Nutrition of the Elderly
By: Charles DeFrancesco
http://www.fitandfunctional.com
Introduction
In many Western countries a proportional increase of the elderly population is seen. In January 1993, the elderly made up about 15% of the Dutch population;
57% of the elderly could be rated among the younger elderly (65–75 years old) and 43% among the very old (75 years and over). A large part of public health expenditure is allocated to medical care for the elderly. Prevention of disease among the elderly is considered an essential element in attempt to control the rising costs of public health. Good nutrition can play a prominent role in disease prevention.
This chapter focuses on the specific dietary requirements of the elderly. After a general introduction to the physiopathology of the ageing process, its consequences for the elderly’s nutritional requirements will be discussed. Information presented in this chapter was largely derived from MUNRO [1984] and a report recently issued by the Dutch Food and Nutrition Council [Voedingsraad, 1995].
Ageing and Ageing Theories
Ageing is accompanied by changes on every level from the molecule to the organism. Ageing can be defined as the sum of all changes taking place in the organism between conception and death. The progressive functional decline in ageing involves an increasing risk of death. The functional changes related to ageing include:
- a decline in quickness of response
- a changed motor and visual coordination
- a decreased interest
- a lowered oxygen consumption
- a decreased capability of adapting to altering conditions
- a decrease in basal metabolism
- a decreased kidney function
- a decreased immune response
- a decrease in gastric juice production
- a reduced feeling of thirst
These functional changes coincide with changes in body composition. The most relevant of these changes are:
- a reduced muscle mass
- an increased fat content
- a decline in extracellular fluid
- hardening of soft tissues
- atherosclerosis
- osteoporosis
Several theories of the ageing process have been proposed. Some of these focus on the decline of organ systems, such as the immune system or the neuroendocrine system, whereas other ageing theories concentrate on the cellular level including the DNA damage caused by free radicals. Genetic factors may also play a role in the ageing process.
No doubt the composition of the diet has its influence on the course of the ageing process. This role is reflected in the role of nutrition in the development of ageing-related diseases such as osteoporosis, type 2 diabetes, cardiovascular disease and cancer.
Two nutrition-based ageing theories have recently taken root: the free radical/ antioxidant theory and the energy restriction theory. The free radical/ antioxidant theory takes as point of departure the damage to tissues, membranes, DNA molecules and enzymes caused by free radicals (in particular oxygen radicals) which are highly reactive because they possess an unpaired electron. These radicals are formed throughout the body as a result of metabolic processes. The body possesses defence mechanisms whose effectiveness declines with age, resulting in a progressively increasing damage and functional decline.
Some feel that the intake of large amounts of antioxidants (vitamin C, vitamin E, b-carotene and other compounds) can retard the ageing process. However, scientific proof for this assumption is still to be awaited.
The energy restriction theory is not really an ageing theory but rather stresses the favorable effect of energy restriction on life expectancy and on the prevention of diet-related chronic diseases which can be of a neoplastic or a non-neoplastic nature. The favorable effect of energy restriction has consistently been found in rodent experiments and appears to be unrelated to the diet composition provided micronutrient supply is adequate. Energy restriction can retard, or even prevent, age-related alterations in immune system, body composition, energy metabolism, motor activity, kidney function, gene expression, composition of connective tissue and the neuro-endocrine system.
To what extent energy restriction is relevant to life expectancy and ageing in man is still unclear. Both a low and a high body mass index (BMI) are associated with elevated mortality rates and no clear-cut relations have been found in the normal BMI range. A recent study by the TNO Nutrition and Food Research Institute into the feasibility and effects of energy restriction in non-obese middle-aged men revealed favorable effects on blood lipid composition without negative side-effects on mental or physical performance parameters.
The Diet of the Elderly
Energy and Protein
Basal metabolism declines with age, as does physical activity. The third factor in energy requirement, food-induced thermogenesis, probably remains unaltered. Although energy requirements decrease with age (Figure 11), no evidence has been found for lowered micronutrient requirements in the elderly relative to younger adults. This implies in practice that the diet of the elderly needs to have a higher nutrient density than that of younger adults. There is little to suggest that protein requirements increase with age. However, obligatory nitrogen losses have been found to be closely correlated with basal metabolism. This could imply that these losses are lower in the elderly than in younger adults. It seems a plausible assumption, however, that the elderly have a lowered utilization efficiency for dietary protein, which makes it probable that the elderly do not have a lower protein requirement than younger individuals. Elderly people usually have a negative protein balance which reflects a decrease in muscle mass. A negative protein balance in the elderly probably cannot be prevented by increasing the protein content of their diet. Loss of muscle mass can best be prevented by physical activity.
Fats and Carbohydrates
A large proportion of independently living elderly people in the Netherlands have too high a percentage of body fat (>30% for men, >40% for women) at an average fat intake. On average, the composition of dietary fat certainly does not meet the guidelines of the Dutch Food and Nutrition Council which recommends an intake of saturated fatty acids not exceeding 10% of total energy intake and a total fat intake not higher than 30–35% of total energy intake.
Food products rich in complex carbohydrates usually are also a rich source of micronutrients and dietary fiber. Dietary fiber is an essential element in the diet of the elderly who frequently suffer from constipation, which is prevented by dietary fiber.
The diet of most elderly people is relatively rich in protein and fat and low in carbohydrates, in particular the complex types. The reason is that, given their lowered energy requirement, the elderly are inclined to stick to the favorite bits in their daily diet. Mostly these dishes are rich in fat and protein (meat, biscuits, cheese, desserts and so on).
Vitamins
Special attention in the elderly’s nutrition should be given to vitamin D and vitamin B-6. There is no convincing evidence for serious deficiencies regarding the other vitamins in apparently healthy elderly. Elderly people who are rarely exposed to sunlight are at serious risk for vitamin D deficiency unless they take supplements. Vitamin D deficiency may result in insufficient utilization of dietary calcium and hence in a loss of calcium from their bones and an elevated risk of fractures. Elderly people who are never exposed to sunlight need supplements providing 400 IU vitamin D daily. Such a quantity of vitamin D cannot be provided by a regular diet.
Several population surveys have demonstrated low plasma pyridoxal 5´-phosphate (PLP) in the elderly. These low PLP levels could be responsible in part for the reduced immune response commonly seen in the elderly. It remains to be established to what extent the low PLP levels in elderly people are a consequence of an inadequate vitamin B-6 intake or of an altered protein metabolism.
Minerals and Trace Elements
Calcium is certainly the mineral attracting most attention in the elderly’s nutrition. Calcium deficiency is said to be associated with osteoporosis. It is highly improbable, on the other hand, that a calcium intake exceeding the recommended level of 800–1000 mg/day can be of much benefit. Physical activity is probably the most effective way of preventing osteoporosis in the elderly. Mechanical stress has a favourable effect on bone mass, whereas a lack of mechanical stress accelerates bone decalcification.
Water
The lowered kidney capacity (urine is less concentrated) and the reduced feeling of thirst render the elderly prone to dehydration. Besides, the elderly’s environment usually has a high temperature and a low relative humidity. An inadequate water supply, whether or not accompanied by a lack of physical activity, may give rise to constipation.
Diet and Medicines
The frequent use of medicines may have its consequences for the elderly’s nutritional status because of interactions between medicines and nutrient metabolism. A detailed discussion of this subject would be beyond the scope this chapter. Briefly, it can be stated that:
- Almost all medicines may give rise to complaints varying from lessened senses of taste and smell to nausea, vomiting and diarrhea or constipation, which may lead to a reduced food consumption;
- Diuretics increase the loss of minerals and fluid;
- Some laxatives may increase fecal losses of water and micronutrients.
References
Munro H.N. [1984]. Nutrition and the elderly: a general overview. J. Am. Coll. Nutr. 3: 341–350.
Voedingsraad [1995]. Advies voeding van de oudere mens, opgesteld door de Commissie
Voeding van de oudere mens, Den Haag.