A Serious Look at Fructose

A study focusing on the effects of consuming fructose versus glucose was published in The Journal of Clinical Investigation (2009;119(5):1322-1334). A multi-university team of researchers recruited 32 men and women between the ages of 40 and 72 to participate in a feeding study. The participants all had a Body Mass Index between 25 and 35 (clinically overweight to clinically obese) and had no history of surgery for weight loss, diabetes, high blood pressure or high triglycerides. Those who already drank 1 or more sugar-sweetened beverage per day were also excluded from the study.

To set a baseline to compare against, the participants spent two weeks eating nothing but the foods provided to them by the researchers. Each person's diet was specifically designed to maintain their current weight and to provide 15% of calories from protein, 30% from fat and 55% from carbohydrates. During this baseline period the subjects gave blood for cholesterol and other tests, received a glucose tolerance test, and had their abdomens scanned to ascertain how much body fat was deposited around their internal organs versus beneath the skin.

Then for the following eight weeks the participants were randomly assigned to one of two groups: a fructose group and a glucose group. While both groups were given 3 daily servings of a sweetened beverage to drink with their three daily meals, one group's drink was sweetened with fructose while the other was sweetened with glucose. For those eight weeks the subjects were instructed to follow their usual diets and to avoid drinking other sugar-sweetened beverages or any fruit juices. At the end of the eight weeks the participants again had their cholesterol checked along with a glucose tolerance test and an abdominal scan.

The researchers found that both groups gained weight over the course of the eight weeks: between 3 and 5 pounds. However, those who were assigned to the fructose group were at markedly greater risk of diabetes: the amount of fat around their internal organs increased markedly while they decreased their sensitivity to insulin. Those in the glucose group, on the other hand, deposited most of their fat beneath the skin. Further, both groups' HDL levels (the good cholesterol) stayed the same while the LDL cholesterol (the bad cholesterol) increased significantly for those drinking the fructose-sweetened beverages.

What this means for you

This is a small study but significant in that it specifically compares glucose with fructose. The results are extremely concerning, but few commercial beverages are sweetened only with fructose: most are sweetened with sucrose, which is half glucose and half fructose. High Fructose Corn Syrup is between 45-58% glucose and 42-55% fructose. Will HFCS affect your visceral fat, cholesterol levels and insulin sensitivity the same way fructose does? We can't yet be sure. What we can be sure of is that sugar-sweetened beverages add a lot of calories to your diet that aren't very satisfying. Drink water, tea or coffee instead.

First posted: January 6, 2010
Updated: March 26, 2024