The sweeteners fructose and glucose may seem almost indistinguishable in taste, but a new study in the Journal of Clinical Investigation suggests that the health benefits – or detriments – of the sugars may not be similar at all. Fructose, in contrast to its relative glucose, appears to have a deleterious effect on heart health, including raising LDL (a.k.a. “bad”) cholesterol and triglyceride levels.

Researchers at the University of California, Davis wished to determine how the two sugars differed in their effects on overweight individuals’ heart health, over a period of 10 weeks. The participants, 32 men and women whose average age was 55, initially lived at the research center for two weeks while the researchers took baseline measurements for each person. During this time, the participants ate a special high complex carbohydrate diet along with either fructose- or glucose-sweetened drinks, which made up 25% of their daily calorie intake. The participants then went back to their normal routines, still drinking the sweetened drinks, for the next six weeks. Finally, the subjects returned to the research center for another two weeks, back on the high-carbohydrate diet, while more measurements were taken.

At the conclusion of the study, the research team, led by Peter J. Havel, found that participants consuming fructose-sweetened beverages showed significant increases in LDL cholesterol, triglyceride levels, blood lipid levels, and intra-abdominal fat (which has been linked to cardiovascular risk), and decreases in their sensitivity to insulin. None of these effects was seen in the participants who drank sucrose-sweetened beverages. Moderate weight gain was observed in both groups, but unlike in the fructose group, the glucose group’s weight gain was not concentrated in the intra-abdominal area.

Havel says that his findings “[suggest] that in the same way that not all fats are the same, not all dietary carbohydrates are the same either.” The authors do note that while there is much controversy surrounding the health risks/benefits of consuming high-fructose corn syrup, this study does not address those issues, as high-fructose corn syrup – a mixture of fructose and glucose – was not included here.

More research will be needed to address the lingering questions: Havel and his team are already at work on the next study, which will compare fructose, glucose, sucrose, and high-fructose corn syrup in obese and normal weight women and men.