The Effects of Aging

Life expectancy at birth is now 75 years, compared with about 47 years at the beginning of the last century. Although it is not inevitable, health and mobility often change and decline with advancing age. The increasing life expectancy observed throughout this century suggests that diet, exercise, and other personal and socioeconomic factors can help prolong good health for most people.

Nevertheless, the chances are great that an individual in the eighth or ninth decade of life will be limited in activity and require health and social services. Many older people (the general term older will refer to people over age 65) suffer from arthritis, heart disease, hypertension, hearing loss, diabetes, obesity, gastrointestinal conditions, liver disease, cancer, and other chronic diseases. Heart disease, cancer, and stroke account for over three-quarters of the deaths among older persons and 50 percent of all days of bed confinement. Such chronic conditions as well as dementia prevent functional independence and increase the need for dietary and other long-term care services.

Until the early 1970's, nutrition services for the older population, with the exception of food stamps, were based almost exclusively in hospitals and long-term care facilities. In 1973, in response to the growing population of older people, to rising health care costs, and to greater interest in preventive health care, the Nutrition Program for the Elderly was established under the Administration on Aging to expand food and nutrition services from the hospital to include communities and homes.

Aging is accompanied by a variety of physiologic, psychologic, economic, and social changes that may compromise nutritional status. Older persons have a prevalence of chronic disease, use medications heavily, and are relatively sedentary.

Many physiologic functions, including the senses of smell and possibly taste, decrease with age. These changes may result in decreased appetite as well as impaired utilization of nutrients and limitations of function.

Dental problems, common in old age, decrease the ability to chew certain foods. Physical disabilities such as diminution of vision may make eating less pleasant. The decreases in basal metabolic rate and physical activity noted with increasing age reduce nutrient needs, however, the intake of calories and essential nutrients may be even lower than these needs. Decreased physical activity also may predispose individuals to the development of osteoporosis.

Changes such as osteoarthritis can affect mobility and decrease an older person's ability to purchase and prepare food. Another possible hinderance to adequate nutrition in the aged is malabsorption, which can be caused by decrease or absence of gastric acid secretion and by interaction with medications commonly prescribed for older persons.

The most common psychologic factor affecting nutrition is depression. Of all psychiatric diagnoses, depression is most strongly correlated with increased mortality, regardless of the age of the subjects, and is most often related to chronic disease and to poverty, which are common among older persons. Neither institutionalization nor solitary living necessarily induces depression, but such life changes may be associated with poor self-esteem, which in turn, can lead to significant changes in eating patterns.

Older people as a group have a lower economic status than other adults. Although the percentage of older individuals living below the poverty level has decreased substantially over the past two decades and is now less than the percentage of those under 65 living in poverty, poverty continues to be too high. The decline in income most often results from retirement from the workforce, the effects of inflation on fixed incomes, death of wage-earning spouse, or failing health. Income and health status have been found to be important determinants of life satisfaction in the older population. Low income is also a major risk factor for inadequate nutrition in older individuals.



Most older people do not live in institutions, although institutional food is likely to meet minimal standards for nutrient content, factors such as lack of choice or limited day-to-day variety may increase the risk of inadequate consumption. Many residents of nursing homes consume a therapeutic diet that may further discourage adequate intake. An important issue for demented institutionalized individuals is that they may not consume the food, not that the menu is inadequate.

Clinical and dietary standards for younger adults may not be appropriate for older persons, yet few data are available on nutritional requirements or recommended intakes of older adults. The RDA's for example, were developed from research on the nutrient needs of younger healthy people. The present standards for adults over the age 50 are, for the most part, identical to those for people aged 23 to 50. Because these standards fail to consider the great heterogeneity of adults whose ages may differ by as much as 50 years and because they were often not developed from actual measurements on older populations, their appropriateness for older persons is not known.

Energy and Nutrient Status of the Older Population

The national dietary and food consumption surveys conducted during the 1970's reported lower energy intakes among older persons than among younger adults. A study of male executives in the Baltimore Longitudinal Study of Aging found a steady decline in average energy expenditure from 2700 kcal per day at age 30 to 2100 kcal per day at 80 years of age. The decline in energy expenditure was attributed to reduced physical activity and to a decline in basal energy metabolism as a result of a reduction in lean body mass with age.

Although it is difficult to interpret dietary intake studies of older persons because of methodological problems, existingstudies almost always reveal decreases in energy intake with age that may also be influenced by income, race, food preference, and drug use. A low-calorie diet may not impair health as long as the nutrient density of the diet is high and can provide adequate amounts of essential nutrients. However, this issue has not been examined in great detail because nutrient requirements in older people remain largely unknown.

Consequently, the increasing level of obesity among older persons, as indicated by higher weight-for-height with age, requires explanation. Whether the inconsistency between reported low energy intake and increasing body weight is due to measurement errors, inappropriate standards, loss of height with age, or lack of physical activity has not been established.

A 30-day continuous metabolic balance study of seven men and eight women, over 70 years of age, who consumed the RDA levels of protein and energy found that about half were unable to maintain nitrogen balance on this level of protein (0.8 g of protein per kg per day). The results suggested that higher intakes were required to meet protein requirements. Because the RDA for protein includes a substantial safety margin and because clinical measurements have rarely found signs of protein deficiency among healthy older persons, it is not possible to conclude from these data that persons with intake below the RDA are protein deficient or that they would benefit from additional protein intake.

Older people, especially Caucasian women, lose bone mineral and have a higher incidence of fractures than younger persons. Metabolic and absorptive factors as well as low intake may contribute to chronic negative calcium balance. Reduced efficiency of calcium absorption may be due to inadequate dietary intake, age related changes in gastric acidity, and/or interactions of intestinal constituents such as fibre, bacteria, and other nutrients. Perhaps in some individuals a negative effect on calcium nutriture may be caused by age-related changes in hormonal control, abberations in vitamin D metabolism, and imbalances of protein, phosphorus, alcohol, and electrolytes with calcium.

The RDA for calcium of 800 mg per day may not be sufficient to maintain calcium balance in populations consuming Western diets. Calcium intake by older people is often marginal, for example, 43 percent of women in nursing homes failed to get two-thirds of their calcium requirement. Women living at home consumed even less calcium than those in nursing homes. Older people may have reduced calcium intake because they avoid dairy products containing lactose, to which they are intolerant.

As with people of all ages, the frequency with which anaemia occurs in the older population and determination of its etiology depend on the criteria used for diagnosis.



Because iron reserves increase with age, studies that examine only dietary intake of iron in older people need to be interpreted cautiously. Low dietary iron intake at one point intime does not necessarily increase the risk for anaemia because iron may still be available from body stores and because iron absorption increases when intake and stores are low. In addition, the type of iron and other components of a meal such as ascorbic acid also influence the amount absorbed. Comparison of older subjects who took iron supplements with those who did not showed no clinically significant differences in the biochemical measures of iron status.

Vitamin deficiency may be a result of decreased dietary intake, absorption defects, decreased hepatic avidity for folate in Laennec's cirrhosis, decreased storage and conversion to active metabolic forms, or excessive utilization, destruction, or excretion.

No comprehensive study of all vitamins and their related enzyme systems has been conducted. Most studies have only examined the status of one or two vitamins. A number of studies have indicated a great risk for vitamin deficiencies in older persons on the basis of low dietary intakes, but such deficiencies are not always confirmed by biochemical or clinical results. In addition, interpretation of biochemical parameters is hampered by lack of data on normal standards for the older population. For example, a New Mexico study revealed that more than one-fourth of the older population consumed less than 75 percent of the RDA's for folate and vitamins B6 and B12 from diet alone. However, biochemical studies failed to confirm that these individuals were at risk for developing clinical symptoms associated with low intakes of these vitamins. Intake of vitamin supplements may explain part of this apparent discrepancy, although analysis showed little statistical difference in mean dietary intake for those individuals taking a specific supplement compared with those who did not take the supplement.

The body pool of ascorbic acid reaches a maximum of approximately 20 milligrams per kilogram. Women require an intake of 75 mg per day and men require an intake of 150 mg per day to achieve this ascorbic acid level in plasma. This finding was supported by a clinical trial that showed that a daily intake of 60 mg was insufficient to maintain this plasma concentration.

Vitamin A deficiency does not seem to be a particular problem in older persons, Although NHANES I and NHANES II (the National Health and Nutrition Examination Surveys) reported that half the study population over age 65 had vitamin A intakes at or less than two-thirds of the RDA, only 0.3 percent of the NHANES older population had low vitamin A blood levels. Whether vitamin A supplement use can account for the observed discrepancy is unknown, but similar data suggest that older individuals can maintain normal vitamin blood levels even with reportedly low dietary intakes.

Previous studies have revealed a generally lowered vitamin D status in older people, chronically ill individuals, and those living in institutions with little or no exposure to sunlight. Because the vitamin D endocrine system is the major regulator of intestinal calcium absorption, a reduced vitamin D status might promote a negative calcium balance in older people.

Two studies in the United States have found dietary intake of vitamin D to be approximately 50 percent of the RDA for older subjects. However, ultraviolet light induced endogenous production of vitamin D is the main external factor in maintaining adequate vitamin D status. Because sunlight exposure activates vitamin D precursors in the skin, it has been recommended that older people obtain at least minimal sunlight exposure (10 to 15 minutes) two or three times a week. Increased sun exposure may help compensate for aging skin's decreased capacity to produce these precursors. Supplements may be necessary to compensate for inadequate sunlight exposure due to seasonal variation in northern latitudes. Moderation of sun exposure should be recommended because overexposure to the sun is a strong risk factor for skin cancer.

There is no evidence that older individuals are deficient either in dietary intake or tissue levels of vitamin E. Despite statements that megadose vitamin E supplements retard the aging process and prevent atherosclerosis and cancer, its use to treat or prevent other conditions has not been established.

Nutritional Supplements

It has been estimated that 37 percent of American adults consume a daily multivitamin preparation, fuelling a $2 billion per year industry. NHANES II indicated that the persons most likely to take supplemental nutrients are less likely to need them, and those most in need of them are least likely to take them. In older persons, vitamin use has increased dramatically in the past decade. Whether such supplements improve the health of these people cannot be determined from existing data, but it is clear that excessive supplementation may be harmful. High doses of the fat-soluble vitamins A and D are toxic.



Drug-Nutrient Interactions

Although older Americans constitute about 12 percent of the population, they use about 25 percent of all prescription drugs. This is not surprising because many chronic diseases associated with aging are managed with prescription drugs. Over half of the older people take at least one medication daily and many take six or more a day for multiple diseases. Cardiovascular drugs (eg. diuretics) are most widely used by the aging population, followed by drugs to treat arthritis, neurologic disorders, and respiratory and gastrointestinal conditions.

Many unwanted drug-nutrient interactions in older persons have been documented. This population requires special consideration because aging per se changes the absorption, disposition, and elimination of drugs. The older person with multiple diseases is at risk for additional drug-nutrient interactions linked to separate drug therapies for primary and secondary health problems. Even over-the-counter antacids, laxatives, analgesics,and vitamin and mineral supplements may result in unwanted drug-nutrient side effects in the older person.

Effects of Nutritional Deficiencies on the Older Population

Severe malnutrition - protein, calorie, vitamin, or mineral - is associated with increased mortality, and the relationship of malnutrition to mortality in older persons is of current interest. Among severely ill or injured hospital patients of any age, protein-energy malnutrition greatly increases the risk for postoperative complications and overall mortality. This association between nutritional status and survival does not prove a casual relationship because poor nutritional status may be the result of the illness or the injury and not its cause.

Several researchers have tried to correlate blood levels of vitamin C and mortality in an aging population. Among patients admitted to an acute care geriatric unit, those with low ascorbate levels had a significantly higher mortality.

Considerable evidence documents an age-related decline in immune competence. Certain of these changes resemble those induced by malnutrition. Thus, malnutrition is clearly related to impaired immune function in older people, and improved dietary intake can at least partially correct these impairments.

If nutritional deficiencies are related to impaired immune function in older people, correcting the deficiencies should improve this function. Among hospitalized patients, intensive nutritional support does increase immunocompetence. Among older people, dietary supplements have been associated with improved antibody responses to viral vaccines, and several studies have reported improved immune function as a result of zinc supplementation. The possible role of zinc deficiency in loss of immune function in older people has received considerable attention.

Whether mental functions necessarily decline with age is questionable, and whether dietary factors can influence mental status in older people is also uncertain. Although large population studies have reported gradual decreases in many mental functions with age, healthy, active older subjects do not display significant decrements. This discrepancy suggests that the reported decrements in mental function are not inevitable age-associated events, rather, such changes are secondary to the various diseases and physical conditions that frequently accompany aging.

Alzheimer's Disease

The prevalence of this disease increases with age, while only 5 to 8 percent of people age 65 and over are affected, 35 percent of those over age 85 are affected. The cost of institutional care alone for Alzheimer's disease patients is estimated to exceed $40 billion per year in direct costs and up to $80 billion per year if indirect cost are considered.

The causes of Alzheimer's disease have not been established, but potential risk factors include age, family history of Alzheimer's disease, and head injuries. Whether nutritional factors can alter the risk for this condition is not known. High concentrations of aluminum have been found in the neurofibrilla-containing neurons of deceased patients, suggesting a relationship between aluminum and Alzheimer's disease.

Because Alzheimer's disease is a neurodegenerative syndrome involving cell loss and dysfunction, and because there is evidence that nutrient variables can affect brain metabolism, it might be speculated that neuro-toxins acquired through the food chain may be involved in brain cell death.

Implications for Public Health Policy

Aging is accompanied by a variety of physiologic, psychologic, economic, and social changes that may compromise nutritional status. However, ways in which the aging process affects energy balance, specific nutrient requirements, and nutrient status remain to be fully elucidated. Older adults may not necessarily have the same nutritional requirements as younger adults, yet current estimates of the nutrient requirements of older persons are based almost entirely on values extrapolated from data from studies of younger adults. The ways in which nutritional status might influence changes in tissue and organ function change with age and may influence the relationships between dietary components and the occurrence of chronic diseases in old age. Until more appropriate age-specific RDA's are established, the current RDA's should continue to be used as standards for nutrient intake of healthy older people.

Older people should consume sufficient nutrients and energy and maintain levels of physical activity that maintain desirable body weight and may prevent or delay the onset of chronic disease. Because it is often difficult to maintain adequate nutrient intake on low-calorie diets, older people should be advised to maintain at least moderate levels of physical activity so as to increase caloric needs. Because many chronic diseases common to older people may originate earlier in life, dietary guidance to prevent them should be provided throughout life.

Older people who do not or cannot consume adequate levels of nutrients from food sources and those with dietary, biochemical, or clinical evidence of inadequate intake should receive advice on the proper type and dosage of nutrient supplements. Such supplements may be appropriate for some older persons, but self prescribed supplementation, especially in large doses, may be harmful and should be discouraged. Older people who suffer from diet-related chronic diseases should receive dietary counselling from credentialed health professionals, and those who take medications should be given professional advice on diets that minimize food-drug interactions.

Nutrition Programs and Services

Food Labels:
Evidence related to the role of diet in the aged currently holds no special implications for change in policy related to food labeling, although the size of the type on the label is a factor for most older consumers. Information provided on the food labels should be scientifically sound, understandable, and nonmisleading.

Food Services:
Food services, especially those receiving Government funds, should be required to pay attention to meeting the caloric and nutrient needs of older clients. Nutritional assessment and guidance should be done at hospital admission or enrolment in or discharge from institutional or community-based services for older adults.

Food Products:
Evidence suggests that older people would benefit from food products that provide a high proportion of available nutrients to calories, that have taste appeal, and that are easy to prepare.

  • The Surgeon General's Report on Nutrition & Health, 1988