Runners need to beware of sugar boosts

The legs are heavy, the heartbeat rapid, the fatigue total. Many long-distance runners have experienced this state. Some then immediately ingest large amounts of glucose. Others say this only makes the fatigue worse.

In his bestselling book “Ultra-marathon Man: Confessions of an All-Night Runner,” American running guru Dean Karnazes writes that he has completely eliminated refined sugar from his diet. Is sugar really so bad? It is a main ingredient, after all, in many energy drinks.

Sugar is a member of the carbohydrate family. Carbohydrates are found in foods are varied as whole-grain bread and vegetables, and enter the bloodstream at different speeds. “Slow” carbohydrates deliver energy longer, while “fast” carbohydrates give an immediate energy boost.

The glycemic index (GI) is a scale that measures how a food’s carbohydrates affect blood sugar levels, noted Thomas Konrad, director of the Institute of Metabolic Research (ISF) in Frankfurt.

High GI carbohydrates such as white bread and sweets cause blood sugar levels to rise very rapidly, Konrad explained. This prompts the body to release the hormone insulin. But is that bad? “Insulin channels excess sugar from the blood into energy storage,” remarked German running coach and author Herbert Steffny, who was a professional marathon runner for many years. This is good during a run, he said, because muscles are supplied with fuel and carbohydrate reserves are built up.

“But you don’t burn calories when you snack in front of the television set,” he said. “Then the insulin works like a fattening hormone.” So when does a runner need sugar? “Someone who likes to push it to the limit sometimes, runs for over an hour or is training for a moderate city run needs a quick source of energy during long training sessions,” said Hans Braun, a nutritionist at the German Sport University in Cologne. Such sources are primarily energy drinks, bars and gels, which contain a lot of sugar.

The question for leisure-time runners, though, is how strenuous must a training regimen be before “fast” carbohydrates are really necessary.

“You don’t need them at all either before or during a normal endurance run of up to an hour,” Steffny said. So leisure-time athletes with no ambitions to run a marathon should ban “fast” carbohydrates from their diet.

After training, too, it is a good idea to fill up the body’s energy stores with “slow” carbohydrates, Steffny said. They are found in foods including potatoes, vegetables, whole-grain bread and oat flakes. Sugar, on the other hand, is a fattener whether you are a runner or not. As a rule, it is unnecessary for most runners’ “normal” training runs.

The body requires a quick energy boost only during long training sessions or competition. Karnazes is a case in point. In his book, he lists the foods he ate during a 199-mile run, which included five chocolate cookies, four peanut butter sandwiches and a cheesecake.

In Braun’s view, it is sufficient for leisure-time runners when about half of their energy comes from carbohydrates.

“Someone training for a race definitely needs more, though,” noted Steffny, who also recommends high-quality protein after training.

“You don’t need powder for that. Low-fat curd cheese, eggs and fish are cheaper,” he said, adding that about a quarter of the calories should come from high-quality oils and fats.

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