Last update: July 2016 - Please read disclaimer before proceeding

 

Dietary nutrient groups

The nutrients in food are divided into two main groups; those present in large amounts, called macronutrients, and those in small amounts, called micronutrients. The macronutrients consist of carbohydrates, fats, fibre and protein, while the micronutrients consist mainly of vitamins and minerals. The table below indicates the energy content and functions in the body of each of these groups. The roles nutrient groups play in causing and preventing illness in Western society are discussed in detail throughout this book. It needs to be emphasized that the majority of Australian diets are not nutrient deficient. In fact, most Australian diets contain too much energy and too much fat. There are, however, a few groups of people who are likely to have micronutrients deficiencies. This issue is discussed in the sections on micronutrients, vegetarian diets, and osteoporosis. The role of antioxidants in disease prevention is also discussed later in this section.

 

Function and energy content of nutrient groups

 

Nutrient

Foods sources

Energy content

Function / use

cal

kJ

Fat - Fatty acids

Mainly animal sources and vegetable oils.

9

37

Mostly stored as fat for later energy use by the body when needed. Also an integral part of cell membranes.

Fat - Cholesterol

Lambs brains, liver, eggs and some seafood.

Synthesis of body compounds including cell membranes and body chemicals, such as steroid  hormones.

Alcohol

Alcoholic beverages

7

29

Used for energy. Alcohol is not converted to fat but is metabolized to provide energy before fat and thus reduces the rate of fat breakdown.

Protein

Meats, fish, poultry, eggs, milk products,  cereals, nuts and legumes, including soy beans, lentils, beans and peas

4

17

Mostly used in the synthesis of body components. Only rarely used as an energy source, such as in starvation.

Carbohydrate -

Starches (complex carbohydrates)

Pasta, potato, breads, cereals, fruit, legumes

4

16

Provides energy for the body’s functions and some energy storage. It is usually stored as glycogen in the liver (and the muscle) but may be converted to fat if consumed in excess. (Glycogen is just many glucose molecules joined together.) The sugar that circulates in the blood and provides energy for the body is glucose. The brain relies almost solely on this glucose for energy and thus it is very important for blood glucose levels to be maintained.

Carbohydrate -

Simple sugars  (sucrose, glucose, fructose, lactose)

Fruit, honey and other sweet syrups

Fibre

Bread, cereals, vegetables, fruit.

0

0

Fibre keeps the bowel functioning normally and has a role in protection of the bowel from cancer causing substances. Soluble fibre can reduce blood cholesterol levels.

Vitamins and minerals

A wide variety of foods is needed, especially vegetables, fruit, low-fat dairy and lean meat.

0

0

They are essential for the synthesis of many body components, especially enzymes. These nutrients have no significant energy function. Some are also important antioxidants.

Water

Fluids, fruit and vegetables

0

0

70% of the body is composed of water.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The major groups listed in the above table (and other nutrition topics) are dealt with in detail in other sections of this web site. (Links to these sections are listed below.)

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Fibre in the diet   

Fibre is defined as any food that passes through the small intestine undigested. Having gone through the small intestine unchanged, all but the lignin component of the fibre (the toughest part) is at least partially broken down (fermented) by bacteria in the large bowel. This process adds bulk to the faeces.
Dietary fibre can be divided into two types – soluble fibre, which can be dissolved in water in the gut forming a viscous solution that adds bulk to the faeces, and insoluble fibre, which can not be dissolved in water. Most fibre-containing foods have both types.

Insoluble fibre and the bowel

Insoluble fibre is beneficial for the bowel, adding bulk to the faeces and increasing its transit speed through the gut. Good sources of insoluble fibre include wheat bran, which is found in cereals and wholegrain breads and sold also as unprocessed or natural bran, brown rice and vegetables. Insoluble fibre helps reduce several bowel diseases, including irritable bowel syndrome, diverticulitis and most probably bowel cancer. The effect on cancer arises by several mechanisms including favourably altering the bacteria in the bowel, which enables a better break down of ingested cancer causing chemicals, and the binding of fibre to some cancer causing chemicals, which aids in their excretion. Also, the extra faecal bulk added by fibre acts to dilute any ingested cancer causing chemicals and this helps reduce exposure of the bowel wall to these chemicals. Fibre also assists with the production of butyric acid, a compound that can slow cancer-cell growth. This occurs as part of the fibre breakdown process in the bowel.

Evidence supporting fibre as a factor in reducing bowel cancer incidence has been brought into question by some data from recent studies and it has been suggested the protective effect of foods high in insoluble fibre is due to other compounds found in these foods, such as antioxidants, rather than the fibre component. However, there is still a large body of evidence that fibre is protective. More research is being done on this topic.

Soluble fibre and cholesterol

Foods rich in soluble fibre reduce plasma cholesterol levels by binding to cholesterol in the gut. This prevents the cholesterol from being reabsorbed back into the body from the small intestine as it is excreted in the feces attached to the soluble fibre. Foods containing soluble fibre include oat bran, barley bran, rice bran (less than oat and barley bran), lentils, dried beans, fruit and vegetables. Insoluble fibre, such as wheat bran, does not bind cholesterol and thus does not help reduce cholesterol levels.

The role of soluble fibre in improving metabolic syndrome
A high fibre diet acts to improve the metabolic sydrome by:

  • Reducing cholesterol (See above)
  • Reducing blood glucose. High fibre diets have a low glycaemic index which helps keep blood glucose levels lower after eating. Also, viscous soluble fibre helps slow dietary carbohydrate (sugar & starch) absoption from the bowel.
  • Soluble fibre may help reduce blood pressure in overweight patients.

High Fibre Diets
A high fibre diet requires at least 30 g of fibre a day, preferably a mixture of soluble and insoluble fibre. This can be gained from a daily intake of all of the following:

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Vegetarian Diets

Vegetarian diets are generally a healthy option, especially if milk products and eggs are allowed in the diet. It is also an increasingly common option, especialy amongst adolescent girls. About 25 per cent of girls choose to be vegetarian at some stage during their teenage years. Whilst some take this option for moral reasons, many do so to lose weight. Luckily, most remain quite well with the incidence of anorexia being about one per cent.

Animal products provide dietary protein, energy and fat. As most Australians take excess fat and energy, the reduction in these that results from a vegetarian diet is often beneficial. However, some vegetarians have an energy deficient diet and are underweight and unhealthy. As egg whites and milk products are rich in good protein, a vegetarian diet that includes these and a good variety of plant proteins is usually not protein deficient. Sources of plant proteins include cereals, nuts and legumes, such as soy beans, lentils, beans and peas.

Vegetarians who choose not to consume milk products and eggs need to be more careful to ensure their protein intake is adequate, both in the total amount and in the types of aminoacids that are present in the protein. (Amino acids are the building blocks of all proteins. Some, called essential amino acids, can not be made by the body and must be obtained from the diet.) Total protein intake needs to be at least 0.7g per kilogram of body weight each day in adults and 1.0g per kilogram of body weight per day in the elderly. A mix of 70 per cent from cereals and 30 per cent from legumes is ideal. Nuts should also be included each day. These foods need to be a large part of the diet to ensure adequate protein and energy requirements. Vegetarians who do not consume milk products or calcium enriched foods, such as calcium enriched soy products, will need calcium supplements.

Vegetarian diets without milk products and eggs often provide inadequate levels of vitamin B12. (As body stores of vitamin B12 are large, a deficiency may not appear for several years after adoption of the diet.) Vitamin B12 deficiency also affects the unborn children of affected mothers causing neurological problems and women of child-bearing age on this diet should take supplements of vitamin B12. This issue should be discussed with a medical practitioner. Vegetarian diets without milk products and eggs are not suitable for children.

Iron can be deficient in some vegetarians and those requiring extra iron, especially teenage girls and pregnant women, may require iron supplements if they have been shown to be iron deficient by a blood test. (A list of foods high in iron appears below in section on vitamins and menerals.)

Hints for preserving protective nutrients in vegetables

  • Cook with fresh vegetables and herbs whenever possible
  • Do not store fresh foods for long periods (a week at most).
  • Store them in a cool, dark place.
  • Keep pieces as large as possible when chopping/slicing.
  • When cooking vegetables, minimise both cooking time and cooking water to reduce vitamin losses. Vitamin losses with cooking vary from about 10 per cent with steaming or micro-waving to about 50 per cent with boiling. Most of the vitamins lost are the water soluble ones. The preferred cooking method should be micro-waving (with little water), followed by steaming, stir-frying and lastly, boiling. If boiling, add food only when the water is boiling and boil in the smallest amount of water possible. Do not soak vegetables before cooking.
  • Do not use copper pots or utensils as they can increase losses of some vitamins, particularly vitamin C.
  • Use cooking water and liquid from canned foods in sauces, gravies etc.
  • Do not use baking powder to preserve vegetable colour during cooking as it increases vitamin losses.
Water soluble vitamins are the ones that are destroyed by cooking and dissolve into water. Maximum losses during cooking vary from 10% for vitamin B-12 to 100% for more unstable vitamins, such as folate and vitamin C. Fat soluble vitamins are more hardy and don’t dissolve in cooking water.

Don't forget the fruit!!

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What is a healthy diet?

There are many nutritional factors that require consideration in formulating a healthy diet and these will be discussed in the rest of this section. Below is a table summarising what most nutritionists and dietitians would consider a healthy diet.

Recommended food intake for a healthy diet low in fat

 

 

Bread, pasta, potatoes (prepared without fat), grains

  • Six serves a day. One serve equals one cup of mashed potato or cooked pasta or cooked rice, three quarters of a cup of breakfast cereal, or one slice of bread or fruit loaf or a small roll.

Meat, fish, chicken, eggs, legumes: Meat must be lean with all visible fat removed and chicken should be skinless.

  • One serve a day. One serve equals 80g of red meat, 100g of cooked chicken or fish, one to two eggs, or 2/3 of a cup of cooked legumes. Foods should be prepared in as little fat as possible. Avoid frying / roasting.)

Vegetables

  • Eat as much as liked, but at least 4 serves per day. One serve equals about half a cup or about 60 to90g. Try to make them the central part of at least some main meals. (For example, vegetarian lasagna or ratatouille.)
  • A wide variety of vegetables is best.
  • Adding a variety of herbs and spices (preferably fresh) to vegetarian dishes improves flavour and they should be an integral part these recipes. They are also nutritionally very beneficial.

Fruit

  • Eat two to three serves a day. One serve equals one medium or 3 small (e.g. apricot) pieces of fruit, about 20 grapes, a cup of berries, or half a cup of canned/stewed fruit; about 120 to 140 g. Fruit is great after a meal or as a filler during the day.

Nuts

  • A small handful several times a week (unsalted). Nuts, especially peanuts, should not be given to young children due to the risk of inhalation.

Milk products

  • Two to three serves a day of low-fat dairy products. One serve equals one cup of low-fat milk or skim milk, or 200g of fat-reduced yoghurt. Low fat cheese is still relatively high in fat and should be used in moderation,
  • Avoid butter and cream.

Fats and oils

  • A maximum of two serves per day. One serve equals one teaspoon of oil for cooking, one teaspoon of margarine or a quarter of an avocado (50g).
  • Monounsaturated oils are best.
  • If using spreads, those containing plant sterols can help reduce cholesterol; or try using avocado.

Indulgences

  • Enjoy a maximum of one to two serves each day. One serve equals two standard alcoholic drinks, a tablespoon of jam or honey, or one cup of home made popcorn.
  • Try to avoid high-fat foods, such as potato or corn chips, sausage rolls and meat pies, chocolate, sweet biscuits and pastries. (For example, a commercially made muffin contains about 24g of fat and 2,200kJ of energy.)

Fluids

  • Water is best. Try to drink at least two litres a day. A jug of iced water at every lunch or dinner should be a household ritual.
  • Low-fat milk (as allowed above) is an equally good choice. A good way of ensuring an adequate calcium intake is to have two to three cups of calcium enriched low-fat milk per day.
  • Alcohol needs to be restricted to two standard drinks per day and alcohol intake should be part of ‘indulgence allowances’. You should also have at least two alcohol free days a week. This does not mean no occasional nights out; although It is important not to increase the risk of harm when consuming alcohol. See section on alcohol use. )
  • Non-sweetened fruit juices should be restricted to one serve per day, about 150ml.
  • Soft drinks and sweetened fruit juices need to be avoided.

 

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