Frontiers in the Nutrition Sciences Proceedings of a Symposium (1989) / Chapter Skim
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From Ecologic Correlations to Metabolic Epidemiology: The Link with Nutrition
From Ecologic Correlations to Metabolic Epidemiology: The Link with Nutrition
Pages 95-110
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From page 95... ...
~ Because epidemiologic studies deal with actual levels of exposure, they can indicate the true magnitude of the effect of the dietary behavior and, therefore, its real public health significance. Thus, they are the primary basis for meaningful risk assessments among individuals.
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From page 96... ...
Although epidemiologic studies provide the essential information on etiology, they are very limited in their ability to elucidate the mechanisms involved in pathologic changes. It is this latter aspect of the study of disease that is best carried out under controlled conditions in the laboratory with animal or human subjects.
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From page 97... ...
Ecologic Correlations Some of the earliest leads in the nutritional epidemiology of chronic disease came from simple correlations of food disappearance data with disease mortality rates. For example, researchers showed that mortality from heart disease in various countries was highly correlated with per capita consumption of dietary fat (Figure 1)
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From page 98... ...
obtained diet histories on representative samples of the population and overcame several limitations of ecologic analyses by correlating nutrient intakes by sex, age, and ethnicity with corresponding cancer incidence rates. They found strong associations between dietary fat, especially saturated fat, and cancers of the breast, prostate, and endometrium (Table 2 and Figure 1)
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From page 99... ...
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From page 100... ...
While ecologic studies based on individually collected intake data, wish'' attention given"to "sex, age, a'''nd other' possible confounding variables, represent an improvement of the per capita estimates from food disappearance data, the problem remains that the exposure and outcome groups are separately identified and may not overlap (ecologic fallacy)
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From page 101... ...
(1987) found similar odds ratios for the association of vitamin A intake with lung cancer among whites in New Mexico, a relatively homogeneous group, whether they used frequency data alone or frequency modified by portion size.
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From page 102... ...
Despite the hazards of the diet history method, it has proven to be a successful tool in epidemiologic research. For example, as estimated from a diet history, saturated fat intake showed a significant association with serum cholesterol level in middle-aged American men, and unsaturated fat and dietary cholesterol showed significant associations (the former inverse)
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From page 103... ...
On the other hand, certain diet-disease associations have been more difficult to establish with any consistency. For example, despite impressive ecologic correlations (shown earlier)
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From page 104... ...
_ ~ ~ ~ e _ ~ e Nevertheless, some epidemiologic studies have used biochemical measurements. For example, at a group level, serum cholesterol has been positively associated with coronary heart disease mortality (Keys, 1980~.
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From page 105... ...
Recently, diet has been the focus of intervention trials involving cancer and coronary heart disease (Greenwald et al., 1987; Multiple Risk Factor Intervention Trial Research Group, 1982~. Such investigations are costly, require considerable nutritional expertise, and for ethical reasons, can only assess the effects of presumed beneficial dietary modifications.
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From page 106... ...
For this reason, efforts in all areas of epidemiologic research, including ecologic analyses as well as case-control, cohort, and intervention studies, should be encouraged. A convergence of findings from many sources by a variety of approaches continues to offer the best hope for identifying meaningful etiologic relationships.
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From page 107... ...
For example, such nutritionists must recognize certain limitations inherent in the conduct of field research on relatively large numbers of subjects or in designing practical methods of dietary assessment when individuals need to be classified precisely in a relative but not necessarily absolute sense.
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From page 108... ...
Further advances are being constrained by methodologic limitations, however, including substantial errors of measurement in the diet history as these measurements are currently implemented, the lack of functional biological markers of specific dietary intakes, an inability to classify subjects into risk groups with sufficient refinement, and unmet needs related to data analysis. Nutritionists who are well trained for this area of research are rare and are very much needed.
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From page 109... ...
1959. Statistical associations between international coronary heart disease death rates and certain environmental factors.
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From page 110... ...
1981b. Diet, serum cholesterol, and death from coronary heart disease: The Western Electric Study.
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