Chapter 31 NUTRITION



While eating has psychosocial and cultural significance in life, the major roles of food intake are to provide nutrients necessary for the development and growth of cells and the replacement of substances required by cells to maintain efficient body function. Information about the ingestion and digestion of food and the absorption of nutrients, is provided in Chapter 33. After the digested nutrients have been absorbed into the blood and lymph, they are distributed to the cells for further chemical processing, which releases the energy necessary for body function. The process of metabolism converts the nutrients into chemical forms that produce energy and rebuild body tissue. The two phases of metabolism are anabolism (or constructive phase), when simple substances derived from the nutrients are converted into complex substances that can be used by the cells; and catabolism (or destructive phase), when these complex substances are reconverted into simpler forms to release the energy necessary for cell function.

The term nutrition is used to describe all the processes by which the body uses food for energy, maintenance and growth. Nutritional requirements vary in response to changes throughout the lifespan. Factors that increase the body’s metabolic demand include the periods of rapid growth during infancy and adolescence, pregnancy and lactation, increased physical activity, and periods of stress, disease or trauma. Metabolic requirements diminish with reduced energy demands, decreased physical activity and age.

Adequate nutrition is partially dependent on the ability of the body to ingest and digest food, to absorb nutrients from the intestine and to excrete waste products. In addition, the quality and quantity of food consumed has an important influence on a client’s current and future health status. A diet containing the essential nutrients for each stage of the lifespan is vital to maintain wellbeing.

Many factors influence a client’s pattern of eating, and include:


A client’s nutritional status is assessed by obtaining information about their appetite, food preferences, height and weight and level of activity, and from observing their general appearance. Observation of a client’s general appearance provides information about their general state of health and their nutritional status. Some characteristics of altered nutritional status are presented in Table 31.1. Assessing the client’s eating pattern and their nutritional status may identify problems or risk factors.


General Cachexia, hepatomegaly, splenomegaly, cardiomegaly, weight loss or gain
Hair Dull, dry or brittle hair; hair thinning or loss
Nails Brittle, broken, ridged or spoon shaped. Pale nail bed
Skin Dry or scaly, bruising or petechiae unrelated to trauma, ulceration, abnormal colour changes, dermatitis
Oral mucosa Pale mucous membrane, ulceration and cracking, ketone-smelling breath
Lips Angular stomatitis, cheilosis
Tongue Swollen or smooth tongue, atrophic papilla, cracking or fissuring
Gums Spongy and/or bleeding gums, gum recession
Teeth Mottled, dental caries, absent teeth
Conjunctiva Pale to reddish-pink
Vision Diminished visual acuity or loss
Cardiac Tachycardia, cardiomegaly, palpitations, angina
Muscles Muscle wasting, atrophy, diminished strength or tone, constipation
Skeleton Curvature of arms or legs, altered gait, shortened stature, fractures
Neurological Altered mood or affect, reduced concentration span, coordination, sensory or motor activity and reflexes, vision loss
Urine Ketonuria, urobilinogen, haemoglobinuria, haematuria

In addition to the physical characteristics associated with poor nutritional status, psychological symptoms may be evident. A client with a poor nutritional status may experience irritability, lethargy, apathy or inability to concentrate. It is possible, however, that these symptoms and the physical signs presented in Table 31.1 may be related to an underlying condition and/or the client’s nutritional status.

Certain groups of clients may be more at risk of a poor nutritional status, including those who are:

To maintain or promote an appropriate intake of food and therefore a good nutritional status, clients should be encouraged to follow the principles of a balanced healthy diet that provides the body with essential nutrients.


A healthy balanced diet is one that consists of foods taken regularly, in sufficient quantities, from each of the basic food groups. A healthy balanced diet is a diet that is composed of 60% carbohydrate, 20% protein and 20% fat. The recommended number of daily servings from each of the five food groups varies slightly according to the client’s stage of development. The five food groups and the recommended daily allowances (RDAs) are:

Nutritional needs of infants and children

Throughout all stages of development, a healthy balanced diet is necessary to provide the nutrients required for the body’s needs. For information on maternal and newborn nutrition, see Chapter 49.

Solids are generally introduced when an infant is about 6 months old, but this varies according to the infant’s needs and development. The term educational diet is sometimes used to describe the gradual introduction of solids. The aim of introducing solids is to wean the infant off milk to prevent such problems as failure to thrive, malnutrition and anaemia, and also to educate the palate to different tastes and textures; eating therefore becomes largely a learning process. Rice cereal, pureed stewed fruit and vegetables are suitable first foods. Because food allergies can be a problem during infancy, it is important that single-ingredient foods are introduced one at a time. If an infant has an adverse reaction to a food, it can then be readily identified and eliminated from the diet. By 6–8 months of age, chewing movements begin and the infant can be introduced to coarser-textured foods.

When the infant begins to grasp objects and put them in their mouth, they may be ready to be introduced to finger foods. When an infant can take fluids from a cup, at about 7–8 months of age, fruit juice may be introduced. Giving fruit juice from a bottle should be discouraged, as this may contribute to the development of jaw and tooth deformity and dental caries, and excessive volumes of fruit juice may result in diarrhoea.

At about 12 months of age the infant should be eating a range of basic foods. The diet should consist of bread and cereals, fruit and vegetables, meat and/or other protein foods, milk and/or milk products and small amounts of butter or margarine. Salt, sugar and fatty foods should be avoided.


From 10 years of age, children’s bodies are developing rapidly to prime the body for reproduction. A pre-puberty growth spurt occurs earlier in girls than in boys, as they store more fat, which initiates adolescence faster (see Chapter 16 for further information). During this time there can be major changes in their selection and volume of food; hormones alter senses such as taste to enable the adolescent to adapt to obtain changing nutrient requirements. Some clients at this age may be vulnerable to self, peer and social influences that may alter their perception of appearance and self-worth and drastically modify their eating habits (see ‘Eating disorders’, later in this chapter).


In addition to the consumption of foods from the five food groups that provide the essential nutrients, dietary requirements need to be considered in terms of energy requirements. Energy is needed for all the chemical and physical activities of the body, such as muscular activity, production of glandular secretions and the synthesis of substances in cells. The amount of energy required by a client is the amount necessary to maintain physiological processes and depends on factors such as age, sex, climate, body build, height and weight, level of physical activity, and usual function or dysfunction.

Energy requirements are increased during periods of rapid growth, for example, during pregnancy, infancy and adolescence and when a person engages in a high level of physical activity. Certain types of body dysfunction, such as hyperthyroidism — a disorder of the thyroid gland — can also increase the amount of energy required. Energy requirements are decreased when a client’s level of physical activity is low, with certain metabolic conditions, such as hypothyroidism, and during stages of development when there is little growth, such as old age.

The two units of measurement that specify the energy value of food are calories and joules. A calorie is defined as the amount of heat required to raise 1 gram of water by 1°C. A joule, which is the standard international (SI) unit of energy and heat, is equivalent to the amount of work performed when a 1 kg mass is moved 1 m by the force of 1 newton. One calorie is equal to 4.184 joules. As joules are very small units, it is more convenient to measure food energy in terms of kilojoules. One kilojoule (kJ) is 1000 joules. (For further units of measurement, see Appendix 2.)

The energy value of the three major types of nutrients are:

Energy expenditure varies with the level of physical activity a client engages in and ranges from about 5 kJ/min during sleep to about 120 kJ/min during heavy physical activity. When the intake of kilojoules is increased or energy expenditure is decreased, weight gain occurs. Conversely, loss of weight occurs when the intake of kilojoules is decreased or energy expenditure is increased.

Basal metabolism is the term used to describe the minimal maintenance of all normal body functions at rest and in the absence of disease. The amount of energy required to support basal metabolism is measured when a client is awake but at complete rest and has not eaten for at least 12 hours. The measurement is expressed as basal metabolic rate (BMR), according to the number of kilojoules consumed per hour per square metre of body surface area (or per kilogram of body weight). The BMR is one diagnostic test commonly used to estimate nutritional needs. Variations in the BMR between clients of the same weight and height may be due to alteration in body composition, such as muscle mass as opposed to fatty tissue, and the presence of certain disease states.

Appendix 7 gives reference ranges for acceptable weight for height for Australians. This table is based on body mass index (BMI) which is calculated using the following formula:

BMI = Weight in kilograms divided by height in metres2

For example, the BMI of a male who is 6 feet (1.83 metres) tall and weighs 115 kg is:


The value obtained when this formula is used should be rounded to the nearest whole number. A BMI value below 20 is common in certain ethnic groups, such as people of Asian descent, and in athletes, but otherwise indicates that a person is underweight. A BMI of 20–25 is within the healthy weight range. A BMI of 25–30 may indicate more muscular build or overweight, while a value of 31–40 is defined as moderate to severe obesity and a value above 40 signifies morbid obesity.


Nutrients are chemical substances in food that provide energy, build and maintain cells or regulate body processes. The essential nutrients are:


Dietary fibre, often referred to as cellulose, is the fibrous parts of food that the digestive system has difficulty in digesting. Fibre creates bulk in the stools, which enhances defecation and is used to prevent or minimise symptoms of certain disorders, such as haemorrhoids, diverticular disease, formation of gallstones, simple constipation and intestinal cancer. Foods with a high fibre content are fruits, vegetables and wholegrain products. Clinical Interest Box 31.1 provides discussion on the effects of constipation on the older client.


Vitamins are a group of organic compounds that, with few exceptions, must be obtained from dietary sources. Although they have no energy value, they are essential for normal metabolic and physiological bodily function. The term vitamin was first used in 1912, and letters of the alphabet were assigned to them as they were discovered. Now that more is known about their composition, the chemical name for a vitamin is frequently used.

Vitamins are classed as being either water or fat soluble. The water-soluble vitamins are easily destroyed during the preparation and prolonged cooking of food. If they are consumed in excess of the body’s need, they are excreted in the urine. Fat-soluble vitamins are oxidised by exposure to air, light and high temperatures. As fat-soluble vitamins are not soluble in water, any excess is stored in the body, and a condition known as hypervitaminosis may occur, which may result in organ failure.

Excessive intake of vitamin A over long periods can result in hypervitaminosis A, a condition characterised by yellow discolouration of the skin (often mistaken as jaundice), loss of appetite and dry itchy skin. Excessive intake of vitamin B may result in allergic-type reactions. Hypervitaminosis D may occur if excessive amounts of vitamin D are taken and is characterised by nausea, vomiting, diarrhoea, general irritability and severe impairment of kidney function. In normal circumstances a healthy balanced diet will provide the body with sufficient quantities of all vitamins without the need for supplemental vitamin ingestion. Table 31.2 describes the functions and effects of vitamin deficiencies.


A person’s normal diet depends on their age, pattern of eating and the food they choose. Dietary requirements may change during illness; for example, a client may avoid eating foods that cause adverse reactions such as indigestion, nausea or diarrhoea. The client’s diet may also need to be adapted as part of their treatment during certain conditions and disease states.

While acknowledging the factors that influence a client’s choice of foods and observing any restrictions to their diet in the management of disease processes, nurses should encourage the consumption of healthy balanced meals, following the principles of good nutrition. The principles of good nutrition are that:

People should become aware of the information contained on the labels of prepared and packaged foods. Notice should be taken of the expiry date, the presence of preservatives and other additives. The listing of ingredients on the container denotes the relative quantities of each, with the major ingredient listed first. The remainder are listed in order of decreasing quantities.

CLINICAL INTEREST BOX 31.2 High rates of malnutrition in elderly

A ground-breaking Australian study involving UNSW has revealed alarming levels of malnutrition in the elderly, with close to 80% malnourished or at risk when first admitted to hospital.

However, early intervention with a dietitian proved doctors could dramatically reduce length of hospital stay and health costs.

The findings follow a one-year study by a team of gastroenterologists, geriatricians and dietitians at Sydney’s Prince of Wales Hospital. The results will be presented at Digestive Diseases Week in Washington on May 19.

The study, led by President of the Gut Foundation, Professor Terry Bolin together with the Prince of Wales Department of Geriatric Medicine and Department of Nutrition and Dietetics, showed that when arriving for admission to hospital 80% of elderly patients were malnourished or ‘at risk’ but their hospital stay could be halved by implementing a nutritional care program. Professor Terry Bolin said:

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Feb 12, 2017 | Posted by in NURSING | Comments Off on NUTRITION

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