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Once popularized as the food that helps the medicine go down, sugar is now blamed as the culprit behind a world-wide epidemic of obesity, type 2 diabetes, and other manifestations of metabolic syndrome, even high cholesterol and heart disease.

Bodies In Motion Are Immune to the Ill Effects of Sugar, Within Limits

Dr. Robert Lustig, an endocrinologist and a specialist in childhood diabetes on the faculty of the University of California at San Francisco, even goes so far as to label sugar as "evil," in a YouTube video now seen over 1,000,000 times.

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Dr. Lustig doesn't just call sugar a source of "empty calories." He labels all kinds of sugar, whether they are sucrose (table sugar), fructose (fruit sugar and a sugar extracted from corn syrup), or glucose (the form of sugar our bodies make from starch) as pure poison. There are no healthy sugars, Lustig and his followers tell us, because sugar only kills.

This is very strong indictment for a compound our bodies can make from lettuce and collard greens and even excess amino acids when we eat lots of high-protein foods. What is the basis of the bugaboo about sugar?

Sucrose, Fructose, and Glucose Sugars

In the 1970's, the Nixon Administration decided that America's security depended on a reliable supply of home-grown food grains, especially corn. Massive subsidies to farmers encouraged production of huge amounts of grain, especially corn. The problem facing the Nixon Administration and the American agriculture industry in general was that massive production of a commodity lowers prices, unless a new use can be found for the crop.

That new use was high-fructose corn syrup. Corn starch can be treated with enzymes so that it releases a mixture of fructose and glucose. Fructose is about twice as sweet as glucose, which is used in some specialized applications, such as the sugar used to make decorations on cakes. Mass production of corn led to mass production of corn syrup, and an extensive advertising campaign to promote high-fructose corn syrup as the healthful alternative to cane sugar. At the time, high-fructose corn sugar was even promoted as a safe food diabetics and dieters.

Since the 1970's, hundreds of studies have found that massive consumption of high-fructose corn syrup is associated with at least many health problems as massive consumption of cane sugar. And since the price of high-fructose corn syrup is lower than cane sugar, North American consumers are fed the corn starch derivative in practically every imaginable mass-produced food.

American health officials operate on the assumption that the problem is eating too much sugar of all kinds. American food marketers operate on the assumption that people buy things that are new to them, so they are now advertising mass-produced food products as containing no high-fructose corn syrup. But Dr. Lustig says they are both wrong, that both kinds of sugar are toxic.

The glucose the body digests from starches, Lustig argues, is used by every cell in the body. Fructose and sucrose (which is itself a combination of glucose and fructose), however, have to be processed in the liver. The problem isn't just consuming too many calories as sugar. The problem, according to Dr. Lustig and other influential commentators such as the New York Times' Gary Taubes, is that both fructose from corn syrup and sucrose table sugar "burn out" the liver's ability to store sugars and cause diabetes, overweight, high cholesterol, high blood pressure, and even some kinds of cancer.


How Exercise Seems to Protect Against the Ill Effects of Sugar


Seven scientists at the University of Bern in Switzerland, publishing their findings in the March 2011 edition of Medicine and Science in Sports and Exercise, have found a "loophole" for avoiding the toxic effects of all three kinds of sugar. The answer to health problems caused by sugar, the Swiss scientists say, is simply to burn off sugar calories before they are consumed.

woman_running_jogging.jpgThe liver converts sucrose and fructose into glucose. It then chemically combines glucose and water to make glycogen, which it stores as an emergency fuel reserve. Muscles do the same thing, on a smaller scale. A healthy adult usually has about 5 to 10 grams of glucose circulating through the entire bloodstream at any one time. That is enough to provide just 20 to 50 calories for exercise. Any more calories burned have to come from a combination of stored sugars, first, and then fat.

Glycogen is turned into glucose to fuel activity, and then it is replenished again after the next meal, at rest.

The Swiss scientists recruited cyclists who would ride through the Alps until they were exhausted. They did magnetic resonance imaging (MRI) to measure the size of the cyclists' livers before, during, and after the ride. Then when the cyclists were completely exhausted, they were asked to drink beverages made with either fructose or glucose (and in a few instances, a beverage labeled as flavored with milk sugar).

The liver scans showed that exhausting exercise depleted the stores of glycogen. Consuming sugar after the ride helped the liver build its stored energy back to normal levels. Two hours after consuming a glucose-flavored drink, the liver increased its volume an average of 2%. Two hours after consuming either fructose or milk sugar (galactose), the liver increased its volume an average of 9%.

Athletes cannot continue exercise without replenishing glycogen in the liver. Replenishing glycogen is also essential for maintaining muscle mass. The Swiss study showed that for athletes, fructose and galactose were far superior to glucose for restoring the body's energy supplies.

This study suggests that  both table sugar and high-fructose corn syrup not only are not toxic, they are superior to the kind of sugar the body digests from "healthy foods," for athletes who work out to the point of exhaustion.

In sedentary people, consuming large amounts of fructose reduces the liver's sensitivity to sugars and leads to diabetes. In people who exercise at a moderate pace for a short period, for example, taking a 30-minute walk, the liver responds to fructose differently, and small amounts of fructose sugar may not be harmful. For most people, this means up to 20 grams (80 calories) of high-fructose corn syrup or table sugar will be tolerated, although unfortunately this may be too much for people who have diabetes.

In athletes who work out with maximum intensity, high-fructose corn syrup and table sugar up to the amount of calories burned may actually be helpful. But it is only possible to consume sugar calories with impunity when you have "paid" for them first, by exercise.
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  • Décombaz J, Jentjens R, Ith M, Scheurer E, Buehler T, Jeukendrup A, Boesch C. Fructose and Galactose Enhance Post-Exercise Human Liver Glycogen Synthesis. Med Sci Sports Exerc. 2011 Mar 10. [Epub ahead of print]
  • Photo courtesy of Celso FLORES by Flickr : www.flickr.com/photos/celso/2401957281/