Your diet should be optimal in both quality and quantity of food, in order to replenish your energy reserves and avoid fatigue or inadequate nutrition. A good diet will help your body perform at its best.
What are the athlete’s specific needs?
Carbohydrates are the best fuel source to provide power for your working muscles. Eating enough carbohydrate before, during and after exercise helps to maintain energy levels, delay fatigue during exercise and support a more rapid recovery. With carbohydrate or "carbs" as the main fuel source, you can maintain your activity for a longer period. Carbohydrate foods should make up more than half your total energy intake. If you are involved in heavy daily exercise, your carbohydrate needs will be even higher and you should make sure you eat enough carbohydrate to meet your increased daily requirements.
Proteins are the building blocks of your body’s muscles and tissues. Most athletes need only slightly more protein than non-athletes. You will usually meet your increased requirements through increased food intake. It is unlikely that you’ll need protein supplements. If you are involved in aesthetic (e.g. gymnastics), weight restriction (e.g. light weight rowing) or endurance sports (e.g. marathon running), you may have higher protein requirements. Foods like meats, legumes and dairy products are good sources of protein.
Fat is important in the athlete’s diet as it provides energy, fat-soluble vitamins and essential fatty acids. However, fat should be eaten in moderation. A low-fat diet is a good approach for everyone – athlete and non-athlete alike. Choose "good" fats such as polyunsaturated and monounsaturated fats which are found in fish, nuts, seeds, canola and olive oils and avocados.
Vitamins and Minerals are the "spark plugs" of physical activity. Some help your body use the energy from carbohydrate, protein and fat. Others help your muscles relax and contract. If you follow a balanced diet, you will generally take in enough essential vitamins and minerals. However, if you are trying to lose weight, you may have low levels of some vitamins and minerals in your diet. Despite the best intentions, some busy people don’t follow a balanced diet, so watch your intake of iron, calcium and zinc, which are especially important for physically active people.
Iron is part of haemoglobin, the part of red blood cells that carries oxygen to your body cells. Oxygen is essential for creating energy in your muscle cells. An iron shortfall, even if it’s small, can affect your physical performance. Female athletes are more prone to low iron levels, as iron is lost through menstruation. Iron from foods occurs in two forms – "haem" iron found in animal foods and "non-haem" iron found in plant foods. Haem iron is readily absorbed by our bodies. In contrast, non-haem iron is poorly absorbed. If you are a vegetarian or eat mainly plant-based foods, you can increase the absorption of iron by adding a vitamin-C rich food (e.g. citrus fruits and juices, kiwi fruit, red capsicum etc) to your meals. For a further boost in iron levels, eat iron-fortified foods (e.g. breakfast cereal). The recommended dietary intake for iron is 7mg/day for adult men and 12-16mg/day for adult women.
||How much iron (mg)?
|90g lamb liver
|100g lean beef
|120g fish (non specified type)
|100g chicken breast
|Non-haem iron sources
|30g bran flakes
|½ cup canned chickpeas
|½ cup spinach
|10 macadamia nuts
Calcium combined with weight-bearing activity helps to increase bone density plus build and maintain strong bones. Adults need a daily intake of 800mg calcium, and the simplest way to meet your requirements is to eat plenty of dairy products. If you are watching your weight, choose low fat dairy products which will still give you a calcium boost. Dairy foods are a good source of carbohydrates as well.
||How much calcium (mg)?
|200g tub yogurt, reduced fat
|2 slices (40g) cheddar cheese, reduced fat
|100g (1/4 cup) small can pink salmon canned in brine (with bones)
|250mL (1 glass) milk (low fat / skim))
|¼ cup mozzarella cheese
|1 cup vanilla ice cream
|¼ cup almonds
|½ cup baked beans, canned in tomato sauce
Magnesium is found in dried fruit, nuts and chocolate. It plays a role in energy reactions, protein production and muscle contraction.
If you would like more information on nutrition for sports performance, the AIS nutrition booklet "A Winning Diet" is highly recommended. To order your FREE copy of "A Winning Diet" or view the booklet online, simply click on the link.
How can I get enough carbohydrate?
Carbohydrate foods include breads, breakfast cereals, rice, pasta, fruit, vegetables and legumes (dried beans and peas). There are smaller amounts of carbohydrate in dairy products like milk and yogurt and foods with added sugars.
Carbohydrates are important to maintain blood-glucose levels during exercise and to replace muscle glycogen. Recommendations for athletes range from 6 to 10g/kg body weight per day. The amount required depends on your total daily energy expenditure, the type of sport/exercise you perform, your gender and the environmental conditions. To calculate your total daily requirement, multiply the amount of carbohydrate you require (6-10g/kg per day) by your body weight. A sports dietitian can help you determine your individual needs.
Your body’s carbohydrate stores are very small and need regular replenishing, generally every 4 to 5 hours (especially if you exercise daily or twice daily). Follow these strategies to achieve a high-carbohydrate intake:
- High-carbohydrate foods should be the number one priority in your meals and snacks and should take up most of the room on your plate.
- Remember, vegetables and salads are good sources of vitamins, minerals and fibre, but they don’t contribute large amounts of carbohydrate. Make sure you include pasta, rice, potatoes or legumes with your main meals.
- Sugar and sugary foods provide carbohydrate and can be used to add extra fuel to your daily carbohydrate intake. Electrolyte drinks, commonly known as "sports drinks" contain water, electrolytes (such as sodium and potassium) and sugar and are a convenient way to top up fuel needs during an exercise / training session. Energy performance bars and gels are a convenient source of carbohydrate during endurance events.
- If you have very high carbohydrate needs, a sports dietitian can help you plan your diet to ensure you meet your requirements.
||How much carbohydrate (g)?
|700mL sports drink (average)
|¾ cup boiled rice
|1 cup cooked pasta
|1 x 200g tub reduced fat yogurt
|2 slices wholemeal bread
|2.5 wheat flake breakfast biscuits
|1 medium banana
|1 medium potato boiled
|1 Tbsp jam
|1 cup cooked cous cous
|½ cup baked beans in tomato sauce
What about the glycaemic index?
We used to think of carbohydrate foods as ‘simple’ or ‘complex’. Foods high in sugars were considered ‘simple’ carbohydrates, as it was assumed they would be digested quickly and cause a rapid rise in blood glucose levels. ‘Complex’ carbohydrates (starches), on the other hand were thought to give a slow gradual rise in blood glucose levels. However, now a carbohydrate can be classified by its “glycaemic index” (GI). As an athlete, you can use knowledge about the carbohydrate content of foods, as well as the GI of such foods, to help optimise your performance.
What is the GI?
The GI is a ranking of carbohydrate foods, based on their effect on our blood glucose (or blood sugar) levels. The GI ranks foods from 0–100. The higher the GI value, the greater the blood sugar response. So, low GI foods raise blood sugar levels just a little, medium GI foods raise blood sugar levels moderately, and high GI foods raise blood sugar levels quite high.
The ranking of GI foods is as follows:
- Low GI foods - less than 55
- Medium GI foods - 55 to 70
- High GI foods - more than 70
GI before exercise
A low GI meal before exercise may help your performance. It does this by providing a sustained release of carbohydrate for your working muscles. However, as well as GI, it is important to consider other characteristics of your food such as the total carbohydrate content, nutritional value, practicality, cost, taste and how comfortable you feel exercising shortly after eating that particular food. It’s best to experiment with different foods before your training sessions and not try anything new just before an important sporting event.
GI during exercise
Eating carbohydrate during exercise, especially prolonged, intense exercise, will provide extra fuel for your working muscles and can improve performance. Moderate to high GI foods are the best choice for this type of exercise, as they act fairly quickly to raise blood glucose levels and provide your muscles with a readily available source of energy.
GI and recovery
High GI foods provide a rapid supply of glucose to your blood and can replace your muscle glycogen stores. It is important to rebuild your glycogen stores so that you have plenty of energy for your next exercise session, particularly if your recovery time is less than eight hours. Drinking a sports drink immediately after exercise is a great way to refuel and they help replace fluids at the same time. Other examples of high GI foods include honey on a bagel, a banana sandwich, watermelon or some breakfast bars.
To find out the GI values for specific foods, or for more information about the GI, visit www.glycemicindex.com.
Should I cut out all fats?
No. Your body needs a certain amount of fat, although typical Western eating patterns well exceed these requirements. For an athlete, eating too much fat can potentially replace some of the energy you need from carbohydrate foods. However, fat is still important in the diet of an athlete as it supplies fat soluble vitamins, essential fatty acids and energy. Eat fat in moderation and choose the "good" fats – polyunsaturated and monounsaturated fats found in fish, nuts, seeds, oils like olive and canola oil and avocado.