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Supplement

Designing Surveillance Systems to Address Emerging Issues in Diet and Health¹

Applied Research Program, National Cancer Institute, Bethesda, MD 20892-7344

	INTRODUCTION

TOP INTRODUCTION REFERENCES

 
Evaluating the nutritional health of the population can be accomplished only with a comprehensive nutritional monitoring system. The papers in this supplement summarize the surveillance questions and needs related to Nutrition and Your Health: Dietary Guidelines for Americans (1) , a federal summary of the latest dietary guidance for the public, based on current scientific evidence; at the same time, it is intended to guide policy in nutrition-related federal programs. The goals of each paper are to review the methods of assessment related to each of the guidelines, to provide benchmark data that could be updated before a further edition, and to identify gaps and limitations of the data in terms of addressing critical questions. Using the Dietary Guidelines as a framework for this supplement provides a way in which to feature the interdisciplinary nature of diet-related research and allows the surveillance data to be linked back to the guidance itself. It is expected that this collection of papers will serve as a tool to provide clarity and insight on each of the dietary guidelines and highlight their ramifications. Questions raised within these papers are representative of the gamut of nutrition-monitoring issues that the National Nutrition Monitoring System will have to address. For example, the paper by Dixon et al. (2) on the variety guideline raises the important question of variety for what purpose. Although a number of methods have been developed to attempt to evaluate variety, most are based on food groups. Given that 75% of foods are consumed currently as mixtures, this seems an increasingly daunting task. The paper on the alcohol guideline by Dufour (3) provides an exceptionally coherent description of the complexity of obtaining, analyzing and interpreting self-reported data on alcohol consumption but also raises the issue of how to capture the many social and system factors that contribute to alcohol consumption and its health effects. A new guideline on food safety addresses an area of increasing concern, particularly with the globalization of our food supply. Three of the four assessments methods for monitoring food safety described by Woteki et al. (4) address individual-level approaches to improving food safety. Innovations in information technology and computerization may facilitate building surveillance systems that will also allow monitoring of the food production and processing systems that contribute to food safety.

This overview and the guideline-specific papers within this supplement identify beneficial and adverse trends in improving nutritional health, the strengths and limitations of the current nutrition monitoring system, and offer suggestions for changes that would advance its capacity to monitor nutritional health. The 1990 legislative mandate to create this system is ending this year; its renewal is critical for providing the support necessary to strengthen this system (5) . It is our hope that these perspectives will present a framework for continuing to build a comprehensive nutritional monitoring system designed to address future needs.

However, in considering whether current systems will answer future questions about the nutritional health of the U.S. population, a step back to consider the many forces influencing nutrition and health in any population might change our perspective and the direction of the systems we all must work to build. Clearly, a major intent of the National Nutrition Monitoring System (6) is to evaluate whether the needs of the population are being met. The focus within this supplement has been on the nutritional health of the population; the needs of the production system in providing food to meet these health objectives is not a focus of this supplement and will not be considered in this overview. To make progress in building a comprehensive food and nutrition surveillance system for the future, these systems should be further developed to encompass the following principles: data must be broad based (beyond individual behavior to environmental and systems influences), more synthesized (among key relationships among closely related factors), more targeted (among different groups in the population) and linked to outcomes (either directly or indirectly by being conducted in populations for which outcome data are available). Further, we must become active innovators in the information systems revolution and use its power to ensure that we are obtaining comprehensive, timely data. Finally, we must all keep in mind that our ultimate purpose in developing such a comprehensive surveillance system is not simply to monitor the nutritional health of the population but to obtain the data that can inform our decisions about how best to effect change and improve nutritional health.

As clearly represented by the papers in this supplement, a major focus of the current National Nutrition Monitoring system has been on the individual and a limited set of related factors, primarily knowledge and attitudes that might influence nutritional habits at the individual level. Some social and economic factors, such as education and income, have been incorporated in a limited way, but the focus remains on the individual as the unit of analysis. Recently, a renewed focus on the tremendous influence of contextual forces at the community and societal levels highlights the need to consider whether our surveillance systems are providing key data at those levels. Similarly, borrowing from the social and economic sciences, it is clear that data on pertinent systems and organizations are essential to understand how best to effect overall change. (7) . Data for many of these elements exist in other surveillance systems, such as more detailed information at the individual or regional level on income and occupation from the Census Bureau, or data on food supply and stores from the USDA. The papers on the fruit, vegetable and grain guidelines highlight how research utilizing data systems on food production and supply can provide a more detailed understanding of the changes in those systems that are required to meet the objective of increasing fruit and vegetable intake at the population level in the United States. One of the exciting promises of advances in information systems is the capacity of geographic information systems (GIS)²to generate linkages among diverse data systems often managed by different public and private organizations. For example, GIS methods can be used to link data on individual level food consumption from the National Center for Health Statistics (NCHS) or USDA with individual or regional level data on income, employment, housing, education and other measures of socioeconomic status and support from the Census Bureau with regional level data on food supply within a defined area. Such linkages would allow us to examine how these factors relate at the local or regional level and might provide a much more specific blueprint of areas in which change is required at local levels.

In addition to data systems that allow synthesis of information on individual, social and systems influences, nutrition surveillance requires that data at the individual level move beyond a narrow focus on food and nutrient intake to encompass the closely related factors of weight and physical activity, and the health conditions that may modify nutrient intake, its subsequent metabolic processing and health effects. The need for a more synthesized guidance and surveillance system is evidenced by the expansion of sections on weight and physical activity within the Dietary Guidelines and within several of the food consumption surveys. For example, limited questions on physical activity and weight control were added to the Continuing Survey of Food Intakes by Individuals (CSFII), and detailed sections on leisure, occupational and household physical activity as well as more expanded sections on weight history have been added to the National Health and Nutrition Examination Survey (NHANES). In terms of other related factors influencing dietary intake and its consequences, the CSFII included questions on knowledge and attitudes that may influence the likelihood of following recommended dietary practices, whereas the NHANES provides a comprehensive assessment of biological interrelationships by collecting data on self-report, physical examination and biological specimens related to major health conditions in the United States. One of the best recent examples of the limitations of a narrow focus on food intake can be seen in the recent declines in fat intake, combined with increases in obesity and sedentary lifestyles. Such findings are commonly attributed to the major focus of nutrition education and food production systems to reduce fat intake without a concomitant message and effort to decrease energy intake and increase energy expenditure.

A series of forces have heightened awareness that national level health surveillance, traditionally focused on nationally representative samples of the general population, must strengthen its capacity for examining issues in more narrowly defined populations. One force has been the major change in the racial and ethnic demographics of the U.S. population, with declines in the proportion of Caucasians and striking increases in the proportions of Latino and Asian Americans. Similarly, health surveillance data have identified health disparities that appear to vary with complex interactions of age, gender, socioeconomic status and racial/ethnic classifications (7) . One of the reasons these disparities have been identified is the growth of targeted studies in defined population groups and the standardization of data being collected at the local or regional level, which allows comparisons of data across diverse surveys and populations. In the 1980s and 1990s, national level nutritional surveillance systems commonly oversampled certain population subgroups, such as the poor and those enrolled in food assistance programs in the CSFII, or the major non-Caucasian racial ethnic groups in the NHANES. However, numbers in these national level surveys were often insufficient to answer questions in population subgroups that were suspected of having specific nutrition-related health disparities. Therefore, in the late 1990s, efforts were initiated within a number of federal surveillance systems, such as those related to monitoring socioeconomic status or disease outcomes, to develop separate surveys of specific population subgroups to address key questions in addition to maintaining general population surveillance. In the National Nutrition Monitoring System, this has been reflected by the development of a new concept within the NCHS of a Defined Population Health and Nutrition Examination Survey in which a less elaborate history and physical examination would occur in specific population groups for a shorter period of time. The focus of this new surveillance system would vary depending on questions identified at the local, regional and national level. Similarly, federal level health agencies responsible for state level health surveillance, such as the Centers for Disease Prevention and Control, have worked at the state level to improve standardization of data collected within state level health surveillance such as the Behavioral Risk Factor Surveillance System. Broad-based sharing and publication of questionnaires that are used in various federal and regional surveys also allow expansions of state-based surveillance, such as the California Health Interview Survey modeled loosely after the National Health Interview Survey, to improve comparability between state and federal level health surveillance.

Finally, to evaluate whether recommended changes in nutrition-related health behaviors at the population level result in beneficial changes predicted from epidemiologic or clinical trial research in selected populations, data on these health behaviors must be linked to data on health outcomes at the population level. For common diseases in the United States, such as heart disease, type II diabetes mellitus or hypertension, these linkages are possible for major population groups at the individual level within existing health surveillance systems such as the NHANES. For less common diseases, such as site-specific cancer, or for more common diseases among smaller population groups, such as the heart disease among Native Americans, the sample sizes of existing nutrition-related health surveys do not allow examination of the effect of these behaviors for the population of interest. Furthermore, the ability to examine contextual issues of social, environmental or system influences can be limited, unless the sampling units of these surveys are designed to allow linkage to other data resources through methods such as GIS. At present, this capacity is limited and most commonly allows linkage only at the level of zip code or census tract. Capacity can be further strengthened if data on an individual’s address can be obtained to allow detailed geospatial placement and, hence, linkage of individual level information on factors such as demographics and food intake to contextual information on social economic environment, social support and food supply at the neighborhood level. In fact, some portion of this linkage is already feasible and likely occurring with existing food-purchasing systems developed by grocery stores and other aspects of the food supply system to monitor which food products sell. Such systems are designed to provide very rapid and ongoing feedback to users and should be evaluated for their potential utility in nutrition-related health surveillance, particularly to evaluate the effect of specific behavioral interventions to change diet. As with all such surveillance systems, an increasing concern is the need to maintain confidentiality of individuals. Such concerns must be addressed before such data collections are likely to be implemented for health surveillance.

Table 1 details the evolution in summary guidance statements to individuals in the Dietary Guidelines. Research should be expanded beyond the level of the individual to clarify the individual, social and system forces influencing nutrition-related health behaviors. Similarly, surveillance efforts must be designed to allow monitoring of these forces at the population level to identify key targets for change in specific populations. With such information, we may be able to chart a set of guidance at a level beyond the individual and more effectively effect change for the future.

View larger version (49K): [in this window] [in a new window]   Figure .

	FOOTNOTES

² Abbreviations used: CSFII, Continuing Survey of Food Intakes by Individuals; GIS, geographic information systems; NCHS, National Center for Health Statistics; NHANES, National Health and Nutrition Examination Survey.

	REFERENCES

TOP INTRODUCTION REFERENCES

 

1. U.S. Department of Agriculture, U.S. Department of Health and Human Services (2000) Nutrition and Your Health: Dietary Guidelines for Americans, Home and Garden Bulletin No. 232, 5th ed. Government Printing Office, Washington, D.C.

2. Dixon L. B., Cronin F. J., Krebs-Smith S. M. Let the Pyramid guide your food choices: capturing the complexities. J. Nutr. 2001;131:461S-472S[Abstract/Free Full Text]

3. Dufour M. If you drink alcoholic beverages, do so in moderation: what does this mean?. J. Nutr. 2001;131:552S-561S[Abstract/Free Full Text]

4. Woteki C. E., Facinoli S. L., Schor D. Keep food safe to eat: healthful food must be safe as well as nutritious. J. Nutr. 2001;131:502S-509S[Abstract/Free Full Text]

5. Committee on Agriculture, 101st Congress (1989) Nutrition Monitoring: Joint Hearing before the Subcommittee on domestic marketing, consumer relations, and nutrition and the Subcommittee on department operations, research and foreign agriculture of the Committee on Agriculture and the Subcommittee on science, research and technology. Sept 21, 1989, 101–29.

6. Bialostosky, K., ed.Interagency Board for Nutrition Monitoring and Related Research (2000) Nutrition Monitoring in the United States: The directory of Federal and State Nutrition Monitoring and Related Research Activities, DHHS Publication no. (PHS) 00–1255.National Center for Health Statistics, Hyattsville, MD (web address http://www.cdc.gov/nchs/).

7. Adler N. E. Marmot M. McEwen B. S. Steward J. eds. Socioeconomic status and health in industrialized nations: social, psychological, and biological pathways 1999 Acad. Sci. Ann. N.Y.

8. Summary Table Comparing All Five Editions of the Guidelines. Online U.S. Department of Agriculture, Center for Nutrition Policy and Promotion. http://www.usda.gov/cnpp/Pubs/DG2000/Index.htm 2000 (accessed Nov. 22, 2000).

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