Nutrition

The link between good health and good nutrition is well established. Interest in nutrition and its impact on sporting performance is now a science in itself.

Whether you are a competing athlete, a weekend sports player or a dedicated daily exerciser, the foundation for improved performance is a nutritionally adequate diet.

Daily training diet requirements

The basic training diet should be sufficient to:

provide enough energy and nutrients to meet the demands of training and exercise
enhance adaptation and recovery between training sessions
include a wide variety of foods like wholegrain bread and cereals, vegetables (particularly leafy green varieties), fruit, lean meat, and low-fat dairy products to enhance long term nutrition habits and behaviors
enable the athlete to achieve optimal body weight and body fat levels for performance
provide adequate fluids to ensure maximum hydration before, during and after exercise
promote the short and long-term health of athletes.

The athlete’s diet

An athlete’s diet should be similar to that recommended for the general public, with energy intake divided into:

more than 55 percent from carbohydrates
about 12 to 15 percent from protein
less than 30 percent from fat.

Athletes who exercise strenuously for more than 60 to 90 minutes every day may need to increase the amount of energy they get from carbohydrates to between 65 and 70 percent.

More recent advice also provides guidelines for carbohydrate and protein-based on grams per kilogram (g/kg) of body weight. The current recommendations for fat intake are for most athletes to follow similar recommendations to those given for the general community, with the preference for fats coming from olive oils, nuts, avocado, nuts, and seeds. Athletes should also aim to minimize the intake of high-fat foods such as biscuits, cakes, pastries, chips, and fried foods.

Carbohydrates and exercise

During digestion, all carbohydrates are broken down into sugar (glucose), which is the body’s primary energy source. Glucose can be converted into glycogen and stored in the liver and muscle tissue. It can then be used as a key energy source during exercise to fuel exercising muscle tissue and other body systems. Athletes can increase their stores of glycogen by regularly eating high-carbohydrate foods.

If carbohydrate in the diet is restricted, a person’s ability to exercise is compromised because there is not enough glycogen kept in storage to fuel the body. This can result in a loss of protein (muscle) tissue, because the body will start to break down muscle tissue to meet its energy needs, and may increase the risk of infections and illness.

Carbohydrates are essential for fuel and recovery

Current recommendations for carbohydrate requirements vary depending on the duration, frequency, and intensity of exercise. Foods rich in unrefined carbohydrates, like wholegrain bread and cereals, should form the basis of the athlete’s diet. More refined carbohydrate foods (such as white bread, jams, and lollies) are useful to boost the total intake of carbohydrates, particularly for very active people.

Athletes are advised to adjust the amount of carbohydrate they consume for fuelling and recovery to suit their exercise level. For example:

Light intensity exercise (30 mins/day): 3–5 g/kg/day
Moderate intensity exercise (60 mins/day): 5–7 g/kg/day
Endurance exercise (1–3 hrs/day): 6–10 g/kg/day
Extreme endurance exercise (more than 4 hrs/day): 8–12 g/kg/day

Sporting performance and glycaemic index

The glycaemic index (GI) ranks food and fluids by how ‘carbohydrate-rich’ they are and how quickly they affect the body’s blood sugar levels. The GI has become of increasing interest to athletes in the area of sports nutrition.

More research is required to confirm the best recommendations for sports nutrition. However, there is a suggestion that low GI foods may be useful before exercise to provide a more sustained energy release.

Moderate to high GI foods and fluids may be the most beneficial during exercise and in the early recovery period. However, it is important to remember the type and timing of food eaten should be tailored to personal preferences and to maximize the performance of the particular sport in which the person is involved.

Pre-event meal

The pre-event meal is an important part of the athlete’s pre-exercise preparation. A high-carbohydrate meal three to four hours before exercise is thought to have a positive effect on performance. A small snack one to two hours before exercise may also benefit performance.

Some people may experience a negative response to eating close to exercise. A meal high in fat or protein is likely to increase the risk of digestive discomfort. It is recommended that meals just before exercise should be high in carbohydrates and known not to cause gastrointestinal upset.

Examples of appropriate pre-exercise meals and snacks include cereal and low-fat milk, toast/muffins/crumpets, fruit salad and yogurt, pasta with a tomato-based sauce, a low-fat breakfast or muesli bar, or low-fat creamed rice.

Eating during exercise

During exercise lasting more than 60 minutes, the intake of carbohydrates is required to top up blood glucose levels and delay fatigue. Current recommendations suggest 30-60 g of carbohydrate is sufficient and can be in the form of lollies, sports gels, low-fat muesli and sports bars or sandwiches with white bread.

It is important to start your intake early in exercise and to consume regular amounts throughout the exercise period. It is also important to consume regular fluid during prolonged exercise to avoid dehydration. Sports drinks, diluted fruit juice, and water are suitable choices. For people exercising for more than four hours, up to 90 grams of carbohydrate per hour is recommended.

Eating after exercise

Rapid replacement of glycogen is important following exercise. Carbohydrate foods and fluids should be consumed after exercise, particularly in the first one to two hours after exercise. To top up glycogen stores after exercise, eat carbohydrates with a moderate to high GI in the first half-hour or so after exercise. This should be continued until the normal meal pattern resumes.

Suitable choices to start refueling include sports drinks, juices, cereal, and low-fat milk, low-fat flavored milk, sandwiches, pasta, muffin/crumpets, fruit, and yogurt.

Protein and sporting performance

Protein is an important part of a training diet and plays a key role in post-exercise recovery and repair. Protein needs are generally met by following a high-carbohydrate diet, because many foods, especially cereal-based foods, are a combination of carbohydrate and protein.

The amount of protein recommended for sporting people is only slightly higher than that recommended for the general public. For example:

The general public and active people – the daily recommended amount of protein is 0.8–1.0 g/kg of body weight (a 60 kg person should eat around 45–60 g of protein daily).
Sportspeople involved in non-endurance events – people who exercise daily for 45–60 minutes should consume between 1.0–1.2 g/kg of body weight per day.
Sportspeople involved in endurance events and strength events – people who exercise for longer periods (more than one hour) or who are involved in a strength exercise, such as weight lifting, should consume between 1.2–1.7 g/kg of protein of body weight per day.

Dietary surveys have found that most athletic groups comfortably reach and often exceed their protein requirements by consuming a high-energy diet. Protein supplements are therefore unlikely to improve your sporting performance.

While more research is required, other concerns associated with very high-protein diets include:

increased cost
a potential negative impact on kidney function
increased weight if protein choices are also high in fat
a lack of other nutritious foods in the diet, such as bread, cereal, fruit, and vegetables.

Using nutritional supplements to improve sporting performance

A well-planned diet will meet your vitamin and mineral needs. Supplements will only be of any benefit if your diet is inadequate or you have a diagnosed deficiency, such as an iron or calcium deficiency. There is no evidence that extra doses of vitamins improve sporting performance.

Nutritional supplements can be found in pill, tablet, capsule, powder or liquid form, and cover a broad range of products including:

vitamins
minerals
herbs
meal supplements
sports nutrition products
natural food supplements.

Before using supplements, you should consider what else you can do to improve your sporting performance –diet, training and lifestyle changes are all more proven and cost-effective ways to improve your performance.

The use of vitamin and mineral supplements is also potentially dangerous. Supplements should not be taken without the advice of a qualified health professional. It’s best if dietary imbalances are adjusted after analyzing and altering your diet, instead of by using a supplement or pill.

It’s also important to remember that if you take supplements, you are at risk of committing an anti-doping rule violation no matter what level of sport you play.

Water and sporting performance

Dehydration can impair athletic performance and, in extreme cases, may lead to collapse and even death. Drinking plenty of fluids before, during and after exercise is very important. Don’t wait until you are thirsty. Fluid intake is particularly important for events lasting more than 60 minutes, of high intensity or in warm conditions.

Water is a suitable drink, but sports drinks may be required, especially in endurance events or warm climates. Sports drinks contain some sodium, which helps absorption. The sodium content of 30 mmol/L (millimoles per liter) appears suitable in sports nutrition.

Using salt tablets to combat muscle cramps is no longer advised. It is a lack of water, not sodium that affects the muscle tissue. Persistent muscle cramps might be due to zinc or magnesium deficiencies.

Things to remember

Good nutrition can enhance sporting performance.
A well-planned, nutritious diet should meet most of an athlete’s vitamin and mineral needs, and provide enough protein to promote muscle growth and repair.
Foods rich in unrefined carbohydrates, like wholegrain bread and cereals, should form the basis of the diet.
Water is a great choice of fluid for athletes to help performance and prevent dehydration.