Diet and cognitive function in old age
The statement that “The central nervous system is exquisitely sensitive to its nutrient supply, and has profound effects on dietary intake” (Rosenberg, 2000) can be applied to the diets of elderly people.
On the one hand, many of the changes and losses of physical and psychological function that accompany old age will affect food intake, while on the other hand, an inadequate dietary intake will influence both the physical and the psychological function of the older generation.
Changes that occur with advancing age
The following age-related physical changes may influence food intake:
- Reduction in muscle mass leading to depressed energy needs, which in turn may result in a reduced intake of protective nutrients.
- Uptake of vitamin A in the body tissues slows down, so higher levels of vitamin A can occur in the blood, particularly in older people who take high doses of supplements that contain vitamin A. This can lead to hypervitaminosis A (see below).
- A decrease in immune function, which makes older people more susceptible to infections and diseases. To counteract this decline in immune function, higher intakes of certain vitamins and minerals may be required.
- Older skin is not able to manufacture as much vitamin D as young skin. Older individuals require more vitamin D and need to spend some time in the sun every day.
- Decrease in vitamin B6 utilisation, which increases the requirement for this vitamin.
- Reduced secretion of stomach acid that influences the absorption of vitamin B12, folic acid, calcium, iron and zinc. Supplementation may be required.
- Problems with eating (loss of teeth, ill fitting dentures, reduction in sensory sensitivity that reduces the sense of smell and taste), which can either expose older people to monotonous diets or make them select foods which have a low nutrient density (biscuits, sugar, cakes, white bread etc.).
- Financial problems, which curtail spending on nutritious food. Many old people do not have enough money to buy foods that supply a variety of protective nutrients. They may be forced to rely on highly refined staple foods, which lack proteins, vitamins, and minerals.
It is, therefore, not surprising that the majority of our senior citizens suffer from a variety of nutrient deficiencies which can predispose them to neurological problems and loss of cognitive function.
Vitamins and minerals
While most older people do not suffer from outright nutrient deficiencies, so-called sub-clinical deficiencies are common. These sub-clinical deficiencies are known to contribute to the decline in brain and nerve function associated with old age.
The following effects of vitamin deficiencies occur in seniors:
- Vitamin B1 (thiamine): Neurological decline which, if left untreated, can cause B1-deficiency syndromes such as the Wernicke-Korsakoff syndrome.
- Niacin (nicotinic acid): The deficiency disease associated with a lack of niacin is called pellagra, which can cause dementia in severe cases.
- Pantothenic acid: Degeneration of the fatty sheath that protects nerves.
- Pyridoxine (B6): Peripheral neuropathy and convulsions in severe cases.
- Folic acid: General irritability and depression
- Vitamin B12 (cobalamin): Peripheral neuropathy and dementia.
- Vitamin E: Degeneration of the central nervous system.
So we can ask if giving nutrient supplements to the elderly will improve their cognitive function? The answer is “Yes”, because a variety of studies have shown that supplementation with B complex vitamins, and/or vitamin E and minerals, improves memory and mental acuity.
However, diet experts throughout the world warn that indiscriminate intakes or overdosing with vitamin and mineral supplements in the elderly (any age group for that matter) should be avoided. Taking mega-doses of vitamins or minerals will generally not increase the positive effects obtained with moderate supplementation.
In addition, excessive intakes of most vitamins and minerals can cause negative side effects. For example, older people may develop hypervitaminosis A because uptake of this vitamin by the body tissues slows down.
Chronic hypervitaminosis A can result in headache, hairloss, cracked lips, dry, itchy skin, enlargement of the liver, and pains in the bones and joints. While most of these symptoms will disappear when the individual stops overdosing on vitamin A, some people may suffer permanent damage to their vision, liver and skeleton.
The solution is for people who are older than 50 to take a single multivitamin and mineral tablet on a daily basis. If you are responsible for the health of aged individuals, make sure that they are not buying additional vitamin and mineral pills from the chemist or health shop, as this could lead to overdosing.
It has been suggested that the RDA for protein prescribed for the older population is inadequate and that instead of 50 g of protein, they should be ingesting the same quantity as younger adults, namely 70 g per day. Protein foods are, however, expensive and many seniors cannot afford to buy meat, fish, eggs, milk and dairy products.
Research indicates that older people have an increased requirement for certain amino acids (tyrosine and tryptophan) and choline (usually obtained from lecithin), which act as precursors for brain chemicals. Adequate supplies of amino acids and choline can be obtained from the above-mentioned protein foods.
If geriatric patients are not able to eat sufficient quantities of healthy food, liquid meal replacements can be used to ensure that they are adequately nourished. Consult your dietician, chemist or doctor about the type of meal replacement your aged parent should use (e.g. high-energy or increased protein, or high-fibre, or vitamin and mineral supplemented products).
Be aware of the problems that your aged mother or father may have with buying, preparing and eating healthy, balanced food. Imagine how tragic it would be if your parent started to lose his/her cognitive abilities just because he/she can’t chew foods properly or has too little stomach acid to absorb important nutrients.
This may sound simplistic, but it is often the case in geriatric patients that small problems, for example, poorly fitting dentures or mouth sores, may make the patient averse to eating food that is difficult for them to chew. Consequently these patients start to subsist on white bread, biscuits, and liberally sweetened tea, which over time will cause sub-clinical nutrient deficiencies and result in mental deterioration. Be aware of these potential problems.
Loss of cognitive function and mental deterioration do not have to be the inevitable consequence of ageing. With the correct diet, and one multivitamin and mineral supplement a day, senior citizens can stay mentally alert for many years.