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Nutrition support 1: risk factors, causes and physiology of malnutrition

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This article discusses the risk factors, causes and physiology of malnutrition

Alison Shepherd, RNutr, MSc, BSc, RGN,
is lecturer in adult nursing and nutrition, De Montfort University, Leicester.

Shepherd, A.
(2009) Nutrition support 1: risk factors, causes and physiology of malnutrition. Nursing Times; 105: 4, 18–20.

This is a two-part unit on nutrition support. Levels of malnutrition are increasing in all age groups. This is a major clinical and public health concern that is often unrecognised and untreated. The British Association for Parenteral and Enteral Nutrition published a report last month, which recommended that all patients should be screened for malnutrition on admission to hospital with follow-up monitoring.

Malnutrition is largely a treatable condition. Therefore, prompt identification, prevention and treatment are vital. Part 1 of this unit outlines the prevalence of malnutrition, its aetiology and the assessment tools to identify those at risk. It also provides a definition of nutrition support with a brief overview of the types of support available.

Learning objectives

  1. Know the definition of malnutrition and be able to describe the different types.
  2. Understand the causes and contributory factors of malnutrition.


Nutrition is essential for life. If a person is unwell, both diet and fluids of the correct types are required, in the correct amounts and at the right time, to enable recovery.

Malnutrition is a nutrient-deficiency state – whether of protein, energy or micronutrients – that causes measurable harm to body composition, function and clinical outcome (NICE, 2006).

It has two forms:

  • Kwashiorkor – this results from a diet that has adequate energy intake from carbohydrates but inadequate protein intake;
  • Marasmus – a state of malnutrition with both inadequate protein and energy intake.

Underweight (BMI<20kg/m2) is typically present in 10–40% of patients admitted to hospital. Many patients are also reported to lose weight during hospital admission (British Society of Gastroenterology, 2006).

In the general population it is estimated that one in seven people aged 65 and over has a medium to high risk of malnutrition.

Prevalence of malnutrition is higher in those living in institutions compared with those living in their own homes (British Association for Parenteral and Enteral Nutrition, 2008).

Research also suggests that 70% of malnutrition in the UK is unrecognised and untreated, which is a significant cause for concern (Schenker, 2006).

BAPEN’s (2009) report, representing the views of 18 carer and patient groups, argues that information, care and treatment in this area often varies in quality and lacks continuity across health and care settings.

Risk factors for malnutrition

Anorexia – a loss of or decreased appetite – accounts for a large proportion of malnutrition in older people (Donini et al, 2008) and can occur for a variety of reasons. These can be divided into two main aspects:

  • Disease-related factors that reduce intake despite the availability of foods. This is thought to be the most common cause of malnutrition in the UK;
  • Inadequate availability of food, quality or presentation of food, which reduces intake (Thomas and Bishop, 2007).

Disease-related malnutrition

Any illness can have an adverse effect on a person’s appetite.

Reduced food intake may be secondary to symptoms of the disease, for example nausea, vomiting and pain (Stratton, 2003).

Loss of appetite may also be attributed to anxiety and depression (Barker, 2006).

People who take medications may also experience unpleasant side-effects that can ultimately reduce their dietary intake (Dunne, 2008). Recent studies report that the use of analgesics, in particular opiates, in outpatient settings can cause reduced appetite (Schuler et al, 2008).

Furthermore, Mathieu (2008) suggested that people taking proton pump inhibitors on a long-term basis may have an increased risk of gastric infection, which could also contribute to the development of malnutrition.

Many diseases can alter or increase nutritional requirements. Cachexia, characterised by dramatic weight loss, is a characteristic in diseases such as cancer, chronic heart failure and kidney disease (Bachmann et al, 2008). In patients with cancer, this is thought to be attributed to alterations in taste and smell, which contribute to loss of appetite (Hutton et al, 2008). Olfactory function is also impaired in patients with end-stage renal disease and may contribute to uraemic anorexia (Raff et al, 2008).

Dysphagia is a symptom that affects 15% of hospital inpatients (Nazarko, 2008). This may be attributed to neurological disorders, such as multiple sclerosis (Pasquinelli and Solaro, 2008).

Increased loss of nutrients or impaired digestion and absorption are also causes of malnutrition (Dunne, 2008). These symptoms mainly occur in patients diagnosed with gastrointestinal disease (Mork, 2007).

Patients placed on nil-by-mouth regimens are also at risk of developing malnutrition. While it is acceptable practice to prevent aspiration post-operatively, fasting regimens are not tailored for individual patients or the timing of their procedures (Webb, 2003). A recent review by Whiteing and Hunter (2008) examined some of the ways in which nurses can enhance patients’ optimal nutritional status during times of fasting.

It is also important to note that tooth loss affects general health and is considered to be a risk factor for malnutrition (Musacchio et al, 2007). People without teeth have difficulty in chewing foods with dentures, which is also associated with compromised nutritional status.

Other risk factors for malnutrition in older hospital patients are their decreased lean body mass and other factors that compromise nutrient and fluid intake (Volkert et al, 2006). These include hospital catering limitations and poor oral hygiene (Patel and Martin, 2008).

Socioeconomic factors

According to Stratton (2007), socioeconomic causes of malnutrition are multifactorial. Such factors include geographical problems, for example difficulties in accessing shops, and increasing frailty contributing to difficulties in preparing and cooking meals (Thomas and Bishop, 2007). Poverty and deprivation both have a significant bearing on the development of malnutrition, particularly in older people (Barker, 2006).

In longer-term elderly care settings, Sloane et al (2008) suggested that close attention should be paid to the presentation of food, making it look and taste more appetising. Close attention should also be paid to making the eating environment within care settings pleasant, with opportunities for social interaction (Thomas and Bishop, 2007).

It is also thought that living and eating alone diminishes food consumption. Hughes et al (2004) highlighted this as a particular problem in older men who live alone.

Physiology of malnutrition

The energy requirements of a healthy person vary depending on a number of factors including: age; gender; body composition; current and past nutritional status; and basal metabolic rate (BMR). BMR may be defined as the metabolic activity required for the maintenance of life including respiration, heartbeat and body temperature.

When people experience illness, injury or surgery, their BMR increases. This causes metabolic stress, which, if uncontrolled, can lead to weight loss and eventually malnutrition (Weekes, 2007).

Without sufficient energy, protein stores in the body are mobilised from skeletal muscle, resulting in loss of lean body mass. This protein is broken down via biochemical oxidation to meet the body’s increased energy needs. If the person’s diet does not contain enough protein, this will lead to a negative nitrogen balance (Bongers et al, 2007). A positive nitrogen balance is essential for tissue repair after illness or major trauma (Soeters et al, 2004).

Consequences of malnutrition in adults

Malnutrition carries both economic and clinical risks. This burden of disease has been shown to double the risk of mortality in hospital patients and triple mortality rates in older people, both in hospital and following discharge (Stratton and Elia, 2007).

These authors also estimated that malnutrition alone costs the NHS£7.3bn annually. Box 1 highlights some of the general complications found in malnourished people.

Box 1. Complications of malnutrition

  • Delayed recovery
  • Impaired immunity leading to sepsis
  • Impaired wound healing
  • Impaired gastrointestinal tract function
  • Muscle atrophy
  • Impaired cardiac function
  • Impaired respiratory function
  • Reduced renal function
  • Increased risk of falls
  • Apathy, depression
  • Impaired psychosocial functioning
  • Altered sleep patterns
  • Impaired thermoregulation, increasing the risk of hypothermia
  • Atrophic skin, leading to pressure ulcers

Sources: National Patient Safety Agency (2008); Stratton et al (2003); McWhirter and Pennington (1994)

Screening for malnutrition

Although nurses are in a prime position to identify and treat malnutrition, it is not solely a nursing responsibility (RCN, 2007).
To this end, the National Patient Safety Agency (2008) suggested that all organisations should have a nutrition steering group with representatives from all staff groups involved in patient care. This group should include nurses, doctors, dietitians, pharmacists and other healthcare professionals (NPSA, 2008).

The management of undernutrition involves screening and early intervention (Tran et al, 2008). Routine screening for malnutrition in high-risk groups in healthcare settings and for those in deprived areas should be a priority (Stratton and Elia, 2007). All hospital inpatients and those attending outpatient departments should be screened on admission and at first appointment. Screening should be repeated on a weekly basis for those in hospital (NICE, 2006).

In essence, nutrition screening should be a quick, simple, general procedure used by all healthcare professionals at the
point of first contact. However, this is not without its difficulties as there are more than 50 published nutrition screening
tools and many more unpublished ones in clinical use. Research has shown that many of these tools have not been tested for reliability or validity and lack an evidence base to substantiate their use within clinical practice.

Nutritional assessment is a more detailed, specific, in-depth evaluation of nutritional status by a qualified dietitian, so that a dietary plan can be implemented. The difference between assessment and screening is often misunderstood, which causes confusion.

NICE (2006) recommended that screening should assess BMI and percentage of unintentional weight loss. It should also consider the time during which nutrient intake has been unintentionally reduced and/or the likelihood of future impaired nutritional intake. For example, this could be highlighted by prolonged pre-operative fasting for specific clinical procedures (Whiteing and Hunter, 2008).

Recommended nutrition tools include the malnutrition universal screening tool (MUST) (BAPEN, 2007) and the simple two-step mini nutritional assessment tool (Wikby et al, 2008).

Nutrition support

The term nutrition support refers to the provision of adequate nutrients to meet the nutritional requirements of patients at risk of developing malnutrition (Barndregt and Soeters, 2005).

The result of nutritional screening should be linked to a care/support plan to ensure that patients receive the nutritional care they need (NPSA, 2008).

This treatment and care should take into account patients’ needs and preferences, based on their ability to consume normal food (Barker, 2006). All those with malnutrition, whether young or old, should be given the opportunity to make informed decisions regarding their care and treatment in partnership with healthcare professionals (NICE, 2006).

Nutritional support has many aims and these are outlined in Box 2.

Box 2: Nutrition Support

Nutrition support aims to:

  • Ensure an adequate energy intake to prevent weight loss and the subsequent metabolism of lean tissue to provide energy;
  • Prevent negative nitrogen balance, which is associated with loss of muscle/lean body mass, reduced immune response and impaired liver function;
  • Provide adequate micronutrients and trace elements to aid recovery and repair of tissues;
  • Maintain fluid balance to ensure the normal functioning of the renal, cardiovascular and respiratory systems.
  • Source: Barker (2006)

Types of support

There are two main types of nutrition support, namely enteral feeding and parenteral nutrition.

Enteral feeding includes the use of fortified foods, snacks and oral nutritional supplements (BSG, 2006). Enteral feeding can also be described as ‘the delivery of nutrients directly into the gastrointestinal tract via a feeding tube’ (Shepherd, 2006). This may include tube feeding via nasogastric or nasojejunal tube, oesophagostomy or percutaneous endoscopic gastrostomy (PEG).

Parenteral nutrition describes the IV administration of a solution containing essential nutrients, namely amino acids, glucose, fat, electrolytes, trace elements and vitamins (Hamilton, 2000). This may be in addition to oral or tube feeding or it may provide the only source of nutrition as total parenteral nutrition (TPN).

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