Introduction

Nutrition plays an important role in optimising an athlete’s sporting performance. Good nutrition and hydration strategies are important before, during and after competition and training.

Effective, scientifically based nutrition and hydration strategies are an important part of maximising athletes’ training benefits and performance during competition, so expert advice regarding nutrition and hydration from a sports dietitian is highly recommended. Unlike doctors and physiotherapists, dietitians rarely travel with sports teams so sports trainers have an especially important role in ensuring athletes comply with nutrition and hydration strategies that have been recommended to them by their dietitian or coach. Therefore, sports trainers should also develop a basic understanding of key sports nutrition principles and be able to recognise signs such as fatigue, cramps or reduced performance that indicate a referral to a dietitian might be appropriate.

Sometimes athletes who are interested in improving their performance develop nutritional habits that are ineffective and occasionally even dangerous. The sports person or athlete may be influenced by advertisements or articles in newspapers, magazines or health food stores that claim particular foods or supplements will improve athletic performance. Sports trainers are well placed to help athletes by encouraging them to seek expert advice from a sports health professional, such as a dietitian or doctor, before commencing non-standard eating plans or using dietary supplements.

Figure 4.1 Australian Dietary Guidelines

Food for Health dietary guidelines

Dietary guidelines were released by the Australian Government Department of Health and Ageing and the National Health and Medical Research Council (NHMRC) in 2005 in their booklet, Food for Health. The guidelines promote healthy eating as well as the importance of leading a physically active lifestyle. The booklet is free to download from the NHMRC website (www.nhmrc.gov.au). It contains information and recommendations by experts about food groups and lifestyle patterns that promote good nutrition and health at each of the stages of a person’s life when dietary needs are different.

The Dietary Guidelines for Australian Adults recommend that adults should:

Adults should also take care to:

The Dietary Guidelines for Children and Adolescents in Australia recommend that children and adolescents should enjoy a wide variety of nutritious foods and be encouraged to:

In addition, care should be taken to:

Energy sources and nutrients for sport

All foods and drinks contain nutrients. The major nutrients are carbohydrates, fat, protein, vitamins and minerals. In addition, dietary fibre and water are vital to life and help to regulate body processes. The sports trainer should appreciate how intricate and sophisticated our food is. Nutrients do not exist in isolation. For example, there is more to an orange than vitamin C and more to meat than protein. Food and fluids are a complex mixture of hundreds of nutrients. Therefore, it is wise to consume a wide variety of foods that provide a balance of all types of nutrients.

Carbohydrates, fat and protein are the energy-giving nutrients. During sport and physical activity, carbohydrates and fats provide the most energy. Protein is also a minor source of energy, especially in long duration activities when the stores of carbohydrate and fats are greatly depleted.

Carbohydrate

Carbohydrates are foods that are broken down by the body into simple sugars. Carbohydrate is the body’s primary source of fuel during everyday activity and exercise. All cells in the human body require carbohydrate for energy. When carbohydrate is consumed it is broken down by the body and stored in muscles and the liver as glycogen. During physical activity, stored glycogen is broken down further to glucose, which provides the fuel for muscle contraction.

Glucose is the human body’s, including the brain’s, most economical energy source and preferred source of fuel. Because glycogen is broken down to glucose during exercise, glycogen stores need to be constantly replenished during and after exercise. High carbohydrate foods restore liver and muscle glycogen stores.

Low levels of carbohydrate may result in fatigue, ineffective training, reduced immunity and reduced muscle mass. The harder an athlete trains, the greater their daily carbohydrate needs.

Carbohydrate serves other important roles in the body, including preserving protein stores and facilitating fat metabolism and the proper functioning of the central nervous system.

Carbohydrate-rich foods include breads, cereals, rice, pasta and other grains, fruit, vegetables, legumes, milk and yoghurt. Sugar, lollies, soft drinks and honey also contain carbohydrate but contain few or no other nutrients.

Carbohydrates are grouped as either:

Carbohydrate-rich foods that are more slowly digested and absorbed are known as low glycaemic index (GI) foods. Low GI foods provide a slower and more sustained energy release. Examples of low GI foods are baked beans, pasta, oats and fruit. A combination of low and high GI foods may be appropriate depending on the type and duration of exercise or sport.

The actual amount of carbohydrate needed can vary significantly depending on the individual athlete’s energy needs. To provide energy for a light to moderate training program, sports dietitians recommend that carbohydrate-rich foods should make up about half of the total energy intake. Athletes in heavy daily training may need to eat even higher levels. In order to meet these daily requirements every meal and snack should be based on carbohydrate-rich foods. A sports dietitian can work with an athlete to develop an eating plan that provides sufficient carbohydrate for their activity levels.

Figure 4.2 Nutritious carbohydrates

Figure 4.3 Less nutritious carbohydrates

Protein

Proteins are made up of amino acids, the building blocks of the human body. There are 20 types of amino acids, of which nine are essential for health, so a balanced diet is required to ensure all are available to the body. Proteins are crucial to the regulation and maintenance of our bodies. Proteins form important structures in the body, such as muscle tissue; they make up a key part of blood; and they help regulate many body functions, such as blood clotting, fluid balance, hormone and enzyme production, visual processes and cell repair. If an athlete does not regularly eat sufficient protein, these and other metabolic processes may be affected. For example, the immune system may no longer function efficiently, which will increase the risk of infection. Protein may also provide a minor source of fuel for exercise.

Proteins fall into two classes:

1. Complete proteins (containing all nine essential amino acids) are found in animal-based protein products; for example, red meat, fish, poultry and dairy foods.

Figure 4.4 Complete proteins

2. Incomplete proteins (lacking in one or more essential amino acids) are found in plant-based protein products; for example, nuts, legumes, tofu, soy products, breads and cereals. However, protein foods can be ‘complemented’ to ensure all amino acids are obtained from the diet. This is especially important for vegetarian athletes.

Figure 4.5 Incomplete proteins

Both strength and endurance athletes need additional protein due to increased muscle building and increased use of protein as a fuel, especially during endurance exercise. Most Australians eat 2–3 times as much protein as they need, and the typical high food intake of most athletes provides a more than adequate protein intake.

Some athletes, such as those in weight-restricted sports, fussy eaters or dieters, may be at risk of not eating enough protein. Poor protein intake may cause loss of muscle mass, slower recovery and serious health problems if continued for a long time.

Conversely, some athletes may be at risk of eating too much protein, particularly those wanting to increase muscle mass or those following certain types of high protein diets designed for weight loss. Some consequences of prolonged excessive protein intake include increased progression of preexisting kidney disease, atherogenic effects, increased urinary calcium excretion and increased fluid loss.