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17 January 2012

The diets of older people: physiological changes

Our population is growing older and with increasing age, nutritional requirements tend to change and the type of dietary problems older citizens face, become more important.

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This is the first of a series of articles that Health24's DietDoc Dr Ingrid van Heerden has written specially aimed at the nutrition of the elderly.

Thanks to advances in medicine, an improved diet and better living conditions, the percentage of people who live to three score and ten, is growing exponentially. In 2001, it was already estimated that 2.9 million South Africans were aged 60 and older. According to predictions the number of senior citizens is expected to increase even more so that the growth rate of the 60+ age group will exceed the growth rate of the total population (Charlton et al, 2001). 

Our population is, therefore, growing older and with increasing age, nutritional requirements tend to change and the type of dietary problems older citizens face, become more important. In this introductory article on "Diets for Seniors", we will consider the physiological changes that occur with ageing that have a drastic effect on the diet and nutrition of our senior citizens.

Physiological changes

Problems associated with the mechanical action of eating which may occur with increasing age that can affect nutrient intake, are as follows:

a) Digestion

Impaired digestion due to:

  • Deterioration of digestive enzyme production and efficiency (for example. a decrease in the amount of lactase enzyme required for the digestion of lactose can occur, which hampers digestion of dairy products and thus decreases calcium intake and absorption ultimately resulting in osteoporosis)
     
  • A decrease in the production of stomach acid (hypochlorhydria), which can occur in up to 30% of older people, leading to lower absorption of vitamin B12 thus causing pernicious anaemia, or bacterial overgrowth in the small bowel which also causes nutrient malabsorption
     
  • Constipation which is a common affliction in the aged due to slower bowel movements caused by inadequate liquid and dietary fibre intakes, and a sedentary lifestyle. Studies have shown that elderly people who suffer from constipation tend to eat fewer meals per day, drink too little liquid, ingest too little energy and suffer from depression. Many medications that are taken on a regular basis by our senior citizens, can also contribute to constipation.
    (Mahan & Escott-Stump, 2000)

b) Mouth and teeth

Oral health problems:

  • Dry mouth or xerostomia due to inadequate production of saliva can affect more than 70% of the senior population and has a significant negative effect on food and nutrient intake. Xerostomia makes chewing and swallowing difficult and leads to avoidance of dry, crunchy or sticky foods.
     
  • Loss of teeth and ill-fitting dentures can seriously affect an older person’s ability to chew food. In fact people who wear dentures are known to chew up to 85% less efficiently than individuals who still have their own teeth! Lack of own dentition can make older people avoid eating meat, fresh fruit and vegetables which causes energy, iron, vitamin C and beta-carotene deficiencies.
    (Mahan & Escott-Stump, 2000)

c) The 3 senses

Loss of sensory perception

  • Reduced taste perception (dysgeusia) and impaired ability to smell (hyposmia) occur commonly in older persons often as a result of factors such as Alzheimer’s disease, medications, surgery, radiation therapy and the normal ageing process. Because seniors have an impaired ability to taste and smell their food, they get less pleasure from eating which can reduce food and nutrient intake; it can also expose older people to the risk of food poisoning because they are not able to taste or smell when a food is spoiled. The lack of these two senses also blunts the metabolic responses of the body, which react to the stimulation of taste and smell, such as the secretion of saliva, gastric acid, pancreas enzymes and insulin.
     
  • Deterioration or loss of sight may also negatively affect food intake because part of the pleasure of eating, is associated with the visual appeal of foods. 
    (Mahan & Escott-Stump, 2000)

d) Metabolism

  • Reduced glucose tolerance
    With each decade of life, our blood glucose levels increase by 1.5 mg/dL thus leading to reduced glucose tolerance and in severe cases to the development of type 2 diabetes
     
  • Reduced resting metabolic rate (RMR)
    As people age and become less physically active their RMR (the energy the body uses to fuel processes like breathing, digestion, blood circulation, etc) can decrease by up to 20%. This means that older people have a lower dietary energy requirement. If they continue to eat as much food as when they were younger and more active, the excess energy will be stored in the form of fat causing overweight and obesity. 
     
  • Deterioration of cardiovascular function
    Older people, particularly women, are more prone to hypertension (high blood pressure) because their blood vessels become less elastic. Raised cholesterol levels are also common leading to heart disease and heart failure. Factors such as obesity, alcohol intake, smoking and diabetes contribute signficantly to an increased risk of cardiovascular disease in seniors.
     
  • Reduced kidney function
    The deterioration of kidney function in older persons can be severe, with up to 60% of normal renal function being lost between the ages of 60 and 80 years. Older persons are thus less responsive to changes in fluid status and the so-called acid-base balance of the body. High protein intakes may overburden the renal system and cause a build-up of protein waste products and electrolytes (e.g. potassium and sodium). 
     
  • Reduced lean body mass, increased body fat
    Among the greatest challenges that older people face, are loss of lean body mass (muscle tissue) and increase in body fat. This loss of muscle tissue or sarcopenia amounts to a decrease of 2 to 3% per decade and contributes to a deterioration in physical function. On the other hand, the body fat percentage in men tends to increase from 15% in youth to 25% at the age of 60 years. In women the increase is even greater, namely from 18-23% in youth to 32% in 60-year-olds. These changes in body composition are due to hormonal changes (lower testosterone production in men, menopause in women), and a reduction in physical activity associated with the ageing process.
    (Mahan & Escott-Stump, 2000)

It is evident that as we grow older our bodies change and deteriorate and that this has a drastic effect on our nutrient and dietary requirements. Next week we will look at how Senior Diets can make provision for these changes to ensure that our ageing population can enjoy their "Golden Years" in good health.

References:
(Mahan LK, Escott-Stump S. 2000. Krause’s Food, Nutrition & Diet Therapy. 10th Ed. WB Saunders Co, Philadelphia; Charlton KE et al, 2001. Poor nutritional status in older black South Africans. Asia Pacific Journal of Clinical Nutrition, Vol 10(1):31-38).

- (Dr IV van Heerden, DietDoc, June 2010)


Any questions? Ask DietDoc


Read more:

Nutrition and the elderly: Coping with eating problems
Good nutrition beyond your 60s


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