By GRETCHEN REYNOLDS
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Sugar is getting a bad reputation. A cover article in The New York Times Magazine several weeks ago persuasively reported that our national overindulgence in fructose and other sugars is driving the epidemics of obesity, diabetes and other illnesses. But that much-discussed article, by the writer Gary Taubes, focused on how sugars like fructose affect the body in general. It had little opportunity to examine the related issue of how sugar affects the body in motion. Do sweeteners like fructose — the sweetest of the simple sugars, found abundantly in fruits and honey — have the same effect on active people as on the slothful?
A cluster of new studies suggests that people who regularly work out don’t need to worry unduly about consuming fructose or other sugars. In certain circumstances, they may even find the sweet stuff beneficial.
The unique role that the various sugars play in exercise is well illustrated by anew study published in March in Medicine & Science in Sports & Exercise. It involved a group of highly trained cyclists and their livers. For the experiment, Swiss and British researchers directed the cyclists, all men, to ride to exhaustion on several different occasions. After each ride, they swallowed drinks sweetened with fructose or glucose, another simple sugar often identified as dextrose on ingredient labels. (Some also drank a milk-sugar sweetener.)
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The liver is often overlooked when we consider organs integral to exercise, but it is an important reservoir of glycogen, the body’s stored form of glucose. All sugars, including sucrose, or table sugar, and high-fructose corn syrup, which usually consists of almost equal portions of glucose and fructose, are converted into glucose, and stored as glycogen, in the body. Strenuous exercise diminishes or