Nutrition is the fourth discipline of triathlon

By Asker Jeukendrup

A good diet is for everyone. A good diet and an active lifestyle will help to prevent may of the modern diseases like obesity, type ll diabetes, cardiovascular diseases etc. In fact poor diet and physical inactivity are currently ranked as the number 1 killer, ahead of smoking!

For elite athletes there is another reason to pay attention to the diet. Diet can also affect performance and sometimes can even mean the difference between winning and becoming last.

I don't think athletes always appreciate the importance of nutrition. Elite athletes spend hours and hours training, the efforts they put into their training are quite remarkable. It is then amazing to see that the diet often receives less attention. What you eat before, during and after training will determine how well your body adapts and thus improves from that training session. It is therefore important to give nutrition as much attention as training!

What do we mean by good nutrition? This is a tricky question and the answer may depend on the goal. Good nutrition will be different for a shot-putter than for an ultra marathon runer and will be different if your goal is sprint triathlon or completing an Ironman. It will be different for someone who does not train and someone who trains 2 hours per day. The requirements of different sports and disciplines can vary quite significantly. There are a few common themes though.

Carbohydrate to fuel training

All training will require energy and this energy has to be provided. The two main fuels for exercise are fat and carbohydrate. Carbohydrate is the fuel of choice and since we can only store relatively small amounts of carbohydrate in our bodies, carbohydrate should be a large component of every athlete's diet. Good sources of carbohydrate are potato, bread, rice, pasta etc. It is often recommended for athletes to have a relatively low fat, high carbohydrate diet. Fat sources such as butter, mayonnaise, which contain quite a bit of energy could be replaced with carbohydrate sources.

A balanced diet

A diet has to be balanced which means it has to be varied to provide all nutrients in sufficient quantities. Eating just pasta would result in a deficiency of various micronutrients (vitamins and minerals). To provide a balanced diet, we should consume sufficient amounts of fruit and vegetables, eat whole grain products and other fibre containing foods, eat meat or fish (although meat could be replaced with carefully chosen protein sources).

Hydration

There is evidence that dehydration (a loss of body water) can impair performance. Athletes are therefore recommended to drink regularly and make sure they are always hydrated. One way to check hydration status is by looking at the colour of urine. A light colour usually means you are well hydrated, a darker colour means you are dehydrated. Sports drinks are developed to replenish water as quickly as possible and they provide a source of carbohydrate as well. These drinks are important for endurance athletes who exercise for many hours, and it is even more important if the exercise is performed in hot conditions. The average person who goes to the gym, could suffice with drinks that contain less carbohydrate or even no carbohydrate.

Recovery

Nutrition plays an important role in recovery. After exercise energy stores have to be replenished, lost fluid has to be replaced and damage (muscle damage) has to be repaired. We need carbohydrate, water and protein for this. When athletes are training hard on a daily basis which for most elite athletes is the case, the choice of food and the timing will determine how quickly they recover and how well they adapt. Nutrition can also help to prevent injuries by speeding up repair of damaged tissues.

Immune system

Strenuous training may suppress the immune system and this may be the reason why anecdotally athletes who are training hard are reporting more colds. Nutrition can help boost the immune system and especially carbohydrate intake during longer training sessions has been shown to reduce the suppression of the immune system.

Sports nutrition myths

There are many myths in sports nutrition. In the sixties athletes were advised to eat a large steak on the morning before a marathon. Now we know this is not the best way to prepare but there are new myths...There is a strong belief that large amounts of protein need to be consumed to build muscle. However, there is no evidence for this at all. Protein is important to build muscle but we don't necessarily need large amounts. The timing of protein intake may be more important than the amount.

There are also many nutrition supplements on the market that claim to make your muscles grow, fat disappear, recover faster, and perform better. Most of these claims are not based on scientific evidence! Even worse, some of these supplements do not contain what they say they do! So supplements are not the way to a healthy and optimal diet. Supplements, as the name suggests, are meant to supplement a healthy diet, not to replace it or compensate for it!

Why sports nutrition is so exciting

As a triathlete I have learned how important nutrition can be. Take for instance one of the ultimate challenges: the Ironman (3.8 km swim, 180 km bike, followed by a 42.2 km run). During an Ironman, you expend 10,000-11,000 kcal (a normal person will expend 2,000-2,800 kcal per day) and some of this energy needs to be supplied during the race. Fluid losses can be substantial: in some races it can be more than 10 litres, and these losses need to be minimised. However, although on the one hand there is evidence that refuelling and rehydrating are important, there are also practical considerations that need to be taken into account. For example, it is not always possible to carry that much food and drinks are sometimes the foods and drinks can cause gastro-intestinal problems. This is what makes the field of sports nutrition so exciting. Every sport and indeed every athlete has individual needs that can only be addressed appropriately by working closely with this athlete and finding out what is optimal for them. In a series of articles over the coming weeks we will discuss all these considerations and come up with some guidelines.

Asker Jeukendrup is Professor of Exercise Metabolism, Director of the Human Performance Lab, Exercise Metabolism Research Group, School of Sport and Exercise Sciences, University of Birmingham.