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Dietary Intake and Dietary Attitudes Among Food Stamp Participants and
Other Low-Income Individuals
EXECUTIVE
SUMMARY
The Food Stamp Program (FSP) is designed to "safeguard the health and
well-being of the Nation’s population by raising the level of nutrition
among low-income households." The program aims to meet this objective
by providing food stamp benefits to low-income households that can be used
to purchase foods from authorized food retailers. The program also
supports nutrition education efforts, by providing funds for states to set
up nutrition education programs (NEPs) for FSP participants. As of fiscal
year 2000, the FSP had agencies with approved NEPs in 48 states and
federal funding for these programs was projected to total $99 million.
In
studying the effectiveness of the FSP, a critical research question
involves determining the relationship between program participation and
dietary outcomes. An unresolved issue in the literature on the effects of
the program is the role of dietary knowledge and attitudes. It is not
known whether participants and low-income nonparticipants differ in their
dietary knowledge and attitudes or whether any such differences influence
their dietary intake. Finally, it is not known whether controlling for any
such differences would influence the estimated relationship between food
stamp participation and dietary outcomes.
This report examines the dietary knowledge and attitudes of low-income
individuals, including FSP participants and nonparticipants, describes
their dietary intake, and estimates participation-dietary intake
relationship. In particular, the analysis addresses three basic
questions:
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What do low-income adults know about healthy eating practices, and how do
they feel about these practices and about their own diets.
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What do low-income Americans eat, and how do their diets stack up against
accepted standards for healthy eating?
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What is the relationship between food stamp participation and dietary
intake among low-income individuals and do differences in the dietary
knowledge and attitudes among participants and low-income nonparticipants
mediate this relationship?
The analysis was based on data from the 1994-1996 Continuing Survey of
Food Intakes by Individuals (CSFII) and the associated Diet and Health
Knowledge Survey (DHKS). These nationally representative data sets were
used to create an analysis file containing about 4,000 low-income and
10,000 high-income preschoolers, school-age children, and adults.
Low-income and high-income individuals were distinguished on the basis of
whether their household income was below or above 130 percent of poverty.
The high-income sample was included to provide benchmark values for the
low-income sample.
Estimates of the relationship between participation and dietary outcomes
were based on regression models in which the dependent variables were the
dietary outcomes, and the independent variables included food stamp
benefits and a wide range of individual and household characteristics.
One limitation of the analysis is that, since experimental methods were
not used, the estimates of the effects of FSP participation on dietary
outcomes may have been biased by unobserved differences between
participants and nonparticipants. Previous studies have cited dietary
knowledge and attitudes as one possible source of this bias. A major aim
of this study is to address this possible methodological weakness by
controlling explicitly for the dietary knowledge and attitudes of
low-income adults to determine whether this affects the estimated
participation-dietary intake relationship. The analysis also controls for
differences between the income and health status of participants and
nonparticipants, as well as many other factors. However, other unobserved
factors that represent the degree to which participants are socially or
economically disadvantaged may remain.
Dietary Knowledge and Attitudes Among
Low-Income Adults
There is room for improvement in two dimensions of dietary knowledge among
low-income adults. Large numbers of low-income adults do not know specific
facts related to the health consequences of particular dietary practices,
such as what health problems result from eating particular types of foods.
Similarly, many low-income adults do not know specific facts related to
what types of dietary practices are healthful, such as what specific foods
they should eat to maintain a healthy diet. More specifically:
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Among
low-income adults, FSP participants and nonparticipants do not differ
significantly in their levels of dietary knowledge according to any of the
three knowledge indicators that were examined.
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In general, low-income adults have lower dietary knowledge levels than
high-income adults. Overall, the high-income group is between 10 and 20
percent more likely than the low-income group to be able to recall
specific pieces of dietary information.
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On average, low-income adults can correctly identify just over half of
a set of health problems associated with specific dietary practices such
as eating too much fat or not enough fiber. More than two-thirds of these
adults know the consequences of being overweight, eating too much fat, and
eating too much cholesterol, while only 40 percent know that not eating
enough fiber is associated with bowel problems, heart problems, and/or
cancer.
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On average, low-income adults know less than half of the U.S.
Department of Agriculture’s Food Guide Pyramid recommendations for the
daily consumption of the five major food groups. They are particularly
unlikely to know that they should consume at least six servings of grain
products and three servings of vegetables daily.
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Low-income adults know an average of just over half of a set of facts
related to the fat or cholesterol content of specific foods. For example,
only 30 percent know that cholesterol is found in animal products like
meat and dairy products and only 47 percent know that hot dogs contain
more fat than ham.
Both low- and high-income adults appear to place great importance on
healthy eating. About 60 percent of each group strongly agrees that
"what you eat can make a big difference in your chance of getting a
disease." Both groups are also likely to place high importance on
following specific healthful dietary practices, such as choosing a diet
that is low in fat and cholesterol and that contains plenty of fruits and
vegetables. Among low-income adults, for example:
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Seventy-two percent feel
that it is very important to choose a diet with plenty of fruits and
vegetables.
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Sixty-four percent feel that it is very important to choose a diet low
in fat.
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Sixty-one percent feel that it is very important to choose a diet low
in cholesterol.
These findings suggest that low-income adults’ relatively low levels of
dietary knowledge, as described above, do not translate into complacency
about their diets. These individuals still feel that it is important to
follow healthful dietary practices and that such practices influence
health outcomes.
Substantial numbers of low-income adults are not confident
that their own diets comply with these healthful dietary practices. They
are likely to believe either that their diets are too low in a key vitamin
or mineral or are too high in total calories or a key macronutrient. In
particular:
FSP participants are more likely than nonparticipants to
believe that their diets are too low in key vitamins and minerals and too
high in key macronutrients. For example, 47 percent of participants and 31
percent of nonparticipants believe their diets are too low in fiber, while
50 percent of participants and 39 percent of nonparticipants believe their
diets are too high in fat.
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Low-income and high-income adults are about equally likely to believe
that their diets are too low in key vitamins and minerals, but high-income
adults are more likely to believe that their diets are too high in key
macronutrients (such as fat).
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Among the low-income group, just over one-third believe their diets are
too low in calcium, fiber, and iron, while 25 percent believe their diets
are too low in vitamin C.
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Among the low-income group, 43 percent believe their diets are too high
in fat, 33 percent believe their diets are too high in sugar and sweets,
and 32 percent believe their diets are too high in calories.
The finding that FSP participants are more likely than nonparticipants to
lack confidence in the quality of their diets is particularly interesting
given that the two groups have similar levels of dietary knowledge and
other types of dietary attitudes. This finding has at least three
potential explanations. First, participants may lack confidence in the
quality of their diets to a greater extent than nonparticipants because of
the nutrition education efforts of the FSP. Second, the difference may
arise because participants are in poorer health than nonparticipants. For
example, Bialostosky and Briefel (2000) found that participants are more
likely than nonparticipants to be obese and to smoke cigarettes. Third,
the difference may reflect a true difference in participants’ and
nonparticipants’ dietary attitudes.
What Low-Income Americans Eat
The diets of low-income Americans can be examined from a number of
perspectives. The analysis in this report examines individuals’ dietary
habits, the foods they consume, their intake of food energy and vitamins
and minerals, and their intake of macronutrients and other dietary
components such as fiber and cholesterol.
Many low-income adults do not
engage in specific dietary habits intended to lower the fat and
cholesterol content of their diets, such as removing fat from the meat
they consume, avoiding fat as seasoning, and substituting or replacing
high-fat foods with lower-fat alternatives. For example, only:
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Twenty-five
percent never put butter or margarine on cooked vegetables.
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Twenty-three percent always use skim or low-fat milk rather than whole
milk.
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Seventeen percent always eat low-fat luncheon meats instead of regular
luncheon meats.
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Thirteen percent eat meat at a main meal less than once a week.
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Forty-one percent always remove the skin when eating chicken.
Low-income individuals consume less than the Food Guide Pyramid
recommendations for the daily consumption of all five major food groups.
Typically, about half of the individuals in a particular age group fail to
meet the minimum servings recommendation for a given food group. For some
foods and some age groups, consumption is especially low.
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Among low-income
individuals in three age groups--preschoolers, school-age children, and
adults--39 to 51 percent consume fewer than six servings of grain products
daily; the Food Guide Pyramid recommends six to eleven servings.
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Sixty percent of preschoolers eat fewer than three servings of
vegetables daily; the Food Guide Pyramid recommends three servings for
this age.
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About 70 percent of school-age children and adults consume less than
two servings of fruit daily; the Food Guide Pyramid recommends two to four
servings.
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Approximately 70 percent of adults consume less than two servings of
dairy products daily; the Food Guide Pyramid recommends two to three
servings.
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Seventy percent of preschoolers eat fewer than two servings of meat or
meat substitutes daily; the Food Guide Pyramid recommends two to three
servings.
With low consumption of the five major food groups, low-income
individuals consume large amounts of the foods in the pyramid tip (such as
fat and added sugar). Among adults, for example, the mean intake of
discretionary fat is 53 grams per day, while the mean intake of added
sugar is 18 teaspoons per day. The intake of these food items in the
pyramid tip is even higher among school-age children.
On average,
low-income individuals’ mean nutrient intake levels exceed the
Recommended Dietary Allowance (RDA) for most vitamins and minerals.
However, substantial proportions of low-income individuals are likely to
have inadequate usual intakes for a number of micronutrients. Using usual
intake below 70 percent of the RDA as the indicator of inadequate intake:
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Preschoolers are most likely to have inadequate intakes of vitamin
E, zinc, calcium, and iron.
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School-age children are most likely to have inadequate intakes of
calcium, vitamin A, vitamin E, zinc, and magnesium.
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Adults are more likely than children to have inadequate intakes; the
nutrients for which large numbers of low-income adults have inadequate
intakes are calcium, zinc, vitamin E, magnesium, vitamin A, vitamin B ,
iron, vitamin C, and folate.
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Adults also have low usual food energy intake levels; 79 percent of
low-income adults have usual food energy intake levels less than the
recommended energy allowance (REA), which is the estimated mean required
intake level among adults. Since 50 percent of adults would be below the
REA if they all met their required intake level, an estimated 29 percent
of adults (79 minus 50) have intakes below their required intake levels.
Among preschoolers, low-income individuals have slightly higher mean
intake levels of several vitamins and minerals than high-income
individuals. This difference is statistically significant for protein,
niacin, folate, and zinc. Among adults, however, the reverse is true.
Low-income adults have significantly lower intake levels of 12 of the 14
vitamins and minerals that were examined.
Overall, low-income individuals are unlikely to meet the Dietary
Guidelines for the intake of macronutrients such as fat, saturated fat,
and carbohydrates, as well as for the intake of other dietary components
such as fiber and sodium. Low-income individuals consume too much of their
food energy in the form of fat or saturated fat and too little of their
food energy in the form of carbohydrates. In particular:
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Few low-income
preschoolers meet the Dietary Guidelines for fat, saturated fat, and
carbohydrates. For example, their mean intake of fat as a percentage of
food energy is 34 percent and only 24 percent meet the dietary guideline
of limiting their fat intake to no more than 30 percent of food energy. In
addition, only 20 percent limit their protein intake to no more than twice
the RDA, and a little over half meet the sodium RDA.
However, nearly four
of five low-income preschoolers meet the dietary guideline of limiting
their cholesterol intake.
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Low-income school-age children have levels of fat, saturated fat,
carbohydrate, and cholesterol intake in relation to the guidelines that
are similar to those of low-income preschoolers. They are much more likely
than preschoolers to meet the dietary guideline for protein but are much
less likely to meet the sodium dietary guideline. Only 29 percent of
low-income school-age children limit their sodium intake to less than
2,400 milligrams.
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Although low-income adults have slightly lower mean fat and saturated
fat intakes than children, they remain unlikely to meet the Dietary
Guidelines for fat and saturated fat intake. For example, only one in
three meets the guideline for fat intake. Most low-income adults meet the
dietary guideline for protein and cholesterol intake. However, their mean
fiber intake is 14 grams, their mean sodium intake is 3,200 grams, and
only 19 and 36 percent meet the Dietary Guidelines for fiber and sodium
intake, respectively.
High-income individuals are much more likely than
low-income individuals to meet many of the Dietary Guidelines. Among
preschoolers and school-age children, the percentages of high-income
individuals meeting the guidelines for fat, saturated fat, carbohydrate,
cholesterol, and (among preschoolers only) sodium intake exceed the
percentages of low-income individuals meeting these guidelines. For
example, the percentages of high-income preschoolers meeting the fat and
saturated fat guidelines are 41 and 28 percent, respectively, compared
with 24 and 14 percent among low-income preschoolers. Among adults,
high-income individuals are more likely than low-income individuals to
meet the Dietary Guidelines for fiber, cholesterol, and sodium.
How Food Stamp Program Participation Affects
Dietary Intake
There is little evidence that FSP participation is related to low-income
individuals’ food group choices. After controlling for individual and
household characteristics and the dietary knowledge and attitudes of
low-income individuals, there are almost no statistically significant
differences in their average consumption of various food groups, including
grain products, vegetables, fruit, dairy products, meat and meat
substitutes, discretionary fat, and added sugar (the exceptions are
significant negative relationships between participation and the intake of
grains among preschoolers, the intake of vegetables among adults, and the
intake of fish among adults).
Subject to the caveat that the analysis does
not control for unobserved differences that may exist between participants
and nonparticipants, it appears that participation does not influence the
number of servings of the major food groups consumed by low-income
individuals.
Participants and nonparticipants consume similar amounts of
vitamins and minerals, on average. Among preschoolers, participation is
insignificantly related to mean intakes of all nutrients except iron, for
which there is a negative relationship. Among school-age children and
adults, participation is insignificantly mean intakes of all nutrients
except folate (for school-age children), for which there is a positive
relationship.
Participants and nonparticipants are equally likely to have
adequate usual nutrient intake levels. There are no significant
differences for any of the micronutrients examined in the percentage of
participants and nonparticipants whose usual intakes exceed 70 percent of
the RDA (the measure of adequacy used in the analysis).
Participation
appears to have little influence on low-income individuals’ intake of
macronutrients and other dietary components. The percentage of
participants and nonparticipants meeting the Dietary Guidelines is not
significantly different, with two exceptions. First, preschoolers who are
FSP participants are significantly less likely to meet the dietary
guideline for saturated fat. Second, adults who are participants are
significantly less likely to meet the dietary guideline for fiber.
Participation is not related to two measures of diet quality
examined--the Healthy Eating Index (HEI) and the Diet Quality Index (DQI).
For each of the three age groups examined, the relationship between FSP
participation and low-income individuals’ HEI and DQI scores is
statistically insignificant.
Participation does not appear to be related to
dietary intake among a set of subgroups examined in the analysis. Most of
the estimates of the effect of participation on intake among subgroups
defined by age/gender, race/ethnicity, health status, and income level
were statistically insignificant. The few estimates of the effect of
participation on intake that were statistically significant did not follow
any systematic pattern.
Where Low-Income Americans Obtain their Food
Low-income Americans obtain most of the food they consume from food
stores. Low-income adults get three-fourths of their food from food
stores, with 18 percent coming from restaurants and 8 percent from other
sources. School-age children get only two-thirds of their food from
stores, with 13 percent coming from restaurants and the rest (20 percent)
coming from other sources (largely school breakfasts and lunches).
Finally, low-income preschoolers get 82 percent of their food from stores.
Food stamp participation is related to where low-income individuals
obtain their food. Among school-age children and adults, participants
obtain more of their food from food stores and less from restaurants and
other sources than nonparticipants, on average. This relationship holds up
even after controlling for individual and family characteristics and other
relevant factors. The most likely explanation for the effect of
participation on where individuals obtain their food is that food stamps
place constraints on where low-income households purchase their food. To
legally use their food stamps, participants must purchase certain foods
from certified food stores.
Reconciling the Findings with Previous
Literature
This report set out to estimate the relationship between FSP participation
and dietary intake after taking into account all the relevant factors
potentially influencing participation. Since previous research had cited
individuals’ dietary knowledge and attitudes as a potentially important
factor not typically taken into account, the analysis in this report
advances the literature by controlling for dietary knowledge and attitudes
in estimating how food stamp participation is related to dietary intake.
Results of the analysis show that low-income individuals’ dietary
knowledge and attitudes do not mediate the relationship between FSP
participation and dietary intake. Controlling for adults’ dietary
knowledge and attitudes does not affect the estimated relationship between
participation and dietary intake. Regardless of their dietary knowledge
and attitudes, food stamp participation is not significantly related to
low-income individuals’ intake of food energy, vitamins and minerals,
macronutrients, or food groups.
The results of this study are consistent
with previous literature on the effects of food stamp participation on
dietary intake. Most previous studies have found that participation is
insignificantly related to the intake of most nutrients. Where significant
relationships have been found, they have not consistently and
systematically been positive or negative.
However, the results of research (including this study) on the effects of
participation on dietary intake appear to be inconsistent with the results
of other research showing that food stamp benefits lead to increases in
food expenditures among low-income households. Other previous studies have
found a positive relationship between a household’s food stamp
participation and the availability of nutrients in their household. If
food stamps lead households to spend more on foods and to have larger
amounts of nutrients available in their homes, one might expect that the
benefits would also lead to increases in the dietary intake of household
members. This study and the previous literature suggest that this is not
the case.
Two methodological issues may partially explain this apparent
inconsistency. First, the studies of the effects of food stamp
participation on food expenditures and nutrient availability use the
household as the unit of analysis, while the dietary intake studies use
the individual as the unit of analysis. It is not clear how food
expenditures or nutrients available in the home are distributed across
household members and across individuals who may not be members of the
household.
Second, the food expenditure and nutrient availability studies are
primarily based on data collected during the late 1970s, while a number of
the intake studies are based on more recent data. Since the implementation
of the FSP has changed over this period, the results of the studies may
reflect changes in the effects of FSP participation over time.
If methodological differences between studies do not explain the pattern
of results, two other factors may explain the lack of a positive
relationship between participation and dietary intake in the face of
estimates of positive effects on food expenditures. First, food stamps may
lead participating households to purchase some foods that nonparticipating
households might obtain for free. For example, participating individuals
might purchase the food they eat instead of obtaining it free from a
friend, relative, soup kitchen, or food pantry. This possibility is
consistent with the finding that, relative to nonparticipants, FSP
participants get more of their food from food stores and less from
"other sources." In addition, if purchased food is wasted or
consumed by nonhousehold members, then an effect of participation on
expenditures (and availability) would not necessarily translate into an
effect on intake.
A second reason why FSP participation might not lead to a positive effect
on nutrient intake may be that participants purchase more expensive forms
of the same foods than nonparticipants. For example, with the additional
resources available, FSP participants may select brand-name foods rather
than generic foods at stores. They may also purchase more convenient
ready-to-eat foods rather than basic staples to use as ingredients in
foods they prepare themselves.
Future Directions for Policy/Research
Additional research is needed to address several issues raised in this
report. Future research should attempt to use a variety of approaches to
determine whether selection bias influences estimated program effects.
With better data, for example, studies may be able to more precisely
control for individuals’ economic circumstances than was possible in
this study. Additional data may also allow researchers to develop
appropriate "identifying variables" that are correlated with
participation but not with dietary intake, as part of a strategy to
address the selection bias issue econometrically. Future research should
also address the question of how FSP benefits influence households’
overall expenditures. Most studies of the effects of FSP on food
expenditures are based on relatively old data collected at a time in which
the FSP had different program rules. Thus, research should examine the
current effects of FSP participation on food expenditures and should also
estimate the effects of participation on household spending on nonfood
goods and services.
The analysis in this report provides circumstantial
evidence that there is a role for increasing efforts to provide nutrition
education and promotion among participants. The study finds that
participants have "moderate" levels of nutrition knowledge--they
are aware of some key aspects of the link between nutrition and health and
of what constitutes good nutritional practices, but they also are unaware
of other key pieces of nutritional information. Assuming that a link
exists between nutritional knowledge and dietary intake (an assumption
supported in part by empirical evidence based on prior research), then
continuing the existing program efforts at promoting nutrition education
among participants may lead to an improvement in the nutritional quality
of participants’ dietary intake. This study, as well as previous
research, shows that additional economic resources provided by FSP
benefits alone may not substantially change participants’ dietary
intake. However, these additional resources, which increase participants’
food-purchasing power, supported by nutrition education aimed at helping
participants make more informed food choices, may provide participants
with the tools and strategies to improve their nutritional intake and
dietary quality.
Last modified: 12/04/2008
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