Special Article
August 1992: 224-229
Nutrition and Aging: Potentials and Problems for Research in Developing Countries Noel W. Solomons, M.D.
The demographic explosion of persons over 60 years of age is a reality in developed and developing countries alike. There is evidence that research on aging and nutrition in Third World countries is growing and developing. Specific research programs, and the linking of these programs in timely multicenter efforts, promise both valuable descriptive research for the benefit of national populations and comparative insights that will help us to learn more, collectively, about the intrinsic nature of the aging process itself.
Introduction
Not too long ago maternal and child health was the major focus of applied nutrition research. Even in industrialized countries, issues of nutrition and diet of the elderly were of remote concern. In the last decade, however, the focus has begun to change to include a greater concern for the health of the elderly' (see Figures l and 2). There has been increasing momentum in this line of research in the industrialized However, its translation into studies in developing countries requires attention to a series of different dimensions and considerations: the applicability of traditional assumptions and techniques of nutritional research; the nature of the environmental, linguistic, cultural, and genetic characteristics of the populations under study; and the goals and intricacies of aging research in a Third World context. The present review examines 1) the new demographic and social realities concerning the oldest segments of developing-country populations; 2) conceptual paradigms for addressing diet and nutrition issues in the elderly; and 3) strategies, includDr. Solomons is Cofounder and Scientific Coordinator of the Center for Studies of Sensory Impairment, Aging and Metabolism (CeSSIAM), Hospital de Ojos y Oidos "Dr. Rodolfo Robles V.," Diagonal 21 y 19 Calle, Zone 11, Guatemala City, Guatemala. 224
ing the pitfalls and limitations, for the design and conduct of research on nutrition and aging and nutritional problems of the aged. The Paradigms A View of Priorities A global view of the Third World, based primarily on knowledge of rural children, would anticipate that for the elderly, as well, undernutrition and specific deficiencies would be rampant, that diets would be monotonous and low in animal protein, and that recurrent infectious diseases would be widespread. Given the traditional abstention from issues of nutrition and aging, especially in developing countries, the first necessity is to test our biases with theoretical research that would define the nutritional situation in any given nation or region and the prevalence and incidence of health- and nutrition-related variables of interest.
Poverty, Aging, and Selective Pressures The sine qua non of underdevelopment is low levels of wealth, resources, and education. Based on experience in child health,' all age groups in developing countries have been traditionally associated with undernutrition (see Table 1). It would be logical to assume that the elderly from the same poor households share similar risks of food scarcity and infectious diseases." Honvarth" provides a conventional roster of risk factors for nutritional problems in the elderly in developed nations (see Table 2). The superimposition of poverty, low levels of education, and poor access to health care in much of the Third World would logically signify an intensification and greater prevalence of these problems. However, another perspective, based on selective pressures, could produce alternative assumptions. If one postulated that those individuals most susceptible-either behaviorally or constitutionally-to adverse conditions would have succumbed Nutrition Reviews, Vol. 50, No. 8
Table 1. Recommendations of Professor C. Gopalan to Decrease the Nutritional Vulnerability of the Third World Elderlya
”
10
0
30 40
20
50 60 AGE
70 80 90 100
Figure 1. The increasingly rectangular Survival Curve. About 80% (stippled area) of the difference between the 1900 curve and the ideal curve (stippled area plus hatched area) had been eliminated by 1980. Trauma is now the dominant cause of death in early life. After Fries; reprinted by permission of the New England Journal of Medicine 1980;303:133.
in early life, leaving the more successful as survivors, it would not be unreasonable to expect adequate nutriture in the Third World elderly. An extension of this model would link resistance to undernutrition in early life not only to less frequent exposure to environmental parasites and pathogens, but also to some genetic adaptation, such as “thrifty genes,” that would maximize metabolic efficiency and nutrient retention. According to this scenario, survivors to old age in low-income nations might, in fact, be characterized by obesity and nutrient overload. Empirical evidence, rather than hypothetical extrapolation from pediatric health, is the legitimate guide.
v)
2
::
70
-
W
60
-
a
n
50 40
10 0
Sustain productivity of the aged (at least into the 60to 70-year old age group) Give special attention to elderly women as an especially nutritionally vulnerable group Ensure the nutritive value of the diet in the context of reduced caloric requirements and intake of the elderly Encourage family support to the aged in preference to state collective care Encourage development of geriatrics as a public health sDecialtv a Adapted from Gopalan C, “Challenges and Frontiers in Nutrition in Asia” (ref. 9).
Nutrient Requirements and Nutrient Intake Recommendations A recent careful analysis of the basis of the recommendations for older persons indicates that mostboth international compilations, such as those of the World Health Organization and the Food and Agriculture Organization, and those of specific nations, such as Canada, Great Britain, and the United States-are based on untested extrapolations from requirements of younger adults rather than on studies of the “healthy” elderly themselves.I2 It is assumed that some general aspects of aging will alter nutrient requirements or dietary recommendations as compared with those of younger populations. This must be tested directly in the elderly. To the extent that life-style, life-long environmental and dietary exposures, and current interactions with pathogens, parasites, foods, and nutrients can condition the uptake or metabolic utilization of nutrients, the elderly in tropical regions of the Third World may have greater or lesser nutrient intake requirements than their peers in Europe and North America.
: -
0
DISABILITY-FREE LIFE
10
20
30
40 5 0 60 AGE (years)
70
80
90
100
Figure 2. Despite the rectangularization of the mortality curve, the public health challenge is to rectangularize the disability curve as well. Currently, with advancing age a large number of years with chronic diseases and disability are to be expected prior to death. Nutrition Reviews, Vol. 50, No. 8
Diet and Health: lmplications for Chronic Disease Risk The fact that food is not just a source of energy and nutrients is reflected in the paradigm of diet and health. 13,14 Nutrients and nonnutrient constituents of the diet (e.g., fiber, aluminum, tin, cholesterol) consumed within certain ranges are implicated in promotion or inhibition of degenerative processes and chronic diseases. The degree to which genetics is involved is often overlooked.I5 For example, individuals who are sodium-tolerant may consume unlimited quantities without vascular consequences. Others, who have a strong familial predis-
225
Table 2. Potential Contributors to Nutritional Problems in Elderly Peoplea Physical Factors . Reduced total energy needs . Declining absorptive and metabolic capacities . Chronic diseases, restrictive diets . Loss of appetite, anorexia . Changes in taste or odor perception . Poor dentition, reduced salivary flow . Lack of exercise * Physical disability (restricting the capacity to purchase, cook, or eat a varied diet) . Drug-nutrient interactions . Side effects of drugs (nausea, altered taste) . Alcoholism Sociopsychological Factors * Depression . Loneliness . Social isolation . Bereavement . Loss of interest in food or cooking . Mental disorders . Food faddism . Lack of self-worth . Inadequate diets caused by cultural and religious influence Socioeconomical Factors . Low income . Inadequate cooking or storage facilities . Poor nutrition knowledge Lack of transportation * Shopping difficulties . Cooking practices resulting in nutrient losses * Inadequate cooking skills (men) a From Horwarth CC, “Dietary Intake Studies in Elderly People” (ref. 11).
position to dysplasia may find that no amount of dietary protective factors can fend it off. Given the potentially long lead time for the promotional phase of damage from the degenerative-disease processes that may be favorably or unfavorably modified by diet, childhood and early adulthood are the more critical periods for concern. Nevertheless, for those who are elderly now, it must still be determined whether there are dietary modifications that can benefit existing or latent conditions. Function and Autonomy In industrialized societies, cultural practices now have more older persons living alone or in intragenerational nuclear families rather than in the traditional extended-family setting. In this context, the paradigm of function, ranging from the ability to perform the basic activities of daily living to interaction in complex social settings, is often seen to be as important as, or even more important than, the 226
freedom from classical morbid conditions. In the context of Third World societies, the cultural place of the elderly in the social structure, the life-style demands of work and home life, and the scarcity of labor-saving appliances signal caution in a strict application of the concepts and instruments used for functional assessment in industrialized societies to elderly populations in developing countries. food Habits and Practices Nutritional anthropologists have found that traditional food practices and beliefs fade with both time and modernizing factors such as highway communication, mass media, and urbanization. However, traditional values are more widespread in developing countries than in industrialized societies, and within a population the oldest sector is the strongest bastion of these values. Food beliefs that influence food intake are worthy subjects of investigation by gerontologic nutritionists. Also, and particularly in the more traditional societies in developing countries, there are interesting intergenerational implications. In extended families, the food beliefs and practices of grandparents and great-grandparents may have a strong impact on the diet, and hence on nutritional status, of their grandchildren and great-grandchildren. These “oldfashioned” ways of selecting, preparing, and allocating foods can be either advantageous or detrimental to the well-being of the youngest members of the household. When multinational, multiethnic, and multicultural studies are involved, the issue of validity16 is highlighted. An elder’s functional autonomy, measured by the ability to get out of bed, for example, will be very different in North America, where the beds are high off the floor, and in Japan, where floor mats are used. Similarly, in Western industrialized nations, milk and dairy product consumption can often be used as a surrogate for total riboflavin intake. However, in countries where the quality of milk is poorly controlled, i.e., in which fluid milk is both adulterated and may be left to sit under display-case lights in plastic bags, true milk riboflavin content may not approach that published in food composition tables. Finally, the cross-ethnic applications of conventional anthropometric indices and their interpretation can represent a validity problem in crossnational research. Queclet’s body mass index (BMI), expressed as kg/m2, has been used to assess the degree of obesity. However, since leg lengths as a proportion of total height vary among ethnic groups,” it is reasonable to conclude that for races with short trunks and long limbs, the BMI standards will overdiagnose obesity. By contrast, those Nutrition Reviews, Vol. 50, No. 8
groups that are long-waisted and short-legged will be underdiagnosed for adiposity. Similarly, as fat distribution to the gluteal region has ethnic determination, both skinfolds and waist-to-hip circumferences may differ across racial groups. The application of uniform cutoff criteria for anthropometric indices in dissimilar ethnic groups is likely to produce errors in estimates of prevalence or risk by virtue of the somatic differences across races. Pitfalls and Caveats in Sampling Aging Populations Perhaps the most difficult aspect of aging research in general is population sampling. The first limitation can be that the total number of persons is insufficient to generate stable prevalence figures. In 1980 it was estimated that in all the underdeveloped countries in the world there were only 10,000 persons over 100 years of age.’ Thus, e.g., if centenarians are being studied in Mexico, the total pool of subjects in the country may be only 100 to 200 individuals. The second limitation is that sampling has an inevitable interaction with the questions of true vs. non-aging’c’8 (see Table 3). The common denominator in enrolling subjects for observation is the representativeness of one’s subsample to the universal population. This remains an imperative in aging research, but the inevitable march of mortality with time reduces the numbers of a given cohort. Mortality and, conversely, survival, are not random, but, rather, are highly In a study presented in Malaysia at the First Asian Workshop on Nutrition in Metropolitan Areas, Changbumrung et al.23found the highest levels Table 3. Sources of Differences Between Young and Old Age Groupsa True aging Intrinsic (genetic) Evolutionary response to the survival imperative of the reproductive cycle and the metabolic cost of tissue repairs Extrinsic (environmental) Accumulated insults from illnesses or environmental mutagens Non-aging Selective survival Characteristics that determine whether individuals in a given cohort will die before a certain age Cohort effects and secular trends Exposures to various external insults that differ in exposure times and groups exposed Differential challenge The ways in which societies treat and the benefits they confer upon members of different age groups a Modified from Health ofthe Elderly (ref. 18). Nutrition Reviews, Vol. 50, No. 8
of cholesterol in the 51- to 60-year age band of Thai men in Bangkok, with a decline in the 61- to 70-year group. In the participatory discussion, a number of possibilities for this association with age were entertained, including the possibility of differential mortality: those with higher lipid levels in the seventh decade are less likely to survive into the ninth decade. At the roundtable on “Nutrition and Malnutrition in the Elderly” of the Fourteenth International Gerontology Congress in Mexico, a collaborative university study of the Chilean elderly24 presented data showing increasing vitamin B,, levels in older cohorts of a cross-sectional study. Were these to be interpreted at face value as improvements in B,, nutriture with age? The discussants formulated a series of alternative explanations that illustrate each of the issues of aging and non-aging shown in Table 3. Among true aging possibilities there were 1) a saturation of liver storage capacity with “spillover”; 2) an age-associated incompetence of the ileocecal valve with backwash of vitamin of colonic origin; 3) an increased prevalence of blood dyscrasias associated with overproduction of transcobalamin 11, or some mild, nonprogressive form fruste of chronic leukemia that could produce a similar distortion. Non-aging disease could also be invoked as an explanation of these findings. In a secular scenario, dietary habits of the nation might have changed over time, or physicians’ practice of giving B,, injections might have varied, with older age groups favored with higher cumulative doses. Finally, most intriguingly (and with the greatest health care implications), there is a selective survival explanation. This assumes that the vitamin B,, status of specific individuals had not changed since age 60, but, rather, that those individuals in the upper part of the B,, distribution had outlived those initially at the lower end. This would account for the mathematics of a rising average, and raises intriguing questions of what advantage for survival and longevity is conveyed by better vitamin B,, status (or the life style or physiological factors that allow for accumulation of the vitamin). In the context of the Third World countries, the current acceleration of urbanization, with migration of populations from their rural origins to burgeoning metropoli, adds another sampling problem for aging research. Not only is survival selective, so also is migration. Thus, studies comparing rural elderly and urban elderly would confront the confounder of the selective motivations that lead some elderly to leave the countryside and others to stay. For the urban elder, the duration of dietary and environmental exposures of rural and urban life and their relative balance over a lifetime are important con227
siderations in the interpretation of any data from a cross-sectional study of urban elders in a developing country. The Potential
Based on distinctions between true aging and nonaging factors, and on the final utility of the knowledge acquired, nutrition and aging research can be divided into geriatric and gerontologic nutrition. Geriatric nutrition focuses on nutritional status changes and dietary problems in the context of illness and disability, and both true aging and nonaging factors are involved. It explores the question of which nutritional and dietary problems need to be corrected in the subgroup of older persons who 1) have survived; 2) have been imbued with certain cultural beliefs and practices; and 3) have received a defined, and generally inferior, portion of the general wealth and resources. For industrialized nations, a rough overall description of the pattern of disease is available. Less-developed countries are handicapped in their pursuit of geriatric nutrition by a lack of descriptive data on the overall health, illness, and disability profile of their older populations. Gerontologic nutrition focuses on nutrition and the aging process. At its best, this pursuit would provide insights into the general principles of the interaction of senescence and the metabolism of nutrients. To the extent that low energy intakes and diets with poor micronutrient density are found among the elderly of developing countries, these situations lend themselves to experimental studies of the dietary and nutritional requirements of older populations. In an industrialized nation, a depletion-repletion design would be necessary in order to study nutrient requirements by the stepwise, dietary-addition approach. In some developing countries, spontaneously deficient individuals can be enrolled. Finally, one of the ways in which true aging and non-aging can be distinguished is through comparative studies in which elderly or multiple-age groups are studied with identical protocols in different setting^.^' Arguably, those effects that are consistent, independent of external environmental circumstances and racial makeup, can be ascribed to the underlying, common, intrinsic senescent process. 1. Fries JF. Aging, natural death, and the compression of morbidity. N Engl J Med 1980;303:130-40 2. Vir SL, Love AG. Nutritional status of institutionalized and noninstitutionalized aged in Belfast, Northern Ireland. Am J Clin Nutr 1979;32:1934-47 3. Jacob RA, Otradovec CL, Russell RM, et al. Vitamin C status and nutrient interactions in a healthy elderly population. Am J Clin Nutr 1988;84:1435-42 228
4. Davis M, Murphy S, Neuhaus J. Living arrangements and eating behaviors of older adults in the United States. J Gerontol 1988;43:596-8 5. Campion EW, deLabry LO, Glynn RJ. The effect of age on serum albumin in healthy males: report from the normative aging study. J Gerontol 1988; 43:M1&20 6. Garry PJ, Chumlea WC, eds. Epidemiologic and methodologic problems in determining nutritional status of older persons. Am J Clin Nutr 1989; 5O(S~Ppl):ll21-35 7. Horowitz A, Macfadyen DM, Munro H, et al. Nutrition in the elderly. World Health Organization. Oxford, UK: Oxford University Press, 1989 8 . de Groot LCPGM, van Staveren WA, Hautvast JGAJ, eds. Euronut-SENECA. Nutrition and the elderly in Europe. Eur J Clin Nutr 1991;45(suppl 3): 1-1 96 9. Gopalan C. Challenges and frontiers in nutrition in Asia. In: Proceedings of the VI Asian Congress of Nutrition (in press, 1992) 10. Gomez F, Ramos-Galvan R, Frank S, et al. Morbidity in second and third degree malnutrition. J Trop Pediatr 1956;22:77-83 11. Horwarth CC. Dietary intake studies in elderly people. In: Bourne GH, ed. Impact of nutrition on health and disease. World Rev Nutr Diet 51. Basel: S. Karger, 1989:l-70 12. Munro HN, Suter PM, Russell RM. Nutritional requirements of the elderly. Annu Rev Nutr 1987;7: 23-49 13. US National Research Council, National Academy of Sciences. Diet and health: implications for chronic disease risk. Washington, DC: National Academy Press, 1989 14. Willett W. Nutritional epidemiology. New York: Oxford University Press, 1990 15. Childs B, Simopolous AP, eds. Genetic variation and nutrition. World Rev Nutr Diet 63. Basel: S. Karger, 1990 16. Cook TD, Campbell DT. Validity. In: Cook TD, Campbell DT, eds. Quasi-experimentation: design and analysis issues for field settings. Boston: Houghton-Mifflin 1979:37-94 17. Roche AF, Malina RM. Manual of physical status and performance in childhood. Vol. 1. New York: Plenum Press, 1983 18. Health of the elderly. Report of a WHO Expert Committee. Technical Report Series 779. Geneva: World Health Organization, 1989 19. Grimley-Evans J. Ageing and disease. In: Evered D, Whelan J, eds. Research and the ageing population. Chichester: John Wiley i3 Sons, 1988:38-47 20. Kirkwood TBL. Evolution of ageing. Nature (Lond) 1977;270:301-4 21. Svenborg A. The health of the elderly population: results from longitudinal studies with age-cohort comparisons. In: Evered D, Whelan J, eds. Research and the ageing population. Chichester: John Wiley i3 Sons, 19883-12 22. Shock N. Longitudinal studies of aging in huNutrition Reviews, Vol. 50, No. 8
mans. In: Finch CE, Schneider EL, eds. Handbook of the biology of aging. 2nd ed., New York: Van Nostrand Reinhold Co., 1985:721-43 23. Changbumrung S, Ratarasam S, Pethlium P, et al. Lipid pattern in the whole serum and individual lipoproteins of Bangkok males. I Asian Workshop on Nutrition in the Metropolitan Area. September 1991, Universiti Peratanian Malaysia, Abstracts 1991:38
Nutrition Reviews, Vol. 50, No. 8
24. Valient S, Jiminez M, Valiente G, et al. Dieta y malnutrition en ancianos chilenos. Presented at the round table on “Nutrition and Malnutrition in the Elderly.” XIV International Congress on Gerontology, Acapulco, 1989 25. Andrews G. Health and aging in the developing world. In: Evered D, Whelan J, eds. Research and the aging population. Chichester: John Wiley & Sons, 1988
229
August 1992: 224-229
Nutrition and Aging: Potentials and Problems for Research in Developing Countries Noel W. Solomons, M.D.
The demographic explosion of persons over 60 years of age is a reality in developed and developing countries alike. There is evidence that research on aging and nutrition in Third World countries is growing and developing. Specific research programs, and the linking of these programs in timely multicenter efforts, promise both valuable descriptive research for the benefit of national populations and comparative insights that will help us to learn more, collectively, about the intrinsic nature of the aging process itself.
Introduction
Not too long ago maternal and child health was the major focus of applied nutrition research. Even in industrialized countries, issues of nutrition and diet of the elderly were of remote concern. In the last decade, however, the focus has begun to change to include a greater concern for the health of the elderly' (see Figures l and 2). There has been increasing momentum in this line of research in the industrialized However, its translation into studies in developing countries requires attention to a series of different dimensions and considerations: the applicability of traditional assumptions and techniques of nutritional research; the nature of the environmental, linguistic, cultural, and genetic characteristics of the populations under study; and the goals and intricacies of aging research in a Third World context. The present review examines 1) the new demographic and social realities concerning the oldest segments of developing-country populations; 2) conceptual paradigms for addressing diet and nutrition issues in the elderly; and 3) strategies, includDr. Solomons is Cofounder and Scientific Coordinator of the Center for Studies of Sensory Impairment, Aging and Metabolism (CeSSIAM), Hospital de Ojos y Oidos "Dr. Rodolfo Robles V.," Diagonal 21 y 19 Calle, Zone 11, Guatemala City, Guatemala. 224
ing the pitfalls and limitations, for the design and conduct of research on nutrition and aging and nutritional problems of the aged. The Paradigms A View of Priorities A global view of the Third World, based primarily on knowledge of rural children, would anticipate that for the elderly, as well, undernutrition and specific deficiencies would be rampant, that diets would be monotonous and low in animal protein, and that recurrent infectious diseases would be widespread. Given the traditional abstention from issues of nutrition and aging, especially in developing countries, the first necessity is to test our biases with theoretical research that would define the nutritional situation in any given nation or region and the prevalence and incidence of health- and nutrition-related variables of interest.
Poverty, Aging, and Selective Pressures The sine qua non of underdevelopment is low levels of wealth, resources, and education. Based on experience in child health,' all age groups in developing countries have been traditionally associated with undernutrition (see Table 1). It would be logical to assume that the elderly from the same poor households share similar risks of food scarcity and infectious diseases." Honvarth" provides a conventional roster of risk factors for nutritional problems in the elderly in developed nations (see Table 2). The superimposition of poverty, low levels of education, and poor access to health care in much of the Third World would logically signify an intensification and greater prevalence of these problems. However, another perspective, based on selective pressures, could produce alternative assumptions. If one postulated that those individuals most susceptible-either behaviorally or constitutionally-to adverse conditions would have succumbed Nutrition Reviews, Vol. 50, No. 8
Table 1. Recommendations of Professor C. Gopalan to Decrease the Nutritional Vulnerability of the Third World Elderlya
”
10
0
30 40
20
50 60 AGE
70 80 90 100
Figure 1. The increasingly rectangular Survival Curve. About 80% (stippled area) of the difference between the 1900 curve and the ideal curve (stippled area plus hatched area) had been eliminated by 1980. Trauma is now the dominant cause of death in early life. After Fries; reprinted by permission of the New England Journal of Medicine 1980;303:133.
in early life, leaving the more successful as survivors, it would not be unreasonable to expect adequate nutriture in the Third World elderly. An extension of this model would link resistance to undernutrition in early life not only to less frequent exposure to environmental parasites and pathogens, but also to some genetic adaptation, such as “thrifty genes,” that would maximize metabolic efficiency and nutrient retention. According to this scenario, survivors to old age in low-income nations might, in fact, be characterized by obesity and nutrient overload. Empirical evidence, rather than hypothetical extrapolation from pediatric health, is the legitimate guide.
v)
2
::
70
-
W
60
-
a
n
50 40
10 0
Sustain productivity of the aged (at least into the 60to 70-year old age group) Give special attention to elderly women as an especially nutritionally vulnerable group Ensure the nutritive value of the diet in the context of reduced caloric requirements and intake of the elderly Encourage family support to the aged in preference to state collective care Encourage development of geriatrics as a public health sDecialtv a Adapted from Gopalan C, “Challenges and Frontiers in Nutrition in Asia” (ref. 9).
Nutrient Requirements and Nutrient Intake Recommendations A recent careful analysis of the basis of the recommendations for older persons indicates that mostboth international compilations, such as those of the World Health Organization and the Food and Agriculture Organization, and those of specific nations, such as Canada, Great Britain, and the United States-are based on untested extrapolations from requirements of younger adults rather than on studies of the “healthy” elderly themselves.I2 It is assumed that some general aspects of aging will alter nutrient requirements or dietary recommendations as compared with those of younger populations. This must be tested directly in the elderly. To the extent that life-style, life-long environmental and dietary exposures, and current interactions with pathogens, parasites, foods, and nutrients can condition the uptake or metabolic utilization of nutrients, the elderly in tropical regions of the Third World may have greater or lesser nutrient intake requirements than their peers in Europe and North America.
: -
0
DISABILITY-FREE LIFE
10
20
30
40 5 0 60 AGE (years)
70
80
90
100
Figure 2. Despite the rectangularization of the mortality curve, the public health challenge is to rectangularize the disability curve as well. Currently, with advancing age a large number of years with chronic diseases and disability are to be expected prior to death. Nutrition Reviews, Vol. 50, No. 8
Diet and Health: lmplications for Chronic Disease Risk The fact that food is not just a source of energy and nutrients is reflected in the paradigm of diet and health. 13,14 Nutrients and nonnutrient constituents of the diet (e.g., fiber, aluminum, tin, cholesterol) consumed within certain ranges are implicated in promotion or inhibition of degenerative processes and chronic diseases. The degree to which genetics is involved is often overlooked.I5 For example, individuals who are sodium-tolerant may consume unlimited quantities without vascular consequences. Others, who have a strong familial predis-
225
Table 2. Potential Contributors to Nutritional Problems in Elderly Peoplea Physical Factors . Reduced total energy needs . Declining absorptive and metabolic capacities . Chronic diseases, restrictive diets . Loss of appetite, anorexia . Changes in taste or odor perception . Poor dentition, reduced salivary flow . Lack of exercise * Physical disability (restricting the capacity to purchase, cook, or eat a varied diet) . Drug-nutrient interactions . Side effects of drugs (nausea, altered taste) . Alcoholism Sociopsychological Factors * Depression . Loneliness . Social isolation . Bereavement . Loss of interest in food or cooking . Mental disorders . Food faddism . Lack of self-worth . Inadequate diets caused by cultural and religious influence Socioeconomical Factors . Low income . Inadequate cooking or storage facilities . Poor nutrition knowledge Lack of transportation * Shopping difficulties . Cooking practices resulting in nutrient losses * Inadequate cooking skills (men) a From Horwarth CC, “Dietary Intake Studies in Elderly People” (ref. 11).
position to dysplasia may find that no amount of dietary protective factors can fend it off. Given the potentially long lead time for the promotional phase of damage from the degenerative-disease processes that may be favorably or unfavorably modified by diet, childhood and early adulthood are the more critical periods for concern. Nevertheless, for those who are elderly now, it must still be determined whether there are dietary modifications that can benefit existing or latent conditions. Function and Autonomy In industrialized societies, cultural practices now have more older persons living alone or in intragenerational nuclear families rather than in the traditional extended-family setting. In this context, the paradigm of function, ranging from the ability to perform the basic activities of daily living to interaction in complex social settings, is often seen to be as important as, or even more important than, the 226
freedom from classical morbid conditions. In the context of Third World societies, the cultural place of the elderly in the social structure, the life-style demands of work and home life, and the scarcity of labor-saving appliances signal caution in a strict application of the concepts and instruments used for functional assessment in industrialized societies to elderly populations in developing countries. food Habits and Practices Nutritional anthropologists have found that traditional food practices and beliefs fade with both time and modernizing factors such as highway communication, mass media, and urbanization. However, traditional values are more widespread in developing countries than in industrialized societies, and within a population the oldest sector is the strongest bastion of these values. Food beliefs that influence food intake are worthy subjects of investigation by gerontologic nutritionists. Also, and particularly in the more traditional societies in developing countries, there are interesting intergenerational implications. In extended families, the food beliefs and practices of grandparents and great-grandparents may have a strong impact on the diet, and hence on nutritional status, of their grandchildren and great-grandchildren. These “oldfashioned” ways of selecting, preparing, and allocating foods can be either advantageous or detrimental to the well-being of the youngest members of the household. When multinational, multiethnic, and multicultural studies are involved, the issue of validity16 is highlighted. An elder’s functional autonomy, measured by the ability to get out of bed, for example, will be very different in North America, where the beds are high off the floor, and in Japan, where floor mats are used. Similarly, in Western industrialized nations, milk and dairy product consumption can often be used as a surrogate for total riboflavin intake. However, in countries where the quality of milk is poorly controlled, i.e., in which fluid milk is both adulterated and may be left to sit under display-case lights in plastic bags, true milk riboflavin content may not approach that published in food composition tables. Finally, the cross-ethnic applications of conventional anthropometric indices and their interpretation can represent a validity problem in crossnational research. Queclet’s body mass index (BMI), expressed as kg/m2, has been used to assess the degree of obesity. However, since leg lengths as a proportion of total height vary among ethnic groups,” it is reasonable to conclude that for races with short trunks and long limbs, the BMI standards will overdiagnose obesity. By contrast, those Nutrition Reviews, Vol. 50, No. 8
groups that are long-waisted and short-legged will be underdiagnosed for adiposity. Similarly, as fat distribution to the gluteal region has ethnic determination, both skinfolds and waist-to-hip circumferences may differ across racial groups. The application of uniform cutoff criteria for anthropometric indices in dissimilar ethnic groups is likely to produce errors in estimates of prevalence or risk by virtue of the somatic differences across races. Pitfalls and Caveats in Sampling Aging Populations Perhaps the most difficult aspect of aging research in general is population sampling. The first limitation can be that the total number of persons is insufficient to generate stable prevalence figures. In 1980 it was estimated that in all the underdeveloped countries in the world there were only 10,000 persons over 100 years of age.’ Thus, e.g., if centenarians are being studied in Mexico, the total pool of subjects in the country may be only 100 to 200 individuals. The second limitation is that sampling has an inevitable interaction with the questions of true vs. non-aging’c’8 (see Table 3). The common denominator in enrolling subjects for observation is the representativeness of one’s subsample to the universal population. This remains an imperative in aging research, but the inevitable march of mortality with time reduces the numbers of a given cohort. Mortality and, conversely, survival, are not random, but, rather, are highly In a study presented in Malaysia at the First Asian Workshop on Nutrition in Metropolitan Areas, Changbumrung et al.23found the highest levels Table 3. Sources of Differences Between Young and Old Age Groupsa True aging Intrinsic (genetic) Evolutionary response to the survival imperative of the reproductive cycle and the metabolic cost of tissue repairs Extrinsic (environmental) Accumulated insults from illnesses or environmental mutagens Non-aging Selective survival Characteristics that determine whether individuals in a given cohort will die before a certain age Cohort effects and secular trends Exposures to various external insults that differ in exposure times and groups exposed Differential challenge The ways in which societies treat and the benefits they confer upon members of different age groups a Modified from Health ofthe Elderly (ref. 18). Nutrition Reviews, Vol. 50, No. 8
of cholesterol in the 51- to 60-year age band of Thai men in Bangkok, with a decline in the 61- to 70-year group. In the participatory discussion, a number of possibilities for this association with age were entertained, including the possibility of differential mortality: those with higher lipid levels in the seventh decade are less likely to survive into the ninth decade. At the roundtable on “Nutrition and Malnutrition in the Elderly” of the Fourteenth International Gerontology Congress in Mexico, a collaborative university study of the Chilean elderly24 presented data showing increasing vitamin B,, levels in older cohorts of a cross-sectional study. Were these to be interpreted at face value as improvements in B,, nutriture with age? The discussants formulated a series of alternative explanations that illustrate each of the issues of aging and non-aging shown in Table 3. Among true aging possibilities there were 1) a saturation of liver storage capacity with “spillover”; 2) an age-associated incompetence of the ileocecal valve with backwash of vitamin of colonic origin; 3) an increased prevalence of blood dyscrasias associated with overproduction of transcobalamin 11, or some mild, nonprogressive form fruste of chronic leukemia that could produce a similar distortion. Non-aging disease could also be invoked as an explanation of these findings. In a secular scenario, dietary habits of the nation might have changed over time, or physicians’ practice of giving B,, injections might have varied, with older age groups favored with higher cumulative doses. Finally, most intriguingly (and with the greatest health care implications), there is a selective survival explanation. This assumes that the vitamin B,, status of specific individuals had not changed since age 60, but, rather, that those individuals in the upper part of the B,, distribution had outlived those initially at the lower end. This would account for the mathematics of a rising average, and raises intriguing questions of what advantage for survival and longevity is conveyed by better vitamin B,, status (or the life style or physiological factors that allow for accumulation of the vitamin). In the context of the Third World countries, the current acceleration of urbanization, with migration of populations from their rural origins to burgeoning metropoli, adds another sampling problem for aging research. Not only is survival selective, so also is migration. Thus, studies comparing rural elderly and urban elderly would confront the confounder of the selective motivations that lead some elderly to leave the countryside and others to stay. For the urban elder, the duration of dietary and environmental exposures of rural and urban life and their relative balance over a lifetime are important con227
siderations in the interpretation of any data from a cross-sectional study of urban elders in a developing country. The Potential
Based on distinctions between true aging and nonaging factors, and on the final utility of the knowledge acquired, nutrition and aging research can be divided into geriatric and gerontologic nutrition. Geriatric nutrition focuses on nutritional status changes and dietary problems in the context of illness and disability, and both true aging and nonaging factors are involved. It explores the question of which nutritional and dietary problems need to be corrected in the subgroup of older persons who 1) have survived; 2) have been imbued with certain cultural beliefs and practices; and 3) have received a defined, and generally inferior, portion of the general wealth and resources. For industrialized nations, a rough overall description of the pattern of disease is available. Less-developed countries are handicapped in their pursuit of geriatric nutrition by a lack of descriptive data on the overall health, illness, and disability profile of their older populations. Gerontologic nutrition focuses on nutrition and the aging process. At its best, this pursuit would provide insights into the general principles of the interaction of senescence and the metabolism of nutrients. To the extent that low energy intakes and diets with poor micronutrient density are found among the elderly of developing countries, these situations lend themselves to experimental studies of the dietary and nutritional requirements of older populations. In an industrialized nation, a depletion-repletion design would be necessary in order to study nutrient requirements by the stepwise, dietary-addition approach. In some developing countries, spontaneously deficient individuals can be enrolled. Finally, one of the ways in which true aging and non-aging can be distinguished is through comparative studies in which elderly or multiple-age groups are studied with identical protocols in different setting^.^' Arguably, those effects that are consistent, independent of external environmental circumstances and racial makeup, can be ascribed to the underlying, common, intrinsic senescent process. 1. Fries JF. Aging, natural death, and the compression of morbidity. N Engl J Med 1980;303:130-40 2. Vir SL, Love AG. Nutritional status of institutionalized and noninstitutionalized aged in Belfast, Northern Ireland. Am J Clin Nutr 1979;32:1934-47 3. Jacob RA, Otradovec CL, Russell RM, et al. Vitamin C status and nutrient interactions in a healthy elderly population. Am J Clin Nutr 1988;84:1435-42 228
4. Davis M, Murphy S, Neuhaus J. Living arrangements and eating behaviors of older adults in the United States. J Gerontol 1988;43:596-8 5. Campion EW, deLabry LO, Glynn RJ. The effect of age on serum albumin in healthy males: report from the normative aging study. J Gerontol 1988; 43:M1&20 6. Garry PJ, Chumlea WC, eds. Epidemiologic and methodologic problems in determining nutritional status of older persons. Am J Clin Nutr 1989; 5O(S~Ppl):ll21-35 7. Horowitz A, Macfadyen DM, Munro H, et al. Nutrition in the elderly. World Health Organization. Oxford, UK: Oxford University Press, 1989 8 . de Groot LCPGM, van Staveren WA, Hautvast JGAJ, eds. Euronut-SENECA. Nutrition and the elderly in Europe. Eur J Clin Nutr 1991;45(suppl 3): 1-1 96 9. Gopalan C. Challenges and frontiers in nutrition in Asia. In: Proceedings of the VI Asian Congress of Nutrition (in press, 1992) 10. Gomez F, Ramos-Galvan R, Frank S, et al. Morbidity in second and third degree malnutrition. J Trop Pediatr 1956;22:77-83 11. Horwarth CC. Dietary intake studies in elderly people. In: Bourne GH, ed. Impact of nutrition on health and disease. World Rev Nutr Diet 51. Basel: S. Karger, 1989:l-70 12. Munro HN, Suter PM, Russell RM. Nutritional requirements of the elderly. Annu Rev Nutr 1987;7: 23-49 13. US National Research Council, National Academy of Sciences. Diet and health: implications for chronic disease risk. Washington, DC: National Academy Press, 1989 14. Willett W. Nutritional epidemiology. New York: Oxford University Press, 1990 15. Childs B, Simopolous AP, eds. Genetic variation and nutrition. World Rev Nutr Diet 63. Basel: S. Karger, 1990 16. Cook TD, Campbell DT. Validity. In: Cook TD, Campbell DT, eds. Quasi-experimentation: design and analysis issues for field settings. Boston: Houghton-Mifflin 1979:37-94 17. Roche AF, Malina RM. Manual of physical status and performance in childhood. Vol. 1. New York: Plenum Press, 1983 18. Health of the elderly. Report of a WHO Expert Committee. Technical Report Series 779. Geneva: World Health Organization, 1989 19. Grimley-Evans J. Ageing and disease. In: Evered D, Whelan J, eds. Research and the ageing population. Chichester: John Wiley i3 Sons, 1988:38-47 20. Kirkwood TBL. Evolution of ageing. Nature (Lond) 1977;270:301-4 21. Svenborg A. The health of the elderly population: results from longitudinal studies with age-cohort comparisons. In: Evered D, Whelan J, eds. Research and the ageing population. Chichester: John Wiley i3 Sons, 19883-12 22. Shock N. Longitudinal studies of aging in huNutrition Reviews, Vol. 50, No. 8
mans. In: Finch CE, Schneider EL, eds. Handbook of the biology of aging. 2nd ed., New York: Van Nostrand Reinhold Co., 1985:721-43 23. Changbumrung S, Ratarasam S, Pethlium P, et al. Lipid pattern in the whole serum and individual lipoproteins of Bangkok males. I Asian Workshop on Nutrition in the Metropolitan Area. September 1991, Universiti Peratanian Malaysia, Abstracts 1991:38
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24. Valient S, Jiminez M, Valiente G, et al. Dieta y malnutrition en ancianos chilenos. Presented at the round table on “Nutrition and Malnutrition in the Elderly.” XIV International Congress on Gerontology, Acapulco, 1989 25. Andrews G. Health and aging in the developing world. In: Evered D, Whelan J, eds. Research and the aging population. Chichester: John Wiley & Sons, 1988
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