NHANES II was conducted by the DHHS National Center for
Health Statistics from 1976 through 1980 on a national probability sample
21
OCR for page 22
22
EATING PA77ERNS, NUTRlTlON, AND BEALTH
of Americans aged 6 months through 74 years who were representative
of the civilian, noninstitutionalized population (McDowell et al., 19811.
The results of this survey provide an opportunity to assess the U.S. pop-
ulation's health and nutritional status and, by comparing the data with
results of earlier surveys, to learn how this status has changed over time.
The NHANES lI sample consisted of 27,801 persons from 64 geographical
locations in the United States. Of these, 20,322 (73~o) were interviewed
and given a standardized physical examination. A detailed description of
the survey design and its operations has been published in the Vital and
Health Statistics Series of He National Center for Heals Statistics (McDowell
etal., 19811.
The NFCS was conducted by the USDA Human Nutrition Information
Service during 1977 and 1978 on a national probability sample of Amer-
ican households that were representative of the 48 coterminous states. It
provides information on household food use over 7 days and household
members' food and nutrient intakes over 3 days. The NECS sample con-
sisted of approximately 15,000 households and 36,Q00 persons residing
in these households. Detailed descriptions of the household and individual
surveys have been published (USDA, 1982, 19831.
IRON
Data from PLANES 11
A primary focus of NHANES II was the characterization of the prev-
alence and possible cause of anemia in the U.S. population. To make this
characterization, the survey team collected and analyzed blood specimens
and reported values for hemoglobin, hematocrit, complete blood count,
mean corpuscular volume, transfe~in saturation, erythrocyte protopor-
phyrin, serum ferritin, serum vitamin By, serum folate, and erythrocyte
folate.
In 1983, at the request of the Food and Drug Administration, the Fed-
eration of American Societies for Experimental Biology (FASEB) con-
vened an expert Scientific Working Group (ESWG) to evaluate the
appropriateness of the NHANES lI measures and methods used, recom-
mend interpretative criteria, estimate the prevalence of impaired iron sta-
tus, and identify groups at greatest risk. Its report (FASEB, 1984a) is the
source of the following discussion.
The ESWG developed two models based on four variables: serum fer-
ritin, erythrocyte protoporphyrin, transferrin saturation, and mean cor-
puscular volume (MCV). The ferritin model is used to estimate early
stages of iron store depletion and is based on measures of serum ferritin,
.
OCR for page 23
NUTRITIONAL STATUS OF THE U.S. POPULATION
23
TABLE 1 Criteria Defining Abnormal Values of Four Measures of Iron
Nutriture for Five Age Groupsa
-
Serum Transferrin E~ythrocyte
Age Femtin Saturation Protoporphynn MCV
(year) (ng/ml) (%) (,ug/dl RBCb) (fl)
1-2 NMC 80 <73
3-4 75 <75
5-10 70 <76
11-14 70 <78
15-74 70 <80
aData from FASEB, 1984a.
bRBC, red blood cell.
CNM, not measured.
erythrocyte protoporphyr~n, and ~ansfernn saturation. The later stages of
iron depletion are estimated with the MCV model, which is based on
measures of mean corpuscular volume, ery~rocyte protoporphynn, and
transfernn saturation. The criteria defining abnormal values for each var-
iable are shown in Table 1. To be categorized as having impaired iron
status, a person had to have at least two of three values in the abnormal
range.
The prevalence estimates derived from the two models are shown in
Figures 1, 2, and 3. Children aged 1 Trough 2 years had the highest
20
-
.
10
o
1 -2
I Confidence interval
Ferritin model
MCV Model
- 9.4
3.9
_
3-4
5-10
Age (Years)
FIGURE 1 Prevalence of impaired iron status for American children aged 1 through
10 years, by model. Data from the second National Health and Nutrition Examination
Survey (FASEB, 1984a).
OCR for page 24
24
EATING PATTERNS, NUTRITION, AND lIEALTl1
20
10
o
I Confidence interval
O Ferritin model
MCV model
B1_~
11-14 15-19 20-44 45-64
Auto (Years)
65-74
FIGURE 2 Prevalence of impaled iron status for American males aged 11 through
74 years, by model. Data from the second National Health and Nutrition Examination
survey (FASEB, 1984a).
20
4-
e,
cad 10
o
9.6
3.4
.
I Confidence interval
LJ Ferritin model
~ MCV model
lt-14 15-19
20-44 45-64 65 74
Age IYearsJ
FIGURE 3 Prevalence of impaired iron status for American females aged 11 through
74 years, by model. Data from the second National Health and Nutrition Examination
Survey (FASEB, 1984a).
OCR for page 25
NUTRITIONAL STATUS OF THE U.S. POPULATION
25
prevalence of impaired iron status (9%) by the MCV model. Because
serum ferritin was not measured in children in that age group, prevalence
estimates using Me fe~ritin model cannot be presented for those children.
As expected, the ferritin model produced slightly higher prevalence es-
timates than did the MCV model for all sex and age groups. The groups
with the highest prevalences were children aged 1 through 2 years, males
aged 11 through 14 years, and females aged 15 through 44 years.
Data from NFCS
Dietary data from the NFCS (Welsh, 1984) indicate that the groups
with the highest prevalences of impaired iron status had the lowest intakes
of Me Recommended Dietary Allowances (RDA) for iron (NRC, 19801.
Children aged 1 through ~ years, males aged 9 through 18 years, and
females aged 9 through 64 years had mean intakes below the RDA (Figure
4~. About 37% of children aged 1 through ~ years and males aged 9
through 18 years of age consumed diets providing at least 100% of the
RDA for iron over 3 days. The comparable figure for females aged 9
Trough 64 years was less Man 20%.
These data indicate that the highest prevalence of impaired iron status
=~ ~
a\) ~ ~
Males Females
74
l
!
~3
~8
1
< 1 1-8 9-18
Age (Years)
19-64 >65
FIGURE 4 Individual intakes of iron: mean percentages of 1980 Recommended
Dietary Allowances (RDAs), by sex and age (3-day average). Adapted from Welsh,
1984.
OCR for page 26
26
EATING PATTERNS, NUTRITION, AND HEALTH
in the United States occurs in those groups with the lowest dietary intake
of iron, expressed as a percentage of He RDA. However, the magnitude
of the numbers is quite different. Although a substantial proportion of the
U.S. population does not report diets containing the full RDA for iron,
the overall prevalence of impaired iron status is low.
VITAMIN C
Assessments of vitamin C have been included in national surveys to
determine the prevalence of scurvy and the proportion of the population
at risk of deficiency. In recent years, interest in the vitamin C status of
Americans has increased as evidence has accumulated for the role of the
vitamin in inhibiting the formation of some carcinogens and for the as-
sociation of the consumption of vitamin C-conta~ning foods with a lower
risk of stomach and esophageal cancer.
Data from NHANES 11
By using data from NHANES it, one can identify and characterize
subgroups of the population with low serum vitamin C. Diet, smoking
habits, and other lifestyle factors that affect serum vitamin C levels can
be examined. As part of He nutritional biochemist assessments, serum
vitamin C was to be analyzed for all persons aged 3 Trough 74 years as
an indicator of vitamin C status. Of the 18,549 persons aged 3 Trough
74 years in the sample, however, the serum vitamin C values were recorded
for only 15,796 (85%~. The determinations were performed at ttie Centers
for Disease Control using a modified calorimetric ascorbic acid method
(Gunter et al., 1985~.
Mean serum vitamin C levels differed by age and sex (Figure 51. For
children, mean levels generadly decreased with age from a high of about
1.5 mg/dl for He 3- through 5-year-old group to 1.1 mg/~! for He 15-
through 17-year-old group. For adults, mean values remained fairly stable,
although there was some increase in values for the older age group. Males
had lower mean levels of serum vitamin C than did females for all the
adult age categories.
The findings are reflected in the prevalence of low serum vitamin C
levels in the surveyed population (Figure 6), where low was defined as
less than 0.25 mg/dl. Very few children had low serum vitamin C levels.
The prevalence of low values generally increased for teenagers, and adult
males had a higher proportion of low values (5.6%) than did females
(2.7%~.
OCR for page 27
NUTRITIONAL STATUS OF THE U.S. POPULATION
1.61
1.4
Cry
`,' 0.8
0.6
\
\
\
\
\
27
Female
- Male
1 1 1 1 1 1 1 1
0 10 20
30 40 50 60 70
Age (Years)
FIGURE 5 Mean serum vitamin C levels of Americans, by age and sex, 1976-1980.
Unpublished data from the second National Health and Nutrition Examination Survey.
10
8t
61
4 -
0
C'
con 4
2f
o
l
~ 0.1 0; T 0.1
~0.0 ~/
M F M ~
3 5 years 6-11 years
1
loll F
l ~
M F
M F
12-19 years
Age and Sex Groups
20-44 years
45-74 years
FIGURE 6 Percentage of Americans with low serum vitamin C levels, by age and
sex, 1976-1980. Low serum vitamin C is defined as less than 0.25 mg/dl. Unpublished
data from the second National Health and Nutrition Examination Survey.
-
OCR for page 28
28
EATING PATTERNS, NUTRITION, AND HEALTH
Following is a list of the major variables generally believed to be
associated with serum vitamin C status:
age, sex, race
poverty status
~ vitamin-mineral supplement use (regular users as opposed to irregular
or nonusers)
~ cigarette smoking (current cigarette smokers; not pipe smokers, cigar
smokers, or nonsmokers)
· oral contraceptive use
· dietary intake of vitamin C
· frequency of consuming foods rich in vitamin C
· fasting or nonfasting examination status
· morning or afternoon examination
· pregnancy status
Many of these characteristics were found to be significantly related to
serum vitamin C.
Because of the relatively high percentage of low serum vitamin C levels
in adults and because of differences between males and females, we
characterized the population aged 20 through 74 years by cigarette-smok-
ing status, dietary supplement use, and poverty Status. Preliminary analysis
of our data (Johnson et al., 1984) had shown these factors to be associated
with serum vitamin C levels.
The percentage of adults aged 20 through 44 years and 45 through 74
years in each of the cigarette-smoking and supplement use categories in
the population are presented in Figure 7. The proportion of current cigarette
smokers was higher in the younger adults. However, regular supplement
use was highest in the 45- through 74-year-old age group. The percentage
of the population in each of the cate~ones was sufficient for more detailed
analysis of the data.
Mean serum vitamin C levels were significantly higher for regular
supplement users (1.3-1.5 mg/dl) than for irregular or nonusers (0.7-1.1
mg/dl) for both males and females in each cigarette-smoking category
(Figure 8~. With one exception, persons in the other smokers/nonsmokers
group had higher mean serum vitamin C levels than did current cigarette
smokers for each sex and supplement-use category.
These differences in smoking and supplement use categories for virgin
C status were even more pronounced when Me prevalence of low serum
vitamin C values (Figure 9) was considered. Males who used supplements
regularly had prevalences less Man 1%, regardless of Weir cigarette-smoking
status. Irregular or nonusers of supplements had higher levels; 45- through
OCR for page 29
NUTR~ION~ STATUS OF THE U.S. POPULATION
70 _
60
50
40
30
20
10
41
~ Regular
59 ~ supplement user
chinarregularlnonuser of
/~ supplements
31
Current
cigarette
smokers
Ages 20~44
Other
smokers!
nonsmokers
29
69
,.
Current Other
cigarette smokers!
smokers nonsmokers
Ages 45~64
FIGURE 7 Current cigarette-smoking status and dietary supplement usage of Amer-
icans, by age group, measured as a percentage of the population, 1976-1980. Un-
published data from the second National Health and Nutrition Examination Survey.
2.0
-
-
~ 1.0
._
E
In
o.o
T T -
_ . , .
M F
__ .
M F
Regular Incubi or
supplement user nonuser
Current c~garene smokers
-
;
~ .
lo:
_ ~ lo_
191 F
Regular
supplement
user
1
M f
Irregular or
or
nonuser
Other smokersinonsmokers
FIGURE 8 Mean serum vitamin C levels of Americans aged 21 through 74 ~rears,
by sex (pregnant women excluded), current cigarette-smoking status, and dietary
supplement usage, 197~1980. Unpublished data from the second National Health and
Nutrition Examination Survey.
OCR for page 30
30
20
15
10
5
EATING PATTERNS, NUTRITION, AND HEALTH
[~3 Regular supplement
5: ~ user
. .
~ ·,
Irregular or nonuser of
supplements
00 ~ 0\
09?~ ~
Current cigarette Other smokers! Current cigarette Other smokers/
smokers nonsmokers smokers nonsmokers
Ages 20-44
Ages 45-74
FIGURE 9 Percentage of-American males aged 20 through 74 years with low serum
vitamin C levels, by age group, current cigarette-smoking status, and dietary supple-
ment usage, 1976-1980. Low serum vitamin C is defined as less than 0.25 mg/dl.
Unpublished data from the second National Health and Nutrition Examination Survey.
20
0
`,, 10
5
o
~ _
_
— o.s-
_ ~ _
~ ;~
... Regular supplement
....... user
~ Irregular or nonuser of
.. ~ supplements
1~ 2~
Current cigarette Other smokers!
smokers nonsmokers
Ages 20-44
Current cigarette Other smokers/
smokers nonsmokers
Ages 45-74
FIGURE 10 Percentage of American females (pregnant women excluded) aged 20
through 74 years with low serum vitamin C levels, by age group, current cigarette-
smoking status. and dietary supplement usage, 1976-1980. Low serum vitamin C is
defined as less than 0.25 mg/dl. Unpublished data from the second National Health
and Nutrition Examination Survey.
OCR for page 31
NUTRITIONAL STATUS OF THE U.S. POPULATION
31
74-year-old males who were current cigarette smokers had the highest prev-
alence (16.4%), followed by 20- through 44-year-old males (9%~.
With one exception, we observed the same pattern for females as for
males (Figure 10~. The percentage of women with low serum vitamin C
was low for all subpopulations that used supplements regularly. Only
current cigarette smolders who did not use supplements regularly had a
prevalence greater than 5%.
Because serum vitamin C reflects dietary intake, we used this
measure to determine the vitamin C content of the diets of males and females
classified by cigarette smoking and supplement use. Figure 11 shows Cat
for median vitamin C intake based on a single 24-hour recall among males,
regular supplement users had higher dietary levels~than did Regular or
nonusers within each age and smoking status category. Intakes by current
cigarette smokers were lower than Rose for the other smoker/nonsmoker
groups for all age and supplement use categories. Two groups had median
vitamin C intakes below We 1980 RDA of 60 ma: We current cigarette
smokers who were uregular or nonusers of supplements in bow age groups.
Figure 12 shows a pattern for females similar to that observed in males.
Within cigareKe-smoking groups, the females aged 45 through 74 years
had higher median intakes than did the younger adult women. The younger
cigarette smokers and other smokers/nonsmokers not taking supplements
had median intakes below the RDA of 60 ma.
The vitamin C density of the diets of male supplement users was higher
than the median intakes of irregular or nonusers of supplements (Figure
131. We observed a similar pattern for females (Figure 141. We also
compared the frequency with which fruits and vegetables high in vitamin
C were consumed and found patterns similar to the median intake and
intake per 1,000 kcal (Figures 13 and 141.
Although the overall percentage of 3- through 74-year-old persons with
low serum vitamin C levels was not large (about 3%), this was not true
for selected populations. There was a much higher percentage of low
serum vitamin C values among cigarette-smoking adults who seldom or
never used vitamin-mineral supplements than would be expected by their
representation in the population. For males, 34% were current cigarette
smokers who did not regularly use vitamin-mineral supplements. In this
group, 71 No of the men had low serum vitamin C. The comparable figures
for women were 25% and 61~o. In contrast, regular supplement users
constituted approximately 20% of the male population, but less than 2%
of the low serum vitamin C group. For women, regular supplement users
constituted about 28% of the population and less than 8% of the low serum
vitamin C group.
Because a smaller proportion of the low-income population reported regular
OCR for page 32
32
110
100
-
CJ) 9o
E
-
0 80 _
~ 70 _
._
(,) 60 _
._
~ 50 _
:. 40 _
, ~
10 _
EATING PATTERNS, NUTRITION AND HEALTH
110
_ ~ supplement user i: ::: :~:
Irregular or .:
- ~ nonuser of :::::.
supplements . . .
c:::::
~ ~ ~.~3j~'
o ~. ~n ~. ~.
Current cigarette Other smokers!
smokers nonsmokers
Ages 2044
53
it'
Current cigarette Other smokers/
smokers nonsmokers
Ages 45-74
FIGURE 1 ] Median vitamin C intake of American males aged 20 through 74 years,
by age group, current cigarette-smoking status, and dietary supplement usage, 1976-
1980. Unpublished data from the second National Health and Nutrition Examination
Survey,
110
100
-
~ 90
-
~ 80
ye
C 70
._
Cal 60
._
I: 50
40
44
£= ~
To-
Current cigarette
smokers
Ages 20-44
-r
;;.;~ Regular
t: A: ~ supplement user
~ ~ Irregular or nonuser of
supplements
86
......
:::::
:~:-:~:~:~-
,.~:,:,
~:i? ,
Other smokers! Current cigarette Other smokers/
nonsmokers smokers nonsmokers
86
:::~::.
a::-::-:-:
.2.: :.:.
::~: ::e
.......
· .::::.
:~:~:~:~:~:
::::::
A:::::
~ l
106
__
......
;~:-:~:~:~:-
:~:~:~:~:~:
·:~:~:~:~:.
......
a:::::
:::.::
.......... 78
:-:-::-:: _
·~ _
...... _
·:~:-:-:-:. _
:::::: ~
a::::: _
:::::: _
:::-::: _
::::: _
:~:~:~:~:~: _
a:::::
:::::
. -.- _
Ages 45-74
FIGURE 12 Mean vitamin C intake of American females (pregnant women excluded)
aged 20 through 74 years, by age group, current cigarette-smoking status, and dietary
supplement usage, 1976-1980. Unpublished data from the second National Health and
Nutrition Examination Survey,
OCR for page 33
NUTRITIONAL STATUS OF THE U.S. POPULATION
80
=
y
lo
~7
E
-
y 40
._
~ 20
._
· -
o
_ 29
1 2
_s
Current cigarette
31
smoicers nonsmokers
Ages 20-44
67/A Regular supplement
user
43
Other smokers! Current cigarette Other smokers/
- smokers nonsmokers
Ages 45~74
Irregular or nonuser of
supplements
~2
25
50
is///
A//.
is//
40
33
FIGURE 13 Median vitamin C intake per 1,000 kcal of American males aged 20
through 74 years, by age group, current cigarette-smoking status, and dietary sup-
plement usage, 1976-1980. Unpublished data from the second National Health and
Nutrition Examination Survey.
80
y
lo
o 60
lo
-
E
0 40
y
._
~ 20
._
._
o
- 27
Regular supplement
25
Irregular or nonuser of
supplements
~5
39
60
__
41
, ~ ~ _
_ ~ ~ _
Other smokers/ Current cigarette
smokers
77
_ ~
Other smokers/
nonsmokers
61
Current cigarette
smokers nonsmokers
Ages 20-44
Ages 45-74
FIGURE 14 Median vitamin C intake per 1,QOO kcal of American females aged 20
through 74 years (pregnant women excluded), by age group, current cigareue-smoking
status, and dietary supplement usage, 1976-1980. Unpublished data from the second
National Health and Nutrition Examination Survey.
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34
EATING PA7TERNS, NUTRITION, AND HEALTH
use of vitamin-mineral supplements than did the general population, we
determined the prevalence of low serum vitamin C by poverty status and
supplement usage (Figure 151. The percentage of regular supplement users
win low serum vitamin C levels was 1% or less, regardless of age, sex, or
income. However, among irregular or nonsupplement users, those below
poverty had higher prevalences of low serum vitamin C. Males aged 45
Trough 74 years had He highest prevalence of low values (24.2%~.
A low serum vitamin C level indicates a low or inadequate intake of
vitamin C, probably with low tissue reserves present. On He basis of this
indicator, we have identified the following subpopulations win lifestyles that
place Rem at high risk for poor vitamin C nutritional status:
· consumers of diets Hat are low in vitamin C because of infrequent
consumption of vitamin C-rich foods and low vitamin C density of these
diets,
· cigarette smokers,
· irregular or noncons~uners of vitamin or mineral supplements, and
· He poor.
0 5 _
C'
ct n no
Regular supplement user
1.0 0.9
Male Female
20-44 years
Male Female
45-74 years
Irregular or nonuser of supplements
24.2
25
, _
20 _
- , ~ PIR < 1
I,, 15 - V77~ PIR >1
¢, 10 7.1
5 _ ~
5.0
~ 3.2
20-44 years
7.9 7.8
45-74 years
FIGURE 15 Prevalence of low serum vitamin C in the United States, by age, dietary
supplement usage, and poverty income ratio (PIR), 1976-1980. Unpublished data from
the second National Health and Nutrition Examination Survey.
OCR for page 35
NUTRITIONAL STATUS OF THE U.S. POPULATION
Data from NFCS
35
Data on vitamin C from the NFCS indicate Rat mean intakes over 3
days exceeded Me RDA for all sex and age groups (Table 2) and that
mean intakes for men were higher than Rose for women aged 9 Trough
64 years. Those win a poverty income ratio (PIR) of 1 or more had higher
mean intakes Can those win a PIR of less Can 1.
TABLE 2 Individual Intakes of Vitamin C, Measured as Mean
Percentage of 1980 RDAs, by Selected Characteristics (3-Day
Average), 1977-1978a
,
Percentage
of RDA
Category
All persons:
Males and females:
1 year
1-8 years
Males
9-18 years
19-64 years
—65 years
Females:
9-18 years
19-64 years
265 years
Poverty status and race:
Above poverty, white
Above poverty, black
Below poverty, white
Below poverty, black
Region:
Northeast
North central
South
West
Urbanization:
Central city
Suburban
Nonmetropolitan
Season:
Spring
Sununer
Fall
Winter
147
226
166
174
145
153
152
128
150
149
152
125
138
160
147
131
159
152
153
136
151
152
140
146
aUnpublished data from the Nationwide Food Consumption Survey.
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36
EATING PANE - S. NUTRITION, ED HE^TH
Lifestyle variables, such as smoking habits and use of supplements,
influence serum vitamin C, which is one measure of nutritional status.
National dietary surveys have not provided the necessary information for
survey analysts to calculate He nutrient contribution of supplements to
daily intakes, and this information may not be available in the future
because of the difficulty of maintaining a vit~nin-mineral supplement
composition data bank. Because 40% of the adult population is presently
taking supplements (Gallup Organization, Inc., 1982), dietary intake alone
is an inadequate predictor of serum vitamin C. What remains to be de-
terrnined is whether a better measure of long-term vitamin C status will
be developed and how it will relate to dietary survey results.
ZINC
Data from NHANES II
In NHANES Il. serum zinc was measured by flame atomic absorption
spectroscopy of serum samples obtained from 14,770 persons aged 3
through 74 years. Although at the time of the survey serum zinc was
recognized as an inadequate measure for the definitive assessment of zinc
nutritional status, the Centers for Disease Control wanted to test whether
conditions could be maintained for trace element determinations in a large
field survey. The ESWG, in which evaluations of iron nutriture were
based on data from NHANES II, also made observations on zinc nutriture
(FASEB, 1984b).
Because serum zinc values differ, depending on the time of blood
collection and fasting, the ESWG recommended that different cutoff points
be used to define low values for samples obtained in the morning for
fasting and nonfasting persons and for afternoon aIld evening samples.
These values are shown ire Table 3.
~ A
TABI-E 3 Cutoff Points Used to Define Low Serum Zinc Values for
Samples Obtained at Different Times of Day and Fasting Conditionsa
Serum
Zinc
Time of Day Fasting Status (,ug/dl)
Morning Fasting 70
Morning Nonfasting 65
Afternoon and Presumed fasting 60
evening
. . . . _
Data from FASEB, 1984b.
OCR for page 37
NUTRITIONAL STATUS OF THE U.S. POPULATION
10
8
6
0
Q
4
2
rid
37
[ ~ Male
Female
T
d~ Al lore
I ~
1 :-:: ::::: ::::::::::
. ..~, .
_ ~
v
3-8 9-19 20-44 45-64 65-74
Age (years)
FIGURE 16 Percentage of Americans with 1QW serum zinc levels, by sex and age.
Data from the second National Health and Nutrition Examination Survey (FASEB,
1984).
Figure 16 shows that the prevalence of 1DW serum zinc values in the
NHANES II sample ranged from 1% in males to 4% in females. The
prevalence of low values was slightly higher in young children and the
elderly than in adolescents and young adults. These observations provide
some indication of groups that should be evaluated in greater depth; how-
ever, serum zinc levels are only suggestive of poor zinc nutriture for
reasons discussed below.
Data on Dietary Intake
No conclusions can be drawn about the adequacy of zinc levels in the
American diet because neither NHANES II nor NFCS estimated zinc
intakes. At the time those surveys were conducted, the data on He zinc
content of foods were not complete enough to make reliable estimates.
The only national-level data on zinc are the per capita availability of zinc
in the food supply (Welsh and Marston, 1983~. Between 1909 and 1981,
the zinc level of the food supply fluctuated between 11 and 13 mg per
capita per day—a level considerably below the RDA of 15 mg for adults
or the RDA of 14.2 mg for the population, which was derived by taking
into account the distribution of sex-age groups within the United States
in 1981.
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38
EATING PATTERNS, NUTRITION, AND HEALTH
Until better methods for measuring nutritional status and more extensive
food composition data are available, national surveys will be unable to
assess zinc nutritional status.
CONCLUSIONS
For such nutrients as iron, vitamin C, and zinc there are various kinds
of survey data, and conclusions about dietary sufficiency can be made
with differing levels of confidence. Dietary surveys (e.g., NFCS) indicate
groups with low intakes; however, because most persons' nutrient re-
quirements are less than the full RDA, these groups may not, in fact, be
malnourished. Thus, dietary surveys only suggest groups at risk for poor
nutritional status. In nutritional status surveys (e.g., NHANES II) bio-
chemical tests are used to determine He prevalence of low or impaired
nutritional status among groups. Those prevalences are usually much lower
than those estimated for at-nsk populations in dietary surveys using the
RDAs as a basis for low intake. When both kinds of survey data coincide,
identifying a group with high prevalence of a biochemical marker of
abnormal nutritional status and with low dietary intake, we have strong
evidence that a diet-related problem exists. However, we must consider
the possibility that some other life-style factor or illness has contributed
to the group's low nutritional status.
REFERENCES
FASEB (Federation of American Societies for Experimental Biology). 1984a. Assessment of the
Iron Nutntional Status of the U.S. Population Based on Data Collected in the Second National
Health and Nutrition Examination Survey, 1976-1980. Life Sciences Research Office. FASEB
Special Publications Office, Bethesda, Md.
FASEB (Federation of American Societies for Experimental Biology). 1984b. Assessment of
Zinc Nutritional Status of the U.S. Population Based on Data Collected in the Second National
Health and Nutrition Examination Survey, 1976-1980. Life Sciences Research Office. FASEB
Special Publications Office, Bethesda, Md.
Gallup Organization, Inc. 1982. Gallup Study of Vitamin Use in the U.S. Survey VI, volume
1. Gallup Organization, Inc., Princeton, N.J.
Gunter, E. W., W. E. Turner, J. W. Neese, and D. D. Bayse. 1985. Laboratory Procedures
Used by the Clinical Chemistry Division, Centers for Disease Control, for the Second Health
and Nutrition Examination Survey (HANES II) 1976-1980. Public Health Service, Centers
for Disease Control, Atlanta, Ga.
Johnson, C., C. Woteki, and R. Murphy. 1984. Smoking, vitamin supplement use, and other
factors affecting serum vitamin C. Fed. Proc. 43(3):666.
McDowell, A., A. Engel, J. T. Massey, and K. Maurer. 1981. Plan and Operation of the Second
National Health and Nutrition Examination Survey, 1976-80. Series 1, No. 15. DHHS Pub.
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NUTRITIONAL STATUS OF THE U.S. POPULATION
39
No. (PHS) 81-1317. Vital and Health Statistics. Public Health Service. U.S. Government
Printing Office, Washington, D.C.
NRC (National Research Council). 1980. Recommended Dietary Allowances, 9th ed. A report
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USDA (U.S. Department of Agriculture). 1982. Food Consumption: Households in the United
States, Spring 1977. Human Nutrition Infonnation Service, Consumer Nutrition Center, Report
No. H-1. U.S. Government Printing Office, Washington, D.C.
USDA (U.S. Department of Agriculture). 1983. Food Intakes: Individuals in 48 States, Year
1977-78. Human Nutrition Information Service, Consumer Nutrition Center, Report No. I-1.
U.S. Government Printing Office, Washington, D.C.
Welsh, S. O. 1984. Iron in U.S. diets. Speech to Washington, D.C., Nutrition Group, Wash-
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Welsh, S. O., and R. M. Marston. 1983. Trends in levels of zinc in the U.S. food supply, 1909^
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Representative terms from entire chapter:
low serum
