Chapter 10: Nutrition in health and illness

Good nutrition is fundamental to good health. It influences management in all branches of medicine. Modern people's health varies from the excesses of inappropriate nutrition, resulting in obesity and various degenerative disorders, to malnutrition and other deficiency states seen in those unfortunates deprived of nutrients.

The essential components of nutrition¹ can be classified as:

• macronutrients—proteins, fats and carbohydrates, which are interchangeable sources of energy and also water

• macrominerals—sodium, chloride, potassium, calcium, phosphate and magnesium

• micronutrients—water-soluble vitamins (e.g. C, B); fat-soluble vitamins (e.g. A, E, K); essential trace elements (e.g. copper, iodine, iron, zinc)

Nutritional factors may play a vital role in the causation of several of the major diseases, such as coronary artery disease, hypertension, diabetes and cancer.

Special diets are important in the management of many hereditary metabolic disorders, such as phenylketonuria and galactosaemia, and several other disorders such as coeliac disease.

Proteins are composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur and iron. They make up the greater part of plant and animal tissue and provide the amino acids essential for the growth and repair of tissue. Protein in the body in muscle, connective tissue and enzymes is constantly being broken down, while dietary protein is hydrolysed to amino acids that are both essential and non-essential. A complete protein is one that contains all the nine indispensable amino acids, namely, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Protein in animal products (fish, meat and milk) is of high quality and that in vegetable products is lower because of a limited supply of lysine (in cereals) and methionine and cysteine (in legumes).³ Vegetarian diets are usually adequate in protein, especially if the combining vegetable groups complement each other in basic amino acid groups. Diets that exclude all animal products may be inadequate, especially in children. Infants and children require 2–2.2 g protein/kg/day.

• High protein content foods—lean beef and lamb, chicken, fish, eggs, milk, cheese, soy beans

• Medium protein content foods—bread, spaghetti, corn, potatoes (cooked), rice (cooked), cabbage, cauliflower

Protein

Energy malnutrition

This is a deficiency syndrome with a reduction in all macronutrients, energy (kilojoules) and many micronutrients due to an inadequate intake of protein and energy foodstuffs.

It is commonly found in infants and children in developing countries but can occur in persons of any age in any country.

Clinically, protein-energy malnutrition has three forms:

1. dry (thin, desiccated)—marasmus

2. wet (oedematous, swollen)—kwashiorkor

3. combined—marasmic kwashiorkor

Marasmus

Clinical features:

• grossly underweight

• gross muscle wasting

• abdominal distension

• no fat

• hungry

• ‘old man's’ face

• no oedema

• normal hair

Caused by a diet low in protein and calories.

Kwashiorkor

Clinical features:

• oedema (feet first then generalised)

• ‘moon’ face

• anorexia

• hair pale and thinned

• apathetic

• skin changes

Caused by a diet low in protein with some carbohydrate, leading to hypoalbuminaemia.

Dietary carbohydrates include simple sugars, complex carbohydrates (starches) and indigestible carbohydrate (dietary fibre). Carbohydrates are the main source of dietary energy. The two most important crops feeding the world are rice and wheat, which are rich in starch. Starch and sucrose account for the majority of carbohydrates consumed in all diets. Carbohydrates that are available in food are:

• sugars—sucrose, lactose, maltose, glucose, fructose

• polyols—sorbitol, xylitol, maltilol, lactilol

• starch—amylose, amylopectin

• dextrose

As long as adequate energy and protein are provided in the diet, there is no specific requirement for dietary carbohydrate. A small amount—100 g/day—is necessary to prevent ketosis.³

The glycaemic index (GI)

The GI, which applies to carbohydrate foods, is a numerical index based on a reference point of 100. It is a measure of the capacity to increase postprandial glucose levels compared to a glucose load. The standard food is glucose, which is given an arbitrary level of 100.

The higher the GI, then the higher the rise in blood glucose level and thus the greater the insulin response. Low-GI foods may improve glycaemic control.

Low-GI foods (<55) include dense wholegrain breads, porridge, most fresh fruits, yogurt and low-fat milk. High-GI foods (>70) include sweet breakfast cereals, potatoes, white bread, watermelon, ripe bananas, dates, white rice and biscuits.

Dietary fat, which is composed mainly of fatty acids and dietary cholesterol, is the most concentrated source of food energy.²

Fatty acids are classified according to the number of unsaturated double bonds:

• nil—saturated (e.g. butyric and stearic acids)

• one—monounsaturated (e.g. oleic acid)

• more than one—polyunsaturated (e.g. linoleic acid, eicosapentanoic acid [EPA], docosahexanoic acid [DHA])

Polyunsaturated fatty acids (two or more unsaturated bonds) can be subdivided into:

• n-6 (e.g. linoleic acid, 2 unsaturated bonds; arachidonic acid, 4 unsaturated bonds)

• n-3—omega-3 fatty acids (e.g. alpha-linolenic acid, 3 unsaturated bonds; EPA, 5 unsaturated bonds; DHA, 6 unsaturated bonds)

The n-3 and n-6 polyunsaturated fatty acids with chain lengths of 18 or more are called essential fatty acids because they are required for vital body functions and animals, including humans, are unable to synthesise them.²

The proportions of saturated, monounsaturated and polyunsaturated fatty acids in the diet are important determinants of health and disease.² The current strategy is to reduce total fat intake and reduce saturated fats and increase unsaturated fats, especially n-3 polyunsaturated fats.

Fish oil contains omega-3 fatty acids, which are considered more potent than the omega-3 fatty acids found in plants. The value of omega-3 fatty acids in preventing cardiovascular mortality has been well proven. They have no effect on cholesterol levels but have a well-documented potent hypotriglyceridaemic effect.⁴

Cholesterol, which is a major constituent of cell membranes, is synthesised by the body and is not an essential nutrient. The plasma cholesterol level, and hence the amount of cholesterol in the diet, has been related to the development of atherosclerosis. However, other factors are related to the development and prevention of atherosclerosis. In the past decade, specific nutrients, especially plant sterols (phytosterols), soy protein and soluble fibre, have been shown to improve the plasma cholesterol profile, which has led to their appropriate inclusion in ‘designer’ foods targeting the health-conscious consumer market.⁴

The first step in nutritional assessment is to identify the high-risk patient.⁵ Those at high risk of nutritional insufficiency include those with a history of obesity, eating disorders, chronic illness, psychological disorders, the elderly, the institutionalised, trauma victims and those with long periods of hospitalisation, including major surgery. Of particular interest is the rate of growth and development in infants and children and the body composition in children and adults.

When taking the history it is appropriate to include a 24-hour recall of foods eaten and ideally get the patient to complete a symptom questionnaire that can then be linked to a computerised nutritional evaluation program, such as Nutricheck.⁵ Evaluate sunlight exposure.

A nutritionally focused physical examination should be performed on each patient at risk, with the emphasis on body weight, waist size, muscle wasting, fat stores and signs of micronutrient deficiencies. Examples of the latter include zinc deficiency, which affects taste and smell and the skin. Deficiencies of vitamins B6 and B12 cause neurological disorders, such as peripheral neuropathy.² Alcoholism and malnutrition affect many systems, including the gastrointestinal system. The oral cavity, especially the gums, teeth and buccal mucosa, are affected by vitamin B complex and vitamin C deficiencies. Bones and joints are affected in scurvy, rickets, osteomalacia and osteoporosis. The important anthropometric measurements include height and weight, skin-fold thickness and waist:hip circumference ratio (refer to CHAPTER 78). Laboratory investigations depend on the clinical examination and should be selective.

In order to help people make healthy choices, the health foundations of several countries have developed recommendations for eating a healthy diet.

The heart-healthy eating pyramid of the Australian Nutrition Foundation (2012)² has a simplified system, namely:

• Eat most—vegetables, dried peas, beans and lentils, cereals, bread, fruit and nuts

• Eat moderately—lean meat, eggs, fish, chicken (without skin), milk, yoghurt, cheese

• Eat in small amounts—oil, margarine, reduced-fat spreads, butter, sugar

The RACGP in its red book⁶ outlines dietary recommendations based on national guidelines. For adults this is summarised as follows.

Enjoy a wide variety of foods each day:

• five serves of vegetables and two serves of fruit

• lean meat, fish, poultry, eggs, tofu, nuts and seeds and/or alternatives

• grains and cereals, mostly wholegrain or high-fibre varieties such as bread, rice, pasta, oats and couscous

• drink plenty of water

Take care to:

• limit saturated fat

• limit salt intake

• limit alcohol intake

• limit sugars and foods containing added sugars, including soft drinks and commercial juice

• limit red meat to 3–4 serves per week and limit or avoid processed meat

• care for food: prepare and store it safely

• encourage and support breastfeeding

What is a serving?²

The following guides represent one serve:

This very impressive prospective, randomised, single-blinded, secondary prevention trial investigated the effects of a ‘Mediterranean’-type diet containing a plant oil rich in omega-3 fatty acids on 605 subjects who had survived their first heart attack. The control group were given a low-cholesterol diet with a mix of unsaturated fats. The intervention group had a diet higher in oleic acid, omega-3 fatty acid, fibre and vitamin C (olive and canola oils were used in food preparation). In this group, the cardiovascular mortality was reduced by 73%. This was far greater than the control group and also for groups taking lipid-lowering agents, and the benefit was independent of any reduction in cholesterol or triglycerides. One explanation is that the antioxidants and phytochemicals in the plant-based diet stabilise the endothelium of arteries.

Some consequent lessons for people with a high-lipid profile are:^4,7

• Eat more fish—at least 2–3 times a week.

• Switch to skim-based dairy products—low-fat milk and yoghurts.

• Eat plenty of fruit, vegetables, nuts and grain food.

• Use monounsaturated (olive) oils and perhaps margarine instead of butter. However, use these cooking oils lightly.

• Use alternative toast spreads, e.g. hummus, baked beans, lentils, salmon.

• Limit intake of dietary cholesterol (less than 300 mg/day). Eat less animal-based food, dairy products, eggs (limit two a week), saturated fats, bakery food, fast food.

The antioxidant issue is still controversial and unclear. Empirical observation of healthy communities over the years indicates good health outcomes, especially with cardiovascular status, in people having an optimal diet containing high levels of vitamins and minerals (especially from fruit and vegetables).

Food antioxidants (see TABLE 10.1) appear to protect against free radicals, which can suppress immunity.

Prime sources of antioxidants in food⁹

• Vitamin C—citrus fruits, berries, papaya, green leafy vegetables

• Vitamin E—seed-like cereal grains, nuts and oils (plants), eggs

• Beta-carotene—orange-coloured and dark-green leafy vegetables

• Selenium—grains, meats, Brazil nuts, fish

• Copper—cocoa, wheat bran, yeast

• Ubiquinone—meats, fish, peanuts

• Phytochemicals—soy, tea, green tea, herbs, apples, onions, cocoa

Folate-containing foods

• Green leafy vegetables—broccoli, spinach

• Wheat grain

• Wholegrain cereals

• Starchy beans—kidney and butter

• Peas, corn, cauliflower

• Nuts

• Avocado

• Liver

• Folic acid fortified foods (e.g. breakfast cereals)

These are rare in our society but can occur sporadically and are not rare in children in some third world countries or in refugees from these countries. Deficiencies tend to be seen as a specific disorder or as a multivitamin effect.

• Vitamin A (beta-carotene/retinol) deficiency causes night blindness and eye disease, as well as dryness with keratinisation of the conjunctivae and cornea. It causes growth retardation in children. Toxicity from overdosage of vitamin A is a serious problem.

• Vitamin B complex

  • – Vitamin B1 (thiamine) deficiency causes beriberi and also Wernicke–Korsakoff syndrome (typically in alcoholics).

  • – Vitamin B2 (riboflavin) deficiency causes growth retardation, dry scaly skin and angular cheilitis.

  • – Vitamin B3 (niacin, nicotinic acid) deficiency causes pellagra.

  • – Vitamin B6 (pyridoxine) deficiency may cause oral soreness, anaemia and CNS dysfunction.

  • – Vitamin B12 (cobalamin) deficiency causes pernicious anaemia and memory dysfunction.

• Vitamin C (ascorbic acid) deficiency is responsible for scurvy. Clinical features: weakness, malaise, fatigue, bleeding swollen inflamed gums, atraumatic haemarthrosis, impaired wound healing, impaired bone growth. One sign is the hyperkeratotic hair follicle with surrounding hyperaemia. Diagnosis by decreased plasma ascorbic acid and X-rays of bones and joints.

• Vitamin D (calciferols) deficiency causes rickets in children and osteomalacia in adults. Clinical features (rickets): impaired growth, skeletal deformities (bow legs, pelvis, ‘rachitic rosary’), inability to walk, bone pain (arms, legs, spine, pelvis), dental deformities, muscle weakness. In adults: muscle weakness, bone pain, bowing of long bones. Diagnosis: low plasma 25(OH)D₃ and phosphate; elevated PTH and alkaline phosphatase; X-rays of joints and long bones of leg.

• Vitamin E (tocopherol) deficiency causes no specific disease but may result in vague, undifferentiated symptoms and anaemia.

• Vitamin K (phylloquinone) deficiency is rare and can lead to an increased bleeding tendency.

• Folic acid deficiency is responsible for pernicious anaemia and neural tube defects in the fetus.

Certain foods can aggravate gout. These include:

• tinned fish (e.g. sardines, anchovies)

• organ meats (e.g. liver, pancreas, brain, kidney)

• alcohol (the major one)

• fizzy, sugary soft drinks

Gout often occurs in males after they binge drink in their late 20s or 30s. Beer is particularly problematic. It is useful to recommend an increase in water consumption. Since gout and hyperuricaemia have a proven association with coronary artery disease, a healthy heart prevention diet is advisable.

Diabetes is an endemic problem in many communities, particularly in Indigenous communities. It is thought that for every two people diagnosed with diabetes, there may be one who is not diagnosed. Prevention of diabetes is very important and diet can play a significant role in this.

As many as 30% of people who suffer from diabetes are now taking insulin and oral hypoglycaemic medications. However, if sufferers can maintain an ideal weight and control symptoms through diet, the need for medications is reduced. Exercise is also very important.

Dietary principles for preventing and control of diabetes include:

• Follow the healthy eating guidelines, especially in regard to fruit and vegetable intake.

• Keep to an ideal weight.

• Eat low-GI foods.

• Limit the consumption of fat and fatty products.

• Eat high-fibre, complex carbohydrates, such as starchy fibre foods, cereals and wholemeal bread.

• Avoid or limit simple carbohydrates (e.g. sugar, concentrated sweets).

• Spread the consumption of carbohydrates throughout the day.

• Make vegetables the main part of your diet.

In summary, the diet for both type 1 and type 2 diabetes is based on achieving ideal weight and following a diet of high-fibre carbohydrates with a low GI and low fat.

Obesity

Refer to CHAPTER 78 for information on management of obesity.

Iron-deficiency anaemia is a common problem in our society, particularly in children from 6 months to 2 years who have been given a lot of cow's milk. In such cases it is important to educate people about iron-rich foods and the quantities they need (see CHAPTER 22).

Healthy males and females

• No more than two standard drinks per day

• No more than four standard drinks on any single occasion

Young people

• People aged under 15 years should avoid alcohol altogether.

• People aged 15–17 years should delay drinking for as long as possible.

Pregnancy and breastfeeding

• No alcohol is the safest option.

Refer to CHAPTERS 21 and 108 for alcohol guidelines.

Coeliac disease occurs as a result of sensitivity to gluten. It is quite common and often undiagnosed. In some cases, it can occur after a bout of gastroenteritis. It can be treated with a gluten-free diet.

• For breakfast, exclude wheat, barley, oats and rye.

• Any food containing gluten (e.g. flour and bread) should be avoided.

• Any food containing hidden ingredients (e.g. stock cubes) should be avoided.

Common ones include:

• wine, particularly red wine

• cheese

• oranges

• tomatoes

• caffeine in some people

Other culprit foods might include amine-rich foods, such as bananas and avocados. It is helpful to ask patients to keep a diary to see if they can find links between what they eat and their migraine attacks. Some varieties of migraine are not linked to diet.

Important advice for treatment of constipation includes:

• Drink a lot of fluids, especially water and fruit juices.

• Eat foods with bulk and roughage (e.g. bran, fresh and dried fruits and wholemeal bread).

Foods that are high in roughage include (in order):

• bran

• carrots

• apples

• lettuce

• cabbage

• peas

• cauliflower

• bananas

• potatoes

Fruits are high in fibre and some are natural laxatives, such as:

• prunes

• figs

• rhubarb

• apricots

• pears

Studies show that most people do not eat enough fruit. According to a recent survey of Victorian schoolchildren, one-third did not have fruit during the day, one-third did have fruit and one-third only had it spasmodically.

The dietary advice for recurrent urinary calculi (CHAPTER 34) includes:

1. Drink at least 2 L of water every day, or more if there is increased fluid loss: this is the most important step.

2. Minimise consumption of foods that contain oxalate or uric acid. Foods that contain oxalate include:

   • chocolate

   • coffee

   • cola and similar ‘soft’ drinks

   • rhubarb

   • tea

   Foods that contain uric acid include:

   • beer

   • red wine

   • red meat

   • organ meats

3. Avoid milk in tea—calcium precipitates oxalate.

4. Avoid processed meats, organ meats (e.g. brain, kidney, liver and sweetbread), yeast spreads and other high-salt foods. Restrict salt intake.

5. Reduce animal protein consumption: restrict to one major meat meal a day (includes chicken and fish).

6. Add citrate-containing fruit juices to the diet, including grapefruit, apple and orange juice.

7. Eat a healthy diet of vegetables and fruit with a high fibre content.

The body needs small amounts of iodine to maintain normal function of the thyroid gland—crucial for normal growth and development. In iodine-deficient areas (in soil and water) there is a high rate of stillbirths, congenital hypothyroidism and cretinism. In adults, deficiency causes goitre and hypothyroidism. The usual intake of iodine in healthy persons is 100–200 mcg day, mostly from iodised salt. An adequate intake is 150 mcg/day with higher requirements for pregnancy (220 mcg) and breastfeeding (290 mcg).¹² Measurement is by urinary iodine levels (WHO replete level standard ≥100 mcg/L and ≥150 mcg/L in pregnancy¹²).

(See www.nhmrc.gov.au)

Encourage and support breastfeeding.

Children and adolescents need sufficient nutritious foods to grow and develop normally.

• Growth should he checked regularly for young children.

• Physical activity is important for all children and adolescents.

Enjoy a wide variety of nutritious foods.

Children and adolescents should be encouraged to:

• eat plenty of vegetables, legumes and fruits

• eat plenty of cereals (including breads, rice, pasta and noodles), preferably wholegrain

• include lean meat, fish, poultry and/or alternatives

• include milks, yoghurts, cheese and/or alternatives

Reduced-fat milks are not suitable for young children under 2 years, because of their high energy needs, but reduced-fat varieties should be encouraged for older children and adolescents.

• Choose water as a drink

Alcohol is not recommended for children.

In addition, care should be taken to:

• limit saturated fat and moderate total fat intake

  • – low-fat diets are not suitable for infants

• choose foods low in salt

• consume only moderate amounts of sugars and foods containing added sugars

Care for your child's food: prepare and store it safely.

(See www.nhmrc.gov.au)

Enjoy a wide variety of nutritious foods.

• Eat plenty of vegetables, legumes and fruits.

• Eat plenty of cereals (including breads, rice, pasta and noodles), preferably wholegrain.

• Include lean meat, fish, poultry and/or alternatives.

• Include milks, yoghurts, cheeses and/or alternatives. Reduced-fat varieties should be chosen, where possible.

• Drink plenty of water.

Also, take care to:

• limit saturated fat and moderate total fat intake

• choose foods low in salt

• limit your alcohol intake if you choose to drink

• consume only moderate amounts of sugars and foods containing added sugars.

Prevent weight gain:

• Be physically active and eat according to your energy needs.

Care for your food: prepare and store it safely.

Murtagh's Patient Education 7th edition:

• Diet guidelines for good health

American Society for Nutrition. <https://nutrition.org>