Associations of Organic Produce Consumption with Socioeconomic Status and the Local Food Environment: Multi-Ethnic Study of Atherosclerosis (MESA)
et al. (2013) Associations of Organic Produce Consumption with Socioeconomic Status and the
Local Food Environment: Multi-Ethnic Study of Atherosclerosis (MESA). PLoS ONE 8(7): e69778. doi:10.1371/journal.pone.0069778
Associations of Organic Produce Consumption with Socioeconomic Status and the Local Food Environment: Multi-Ethnic Study of Atherosclerosis (MESA)
Cynthia L. Curl 0
Shirley A. A. Beresford 0
Anjum Hajat 0
Joel D. Kaufman 0
Kari Moore 0
Jennifer A. Nettleton 0
Ana V. Diez-Roux 0
C. Mary Schooling, CUNY, United States of America
0 1 Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, United States of America, 2 Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, 3 Departments of Environmental and Occupational Health Sciences, Epidemiology and Medicine, University of Washington, Seattle, Washington, United States of America, 4 Department of Epidemiology, University of Michigan , Ann Arbor , Michigan, United States of America, 5 Department of Epidemiology, University of Texas Health Science Center , Houston, Texas , United States of America
Neighborhood characteristics, such as healthy food availability, have been associated with consumption of healthy food. Little is known about the influence of the local food environment on other dietary choices, such as the decision to consume organic food. We analyzed the associations between organic produce consumption and demographic, socioeconomic and neighborhood characteristics in 4,064 participants aged 53-94 in the Multi-Ethnic Study of Atherosclerosis using logbinomial regression models. Participants were classified as consuming organic produce if they reported eating organic fruits and vegetables either ''sometimes'' or ''often or always''. Women were 21% more likely to consume organic produce than men (confidence interval [CI]: 1.12-1.30), and the likelihood of organic produce consumption was 13% less with each additional 10 years of age (CI: 0.84-0.91). Participants with higher education were significantly more likely to consume organic produce (prevalence ratios [PR] were 1.05 with a high school education, 1.39 with a bachelor's degree and 1.68 with a graduate degree, with less than high school as the reference group [1.00]). Per capita household income was marginally associated with produce consumption (p = 0.06), with the highest income category more likely to consume organic produce. After adjustment for these individual factors, organic produce consumption was significantly associated with selfreported assessment of neighborhood produce availability (PR: 1.07, CI: 1.02-1.11), with an aggregated measure of community perception of the local food environment (PR: 1.08, CI: 1.00-1.17), and, to a lesser degree, with supermarket density (PR: 1.02: CI: 0.99-1.05). This research suggests that both individual-level characteristics and qualities of the local food environment are associated with having a diet that includes organic food.
Funding: This research was supported by the United States Environmental Protection Agencys Science to Achieve Results (STAR) Fellowship Program
(FP917129), by contract R01 HL071759 from the National Institutes of Health, by grants ES013195 and 5P30ES007033 from the National Institute of Environmental
Health Sciences, and by contracts N01-HC-95159 through N01-HC-95165 and N01-HC-95169 from the National Heart, Lung, and Blood Institute. The funders had
no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
The National Organic Program (NOP) of the United States
Department of Agriculture permits food to be certified organic
when grown without use of specified pesticides and synthetic
fertilizers . In the US, sales of organic food have grown steadily
in the past two decades, from $1 billion in 1990 to $26.7 billion in
Little research to date has examined the direct effect of organic
food consumption on health , but several studies have shown
that consumption of organic food, and particularly organic
produce, can significantly reduce pesticide exposure . The
American Academy of Pediatrics recently released a report
concluding that organic diets expose consumers to fewer pesticides
associated with human disease . This conclusion was based, in
part, on several studies of pesticide exposure in children and
pregnant women that suggest even relatively low exposures to
certain agricultural pesticides may be associated with
developmental and neurocognitive effects, such as decreased gestational
age at birth and birth weight, and increased attention
deficithyperactivity disorder and decrements in memory and IQ .
Choice of organic food is also an opportunity to support farming
practices that can reduce risks to farmworkers and promote
ecological health [7,14].
Everyone may not have equal access to organic food, and thus
may not have equal ability to make these choices. Organic food is
more expensive that conventionally grown food, and it also may
not be equally available in all communities. Research suggests that
residents of neighborhoods with better access to healthy foods tend
to have healthier diets . We hypothesize a parallel in respect to
organic food consumption, specifically that residents of
neighborhoods with better access to organic food may be more likely to eat
The purpose of this study is to examine the relationship between
organic produce consumption and individual demographic and
socioeconomic factors including sex, race/ethnicity, age, income,
education, metropolitan area and employment status in a
multicity, multi-ethnic cohort. We further explore the relationship
between organic produce consumption and three complementary
measures of the local food environment intended to represent food
accessibility: 1) Geographic information system (GIS) based
supermarket density, 2) self-reported assessments, and 3)
aggregated survey responses of independent informants.
Materials and Methods
This cross-sectional study investigates the organic produce
consumption habits of participants in the Multi-Ethnic Study of
Atherosclerosis (MESA). MESA was initiated in 1999 by the
National Heart, Lung, and Blood Institute to investigate
subclinical cardiovascular disease among 6,814 participants from six US
areas: Baltimore City and Baltimore County, Maryland; Chicago,
Illinois; Forsyth County, North Carolina; Los Angeles County,
California; New York, New York; and St. Paul, Minnesota .
Participants were recruited using both random-digit dialing and
brochures mailed to households in targeted areas, and were aged
45 to 84 years at enrollment with an approximately equal gender
ratio. The MESA cohort is 39% Caucasian, 28% African
American, 22% Hispanic, and 12% Chinese-American. The
study was approved by the institutional review board at each site,
and all subjects gave written informed consent. This includes the
IRBs at UCLA, Columbia University, Johns Hopkins University,
the University of Minnesota, Wake Forest University, and
Most data collection in MESA is structured around a series of
clinical exams, scheduled at approximately two year intervals. The
baseline exam occurred between July 2000 and July 2002, and the
most recent exam, Exam 5, spanned April 2010 through
February 2012. The analysis presented here primarily employs
data collected at Exam 5. All participants attending this exam were
asked to complete a food frequency questionnaire that inquired
about eating habits over the previous year and included items
about organic produce consumption. Specifically, participants
were asked how often the fruit and vegetables they ate were
organically grown, defined as [having] a USDA Organic
label, purchased locally from an organic farm, or grown without
pesticides in a home garden. Options were Seldom or Never,
Sometimes, and Often or Always. For the primary analysis,
participants who reported that they sometimes, often or always ate
either organic fruit or organic vegetables were categorized as
organic consumers, and those who reported that they seldom or
never ate organic fruit and organic vegetables were categorized as
non-consumers. A separate, secondary analysis restricted the
definition of organic consumers to just those who reported they
often or always consumed organic fruit and vegetables.
We hypothesized organic consumption to be associated with
individual-level factors, including sex, age, race/ethnicity,
metropolitan area, marital status, per capita income [total household
income divided by number of persons living in the household],
education, and employment status. With the exception of age, all
variables were evaluated categorically.
We also hypothesized a relationship between organic
consumption and a set of complementary measures of the local food
environment, after control for individual-level variables.
Specifically, we hypothesized organic produce to more likely be
consumed by individuals living in areas with more supermarkets
and where there is a perception of a larger selection of produce in
general. These measures were developed by the MESA
Neighborhood Study, an ancillary study to MESA that characterized the
local food environments of MESA participants . Each
measure is briefly described here.
The first was a GIS-based measure representing the density of
supermarkets within 1 mile of participants homes. The density of
supermarkets was determined using data obtained from the
National Establishment Time Series (NETS) database from Walls
and Associates . Additional supermarket data was obtained
from Nielsen/TDLinx to enhance the identification of
supermarkets . Supermarkets were defined as grocery stores (SIC code
#5411) with at least $2 million in annual sales or at least 25
employees. Participant addresses were geocoded using TeleAtlas
EZ-Locate web-based geocoding software , and simple
densities per square mile were created for 1-mile buffers around
each address using the point density command in ArcGIS 9.3.
The second measure was the participants self-report of the
selection of fruits and vegetables available in their neighborhoods,
defined as the area within approximately 1 mile of their home
(MESA self-reports). At Exam 5, participants were asked the
extent to which they agreed with the statement A large selection
of fresh fruits and vegetables is available in my neighborhood,
and responses were coded on a five-point Likert scale (strongly
agree; agree; neutral; disagree; and strongly disagree).
The third measure, the Aggregated Neighborhood Survey
(ANS), was constructed by aggregating responses of multiple
respondents residing in each participants census tract (as a proxy
for neighborhood). Survey respondents used in the calculation of
the ANS included other MESA participants living within a given
census tract as well as other residents in those census tracts who
were included to increase the sample size in areas with few MESA
respondents . This supplementary survey was conducted on a
random sample of residents in selected tracts, identified through
address-based sampling methods. Availability of healthy food was
ascertained based on responses to three survey items: A large
selection of fresh fruit and vegetables is available in my
neighborhood, A large selection of low-fat food is available in
my neighborhood, and The fresh fruits and vegetables in my
neighborhood are of high quality, with responses coded on
fivepoint Likert scales. Conditional empirical Bayes estimates, which
borrow information across all tracts in order to increase reliability,
were derived from three level hierarchical linear models to account
for the nested structure of the data .
For both individual and neighborhood analyses, we first
conducted bivariate comparisons exploring the relationship
between each variable and organic consumption, using either
chi-squared tests or log-binomial regression, as appropriate. We
then included the full set of individual-level variables in a
logbinomial regression to model the association with organic
consumption. Individual-level variables found to be statistically
significant in the full model were included in the analyses of
organic consumption and the local food environment.
Logbinomial models were used in the primary analysis due to the
relatively high prevalence of sometimes, often or always
consuming organic produce (40%, n = 1,644). In the secondary analysis,
where the outcome was the smaller set of individuals who reported
they often or always consumed organic food (5%, n = 204), we
employed logistic regression models.
The relationship between each measure of the local food
environment and organic consumption was evaluated separately
with and without control for individual-level variables. For each of
these measures, we also examined the impact of including a
random intercept for census tract. In sensitivity analyses, we
examined the effect of stratification by education and income
category in the individual-level analyses. All analyses were
conducted in SAS v9.3 [Cary, NC].
Of the original MESA cohort (n = 6,814), 4,466 (66%)
participated in Exam 5 and responded to the questions on organic
consumption habits. Complete demographic and socioeconomic
data were available on 4,064 participants (see Figure 1). Overall,
204 (5%) reported often or always eating both organic fruit and
organic vegetables, 1,440 (35%) reported that they sometimes
ate organic fruit and/or organic vegetables, and 2,420 (60%)
seldom or never ate organic produce.
Organic Produce Consumption and Individual-Level
Table 1 shows descriptive individual-level statistics by reported
organic consumption habits. In bivariate analyses, organic
consumption was significantly more common among women,
younger individuals, and those currently employed. Metropolitan
area was also significantly associated with organic consumption, as
were higher per capita household income and education.
Table 2 shows the associations between individual-level
variables and organic consumption in a multivariate log-binomial
regression model including all variables with statistically significant
bivariate associations. Race/ethnicity was also included because of
the importance of this variable in this cohort and to diet in general.
After accounting for other individual-level factors, women were
more likely to be organic consumers than men (prevalence ratio
[PR]: 1.21, confidence interval [CI]: 1.121.30, p,0.0001).
Chinese participants were less likely than other participants to
be organic consumers, though this difference was not large and
overall, race/ethnicity did not show a statistically significant effect.
Age was highly associated with organic consumption; for every
+10-year increment in age, there was a 13% reduction in the
likelihood of being an organic consumer.
Metropolitan area was also significantly associated with organic
consumption in this cohort: participants living in more the
populated cities (Chicago, LA and New York) were more likely
to be organic consumers compared to those living in
WinstonSalem, Baltimore and St. Paul. Education was found to be an
important predictor: comparing the highest and lowest education
categories (less than high school compared to graduate school)
resulted in a 68% greater likelihood of organic consumption.
Being in the highest income category compared to the lowest
(per capital household income of ,$14,999 versus .$45,000) was
associated with a 10% greater likelihood of organic consumption,
but the overall relationship between organic food consumption
and per capita household income was not statistically significant
(p = 0.06), and higher income was not always associated with
greater consumption. For example, participants with per capita
household income between $15,000 and $25,000 were less likely to
consume organic produce than those in the ,$15,000 category.
Employment status was not associated with organic consumption
in multivariable analyses. Results were not sensitive to
stratification of the sample; prevalence ratio point estimates were similar
when restricted to just those participants in the lower and higher
education and income brackets (data not shown).
Organic Produce Consumption and the Local Food
Of those participants included in the individual-level analyses,
84% (n = 3,428) consented to MESA Neighborhood and had
complete data for the neighborhood-level analyses (see Figure 1).
The distribution of demographic and socioeconomic
characteristics between this group and those shown in Table 1 is nearly
identical. Table 3 shows the frequency of organic consumption
among these participants by each measure of the local food
environment. In bivariate analyses, whether measured by
selfreport, supermarket density, or ANS score, participants for whom
accessibility was greater were more likely to be organic consumers.
This association remained in fully adjusted models as well
(Figure 2). After adjusting for individual-level variables,
selfreported produce availability within a participants neighborhood
was positively associated with organic consumption; each unit
increase on the Likert scale, was associated with a 7% greater
likelihood of eating organic food (PR: 1.07, CI: 1.021.11,
p = 0.002). The ANS score analysis also suggested an effect of
local food environment on organic consumption; the likelihood of
being an organic consumer was 8% higher per interquartile
change in score (0.5 units) (PR: 1.08, CI: 1.001.17, p = 0.05).
Inclusion of a random intercept for each census tract did not
substantially modify estimates or standard errors in any of the
three models. The GIS-based supermarket density measure was
not significantly associated with organic consumption after control
for individual-level variables, though the direction of the effect was
Table 1. Demographic and socioeconomic characteristics of the Multi-Ethnic Study of Atherosclerosis cohort at Exam 5 (2010
2012), by organic produce consumption habits.
Never or rarely consume organic produce Sometimes, often or always consume organic produce Bivariate analysisa
Total sample (n = 4,064) 2420
ap-values derived from either chi-squared (gender, race, marital status, metropolitan area and employment status, per capita income, education) or log-binomial
bThe age distribution is shown in categories for display purposes, but was modeled as a continuous variable in a log-binomial regression.
unchanged (PR: 1.02, CI: 0.991.05, p = 0.16). All individual
factors associated with organic consumption remained significant
with the inclusion of the measures of the local food environment.
Frequent Organic Consumers
While the primary analysis aimed to understand the factors
associated with the decision to consume organic produce at least
occasionally, this secondary analysis explored the question of
whether individual and local food environment factors were
Per capita household income
Less than high school
Unemployed or Retired
Continuous, per 10 years 0.87
High school degree
lowest and highest income groups were more likely to report that
they often or always consumed organic produce, and the middle
income groups were significantly less likely to be frequent organic
However, in contrast to the results of the primary analysis, the
local food environment was not associated with the decision to
often or always consume organic produce. Though density of
supermarkets within 1 mile of the residence remained strongly
associated with organic produce consumption in bivariate analyses
(p = 0.0002), aggregated neighborhood survey and self-report of
accessibility were no longer significantly associated (p = 0.09 and
p = 0.17, respectively). Further, once individual-level variables
were accounted for in a fully adjusted model, no significant
relationship was found between often or always consuming
organic produce and any of the measures of the local food
environment (supermarket density: OR = 1.05, CI = 0.951.17;
self-report: OR = 1.00, CI = 0.851.17; ANS Score: OR = 1.01,
CI = 0.521.98).
To our knowledge, this is the first study to examine the
associations of both individual and neighborhood characteristics
and organic food consumption. We found that both are associated
with this dietary choice. Women, younger individuals, those with
higher education, and those living in more urban areas were more
likely to consume organic produce. Neither race/ethnicity nor per
capita household income was strongly associated with organic
produce consumption. We found that characteristics of the local
food environment, such as produce availability, were associated
with the decision to consume organic produce at least occasionally.
Organic food consumption is increasing; consistent with our
findings, several studies over the past decade have reported that 40
to 50% of individuals and households purchase organic food at
least occasionally . However, the specific factors associated
with organic food consumption have not been well understood, as
early studies painted contradictory pictures of the socioeconomic
status and demographics of organic food consumers.
Organic food consumption has been found to be associated,
variously, with higher education , lower education , or
not associated with education at all . Results were also mixed
for the relationship between income and organic food; some
studies observed consumers with high incomes to have less
tolerance for food with blemishes and to be less likely to purchase
organic food , while others found people with higher income
to be more likely to make organic purchases [28,30], and others
found no association . Findings with respect to age and
ethnicity were also inconsistent; in fact, the only demographic
attribute to be reliably associated was gender, with women
purchasing more organic food than men [28,3031]. However, all
of these studies employed convenience samples, and typically
included people who were already shopping at either food
cooperatives or at expensive specialty grocers, missing substantial
segments of the general population. More recent research has
capitalized on Nielsen Consumer Panel studies, in which
thousands of American households are provided handheld
scanners to scan each item they purchase [24,27,33]. These
studies have consistently found higher income and education to be
associated with purchasing organic food, but age and ethnicity
have continued to show inconsistent effects.
Our results are consistent with previous research showing that
women purchase organic food more frequently than men, and
associated with more frequent organic produce consumption.
Here, the definition of organic consumers was restricted to those
who reported that the fruit and vegetables they ate were often or
always organic. In general, the relationships between organic
produce consumption and individual-level factors were similar to
those reported in the primary analyses. In fully adjusted models of
individual factors, female gender, younger age, more urban
metropolitan areas, and higher levels of education were all
significantly associated with often or always consuming organic
produce, as was the case in the primary analysis. Race/ethnicity
and marital status were not significantly associated with organic
produce consumption. Per capita household income was
significantly associated with often or always consuming organic
produce (p = 0.04), but the relationship was not linear. Instead, the
Total sample (n = 3,428)
Quartile 1 (00.3 per sq mile)
Quartile 2 (0.30.6 per sq mile)
Quartile 3 (0.61.6 per sq mile)
Quartile 4 (1.611.8 per sq mile)
Disagree or strongly disagree
Agree or strongly agree
Aggregated Neighborhood Survey (by quartile)
Density of supermarkets within 1 mile of residence (by quartile)
Self-report: A large selection of fresh fruits/vegetables is available in my neighborhood
Never or rarely consume organic produce
ap-values derived from log-binomial regression with variables specified as continuous.
with the Nielsen Consumer Panel studies observation that higher
education is associated with more organic food purchasing. In
MESA, older participants were less likely than younger
participants to consume organic food. However, since all participants in
this study were aged 45 and older, this result could also be
consistent with a U-shaped relationship between age and
organic consumption, in which middle aged people are more
likely to consume organic food than both younger and older
individuals, as other researchers have suggested .
The relationship between per capita household income and
organic produce consumption was sensitive to adjustment for
other individual level variables, and to the categorization of
organic consumers. In bivariate analyses, self-report of either
sometimes or often or always consuming organic produce was
strongly associated with income category, but the strength of this
relationship was attenuated by adjustment for other individual
level factors. When restricted to individuals who often or always
consumed organic produce, the relationship with income was
decidedly non-linear; individuals with the lowest and highest per
capita household incomes were more likely to report frequent
consumption of organic produce.
To our knowledge, this is the first study to examine geographical
differences in organic food consumption; we found participants in
more populated cities (Los Angeles, Chicago, and New York) to
consume more organic food than those in less densely populated
regions (St. Paul, Winston-Salem and Baltimore). This difference
may also be related to the local food environment and food access;
more research is needed to fully understand the relationship
between organic food consumption and urbanicity.
Local Food Environment Findings
Over the past decade, the US obesity epidemic and in
particular, disparities in obesity prevalence has led the public
health community to think much more broadly about factors
influencing diet. No longer are dietary motivations understood
only in the framework of individual lifestyle choices. Instead, the
food environment has been increasingly recognized as important
to diet [15,18,3539], and the results of this study are consistent
with the idea that this environment influences a variety of dietary
While this is the first study to explicitly investigate the
relationship between the local food environment and organic
consumption, it is not the first study to look at factors beyond
demographics and socioeconomics on this dietary choice. Zepeda
and colleagues explored the motivations behind organic food
consumption in a national survey of nearly 1,000 US adults
[23,40]. When variables related to food beliefs and shopping
habits were considered, organic food consumption was not found
to be associated with direct economic variables, such as household
income or weekly food expenditures. Instead, the important
factors in choosing organic food included both personal beliefs and
opportunity, where opportunity was defined as shopping at food
venues where organic food was more likely to be available. This
represents a different approach to exploring the influence of food
accessibility on organic consumption, but the results are consistent
with our finding that access may play an important role in the
decision to at least occasionally consume organic foods. The results
from our secondary analysis support the notion that personal
beliefs may matter, perhaps particularly for those who often or
always consume organic food. This relatively small group of
people may be willing to go out of their way to make this dietary
choice, even if produce and supermarkets are not readily available
in their neighborhoods.
A primary limitation of this study was the lack of a direct
measure of organic food availability. Instead, we employed
supermarket density and both self-report and community
perception of availability of produce and healthy food as proxies for
organic food availability. The USDAs 2009 report, Marketing
US Organic Foods: Recent Trends from Farms to Consumers
shows that sales of organic food from conventional supermarkets
and groceries now account for 46% of the total organic market
share, with natural-products retailers and direct markets each
accounting for another 44% and 10%, respectively . This
report also states that organic food is now available in more than
80 percent of all supermarkets. Given this high proportion of
supermarkets in which organic food is available, we believe that it
is reasonable to assume that areas with more supermarkets are also
more likely to provide greater access to organic food. In addition,
organic produce is more likely to be available in areas with a
greater selection of produce in general. However, further research
including more specific measures of organic food availability is
Recent literature has shown that subjective and objective
measures of the local food environment do not always agree [42
43], and so we investigated three complementary measures of the
local food environment, each with strengths and weaknesses.
Supermarket densities are the most objective of the three but rely
on the assumption that supermarkets offer organic foods. Further,
the use of supermarket density within a straight-line distance
neglects actual travel patterns along road networks and further
assumes that people reliably shop at supermarkets near their
homes. Recent research by Drewnowski et al. suggests that this
assumption may not accurately reflect actual shopping patterns
. Self-reports reflect each individuals perceptions but their
interpretation is affected by the possibility of same source bias,
which may arise when using self-reports of the food environment if
a persons behavior affects their reported perceptions of access to
healthy foods. The strength of aggregate survey measure is that
averages of multiple respondents are likely to eliminate the
influence of individual subjectivities and eliminate the possibility of
samesource bias. However, it may not accurately reflect access
for a particular participant. The consistency of associations across
the three types of measures increases confidence that the local food
environment plays a role in organic consumption habits.
We chose to focus on organic produce rather than other food
types. This was intended to be consistent with previous studies
evaluating the relationship between consumption of organic food
and organophosphate pesticide exposure . Over 33 million
pounds of organophosphates are applied annually in the US
more than any other class of insecticides and their metabolites
are found in the urine of 94% of the US population . These
compounds are registered for use on a wide variety of fruits and
vegetables, but are not widely used in the production of meat or
dairy . We do not expect that this decision had a large impact
on our results, as recent USDA research shows that US retail sales
of organic fruits and vegetables are larger than all other organic
food categories combined . However, it is worth noting that
there are several other categories of organic food not considered
This study demonstrates that both individual- and
neighborhood-level characteristics are associated with the decision to
consume organic produce at least occasionally, and provides
further evidence of the impact of food access on dietary choices.
While previous research has shown that healthy food
environments are associated with healthy diets, this is the first study to
explore the relationship between the local food environment and
organic food consumption. While it remains unclear whether or
not there is a health benefit to eating organic food, there is
growing evidence that consumption of organic food can reduce
pesticide exposure and that, at least for some segments of the
population, even low levels of pesticide exposure may have health
effects. There are also other reasons that people may choose to eat
organic food, including concerns for farmworker safety and
ecological health. Allowing everyone equal ability to make this
choice may present yet another argument for leveling the playing
field of food accessibility.
Conceived and designed the experiments: CLC JDK. Performed the
experiments: CLC. Analyzed the data: CLC. Wrote the paper: CLC.
Developed metrics of food access: KM AVDR. Provided social
epidemiology expertise, statistical code and manuscript editing: SAAB
AH. Developed the food frequency questionnaire, provided nutrition
expertise and manuscript editing: JAN.
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