Dear Speed Lab,
It seems that many sports drinks and some energy bars contain high-fructose corn syrup. Having done some research on this ingredient, I've noticed that high-fructose corn syrup is being implicated in the obesity epidemic.
What's your opinion on high-fructose corn syrup being included in sports drinks? If it truly is "the devil's candy," shouldn't athletes stay well clear of this particular ingredient, especially since we consume large amounts of sports drinks and energy bars?
Paul S. — Gainesville, Florida
Dear Paul,
High-fructose corn syrup is extremely sweet and inexpensive to produce. It is manufactured by enzymatically changing the glucose in cornstarch to fructose. High-fructose corn syrup is added to canned and frozen fruits to preserve the structure of the fruit because it penetrates the fruit easily and preserves the natural form, flavor and color.
When added to soft drinks, it adds body without changing or masking flavors. It can be found in fruit-flavored drinks, energy bars, and a whole array of other food items such as cookies, gum, jams, jellies and baked goods. An advantage of high-fructose corn syrup is that it tastes sweeter than refined sugar, making it a popular ingredient for food manufacturers because it enables them to use less.
The World Health Organization (WHO) recommends limiting intake of added sugars found in food and drink to no more than 10 percent of daily calories, a step WHO claims could help stop the worldwide rise in obesity that is fueling the increasing prevalence of such chronic diseases as type 2 diabetes. The WHO recommendation is much stricter than any that U.S. groups have proposed, but increasingly, it's not just the growing consumption of foods with added sugars that concerns some nutrition experts.
What has also changed during the past four decades, as USDA figures show, is the type of sweeteners consumed, a trend that some studies suggest may undermine appetite control and possibly play a role in weight gain. In 1966, refined sugar, also known as sucrose, was by far the most popular sweetener, accounting for 86 percent of sweeteners used according to the USDA.
Today, sweeteners made from corn are most popular, with up to $4.5 billion in annual sales and accounting for 55 percent of the sweetener market. That change largely reflects the steady growth in usage of high-fructose corn syrup, which climbed from zero consumption in 1966 to 62.6 pounds per person in 2001.
How the Body Absorbs Sugar
Fructose is absorbed by the body differently than other sugars, and it does not register in the body metabolically in the same way that glucose does. For example, consumption of glucose triggers a cascade of biochemical reactions by increasing insulin release from the pancreas, enabling sugar in the blood to be transported into cells, where it can be used for energy.
Glucose also increases the production of leptin, a hormone that helps regulate appetite and fat storage, and it suppresses another hormone produced by the stomach called ghrelin that helps to regulate food intake. It has been suggested that when ghrelin levels drop after a carbohydrate meal (containing glucose), hunger declines.
However, fructose seems to behave more like fat with respect to the hormones involved in regulation of body weight. Fructose does not stimulate insulin secretion, increase leptin production or suppress production of ghrelin. This suggests that consuming a lot of fructose, like consuming too much fat, could contribute to weight gain.
Another concern is the effect of fructose on the liver, where it is converted into the chemical backbone of triglycerides more efficiently than glucose is. Triglycerides, which are found in low-density lipoproteins (LDL), the most damaging form of cholesterol, have been linked to an increased risk of heart disease. It has been shown that fructose produces significantly higher plasma triglyceride levels than does glucose in male test subjects.