Many people think that sugar is the root of all evil. But is it any different for triathletes?

Is sugar bad for you? Sugar is the cause of all health problems. Sugar improves performance. Sugar is essential for athletes. Confused? I’m not surprised. There are so many mixed messages out there about sugar, and what it does for the body. In this article I aim to present the facts about sugar and its role for triathletes and exercise.

‘Sugar’ is the generalised term for sweet-flavoured carbohydrates. There are many different types of sugars, depending on the molecular structure. Sugars can be simple monosaccharides such as glucose or fructose, through to disaccharides such as sucrose (table sugar) and lactose (milk sugar). Sugar is found naturally in many foods, particularly fruit and vegetables. The processed versions we add to our cup of tea in the morning come from crops such as sugar beet and cane sugar. Sugar has been available in the human diet since ancient times, but prior to the 19th century it was an expensive luxury. Since then it has become cheap, spawning a huge industry.

So is sugar good or bad for you? As with most nutritional research there is no conclusive answer from the evidence we currently have. If you search, you will almost certainly find evidence that sugar is a terrible thing that we should all avoid, as too much of it can lead to type 2 diabetes, cardiovascular disease and Alzheimer’s.

There is also good evidence that blood sugar control is essential to allow the body to function effectively and maintain a healthy weight, and if eaten to excess sugar will lead to fluctuations in blood sugar, particularly if the individual does not exercise regularly.

In terms of peer-reviewed evidence, when sugar is substituted for other carbohydrates in a calorie-controlled diet, there seems to be little evidence of a negative health effect. However, if sugar is added on top of your normal diet then there is increasing evidence that the sugar can indeed have a negative impact on your health and lead to weight gain – but we all know that eating too much is bad for you.

What is undeniable is that sugar only contains carbohydrates and is therefore seen as an ‘empty’ – ie nutritionally poor – food. Where possible it is more effective to consume foods that also contain vitamins, minerals, fibre and other nutrients. In other words, if you need a sugar hit, go for fruit.

While the effects of sugar on health are inconclusive, the effects of sugar on endurance performance are most certainly conclusive – sugar keeps you going. Some seminal studies from the University of Texas in the 1980s showed that fatigue during endurance exercise coincides with a drop in blood sugar.

However, when blood sugar is maintained, endurance performance improves. The simplest way to maintain blood sugar is by taking on board a simple sugar-based drink during exercise. Most of the research is based on the use of glucose, a simple monosaccharide. Most research would suggest a two to five per cent improvement in performance lasting longer than one hour when you ingest a simple sugar such as glucose.

However, not all sugars are created equal. Glucose is used by the body most effectively, where it has been shown that the body can use approximately one gram per minute of exercise as fuel. Fructose is used at a much slower rate, approximately 0.4g per minute of exercise. The real magic happens when you combine the two, and you can increase the use of the sugar as fuel by 50%, which leads to an eight per cent improvement in performance over three hours of exercise when compared with glucose alone.

So the evidence clearly shows that sugar improves endurance performance over one hour in duration, with a mixture of glucose and fructose being most effective. Outside of using sugar during exercise, the evidence for its use or harmful effects are inconclusive. However, as a triathlete you need to get as much quality nutrition as possible and simple, refined sugars come with no other nutrients. So it’s a much better idea to stick to fruit when you need a sweet hit. is the online home of Triathlon Plus – the best source of triathlon training advice, triathlon gear reviews and triathlon news.

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