Vitamin and Mineral Supplement Use by Older Rural Adults

Journal of Gerontology: MEDICAL SCIENCES
Copyright 2000 by The Gerontological Society of America
2000, Vol. 55A, No. 10, M613–M617
Vitamin and Mineral Supplement Use by
Older Rural Adults
Mara Z. Vitolins,1 Sara A. Quandt,1 L. Douglas Case,1 Ronny A. Bell,1 Thomas A. Arcury,2
and Juliana McDonald1
Departments of 1Public Health Sciences and 2Family and Community Medicine, Wake Forest University School of Medicine,
Winston-Salem, North Carolina.
Background. Vitamin and mineral supplement products are widely consumed by older adults. This study describes
supplement product use in a multiethnic rural population, relates supplement usage to dietary nutrient intake, and deter-
mines predictors of supplement usage.
Methods. Data are from a population-based sample of 130 community-dwelling adults aged 70 years and older in
two rural North Carolina counties. The sample was 34% African American, 36% European American, and 30% Native
American. Interviewer-administered semiquantitative food frequency questionnaires were used to obtain data on usual
diet and supplement use. In-home interviews allowed verification of supplement composition. Intakes from diet and sup-
plement products were examined for vitamins A, E, B6, C, folate, iron, zinc, and calcium.
Results. Of those who participated in the study, 47% reported using one or more supplement products. African
Americans were significantly less likely to take supplements than Native Americans or European Americans. Based on
dietary intakes, 65% of the participants were deficient (?2/3 recommended dietary allowance [RDA]) for at least one
nutrient. The use of supplement products for the eight nutrients investigated was not related to dietary nutrient defi-
ciency. For all nutrients investigated, except iron and calcium, a greater proportion of those without dietary deficiency
took a supplement product than those with deficiency. Using logistic regression, ethnicity (European American and Na-
tive American), and gender (women) were significant predictors of supplement use.
Conclusions. These findings suggest that although both dietary deficiencies of vitamins and minerals and supple-
ment use are relatively high in this population, there is no association between supplement use and deficient dietary in-
takes for the eight nutrients examined. Health care providers should be aware that nutritional counseling and guidance
on appropriate supplement usage is needed in this population.
ITAMIN and mineral supplement products are widely
whole, rural adults have lower levels of education, lower in-
Vconsumed by older adults in the United States. De- comes, and problems accessing health care because of is-
pending on the population studied, rates of usage range
sues of distance, transportation, and limited health care op-
from 26% to 80% (1,2). Most studies have reported that
tions. All of these reasons, plus limited grocery store
supplement use is more frequent among women, the well-
options, more expensive groceries at those stores, and re-
educated, the typically healthy, and those who have higher
duced ability to engage in home food production with ad-
incomes (3,4). Because most studies have been small, there
vancing age, may place older rural adults at particular risk
has been limited examination of ethnic variation in supple-
for nutrient deficiencies (10).
ment use. When ethnicity has been studied, research has
This study responds to some of these shortcomings in ex-
found elderly minority persons less likely to use vitamin
isting studies by focusing on supplement use in a multieth-
and mineral supplements (5–7).
nic population in a rural area with a moderately high rate of
The dietary requirements of adults change as they grow
poverty. The purpose of the study is as follows: (i) describe
older, placing older adults at nutritional risk because of a
supplement product use by ethnicity, gender, and other se-
decreased need for energy, but a constant or even increased
lected demographics among older rural adults living in
need for some vitamins and minerals (8). Vitamin and min-
North Carolina; (ii) relate supplement usage to adequacy of
eral supplements provide a means of ensuring adequate in-
nutrient intake from diet; and (iii) determine predictors of
takes of such nutrients, but few studies have examined their
degree of supplement usage in this population.
usage in terms of nutritional risk. That is, are supplement
users consuming supplement products to correct inadequate
METHODS
intakes from food? Because most supplement users take
supplements on individual initiative rather than physician
Sample
advice (9), it is likely that supplement use is not based
The sample consisted of 130 community-dwelling resi-
solely on nutritional risk.
dents aged 70 and older from two counties in North Caro-
Older rural adults have been recognized as a group at
lina. The counties were chosen because they are largely ru-
possible risk for health and nutritional problems. As a
ral and have sizable elderly minority populations (37% of
M613

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M614
VITOLINS ET AL.
the adults 65 years and older are African American or Na-
was applicable for the whole year. Because interviews took
tive American). The older adult populations of these coun-
place in the home, interviewers were able to document the
ties experience high rates of poverty. The 1990 census re-
type, brand, and composition of supplements taken. Data
ports a poverty rate of 32.4% for one county and 26.1% for
were collected on frequency of supplement usage (pills per
the other (11). Participants were recruited using a site-based
day, week, or month) and dosage per pill. Eight vitamins
strategy designed to produce a sample representative of the
and minerals were assessed in the analysis presented here:
range of health and socioeconomic statuses present in the
calcium, iron, zinc, folate, and vitamins A, C, E, and B6. In-
population of these counties (12). In this sampling plan, a
take for these was calculated from all supplements reported,
set of 45 “sites” was recruited, including congregate meal
including combination supplements (e.g., multivitamins)
programs, churches, social clubs, veterans organizations,
and single nutrient supplements.
and social service agencies, such that the members or clien-
tele of these sites represented a cross-section of the commu-
Measures
nity. Elderly persons were then recruited by research per-
Three measures of daily intake were created for each partic-
sonnel from the roster of clients at each site with the
ipant for each of the eight nutrients of interest. Dietary intake
assistance of site directors (e.g., senior center directors, club
of each vitamin or mineral was calculated from the food
officers, and ministers). Older minority adults and men
items of the FFQ, supplement intake was calculated from
were overrecruited so that valid comparisons could be made
the vitamin and mineral supplement items of the FFQ, and
between ethnic groups. This sampling and recruitment plan
total intake was obtained by summing the dietary and sup-
provided a means to recruit a sample representative of these
plement intakes. Participants were considered deficient for a
two counties while gaining entrée to the communities
particular nutrient if their dietary intake for that nutrient was
through introductions by community members (13).
less than 2/3 of the recommended dietary allowance (RDA)
for persons aged 51 years and older. Participants were
Data Collection
coded as supplement users if they reported any vitamin or
Data were obtained in face-to-face interviews conducted
mineral supplement usage, and supplement nonusers if they
in participants’ homes. In a few cases, participants chose to
reported no supplement usage. To assess the degree of sup-
be interviewed at another location, usually a senior center.
plementation, the number (0 to 8) of nutrients obtained
Demographic and personal data included gender, ethnicity,
through supplements was calculated for each participant.
age, marital status, tobacco use (smokeless and smoked),
weight, chronic conditions, and number of prescription med-
Data Analysis
ications. Weight was measured using a professional quality
Chi-square tests were used to assess the association of defi-
portable scale (Health O-Meter, Bridgeview, IL).
ciency and supplement use with the participant’s demo-
Dietary data collection was designed to measure usual di-
graphic characteristics. Logistic regression was used to assess
etary intake over the preceding year. Data were collected
which characteristics were jointly predictive of deficiency
using the semiquantitative food frequency questionnaire
and supplement use. Age, weight, gender, ethnicity, marital
(FFQ) component of the National Cancer Institute Health
status, number of chronic conditions, and number of prescrip-
Habits and History Questionnaire (14). The version used
tion medications were included in the model. A backward-
had been modified to improve ethnic food choices and vali-
stepping algorithm was used to remove nonsignificant factors
dated (15). The FFQ has been validated for use in an older
from the model. Regression techniques were then used to
population and was used to assess dietary intake for the
assess which factors were predictive of the degree of sup-
Third National Health and Nutrition Examination Supple-
plementation. The significance level used was p ? .05.
mental Nutrition Survey of Older Americans (16,17).
Specific steps were taken to overcome known problems
RESULTS
of underreporting on FFQs (17). Interviewers attended a
Study participants ranged in age from 70 to 94 years with
training session devoted to FFQ dietary data collection and
a median of 78 years. Eighty of the 130 participants (62%)
completed practice interviews. The FFQ was interviewer-
were women (Table 1). Forty-four (34%) were African
administered with response categories printed in large font
Americans, 47 (36%) were European Americans, and 39
on cue cards to assist respondents. Interviewers used stan-
(30%) were Native Americans. Forty-nine (38%) were cur-
dard techniques that included extensive probing to obtain
rently married. All but seven of the participants had at least
complete data (17). FFQ administration took 30 to 60 min-
one chronic condition. Most participants (81%) were taking
utes. Interviewers were knowledgeable about local food
prescription medications, and the number of medications
preparation and consumption patterns, which increased their
ranged from 0 to 20.
ability to interpret local food names and probe for appropri-
Table 1 compares characteristics of supplement users and
ate condiments and preparation techniques. The data col-
nonusers. A higher proportion of women and a higher pro-
lected were analyzed using the DietSys software package
portion of those married took supplements, but none of
(National Cancer Institute, Bethesda, MD) (17). Quality as-
these associations was statistically significant. However, the
surance procedures included double-entry of all data and
association between ethnicity and supplement use was
edit checks for extreme values.
highly significant ( p ? .001). Sixty-four percent of Euro-
As part of the FFQ, participants were asked if they took
pean Americans took supplements, compared with 51% of
any vitamin or mineral supplements during the past month.
Native Americans, and only 25% of African Americans.
The assumption was made that the 1-month intake pattern
Not only did African Americans take supplement products

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VITAMIN AND MINERAL SUPPLEMENT USE
M615
Table 1. Supplement Use by Subject Demographics
Nutrient intake, dietary deficiency, and supplement product
use are shown in Table 2. There was considerable variation
Supplement
Supplement
by nutrient in the number of participants with deficient di-
Users
Nonusers
Total
(n 61)
(n 69)
etary intakes, ranging from 0% for folate to 60% for zinc.
?
?
Eighty-four participants (65%) were deficient in at least one
Characteristic
n
(%)
n
(%)
n
(%)
p Values
of the eight nutrients; 23 (18%) were deficient in one, 33
Age
.797
(25%) in two, 13 (10%) in three, 9 (7%) in four, 2 (2%) in
70–79
78
(60)
37
(47)
41
(53)
five, and 4 (3%) in six nutrients.
80–89
48
(37)
23
(48)
25
(52)
Sixty-one participants (47%) supplemented at least one of
90?
4
(3)
1
(25)
3
(75)
the eight nutrients. Of those who took supplement products,
Gender
.211
over half (33 of 61, 54%) supplemented all eight, primarily in
Female
80
(62)
41
(51)
39
(49)
Male
50
(38)
20
(40)
30
(60)
the form of multivitamin pills. Supplementation of each of the
Ethnicity
.001
eight nutrients occurred to a similar degree (Table 2). The
African American
44
(34)
11
(25)
33
(75)
least supplemented nutrients were zinc, iron, and vitamin A,
European American
47
(36)
30
(64)
17
(36)
each supplemented by 28% of the participants. The most
Native American
39
(30)
20
(51)
19
(49)
common supplement nutrients were vitamins E and C, sup-
Marital status
.467
plemented by 38% and 41% of the participants, respectively.
Married
49
(38)
25
(51)
24
(49)
Single
81
(62)
36
(44)
45
(56)
Table 3 shows supplementation of each nutrient by di-
Chronic conditions†
.093
etary deficiency status of participants. Supplement use was
None
7
(5)
1
(14)
6
(86)
not related to dietary deficiency. Indeed, for six of the eight
1–2
87
(67)
46
(53)
41
(47)
nutrients (vitamin A, vitamin E, folate, vitamin B6, vitamin
3?
35
(27)
14
(40)
18
(62)
C, iron, and zinc), a greater percentage of participants who
Tobacco use
.122
were not deficient supplemented that nutrient than those
Yes
17
(13)
5
(29)
12
(71)
No
109
(87)
54
(50)
55
(50)
who were deficient. For example, 38% of participants con-
Prescription medication
.414
suming an adequate amount of zinc in their diets supple-
None
19
(15)
5
(26)
14
(74)
mented zinc compared with only 21% of those whose di-
1–2
44
(34)
22
(50)
22
(50)
etary levels were deficient.
3–4
35
(27)
18
(51)
17
(49)
Logistic regression was used to determine which factors
5–6
17
(13)
9
(53)
8
(47)
jointly predicted whether a person used any supplements
7?
15
(12)
7
(47)
8
(53)
(Table 4). Of those variables entered in the regression, three
†Chronic conditions ? diabetes, stroke, cardiovascular disease (hypertension,
remained significant or of borderline significance. Ethnicity
heart trouble, circulatory problems), arthritis, asthma, cancer.
( p ? .0005) and gender ( p ? .0382) were significantly asso-
ciated with using supplements. The odds of taking supple-
ments were 5.70 and 3.55 times higher for European Ameri-
less often, they supplemented fewer of the eight nutrients
cans and Native Americans, respectively, compared with
we investigated than the men and women of other ethnici-
African Americans. Women had a 2.78 times greater odds
ties (data not shown). Of the 30 European Americans taking
of taking supplements compared with men. Marital status
supplement products, 19 (63%) supplemented all eight of
was of borderline significance ( p ? .0819), with married
the nutrients. This compares with 50% (10 of 20) of Native
men and women more likely to take supplements compared
Americans and 36% (4 of 11) of African Americans.
with those not married.
Table 2. Nutrient Intake, Deficiency, and Supplement Use
Dietary Deficiency
Supplement Use
Supplement Intake
Dietary Intake
Nutrient
RDA
(Mean ? SD)
n
(%)
n
(%)
Mean ? SD
Range
Vitamin A
5000 (IU)
9496.7 ? 6063.0
7
(5)
37
(28)
5443.1 ? 2603.0
714.3–16000
Vitamin E
12.9 ? 6.8
15
(12)
50
(38)
145.6 ? 275.8
2.9–1020.1
Men
10 (mg ?-TE)
Women
8 (mg ?-TE)
Folate
361.3 ? 165.1
0
(0)
43
(33)
441.2 ? 177.8
57.1–800
Men
200 (?g)
Women
180 (?g)
Vitamin B
?
?
6
2.0 (mg)
1.8 0.9
50
(38)
43
(33)
3.0 2.1
0.3–10.0
Vitamin C
60 (mg)
152.8 ? 77.6
1
(1)
53
(41)
391.1 ? 401.5
8.6–1560.0
Iron
10 (mg)
11.6 ? 4.9
16
(12)
36
(28)
19.0 ? 6.0
2.6–36.0
Zinc
8.6 ? 4.1
78
(60)
36
(28)
15.2 ? 4.6
2.1–30.0
Men
15 (mg)
Women
12 (mg)
Calcium
800 (mg)
789.0 ? 357.3
31
(24)
46
(35)
463.4 ? 700.5
18.6–4200.0
Notes: RDA ? recommended dietary allowance; ?-TE ? ?-tocopherol equivalents.

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M616
VITOLINS ET AL.
Table 3. Supplement Use for Each Nutrient,
ated with such behaviors as active lifestyle, not smoking,
by Dietary Deficiency Status
and cancer screening (4,18).
This study goes beyond previous studies of older adults
Taking Specific
to examine vitamin and mineral supplement usage in the
Supplement
Dietary
context of dietary intakes. These results indicate that there is
Nutrient
Deficiency
n
n
(%)
little association between dietary deficiency and supple-
Vitamin A
No
123
36
(29)
mentation for the eight nutrients examined. Those persons
Yes
7
1
(14)
taking supplements are more likely to have adequate diets
Vitamin E
No
115
44
(38)
for these nutrients than those who do not. This leads to the
Yes
15
6
(40)
speculation that both diet and supplementation behaviors re-
Folate
No
130
43
(33)
flect similar knowledge and beliefs about health promotion,
Yes
0
—
(—)
Vitamin B
No
80
29
(36)
rather than attempts to compensate for dietary deficiencies.
6
Yes
50
14
(28)
In other studies of the general adult population, supplement
Vitamin C
No
129
53
(41)
users have been found to consume more fruits, vegetables,
Yes
1
0
(0)
and dairy products (4,18).
Iron
No
114
31
(27)
Only a subset of nutrients essential for health and func-
Yes
16
5
(31)
tioning was examined in this study. Yet even with this small
Zinc
No
52
20
(38)
Yes
78
16
(21)
group of nutrients, 65% of all participants had diets that
Calcium
No
99
34
(34)
were deficient in one or more nutrients, highlighting the dif-
Yes
31
12
(39)
ficulty these older adults have in planning, obtaining, or
consuming a nutrient-dense diet. Although recommending
vitamin and mineral supplements remains a controversial
CONCLUSIONS
topic (17,18), vitamin-mineral supplementation may be the
The demographic distribution of vitamin and mineral
best way for this group to get the nutrients they need if they
supplement usage found in this study is quite similar to that
are unable to consume a well-balanced diet (19,20).
reported in other studies, with women and married persons
This study used the most recent recommended dietary al-
more likely to report using supplement products (3–7). This
lowances (RDAs) as a reference standard for evaluating di-
study extends previous research by demonstrating this dis-
etary intakes (21). These will eventually be replaced by the
tribution in a rural and largely minority community with a
dietary reference intakes (DRIs), which are currently under
relatively high poverty rate. One of the limitations of this
development. The DRIs will provide estimates of nutrient
study was that income data were not collected. The decision
needs based on more current research and expand the focus
not to gather these data was made because it would likely
of recommendations from deficiency diseases to long-term
have resulted in considerable missing data if respondents re-
health, including chronic disease (22,23). They were not
fused to answer the questions. In addition, the preliminary
used in the present study because they are not yet available
research to gain entrée into these communities showed that
for all nutrients and some are only available in prepublica-
older adults had been sensitized by children and by senior
tion form. Examining the DRIs proposed for some nutrients,
service organizations to regard such questions as part of at-
however, shows that the present study presents a very con-
tempts by outsiders to defraud older adults (13).
servative estimate of vitamin and mineral deficiency in this
Ethnicity was strongly associated with supplement use,
rural population. For example, the DRIs will recommend an
with African Americans significantly less likely to use sup-
increase for folate to 400 ?g of dietary folate equivalents in
plements than any other group. Further study is necessary to
the daily reference standard for adults within the age range
understand why this is the case and why European Ameri-
of our study participants. Had this figure been used in these
cans and Native Americans are similar in usage. It is possi-
analyses, 34% of the elderly persons studied would have
ble that there is greater emphasis on preventive health be-
been considered deficient in folate, compared with 0% us-
haviors among these groups. Previous studies in the general
ing the current RDAs. Similarly, the DRIs will recommend
adult population have shown that supplement use is associ-
an increase in the daily reference standard for older adults
for calcium to 1200 mg. Had this figure been used, 61%
rather than 24% of the elderly persons studied would have
been considered deficient in calcium. Thus, the use of the
Table 4. Factors Associated with Supplement
DRIs in future research will likely classify even more older
Use—Multivariate Results
adults as deficient for those nutrients most closely associ-
ated with chronic disease and disease prevention.
Characteristic
OR
95% CI
p Value
The present study collected cross-sectional supplement
Ethnicity
.0005
use data. More accurate assessment of supplement use can
European American vs African American
5.70
2.24–14.54
be obtained in longitudinal designs (24), and these should
Native American vs African American
3.55
1.36–9.28
be the focus of future research. The use of biomarkers of nu-
Gender
.0382
Female vs male
2.79
1.06–7.35
tritional status would further strengthen future studies by
Marital status
.0819
providing a means to verify nutrient excesses and deficien-
Married vs single
2.29
0.88–5.96
cies. Regardless of the limitations of the present study, its
Notes: OR ? odds ratio; CI ? confidence interval.
findings indicate that vitamin and mineral supplement prod-

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VITAMIN AND MINERAL SUPPLEMENT USE
M617
ucts are frequently used by rural adults, but intake is related
12. Arcury TA, Quandt SA. Participant recruitment for qualitative re-
to gender and ethnicity, not dietary deficiency. Health care
search: a site-based approach to community research in complex
societies. Hum Organ. 1999;58:128–133.
providers should be alert to this and counsel their patients
13. Quandt SA, McDonald J, Bell RA, Arcury TA. Aging research in
accordingly.
multi-ethnic rural communities: gaining entrée through community in-
volvement. J Cross-Cultural Gerontol. 1999;14:113–139.
Acknowledgments
14. Block G, Hartman AM. Data collection and data management. In:
Block G, Hartman AM, eds. DIETSYS Version 3.0 User’s Guide. Be-
This research was supported by the National Institute of Health (Grant
thesda, MD: National Cancer Institute; 1994:15.
AG 13469).
15. Mayer-Davis B, Vitolins MZ, Carmichael S, et al. Dietary assessment
Address correspondence to Sara A. Quandt, PhD, Department of Public
in a multi-cultural epidemiologic study. Ann Epidemiol. 1999;9:314–
Health Sciences, Medical Center Boulevard, Wake Forest University School of
324.
Medicine, Winston-Salem, NC 27157-1063. E-mail: squandt@wfubmc.edu
16. Mares-Perlman JA, Klein BEK, Klein R, Ritter LL, Fisher MR,
Freudenheim JL. A diet history questionnaire ranks nutrient intakes in
middle-aged and older men and women similarly to multiple food
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Received June 23, 1999
11. Census of the United States. Washington, DC: U.S. Bureau of the Cen-
Accepted January 24, 2000
sus; 1990.
Decision Editor: William B. Ershler, MD

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