Throughout life, nutrition is an important determinant of health, physical and cognitive function, vitality, overall quality of life, and longevity. The quantity and variety of available foods, as well as the meaningfulness of the social interactions provided by meals, are important to psychological well-being. The composition of the diet and the amount that is consumed are strongly linked to physiological function. When a well-balanced diet is not maintained, malnutrition may develop with consequent detrimental effects on health and well-being.
Malnutrition can have many manifestations. As outlined in Chapter 40, a diet that is deficient in one or more required nutrients (e.g., calories, protein, minerals, fiber, or vitamins) can lead to a state of nutritional deficiency. The greater the magnitude and duration of the nutritional deprivation and the more fragile the individual, the more likely nutritional deficits will produce noticeable body compositional changes, functional impairments, or overt disease. Even borderline dietary deficiencies can have important health consequences such as producing subtle organ system impairments, diminished vitality, or increasing the individual's susceptibility to disease. Protein and protein-energy undernutrition are two of the most common, frequently unrecognized, and potentially serious forms of nutritional deficiency. The prevalence of these conditions is particularly high among chronically ill older individuals and those in hospitals, nursing homes, and other institutional settings. Although there is a complex interrelationship between nutrition, disease, and clinical outcomes, protein and protein-energy undernutrition appear to be significant contributors to disease-related morbidity and mortality in these populations. At the other end of the spectrum, the persistent consumption of excess quantities of one or more nutrients can have similar untoward consequences. Forms of malnutrition that result from excess consumption include hypercholesterolemia, hypervitaminosis, and obesity. Studies indicate that obesity is the most common nutritional disorder of advanced age in western societies with a high prevalence among the noninstitutionalized free-living elderly. Many obese older individuals have other nutritional disorders. Among chronically ill or functionally debilitated obese older individuals, protein undernutrition is a common, serious, and frequently unrecognized problem that can develop for many reasons including an imbalanced diet, disease, and inactivity.
Recognizing and maintaining an optimally balanced diet is an important challenge, particularly as individuals age. The challenge is particularly great for older people who already are malnourished, especially if they have nutritional disorders that developed earlier in life, such as obesity, osteoporosis, or protein undernutrition. Even healthy individuals often fail to maintain an optimal diet owing to lack of knowledge, resources, or willpower. The process of aging can introduce other factors including acute and chronic disease, physical disabilities, social isolation, use of multiple medications, depression, impaired cognitive ability, and disregulation of appetite control that may contribute further to poor eating habits and the development or exacerbation of nutritional disorders. In turn, inappropriate dietary intake and poor nutritional status can impact the progression of many acute and chronic diseases such as coronary heart disease, cancer, stroke, diabetes, and osteoporosis, which are among the 10 leading causes of death in the United States. The 1988 Surgeon General's Report on Nutrition and Health noted that two-thirds of all deaths within the United States are because of diseases associated with poor diets and dietary habits.
Assessing the quality of the diet of elderly persons is critical to addressing issues relevant to their health and nutritional status. Such an assessment must be based on knowledge of what constitutes a balanced diet for a given individual. The goal of this chapter is to identify an approach to nutrition evaluation and management that takes into account the unique needs, limitations, and desires of each elderly individual. The chapter starts out by examining the interrelationship among nutrition, activity, disease burden, and health outcomes and then focuses on age-related changes in body composition, lifestyle, and appetite regulation that affect nutritional status and nutrient requirements. Also included is a discussion of specific dietary considerations related to optimal health requirements.
Although nutrition is a vital component of good health, it cannot be evaluated in isolation. The relationship between nutrient intake and health is influenced by other factors, most notably activity level, disease burden, and advancing age. A basic understanding of these interrelationships is essential in order to assess the potential benefits and limitations of nutritional interventions.
Nutrition and physical activity are closely linked, each having vitally important and interacting effects on body composition, functional ability, and well-being. The balance between nutrient intake and physical activity is particularly important in determining muscle mass and strength, body fat content and distribution, and bone density and resilience. In recognition of the importance of the interrelationship between nutrition and activity on health, the U.S. Department of Agriculture (USDA) has released the MyPyramid food and activity guidance system. The MyPyramid symbol (Figure 38-1), which replaces the prior food pyramid, is designed to emphasize this interrelationship. The symbol is also designed to convey the message that variety, proportionality, moderation, gradual improvement, and personalization are all important in both diet and exercise prescriptions. Consumers can go to the MyPyramid Web site (www.mypyramid.gov) to learn more about this system and to obtain a detailed assessment and analysis of their current eating and physical activity habits.
MyPyramid.gov, U.S. Department of Agriculture, Center for Nutrition Policy and Promotion, April 2005, CNPP-15, http://www.mypyramid.gov
To preserve existing muscle mass and strength, it is necessary to maintain both an adequate level of physical activity and a balanced diet that includes sufficient protein, energy, vitamins, and minerals to meet metabolic demands and prevent negative nitrogen balance (as discussed in detail below). It is not known precisely what level of physical activity is needed to prevent loss of existing muscle mass and strength in older adults. However, studies indicate that even a week or two of bed rest or similar degrees of activity ...