BURGER, BANANA, OR BEER?

Dr Jonathan King



Endurance athletes are very aware of their diets, and as there are many many products on the market claiming to enhance performance, fact is often confused with myth, as there are so. Nutrition does have a noticeable effect on performance, and using common scientific sense is better than spending a fortune on pills and potions.

For optimal performance in endurance events, athletes need 60-70% energy as carbohydrates. Carbohydrates are our main fuel source when exercising; our bodies can store enough carbohydrates to last less than 2 hrs, running at 85% of maximal speed. The body uses fats as a high-energy source, but allows exercise at only 50% of maximal speed. Many of us have experienced "hitting the wall" during a long race, when carbohydrate stores are depleted. In reality, the body uses a combination of fuels, which enables us to perform for much longer periods of time.

Studies on athletes whose diets contained 40% carbohydrates showed that the muscle glycogen decreased on consecutive days with daily training. This resulted in diminishing performance and tiredness. A high carbohydrate diet and a structured training program can minimise this to a large extent.

For a 60 kg athlete training for a marathon, daily consumption of 500-600 g carbohydrates a day is recommended. In food terms this is:

* 200g egg pasta

Protein can be made up with 100g lean steak and 30g low fat cheese. Vitamins and minerals are important too, and a range of vegetables will cover much of this need.

This sounds like a lot of food, but is an essential part of the training day. Carbohydrate drinks can substitute for solid food, as eating can be time consuming!

Vegetarians have to be particularly careful, as there is an increased risk of iron and Vitamin B12 deficiency.