Causes of malnutrition
The “anorexia of ageing”6,7
Appetite and food intake often decline with ageing. Older people tend to be consistently less hungry than younger people,
eat smaller meals, have fewer snacks between meals and also eat more slowly.8 Between age 20 and 80 years,
there is on average, a decrease in energy intake of approximately 30%. When this decline in energy intake is more than
the decrease in energy use that is also normal with ageing, then there is loss of weight.8
Most people lose weight as they age, but the amount lost is variable and those that are already lean, also lose weight.
The problem with this weight loss is that it is not only unwanted adipose tissue that is lost but lean skeletal muscle.9 The
loss of lean tissue is associated with reductions in muscle function, bone mass and cognitive function, anaemia, dysfunction
of the immune system, slow wound healing and recovery from surgery, and consequentially an increase in both morbidity
and mortality.8,9 Although lean muscle can be regained in younger people this is often not the case for elderly
people. This means that being underweight becomes more of a health problem in older age, than being overweight.
Increasing age has several effects on gastrointestinal function. Secretion of gastric acid, intrinsic factor and pepsin
is decreased, which then reduces the absorption of vitamin B6, B12, folate, iron and calcium. Other gastrointestinal problems
such as gastritis and gastrointestinal cancers can reduce nutritional status.10
A hypermetabolic state where there is increased resting energy use can be caused by acute respiratory or urinary infections,
sepsis, cirrhosis of the liver, hyperthyroidism and the hyperactive state found in some people with dementia or Parkinson’s
disease.10 Chronic obstructive pulmonary disease (COPD) can cause anorexia and physical problems related to
shortness of breath (see here).
In addition to the “anorexia of ageing”, there are physical, social, cultural, environmental and financial
reasons for an inadequate diet.1,8
Poor appetite: illness, pain or nausea when eating, depression or anxiety, social isolation or living
alone, bereavement or other significant life event, food aversion, resistance to change, lack of understanding linking
diet and health, beliefs regarding dietary restrictions, alcoholism, reduced sense of taste or smell.
Inability to eat: confusion, diminished consciousness, dementia, weakness or arthritis in the arms
or hands, dysphagia, vomiting, COPD, painful mouth conditions, poor oral hygiene or dentition, restrictions imposed by
surgery or investigations, lack of help while eating for those in hospitals and rest homes.
Lack of food: poverty, poor quality diet (home, hospital or rest home), problems with shopping and
cooking, ethnic preferences not catered for, particularly in hospitals and rest homes.
Medicines: medicines can alter nutritional status in numerous ways, e.g. anorexia, decreased or altered
taste, dry mouth, confusion, gastrointestinal disturbance including nausea, vomiting, diarrhoea, constipation, dyspepsia.
Incorrect use of medicines may also cause problems, e.g. hypermetabolism with thyroxine and theophylline.10
Impaired digestion and/or absorption: Medical and surgical problems affecting stomach, intestine, pancreas
and liver, cancer, infection, alcoholism
Altered requirements: Increased or changed metabolic demands related to illness, surgery, organ dysfunction
Excess nutrient losses: Vomiting, diarrhoea, fistulae, stomas, losses from nasogastric tube and other
Illness related Malnutrition: Some disease states also increase the risk of malnutrition. For example
chronic respiratory, gastrointestinal, liver and kidney diseases, cancer, HIV, AIDS, stroke and surgery.1
Surgery: The metabolic changes caused by surgery, the increased demands required for successful healing,
sepsis and the stress of the surgical procedure itself, all increase energy needs.11 To supply this energy,
protein stored as muscle is broken down and amino acids released. A septic state will increase this muscle breakdown further.
Nutritional requirements must meet these increased needs. Furthermore, patients may already be malnourished due to the
illness that led to their surgery.
Once discharged, there will be ongoing higher nutritional needs during the recovery phase, although muscle lost may
never be regained. Oral nutritional supplements may be useful during the recovery period, particularly if there are modifications
to dietary intake as a consequence of the surgery, e.g. texture modification, low residue diet.
Cancer: People with cancer are often malnourished. Physical and metabolic changes can be compounded
by social and psychological problems.12 Treatment adverse effects such as taste changes, nausea or swallowing
difficulties also result in a reduced food and nutrient intake. Cancer may result in cachexic syndrome which is a state
of complex metabolic changes associated with anorexia, progressive weight loss and depletion of reserves of adipose tissue
and skeletal muscle. Weight loss adversely affects treatment tolerance and survival outcomes.
Nutritional advice tailored on an individual basis should be given at an early stage to help prevent nutritional deficiencies.13 Loss
of appetite, pain, nausea and vomiting all contribute to poor oral intake. Prednisone may be used to stimulate appetite,
but its effect tends to be short lived.14
Oral nutritional supplements can be beneficial when a normal balanced diet cannot be tolerated. These supplements help
prevent malnutrition but eventually cannot halt the cachexic state associated with many end-stage cancers.
Chronic Kidney Disease (CKD)15 Nutritional requirements for people with CKD vary widely.
In general, they require a diet that promotes adequate nutrition, minimises biochemical abnormalities and delays the progression
of CKD. In later stages of CKD appetite is often poor and there is a high risk of malnutrition.
Guidance should be given to ensure the protein intake meets the recommended daily intake for the patients’ age
and gender and adequate energy is consumed. Micronutrients such as potassium and phosphorous should only be restricted
if blood levels are elevated. The aim of treatment is to prevent malnutrition.
People requiring haemodialysis have some differing needs – they require 1.2 – 1.4 g/kg/day of protein due
to losses in the dialysate. Some people may require adjustment of micronutrient intake, but this is dependent on the individual’s
clinical and biochemical profile.
There are specialised renal nutritional supplements available on the Pharmaceutical Schedule. These are indicated for
patients requiring volume and potassium restrictions. For many patients, standard oral nutritional supplements will be
suitable in the first instance.