Nutrition Advice

INTRODUCTION

Recommendations of the Australian Nutrition Foundation for a heart-healthy eating program are:

• 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 essential components of nutrition can be classified as:

• macronutrients—proteins, fats and carbohydrates (all interchangeable sources of energy) and water

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

• micronutrients—water-soluble vitamins, e.g. C, B; fat-soluble vitamins, i.e. A, E, D, K; and essential trace elements, e.g. Cu, I, Fe, Zn, Mn, Se

PROTEIN

Proteins make up the greater part of plant and animal tissue and provide the amino acids essential for the growth and repair of tissue. 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 (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). Infants and children require 2–2.2 g protein/kg/d.

• 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

CARBOHYDRATES

Main source of dietary energy. Carbohydrates that are available in food are:

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

• polyols—sorbitol, xylitol, maltitol, lactitol

• 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/d—is nec. to prevent ketosis.

FAT

Dietary fat, which is composed mainly of fatty acids and dietary cholesterol, is the most concentrated source of food energy. 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, eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA])

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, incl. humans, are unable to synthesise them.

Trans-fats, which are considered unhealthy, are created artifically by partial dehydrogenation of unsaturated fatty acids.

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

GENERAL DIETARY GUIDELINES FOR AUSTRALIAN ADULTS (NHMRC)

Enjoy a wide variety of nutritious foods

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