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rig
Improving the Diet and Health of
Individuals and Populations
Until quite recently, eliminating nutritional deficiencies was the ma-
jor focus of community or population nutrition programs. From a public
health perspective, dealing with these conditions was relatively straight-
forwarc3, through governmental requirements for food fortification and
the use of vitamin and mineral supplements in high-risk persons.
Over the past several cJecacles, a new era of nutritional science has
unfolclecl. Researchers have begun to detect important relationships be-
tween diet and the development of major chronic cliseases, such as coro-
nary heart disease, diabetes, hypertension, and cancer. In many instances,
the diet-disease relationships reflect nutrient excesses rather than defi-
ciencies. However, dealing with these diet-ctisease relationships from a
public health perspective is not straightforward. Manipulating the food
supply and using supplements alone cannot ensure adequate or "optimal"
nutriture to prevent these diseases, which constitute the major causes of
mortality in the United States. Inclividual responsibility for appropriate
food selection must be an essential aspect of nutrition intervention pro-
grams. Yet food choices depend on many factors, including nutrition knowl-
edge, motivation, economics, food availability, and others. Furthermore,
as outlined in earlier chapters, our increased scientific sophistication is
making it possible to stratify the population based on genetically cleter-
mined susceptibility factors, so interventions may not have to be applied
equally to everyone. Exciting opportunities for research in public health
180
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IMPROVING THE DIET AND HEALTH OF INDIVIDUALS AND POPULATIONS lS1
nutrition related to diet and disease interactions are numerous and hold
vast potential for improving the health of the nation.
While a portion of the U.S. population suffers from diseases often
related to excess consumption of certain food components, others go hun-
gry. The extent of hunger and food insecurity in this country is unknown,
but awareness of the problem is growing as it receives more public and
scientific attention Understanding the causes and consequences of food
insecurity and hunger and developing effective interventions are major
challenges facing public health nutritionists. Since an uneven distribution
of the food supply is thought to be the underlying cause of this problem,
federal food assistance programs have been implemented over the past 20
years to improve access to food for the most vulnerable groups, such as
infants, pregnant and lactating women, the poor, and the aged. While
effective, a contemporary evaluation is needed of the impact of these
programs in the context of today's social and economic problems.
Better measuring tools are required to monitor the impact of inter-
vention programs, whether they provide food and services or promote
behavior change through education, price incentives, convenience, or mocli-
fication of the food supply. Ideally, nutrition assessment tools and meth-
ocis should be simple, accurate, inexpensive, specific, and sensitive to small
changes. Our knowledge of food composition needs to be enhanced, and
databases must inclucie nonnutritive components of food that influence
health (e.g., fiber). New biological markers of nutrient intakes will be
especially useful to validate dietary assessment methods.
Evaluating programs includes studying their operations, logistics, or-
ganizational behavior, and personnel motivation. Evaluating participation
in intervention programs and their systems of food delivery requires studying
the various determinants of householct and individual behavior. Evaluat
ing strategies for promoting behavior change requires an assessment of
the determinants of, and constraints on, the behaviors of interest. Investi-
gators need a wide range of skills and knowledge to perform these assess-
ments, yet all fall outside the traditional field of nutritional science. What
is required is a new kind of nutrition professional who combines these
areas of training. Current attempts by nutritional professionals to increase
the prevalence of breastfeeding in the United States have been relatively
unsuccessful in the past decade. This may be due in part to the fact that
the need or desire for women to work outside the home has not been
considered and incorporated into breastfeeding promotion efforts. Nutri-
tion professionals must be able to integrate nutrition science with the
beliefs and values of society in order to motivate behavior change.
Chapter 2 highlights some of recent accomplishments in the nutrition
and food sciences and identifies research needed to implement effectively
new laboratory findings in these disciplines. Iron nutriture is a particu
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82
OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
larly challenging issue discussed in that chapter. Iron deficiency is of
special concern because it may affect the physical and mental develop-
ment of infants and young children. However, as many as 10 percent of
the U.S. population is at risk for hemochromatosis and iron overload.
Intervention approaches need to be developed and tested that ensure that
iron-fortified foods reach the population at risk of iron deficiency without
putting those with hemochromatosis, or those prone to the disorder, at
risk.
Recently, epidemiological studies have shown that some neural tube
defects (NTDs) can be prevented by folio acid when taken prior to and
during the first trimester of pregnancy (see Chapter 2~. Fortification of
foods with folic acid is a potential intervention, therefore, to reduce the
risk of NTDs. However, this kind of intervention presents difficult public
policy issues because it would lead to most people consuming more folio
acid than they do now. This could pose risks to some, especially those
with underlying vitamin B. deficiency. Alternatively, all fertile women
may be advised to take a folio supplement or to increase their intake of
folate-rich foods. The choice is one of altering the food supply or altering
the nutrition messages for women of childbearing age and motivating them
to change their food habits. The costs and benefits of each approach
needs to be investigated, not only for this particular issue, but for many
other public policy issues in nutrition as well.
Information provided in Chapter 4 shows that food science and tech-
nology has made enormous strides in providing high-quality, safe, and
wholesome food that has been modifies] to help consumers more easily
meet dietary recommendations. For example, the number of low-fat food
items available in supermarkets and restaurants has increased substan-
tially in recent years. However, only a minority of individuals in this coun-
tr,v meet dietary recommendations. This is because modification of the
food supply is only part of the process. In addition, consumers need the
knowledge to make healthy food choices in supermarkets and restaurants,
the motivation to make changes in food selection practices, and the avail-
ability of health-promoting foods to maintain the changes over the long
term. Actions based on a comprehensive understanding of the interaction
between economic and health policies, societal values, and individual and
household behaviors and food attitudes must be combined with efforts of
the food industry to alter the food supply. Research bridging the gap
between the biological science of nutrition and the behavioral and social
sciences is required to accomplish the complicated task of influencing
long-term choices in food habits.
The special concerns of the most vulnerable groups in the population
(infants, pregnant and lactating women, the poor, and the aged) are out-
lined in Chapter 5. Nutritionists charged with the responsibility for im
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IMPROVING THE DIET AND HEALTH OF INDZVIDUALS AND POPULATZONS 1S3
proving the dietary and health of groups in the future need to do more
than simply provide information. Instead, the information needs to be
presented in a manner that makes it relevant to the recipient, which in-
cludes integrating the messages into the cultural and social values of the
group. In other words, the messages need to be tailored to the values of
specific communities and population groups. For example, the increasing
prevalence of obesity among the poor reflects, at least in part, the absence
of effective communication between nutrition professionals and the disad-
vantaged. The development of models or approaches for modifying nutri-
tion messages that better fit a community or specific minority group is an
important research challenge for the future.
A new kind of nutrition investigator is needed who researches issues
at the interface between the nutrition and populations and the behavioral
and social sciences. This chapter identifies selected research opportuni-
ties for this new breed of nutrition scientist in three general areas re-
ducina the risk of diet-related diseases reducing the risk of food insecurity
O , (, ~ ~ ~ ,
and hunger, and improving the methods and tools for nutritional assess-
ment, monitoring, and evaluation. Several interesting and exciting needs
and opportunities for research are identified for each area. Our examples
are meant to be illustrative, not comprehensive.
REDUCING THE RISK OF DIET-RELATED DISEASE
Research during the past several decades has identified several im-
portant relationships between diet and chronic disease, such as coronary
heart disease, diabetes, hypertension, and cancer. Few of these relation-
ships have been established with absolute certainty, and they are con-
stantly being refinecl. Nevertheless, a large literature on diet and chronic
disease now exists and provides a basis for interim dietary recommenda-
tions to the public. Three influential reports have helped establish a con-
sensus on dietary patterns to promote health and reduce the risk of chronic
disease the 1988 Surgeon General's Report on Nutrition and Health, the
1989 National Research Council report Diet and Health: Implications for
Reducing Chronic Disease Risk, and the 1990 Dietary Guidelinesfor Americans
by the U.S. Departments of Agriculture (USDA) and Health and lIuman
Services. Their recommendations include maintaining appropriate weight,
reducing consumption of fats and cholesterol, and eating a variety of foods,
notably more grain products, fruits, and vegetables. While there is broad
agreement as to what constitutes a healthful diet, motivating people to
adopt healthful lifestyles remains a formidable challenge for nutrition pro-
fessionals.
Three strategies to meet this challenge were proposed by the Food
and Nutrition Board in its 1991 report Improving America's Diet and
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
Health: From Recommendations to Action. This report identifies the gov-
ernment, the food industry, health-care professionals, and educators as
key groups to implement dietary recommendations. It calls for (1) govern-
ment and health-care professionals to become more active as policymakers,
role models, and agenda setters, (2) improving the public's knowledge calf
ˇ. - 1 ˇ . .1
1 0 1 -
nutrition anct Increasing their opportunities to practice good nutrition,
and (3) increasing the availability of health-promoting foods.
We discuss below the research opportunities for motivating inclividu-
als to meet dietary recommendations. We consider two general factors
that influence food habits sociocultural and behavioral.
Sociocultural Factors in Diet Selection
While genetic and physiological determinants shape individual food
preferences and aversions, the translation of these into behavior diet
selection is mediated by sociocultural factors. Research on diet selection
has traditionally focused on identifying factors that result in similarities in
food consumption patterns among people in groups. More recent work
has (1) broadenect the array of variables used to differentiate people into
food-consuming groups, (2) begun to focus on sources of variation in be-
havior within groups, and (3) sought to identify factors in the larger soci-
ety that regulate continuity and change in food behavior, both in the
lifetimes of individuals and through time in groups.
Research Opportunities
Define intergroup variables that determine variation in food consumption
Fooclways have long been recognized as powerful metaphors of group
identity. Consumption of, and preference for, a particular cuisine have
been used to attribute group membership to individuals. In the Unitecl
States, it has been assumed consistently that ethnic groups, regional popula-
tions, and rural or urban distinctions were the primary lines along which
eating could be differentiated. Anthropological work during Worlc! War II
reinforced this assumption by using such groups as units of analysis. CIas-
sic studies in this country documented the conservative nature of fooc3ways
even as groups migrated.
The assumption that ethnic and regional foodways are strictly conser-
vative is now being challenged. Recent research shows that food con-
sumption patterns are (lynamic, responsive, and continually shaped an
reinforced by social interaction. The extent to which floodways remain
unchanged is determined by the pattern of activities of group members.
Outmigration, intermarriage, and occupational and educational mobility
are ah factors that change social interaction and thus tend to be followed
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IMPROVZNG THE DIET AND HEALTH OF INDIVIDUALS AND POPULATIONS 1S5
by change in floodways. Investigations are needed to establish the circum-
stances under which foodways are likely to be most dynamic and how the
direction of change can be predicted and modified.
The variables now seen as critical in differentiating Americans into
food-consuming groups are more structural than cultural. For example,
gender-based differences in control of household resources and control of
decisions about food consumption have been implicated in the food habits
and nutritional status of women and children. At the same time, research
shows that there are gender-specific ideologies for classifying foods. Such
ideologies form part of the cognitive framework within which food con-
sumption choices are made.
Age is another factor instrumental in determining food consumption
patterns. Certain foods are consumed more frequently by older people
than the rest of the population, and the patterns of consumption (e.g.,
meals vs. snacks anti timing of eating) vary with age. Research is needed
to disentangle biological effects of aging (such as sensory and digestive
changes) from social effects (such as changes in household composition)
and from cohort, or age-group, effects. The latter are particularly impor-
tant in understanding food behavior because the food experiences of co-
horts differ dramatically and shape current preferences. Other significant
cohort similarities, such as the availability of particular foods or food tech-
nology, may affect food habits.
Research on nutrition that takes social class differences in the United
States as its point of departure finds that certain food habits may be
better explained by a combination of class attributes such as income, edu-
cation, and occupation than by the more traditional ethnic distinctions.
For example, trends in breastfeeding incidence anct duration during the
last several decacles follow income and education lines, with better-edu-
cated women and those with higher incomes leading the trend toward
bottIe-feeding in the 1950s and 1960s, then back to breastfeeding in the
1970s and 1980s. In all areas of public health nutrition, research is needed
to determine when social class influences food consumption through atti-
tucles toward ancI beliefs about food and when it acts as a constraint
through Tow income and education on the ability to obtain adequate food
and nutrients.
Determine factors that modify intragroup or individual variation in food
consumption A recent refocusing of attention in the social sciences to-
warcI small-group and individual analyses promises to be especially impor-
tant for understanding food consumption and developing interventions to
mollify food habits. Through both qualitative and quantitative studies,
researchers have established ways of detecting sources of intrainclividual
as well as intracultural variation. This change in focus is reflected in the
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1S6
OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
movement from seeking meaning and explanation of food consumption
and nutrition at group levels to an emphasis on the household as the arena
in which food consumption takes place. Similar households develop dis-
tinctive strategies of acquiring and distributing food to household mem-
bers. These patterns may reflect preferences by are or vender of house
~ AL J O O
1 1 1 1 r 1 r . ~
nolct members, stages ot the family developmental cycle, or more subtle
and idiosyncratic behavioral patterns. The impact of intrahousehold dif-
ferences in food consumption should be a focus for both domestic and
international research on child health and survival.
Research on cyclic patterns of food consumption reflects attempts to
understand sources of intragroup variation. Particularly for agricultural
populations, seasonal cycles of labor and food availability are critical de-
terminants of food consumption. Even within industrialized populations,
cycles of food consumption have been found, reflecting patterns of work,
leisure, ritual, anti life-cycle events.
There is clear evidence that food consumption by individuals or groups
cannot be viewed in isolation. Sociocultural factors such as age, gender,
and income play a part in determining food choice. But food consumption
must also be viewed as part of a larger system within which individuals
make choices. This system sets several parameters for food choice: eco-
nomic (e.g., how much income is available for food purchases9), environ-
mental (e.g., what foods are readily available?), and ideological (e.g., what
foods are considered appropriate and good to eater. Research is needed
that considers all of these parameters as viable explanations for food con-
sumption patterns. A better understanding of the sources of intragroup
variation in food consumption could be obtained through multiple-method
research designs that integrate qualitative ant] quantitative techniques.
Behavioral Strategies for Lifestyle Change
While improving the public's diet and health is the major goal of
public health nutrition, motivating and assisting people to translate di-
etary guidelines into permanent dietary change remains a formidable challenge
to health professionals. Recent dietary recommendations emphasize the
need for individuals to reduce fat consumption to 30 percent or less of
total daily calories. Attempts to achieve this goal have been only partly
successful. The observed (recline in consumption of some overt sources of
fat (e.g., red meat and whole milk), especially among women, has been
offset by increased intake of fats and oils, other dairy products, and frozen
desserts. Total fat consumption has not declined substantially, and experts
fear that consumers have simply learned to replace one fat source with
another (which may or may not be advantageous to health).
Implementing dietary recommendations on a population-wide basis
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ZMPROVZNG THE DIET aND HEALTH OF INDIVIDUALS AND POPULATIONS 1S7
provides exciting new areas for collaboration between nutrition specialists
and behavioral scientists. Diet, of course, is only one factor influencing
health and well-being. Other personal health behaviors (e.g., not smoking
and getting exercise) and the appropriate use of health-care services are
also linked to disease risks and should not be overlooked in health promo-
tion efforts.
Research Opportunities
Identify the barriers to changingfood habits Implementing dietary guidelines
across the United States requires that many sectors of the population
modify their eating habits toward a more healthy diet. However, most
people find that reducing the consumption of foods rich in total fat and
saturated fat and increasing consumption of vegetables, fruits, grains, and
legumes is no easy task. There are many barriers to healthy behavior
change that range from lack of motivation and not perceiving immediate
improvements in health to long-standing food preferences and socially
influenced dietary patterns. The traditional strategy for dietary change has
been nutrition education. However, improving knowledge is not suffi-
cient. Consumer attitudes, beliefs, and motivations must be changed as
well.
Strategies for health behavior change have been based on a variety of
theoretical constructs and models. These include the health belief model,
which explains health-related behavior largely in terms of individual atti-
tudes and beliefs. The theory of reasoned action addresses the attitudes to
a given behavior and evaluations of probable behavior outcome. The in-
tention to act is determined by a respondent's attitudes toward the action
and their perception of likely outcome relative to some subjective norm.
The social learning theory predicts consumer behavior by employing such
key constructs as incentives, outcome expectations, and self efficacy. A
more recent cognitive-behavioral model of relapse prevention addresses
such concepts as self esteem and loss of control. Additional theoretical
frameworks include the stages of change model, the diffusion theory, and
the social support model, to name a few.
For the most part, these models and strategies address behavioral
change at the behavioral level. The health belief model was initially ap-
plied to compliance with prescribed medical regimens and the use of
medical care and other health services. The stages of change model was
developed originally to study behaviors associated with smoking cessation
by individuals. Other models have been variously applied to smoking ces-
sation, addictive behaviors, seat-belt use, adherence to exercise programs,
and weight loss.
There have been many fewer studies on the applications of the exist
O) ,
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1SS
OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
ing strategies for behavioral change to dietary interventions, either in in-
dividuals or in communities. Several studies have applied the theory of
reasoned action to predict the consumption of high-fat foods. They re-
ported individual beliefs and outcome evaluations linked to the consump-
tion of milk, cheese, ice cream, and other high-fat foods. Other studies
have attempted to use attitudes to dietary fats as a potential predictor of
fat consumption.
Nlery few studies have addressed the application of the strategies for
behavioral change to the dietary behavior of populations. One critical
question is whether the stages of change model can be generalized to
dietary behavior change in communities. Given the complexity of food
habits, it is unclear how the progress from one stage to the next is to be
defined, monitored, and evaluated. Another critical question concerns
motivation and the recruitment of populations at risk from the precontempla-
tion stage to contemplation and to action.
Food habits at the community level are influenced by social nutrition.
Studies on dietary change need to examine those cultural and environ-
mental factors that promote or prevent the initial dietary change and its
maintenance. Some interventions have been based on societal or system
changes, addressing the role of grocery stores, restaurants, schools, day-
care programs, and senior-citizen centers in improving the diet of indi-
viduals and groups. In some studies, dietary interventions have been tar-
geted to point-of-purchase selections in supermarkets. Dietary-change studies
have also involved the workplace, community organizations, and social
groups. Among the topics for research are the acculturation of newly ar-
rived immigrants and ethnic minorities and its impact on nutrition and the
role of community organization and community structures in promoting
better nutrition.
Initiate and evaluate population-based dietary intervention programs Most
past intervention programs have focused on reducing or eliminating alco-
hol and drug use, smoking cessation, and weight loss. Applying behavioral
change strategies to specific dietary interventions in communities is rela-
tively new. While eating and smoking behaviors are fundamentally dis-
tinct, it may be that some of the basic tenets of population-based ap-
proaches to smoking cessation may be adapted to dietary change. Among
potential options are the workplace approach, community organization
approach, and use of the mass media, all of which have been used in
smoking-cessation studies.
Behavioral scientists view the workplace as being midway between the
individual process of behavior change and the more complex community
or social setting. Past workplace interventions have addressed smoking
, high blood pressure control, increasing physical activity, and
cessation
-
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IMPROVING THE DIET AND HEALTH OF INDIVIDUALS AND POPULATIONS 189
weight loss. Community organization has been one strength of the Minne-
sota lIeart Healthy Program, which was designee! to lower the risks of
coronary heart disease through intervention at the community level. The
Stanford Five-City Multifactor Risk Reduction Project was a 14-year pro-
gram of community organization and education, largely through the mass
media, that successfully lowered risk factors such as smoking, blood pres-
sure, and blood cholesterol concentrations.
While applications of the existing models and approaches to dietary
behavior change open new opportunities for nutrition research, it is im-
portant to note that eating behaviors are in many ways unique and present
specific challenges. First, food habits and body weight are likely to be
influenced by genetic, physiological, and other biological factors that di-
etary interventions must take into account. Second, barriers to dietary
change may be psychological, cultural, social, economic in nature, or some
combination of these. Efforts to change dietary behavior must be sensitive
to issues of age, gender, income, ethnic background, and religion. Third,
while the goal of drug abuse or smoking programs is the elimination of the
behavior, that is not the case for eating behaviors; the goal is not cessation
but modification toward some agreed-upon optimum. Since there is little
agreement regarding desirable body weights or amount of fat in the diet,
for example, dietary goals often appear ill-defined. Fourth, the link be-
tween diet, nutritional status, and chronic disease varies among individu-
als. Some are resistant to dietary interventions and show no improvement
in cardiovascular-disease risks even after adhering to dietary guidelines.
The individual variability of response is very likely to affect participant
compliance with a dietary intervention. Consequently, an integral compo-
nent of population-based dietary interventions is an evaluation of the effi-
cacy of tl~e proposed dietary change and its impact on community health.
REDUCING THE RISK OF FOOD INSECURITY AND HUNGER
It is ironic that in a country where there is a surplus of food, some
people go hungry. A markedly uneven accessibility characterizes the food
supply in the United States. This problem has been recognized over the
past several decades but is now coming into sharper perspective with
renewed public and scientific attention. It will continue to pose chal-
lenges for both research and practice in public health nutrition into the
next century.
Research Op portunities
Document the extent of food insecurity and hunger in the United States
The first step in addressing issues related to food distribution is to clarify
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
the definitions used. Nationwide surveys searching for malnutrition as
measured by anthropometric techniques and clinical tests typically find it
to be a rare condition. As measurable malnutrition may be the end of a
continuum of food availability, it has been argued that "hunger" may be a
more appropriate term and that it should include an inability to obtain
adequate food even if the shortage is not orolonaed enouah to cause
1 ~ O
health problems. Further refinement of the definition has resulted in a
conceptual framework identifying four components of hunger at both in-
dividual and household levels: (1) quantity of food (Is the household sup-
ply depleted? Is individual intake sufficient?), (2) quality of food (Is household
food suitable? Are individual diets adequate?), (3) psychological (Is there
general anxiety about food? Do individuals feel deprived and lacking in
choice?), and (4) social (Must unacceptable means be used to acquire
food? Are eating patterns disrupted?. Together, these components make
up what has come to be termed "food security" or "food insecurity." Nu-
tritionist Cathy Campbell states that:
Food security is access by all people at all times to enough food for an
active, healthy life, and at a minimum includes the following: 1) the
ready availability of nutritionally adequate and safe foods and 2) the
assured ability to acquire personally acceptable foods in a socially accept-
able way. Food insecurity exists whenever the availability of nutritionally
adequate, safe foods or the ability to acquire personally acceptable foods
in socially acceptable ways is limited or uncertain.
lIunger as a physical sensation caused by lack of food need not be
present for persons or households to lack food security. Further, aspects
of personal and social values and preferences are integral to the definition
of food security. This means that measures of food security specific to
different population segments need to be developed. Some research has
been conducted to develop measures for women and children and rural
populations, but more are needed for the elderly, ethnic minorities, the
homeless, and other hard-to-reach groups.
Once appropriate measures of food security have been developed,
they must be integrated into existing nutrition monitoring and surveiT-
lance programs. Some measures were introduced and pilot-tested in the
Third National Health and Nutrition Examination Survey (NHANES III),
but they need to be developed and refined further.
Investigate the causes and consequences of food insecurity and hunger
These will be major tasks for future public health nutritionists, requiring a
modification of the research designs typically used by investigators in the
field. Survey methods as traditionally used in national or state probability
samples are frequently not adequate to document many groups at risk of
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l9S
OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
States. In sum, we need to evaluate the design and effectiveness of federal
food assistance programs in the context of today's social and economic
problems.
IMPROVING METHODS AND TOOLS FOR NUTRITIONAL
AS SE S SME NT, MONITORING, AND EVALUATION
Nutritional assessment is typically defined as the interpretation of
information obtained from dietary, biochemical, anthropometric, and clinical
assays of nutritional status. This information is used to assess the health
status of individuals or populations as influenced by their intake and utili-
zation of nutrients. Nutrient deficiencies in the United States are most
often associated with poverty. Pregnant women, infants, young children,
the elderly, alcohol and drug abusers, and persons suffering from pro-
longed injury or illness are at greatest risk of malnutrition caused by di-
etary deficiencies. Nutritional assessment of individuals is an essential
component of health care ancI forms the basis for nutritional intervention
in clinical or home-care settings.
The components of nutritional assessment are sensitive to different
stages of nutritional deficiency. Generally, clinical symptoms or classic
anatomical signs that are apparent during a medical examination (e.g.,
xerophthalmia) reflect prolonged and severe nutritional deficiencies. Ear-
lier stages of nutritional deficiencies are detected through biochemical or
laboratory assessment methods. Advances in assessing the unique bio-
chemistry of individuals should enable nutrition experts in the future to
provide dietary recommendations tailored to a particular person.
Research Opportunities
Develop biochemical markers of nutritional status Some period of deple-
tion of body nutrient stores precedes the signs and symptoms of nutri-
tional cleficiencies. Laboratory tests of nutritional status are typically based
on (1) nutrient concentrations in body fluids or tissues, (2) urinary excre-
tion of nutrients or their metabolites, (3) nutrient-dependent enzyme ac-
tivities, (4) metabolic responses to a nutrient load, and (5) nutrient-
dependent physiological functions such as immune function and taste acu-
ity. Static biochemical tests include assays of albumin or iron concentra-
tions in serum, vitamin A concentrations in plasma, zinc in hair, and con-
centrations of creatinine in urine. Functional tests focus on nutrient-dependent
physiological functions in tissues or the entire body. For example, one
method of diagnosing vitamin A deficiency is to measure the time to see a
dim light after bleaching totally the rhodopsin in the eye. This functional
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IMPROVING THE DIET AND HEALTH OF INDIVIDUALS AND POPULATIONS 199
test is called the dark adaptation response. The ability to detect or to
discriminate tastes has been used to evaluate zinc status.
Biochemical tests of nutritional status are often influenced by physi-
ological factors other than the depletion of nutrient stores. These may
include diurnal variation, physical exercise, hydration status, drug use,
disease state, or even the habitual diet. For example, urinary creatinine or
the creatinine-height index can help to estimate the muscle mass of indi-
viduals who consume little or no animal protein. However, this test is not
appropriate for those consuming creatinine-containing animal products.
Other factors influencing the usefulness of biochemical tests are the pre-
cision, specificity, and sensitivity of the analytical method.
Many research opportunities exist to design and develop laboratory
assays of nutritional status. Ideally, such tests should be simple, accurate,
and reproducible methods of detecting initial stages of nutrient depletion.
Assays for use in large population-based studies should also be inex~en-
sive, rapid, minimally invasive, and preferably automated.
1
Research in this area has focused on developing novel biomarkers of
nutritional status. For example, concentrations of metallothionein, a zinc-
binding protein, depend on dietary zinc status. Metallothionein assays in
erythrocytes may prove to be a much needed biomarker of zinc nutriture
in humans. Similarly, understanding the role of vitamin E in lipid peroxida-
tion has led to the development of the breath pentane test and the release
in vitro of malondialaldehyde from erythrocytes. Another new technology
for assessing nutritional status involves the use of stable isotopes. For
example, the use of deuterium-labeled vitamin A provides an accurate,
reproducible method of measuring total body vitamin A stores in vivo.
Medical technology has translated successfully some biochemical as-
says of nutritional status into automated assays suitable for field use. For
example, plasma glucose and cholesterol concentrations can be measured
rapidly using minimal amounts of blood. New applications of medical technol-
ogy will permit rapid screening of large population samples in epidemio-
logical studies and lead to better identification of subgroups at risk.
Develop simple, specific anthropometric measures of nutritional status
Anthropometric measures are widely used to assess body composition and
growth. Nutritional anthropology is defined as the measurement of the
physical dimensions and the composition of the human body at different
ages and degrees of nutrition.
Anthropometric measures typically used in clinical assessments in-
clude weight and stature, skinfold thickness at multiple sites, and mid-arm
circumference. They may be used, respectively, to calculate body mass
index (BMI = weight/height2, a measure of overweight), and to estimate
total body fat, and to gauge muscle mass. Measures for use with children
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
include weight for age, height for age, and head circumference for age,
the latter used as an index of protein status during the first two years of
life.
Generally, anthropometric data are interpreted using reference stan-
dards that are most often cross-sectional data from national or interna-
tional surveys. NHANES data are a common reference source for heights
and weights of children, while Metropolitan Life Insurance tables (the
1959 or 1983 versions) remain useful guidelines for adults.
Clinical assessments of body composition use numerous labor-inten-
sive an(1 invasive procedures, ranging from underwater weighing to total
body potassium measures, total body water, total body electrical conduc-
tivity, computerized tomography, and ultrasound. Such methods are often
based on specific assumptions, each with limitations. Methods of assessing
bo(ly composition are often develope(1 and vaTi(latecl using healthy young
men as subjects. Their applicability to the hotly composition of pregnant
women, infants, children, and older indivicluals is sometimes unclear. Bio-
logical methods for measuring body composition, with rare exceptions
(such as the bioelectric impedance measure, which is, however, sensitive
to hydration status), are unsuitable for use outside the laboratory. Field
researchers still rely on anthropometric measures of height and weight,
skinfoIcT thickness, and waist and hip circumferences to assess nutritional
status.
Anthropometric measures typically use cutoff points to classify indi-
viduals by nutritional status. Those points are somewhat arbitrary and are
often established by reviewing anthropometric characteristics of individu-
als with clinically significant malnutrition. Few stepped cutoff points are
suitable for use over the entire range of nutritional status, from adequate
to malnourished to severely deprived. Another research challenge is posed
by the need to develop reference standards for anthropometric measures
that are age- gentler-, and race-specific. The development of minimally
invasive body-composition assays for use with large populations wouIcl
also help epidemiological studies.
Improve the sensitivity and specificity of dietary intake assessment
methods The first stage of a nutritional deficiency is identified by di-
etary assessment methods. In clinical settings, this assessment is usually
performed in a face-to-face interview between patient and a trained dieti-
tian. The standard dietary history method estimates typical patterns of
food consumption over a two-week period, and it is generally user! in
conjunction with a computerized analysis of nutrient intake. The dietitian
uses the results of this assessment to provide the patient with specific
dietary advice.
An alternative procedure using multiple-day food records or food dia
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IMPROVING THE DIET AND HEALTH OF INDIVIDUALS AND POPULATIONS 201
ries places a greater burden on the subject. Following appropriate instruc-
tions, the subject maintains a record of his or her food consumption over
a period of days (generally four or seven), making entries at the time food
is consumed. This is the preferred procedure in many clinical settings.
Food records are also the chief means of data collection in some epide-
minln~ical .st~die.s of food consumption such as USDA's Nationwide Food
-- D- ~ 1~ 7 ~ 1 . . ~ ~ , ~ ~
Consumption Survey. Major l~m~tahons ot this technique include the need
for high motivation and literacy by Participants and substantial costs in
collecting and Processing the civet recorcts.
) J 1
1 ~ . ~
O - - L A
As might be expected, the larger the population sample, the shorter
the time interval requires! to assess accurately population (not individual)
food intakes. Large-scale epidemiological studies such as NHANES II,
with upward of 20,000 respondents, have tended to rely on interviews
using a single 24-hour recall. In this procedure, respondents are asker! to
recall all foods and beverages consumed within the previous 24 hours.
Self-aclministered food frequency questionnaires (FFQs) have become
a popular method of assessing habitual food intakes over time, usually a
period of one year. FFQs typically consist of a list of food names, a
semiquantitative estimate of portion size, and a set of response options.
They force subjects to give precodecT responses but have the advantage of
being readable through optical scanners and processible by computers.
Studies of FFQs indicate that carefully designed forms provide adequate
information at very Tow cost, making large studies possible. Such ques-
tionnaires provide data on the consumption of specific food groups and
nutrients, which can be useful in studies of disease causation. However,
because FFQs may be insensitive to unusual foods, portions, or methods
of preparation, they may not be suitable for comparisons among various
ethnic and cultural groups.
One problem with the classic techniques of dietary intake assessment
is their reliance on the respondents' memory, which can be remarkably
selective. Subjects overreport the consumption of health-promoting foods,
while downplaying or omitting altogether the consumption of foods high
in calories, fat, sugar, and salt.
Among the research challenges are development of rapid and accu-
rate measures of dietary intake. One recent development is the use of
repeated telephone- administered 24-hour food recalls , increasingly used
instead of food records. Since keeping food records may after dietary
patterns, some investigators believe that unscheduled telephone interviews
provide a more reliable assessment of food intake. Some FFQs have been
shortened and redeveloped for administration over the phone. Validating
dietary assessment tools is always difficult. New biomarkers of nutrient
intakes are needed to validate new methods for assessing intakes.
Another research opportunity is the study of people's attitudes toward
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_ _ _ 1 1 ~1 1 . .
OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
nutrition and diet. Cognitive bias may result in under- or overreportin˘, of
food intake. The frequency estimates of food consumption using an FFQ
are- Ply susc~epr~e to reporting errors, and different types of bias
may operate for men and avowed. Studies on this topic would combine
Loth psychology and nutrition and offer an ideal onnort,~nitv for rnil:~ho-
ration across disciplines.
1 1 J ~1 ~ ~L At ~
A third research opportunity is provided by the study of nutrient in-
teractions. Generally, FFQs and other techniques for assessing dietary
intake are used to correlate nutrient intake with nutritional status and the
risk of chronic disease. However, foods or nutrients should not be viewed
in isolation, since absorption of nutrients from one food may be influ-
enced by other foods in the diet. A classic example is that essential amino
acids must be present in order for the body to make optimum use of
protein. A recent paper on the absorption of beta-carotene makes a simi-
lar point: absorption of beta-carotene was minimal when this antioxidant
was taken during fasting, but it increased sharply when accompanied bv a
, . ~ 1 ~
meal containing 200 g of fat from ice cream. Nutrient status may depend
on the consulnption of fonAs that avails not cn,~rc~ rip that n~,tri~nt
influence its absorption.
~ ~,
Dietary intake assessments usually depend on two steps: determining
food intake using one of the techniques described above and calculating
nutrient intake based on the nutrient composition of the foods consumed.
At present, information on nutrients in foods is provided through updates
of USDA Handbook No. S. Recent updates include data on the fatty acid
and fiber contents of selected foods. However, information for solve nu-
trients is very incomplete. For example, the USDA database does not
distinguish between complex and simple carbohydrates. It often cannot
supply information on the amount of the antioxidant nutrients in foods
that are the subject of much research (see Chapters 2, 3, and 5~. Little
information is available on the composition of ethnic foods. Major re-
search opportunities in this area include determining the nutrient compo-
sition of foods consumed almost exclusively by minorities and new immi-
grants to this country.
Develop standardsfor assessing dietary intakes of individuals The inter-
pretation of information from dietary surveys must sometimes be com-
pared to one or more recognized standards of adequate nutrient intake.
Nutrient intakes in the United States are usually compared to the recom-
mended dietary allowances (RDAs). But since RDAs are typically set at
levels that exceed the estimated average need of the nutrient, intakes
below the RDAs do not necessarily indicate nutrient deficiency.
Research opportunities in this area include development of standards
for nutrient intake that quantitate the probable risk of nutrient deficien
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IMPROVZNG THE DIET AND HEALTH OF INDIVZDUALS AND POPUl,ATIONS 203
cies. Furthermore, with the current emphasis on disease prevention, con-
sideration should be given to developing recommended intakes for food
components that are not essential nutrients (e.g., carotenoids and dietary
fiber) but whose consumption may influence nutritional status and health.
Standards defining excessive intake of nutrients are also needed.
Develop new tools for nutrition monitoring Nutrition monitoring is de-
fined as the ongoing description of nutrition conditions in the population
for the purpose of planning interventions, analyzing the effects of policies
and programs, and predicting future trends. Assessing the diet of popula-
tion subgroups defined in socio`?~ono~ni~ t`?r,onc h`-lr~c to Aet`~r~i'a~ the
.. . ~ ~ r
nu~r~nona~ needs of groups at risk because of policy or economic reasons
and to design and evaluate intervention programs.
Nutrition monitoring typically encompasses five types of measurements:
health and nutritional status, food consumption, dietary knowledge and
attitudes, food composition, and food supply measurements. Some of these
measurements were reviewed earlier in this chapter. Measurements are
made at different points along a "nutrition continuum" that ranges from
food production to consumption and eventually to the health status of
individuals and groups.
Information derived from nutrition monitoring forms the basis for
policy decisions such as those on food fortification, food safety, food label-
ing, nutrition education, public health interventions, and food assistance.
Therefore, all surveys and surveillance systems must be firmly grounded
in research. Methods of assessing dietary intakes and nutritional status,
food composition databases, and reference standards are all products of
basic and applied research. These products must rest on a firm foundation
of fundamental research that ranges from basic biochemistry to epidemi-
ology, encompassing food composition, nutrient bioavailability, nutrient
requirements, and the role of nutrition and diet in the etiology of chronic
disease.
The current research challenges for nutrition monitoring arise from
the changing food supply and rapidly changing demographic profile of the
U.S. population. The introduction of new products into the food supply,
such as reduced-calorie foods, biotechnology-derived foods, and foods pro-
duced using new processing techniques, makes it difficult to keep food
composition databases up-to-date and for people to describe accurately
what they have eaten. The increasing ethnic diversity of our society and
the increasing consumption of meals away from home seem to require the
development of novel methods of data collection and analysis that are
sensitive to the issues of ethnicity, gender, education, and socioeconomic
status.
Research opportunities in this area include gathering more compre
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
hensive data on populations that are at highest nutritional risk. Such populations
include infants, adolescent girls, pregnant and lactating women, anct the
elderly, as well as groups not adequately covered in current nutritional
surveys, including Native Americans and other ethnic minorities, newly
immigrated ethnic groups, and the homeless. New sampling techniques
need to be developed to reach these populations, and questions of ad-
equate sample size need to be studied in greater detail. For example, how
precisely do we need to estimate intake for each demographic group?
How finely do these groups need to be characterized by such variables as
race, age, gender, income, education, or religion? To what degree can
statistical modeling be used to identify subgroups at risk? How useful is
the currently used telephone screening method for identifying subgroups
at risk and targeting them for more detailed study and potential nutri-
tional intervention?
Novel methods of data collection are needed to characterize issues of
literacy and cultural differences in food preparation. Innovative ways of
collecting food intake data from the very young ancI the very old need to
be developed. The validity of proxy reports by parents regarding the di-
etary intakes of young children has been called into question, especially if
the children are away from their parents in day care or at school. Efforts
should be made to test the validity of proxy reports or to find alternative
ways of obtaining dietary information. Identifying effective ways of col-
Tecting fooct intake data from elderly persons who require long-term care
is another priority area for further research.
Develop new, strategies for evaluating nutrition interventions The goal of
many nutritional interventions is to improve health behaviors. While the
basis for nutrition interventions may be clinical, laboratory, and epidemio-
logical studies, successful implementation often falls within the purview
of the social and behavioral sciences.
The nutrition community has been criticized for its failure to evaluate
the effectiveness of its intervention programs. One important reason for
this failure may be that nutrition professionals often lack training in the
social and behavioral sciences. The successful implementation of nutrition
programs depends on many factors, which may include an accurate assess-
ment of staff requirements in relation to staff availability; costs in relation
to cost constraints; availability of other resources, including equipment,
supplies, and infrastructure; and political pressures and constraints. In
addition, the needs, practices, and constraints on the target population
need to be considered. Examples of these include the direct and indirect
cash costs of participation, time costs of participation, level of knowledge
and information about the intervention, conformity with the habits and
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IMPROVING THE DIET AND HEALTH OF INDIVZDUALS AND POPULATIONS 205
preferences of the population, cultural expectations, and issues of social
acceptability.
Many programs have failed because of one or more of these factors.
Participation in the Food Stamp Program has been limited by the incon-
venience and length of time it takes for certification as well as by lack of
knowledge about the program, particularly by non-English-speaking im-
migrants new to this country. The essentially obsolete Commodity Food
Distribution Program had limited effect because of the inconvenience to
participants of receiving a month's worth of food at once and because
some participants were unfamiliar with the foods and did not know how to
prepare them. Efforts to promote breastfeeding have often been unsuc-
cessful because the educational messages did not help the target groups
overcome important cultural and social constraints.
Many nutrition interventions require the target population to change
its behavior in some way, usually by altering food consumption patterns.
For example, the nationwide Five-a-Day for Better Health program aims
to increase the consumption of fruits and vegetables to five or more serv-
ings per day. However, this goal is well above the current estimates of
fruit and vegetable consumption in the U.S. population. The USDA's own
data have shown that the consumption of fruits and vegetables among
women actually declined between 1977 and 1985, with the greatest drop
(approximately 20 percent) among low-income respondents.
Attempts to change dietary behaviors cannot succeed without an un-
derstanding of the network of causal factors that determine food choice
and the contexts in which the dietary behaviors take place. Studies of taste
and the development of food preferences (see Chapter 5) fall outside the
traditional field of nutrition science. The fields of program operations and
logistics, personnel motivation, and organizational behavior have also been
outside the purview of nutrition science, even though they are an integral
component of nutrition practice. Future nutrition professionals should
combine these areas of training at the graduate level.
Develop methods for assessing creative new interventions using computer-
assisted decision-making models Health and nutrition interventions are
of three general types. There are those that deliver services and provide
food, such as WIC, or provide food only, such as the various school-based
and other child-feeding programs and the Food Stamp Program. There
are also those that promote behavior change through education in schools
and by the media, by providing information through nutrition labels and
advertising, or by incentives that may include lower prices or added con-
venience. Finally, there are interventions that attempt to change dietary
patterns without requiring much conscious behavior change, such as nu-
trient fortification or altering the composition of foods.
-
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
Tl~e design and evaluation of successful healtl~ and nutrition interven-
tions requires an expanded understanding of national agricultural and economic
policies, individual and household behavior, and their determinants. The
complex interaction between national food policies, household and indi-
vidual behavior, and the health and nutritional status of the individual are
depicted in Figure 6.1. Evaluation of this entire spectrum is, of course,
beyond the means of a single investigator. However, mathematical model-
in~, techniques, driven by advances in computer technology, allow infor-
mation from large-scale surveys to be integrated with household or indi
Research //
Results //
/ / Data
/ / Needed
/ / for
/ / Decision-
making
NUTRITION POLICY-MAKIN~
Primary Federal Coordinating Bodies:
Department Level- |
ˇ DHHS Nutrition Policy Board I
ˇ USDA Subcommittee on Human Nutrition I
Components:
ˇ Public health and food assistance
programs
ˇ Nutrition information and education
programs
Food production and marketing
Food safety, labeling, and fortification
regulation
Dietary guidance
Health objectives
Military food service systems
\\ Needs
\\ for Date
Data \ \
Decisions \N
/ NUTRITION RESEARCH
Federal Coordinating Body:
Interagency Committee on Human
Nutrition Research
Components:
ˇ Nutrition monitoring research
ˇ Nutrient requirements throughout
the life cycle
ˇ Research on the role of nutrition in
etiology, prevention, and treatment
of chronic diseases and conditions
ˇ Nutrient content, bioavailability
and interactions
ˇ Nutrition education research
ˇ Economic aspects of food consumption
ˇ Knowledge/attitudes' relationships to
': : ~
NUTRITION MONITORING \
Federal Coordinating Body:
interagency Board for Nutrition
Monitoring and Related Research
Components:
ˇ Nutrition and related health
ˇ Food and nutrient consumption
ˇ Knowledge, attitudes, and behavior
ˇ Food composition
ˇ Food supply
~Research Results <~
Data for Research
FIGURE 6.1 Relationships among nutrition policy-making, research, and Won
taring. From Fed. Reg. 564709~:55716-55767.
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IMPROVZNG THE DIET AND HEALTH OF INDIVZDUALS AND POPULATIONS 207
vidual data. For example, a model of the socioeconomic, nutritional, and
health status of a specific population group can be formulated using sur-
vey data from several sources. This model can then be used to test several
potential nutritional intervention programs with the help of computer-
assisted decision-making modeling techniques. Based on the outcome of
this initial testing, one or more programs may be selected for field testing.
The results of those field tests could be incorporated into the computer
model to refine and target the intervention further before it is widely
implemented.
Using this technology requires skills not ordinarily learned in nutri-
tion science programs survey techniques in contrast to laboratory re-
search techniques, economic and other social science approaches to un-
derstanding behavior in contrast to laboratory and clinical measurements,
and familiarity with mathematics and computer science technology in con-
trast to biological procedures. The developers of successful intervention
strategies in the future are likely to be those who have learned these skills
and have specialized knowledge of nutrition, food consumption, and health
status.
CONCLUDING REMARKS
Developing successful and comprehensive programs to improve the
diet and health of populations involves four distinct steps: (1) identifica-
tion of the problem, (2) development and implementation of an interven-
tion, (3) evaluation of the response, and (4) modification of the interven-
tion, based on the response. Specific and sensitive tools to monitor and
assess the physiological response of individuals and populations are re-
quired for this process. Central to the long-term success of any public
health program is incorporation of successful aspects of the program into
food and nutrition policies of governmental agencies and food industries.
Challenges in public health nutrition for the future include develop-
ing successful interventions and policies to reduce the risk of diet-related
diseases and the incidence of hunger and food insecurity anct monitoring
the impact of those policies. New computer technologies are enabling
scientists to estimate food and nutrient intakes of large groups, to store
and interpret a vast array of survey data, anci to build decision-making
model systems for testing potential interventions. Complex and multidisciplin-
ary interventions in the future may be evaluated in the laboratory using
computer-assisted models before expensive field trials are undertaken.
Previous nutritional interventions, which used either food fortification
or vitamin and mineral supplementation approaches, were relatively easy
to carry out and their results were easily observed. The nutritional chal-
lenges of today are much more complex, spanning dietary excesses and
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OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES
disease to inadequate food distribution and hunger. The targets of poten-
tial interventions range from the macro level of national agricultural and
health policies to the micro level of household and individual food behav-
iors. Future interventions to deal with these complex problems will need
to integrate findings from the basic behavioral sciences with agriculture,
economics, political science, and the other social sciences. This process
will provide many new, exciting research opportunities for nutrition and
food scientists.
Representative terms from entire chapter:
food assistance
