Glucose, Sucrose or Fructose: Is One Better Than Another?

It’s impossible to figure out through taste alone what gives our favorite soft drink or yummy dessert that perfect sweetness we have come to crave. And the complicated ingredient names on the nutritional labels usually leave us clueless as well. But even if we can’t tell the difference between sucrose, glucose and fructose, our bodies apparently can.

In a new study published this week in the Journal of Clinical Investigation, researchers from the University of California, Davis randomly assigned 32 overweight or obese men and women to drink three daily servings (25 percent of their daily energy requirements) of a glucose- or fructose-sweetened beverage for 10 weeks. The participants had an average age of 50 and a body mass index of 29. They were instructed to follow their normal diet but not to drink any other sugary drinks, including fruit juice.

At the end of the study period, both groups had gained similar amounts of weight, but those consuming fructose-sweetened drinks showed an increase in intra-abdominal fat, the kind that embeds itself between tissues in organs, became less sensitive to insulin (the hormone released by the pancreas that controls blood sugar), and showed signs of dyslipidemia—elevated blood levels of lipids. The fructose group also showed increased fat production in the liver, elevated LDL or bad cholesterol and larger increases in blood triglycerides. The group drinking glucose-sweetened beverages showed none of these changes.

“This suggests that in the same way that not all fats are the same, not all dietary carbohydrates are the same either,” says Dr. Peter J. Havel, professor of nutrition at the University of California Davis and lead author of the study. He added that most of the sugar present in market and restaurant products is not glucose, but rather high fructose corn syrup or sucrose (each a combination of glucose and fructose). He further held that it is difficult to find anything that’s mainly glucose, which means that almost all sweeteners could contribute to weight gain and metabolic changes that could increase the risk of heart disease and diabetes.

Havel said the findings could be important given that in 2005, the average American consumed 141 pounds of added sugar, a sizeable proportion of which came through drinking soft drinks. Consumption of sugars and sweeteners in the U.S. went up by 19 per cent between 1970 and 2005, according to a commentary accompanying the study.

“This study provides the best argument yet that we should either decide to consume less sugar-sweetened beverages in general, or that we should conduct more research into the possibility of using other sweeteners that may be more glucose-based,” says Matthias Tschoep, an obesity researcher at the Obesity Research Center in the University of Cincinnati, and author of a commentary accompanying the study. “It’s an unbelievable piece of work.”

However, Dr. David Jenkins, who holds the Canada Research Chair in nutrition and metabolism at the University of Toronto, is of a differing opinion. He says fructose is no worse than glucose if taken in moderation. “We’re talking about excess in people who are gaining weight, people who are overweight to begin with and people who are not exercising to begin with,” Jenkins said.

Havel’s research team is currently in the early stages of a study comparing the metabolic effects of fructose, glucose, sucrose (table sugar), and high fructose corn syrup in normal and obese men and women.