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 the Journal 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 the American 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.
- 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.
- 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.
- 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.
- 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).
Dr. Mickleborough is an associate professor of exercise physiology at Indiana University. He is a former elite-level athlete who placed 18th overall (08:55:38) and second in the run (02:52:13) in the 1994 Hawaii Ironman World Championships.