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
