Should I Worry About High-Fructose Corn Syrup?

Photo: Luke Smith/Active.com

By Tim Mickleborough, PhD

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.

These scientists who performed this research concluded that diets high in added fructose may be undesirable, particularly for men, and that glucose may be a suitable sugar replacement¹. Other research suggests that fructose may alter magnesium levels in the body, which could in turn accelerate bone loss according to a USDA study published in 2000 in theJournal of the American College of Nutrition.

Elliot., et al.² examined evidence from multiple studies as to whether fructose consumption might be a contributing factor to the development of obesity and the accompanying metabolic consequences observed in insulin resistance syndrome. They concluded that large quantities of fructose from a variety of sources, including table sugar and high-fructose corn syrup, induce insulin resistance, impair glucose tolerance, produce high levels of insulin, elevate a dangerous type of fat in the blood and can cause high blood pressure in animals.

However, these researchers also state that although energy intake, body weight and adiposity all increase in animals, less information is available in humans. And a barrage of more recent studies has seriously undermined the proposed HFCS-obesity link. A special supplemental issue of theAmerican Journal of Clinical Nutrition contained five studies that concluded that HFCS is no better or worse than table sugar in terms of causing weight gain.

HFCS and Athletes

Athletes should be aware of the following facts. First, added fructose in the forms of sucrose and high-fructose corn syrup does not appear to be the optimal source of carbohydrate in the diet. Secondly, the concerns that have been raised about the addition of fructose to the diet as sucrose or high-fructose corn syrup should not be extended to naturally occurring fructose obtained from fruits and vegetables.

It is worth mentioning that many of the studies examining the effects of fructose use pure fructose rather than the combination of fructose and glucose found in corn syrup. It is also worth pointing out that there is no single reason for the obesity epidemic or the onslaught of diabetes in America. What does appear to play a major role though is a lack of physical exercise.

With regard to the specific issue of the use of HFCS in ergogenic aids such as sports drinks, research suggests that it is not problematic and may even be beneficial. Studies by Asker Jeukendrup and colleagues at the University of Birmingham have shown that carbohydrates are absorbed and metabolized at a faster rate in sports drinks containing glucose and fructose than in sports drinks containing glucose alone, resulting in superior endurance performance.

The reason appears to be that because the two sugars are processed through different pathways, they can be processed simultaneously. In any event, sugars of any kind in sports drinks are extremely unlikely to contribute to weight gain if consumed during workouts, as these sugars are used immediately to fuel muscle contractions.

References:

1. Bantle, J.P., S. K. Raatz, W. Thomas and A. Georgopoulos. "Effects of Dietary Fructose on Plasma Lipids in Healthy Subjects." American Journal of Clinical Nutrition 72 (2000): 1128 -- 1134.
2. Elliot, S.S., N.L. Keim, J.S. Stern, K. Teff and P.J. Havel. "Fructose, Weight Gain and the Insulin Resistance Syndrome." American Journal of Clinical Nutrition 76 (2002): 911-922.
3. Melanson, K.J., T.J. Angelopoulos, V. Nguyen, L. Zukley, J. Lowndes, and J.M. Rippe. "High-Fructose Corn Syrup, Energy Intake, and Appetite Regulation." American Journal of Clinical Nutrition 88.6 (2008): 1738S-44S.
4. Jeukendrup, A.E.,and L. Moseley. "Multiple Transportable Carbohydrates Enhance Gastric Emptying and Fluid Recovery." Scandinavian Journal of Medical Science in Sports Nov. 3, 2008 (Not yet printed).