Fructose but Not Glucose Consumption Linked to Atherogenic Lipid Profile

Emma Hitt, PhD

July 05, 2007

July 5, 2007 -- Fructose, a sugar used for sweetening most soft drinks in the United States and elsewhere, has been linked to an increased atherogenic profile relative to glucose in a short-term study of overweight/obese adults.

Peter J. Havel, DVM, PhD, a research professor from the Department of Nutrition at the University of California, Davis, and colleagues presented the findings at the American Diabetes Association 67th Scientific Sessions in Chicago, Illinois.

"Soft drink consumption is, for most people, the largest source of dietary fructose," Dr. Havel told Medscape. "Of course, fructose is present in fruit too, but at much lower levels, and...fruit contains many other nutrients."

Dr. Havel and colleagues studied 23 subjects with a body mass index of 23 to 35 kg/m 2. In the beginning of the study, participants stayed in a clinical facility for 2 weeks while consuming an energy-balanced diet containing a moderate (30%) level of fat and 55% complex carbohydrates. Baseline blood measurements were made.

Subjects then began an 8-week outpatient intervention, consuming drinks that made up 25% of their daily energy needs. The drinks were sweetened with either fructose (n = 13) or glucose (n = 10). The rest of the participants' diet was self-selected.

At the end of the 8-week intervention, subjects returned to the clinical facility for 2 additional weeks and consumed either glucose- or fructose-sweetened beverages along with the same energy-balanced diet consumed during the first 2-week stay.

Relative to baseline, 24-hour postprandial triglyceride profiles were increased by 212% ± 59% in the fructose-consuming group ( P < .0001). In contrast, levels declined by about one third (-30% ± 23%) in the glucose-consuming group. In addition, fasting plasma levels of low-density lipoprotein cholesterol (LDL-C); apolipoprotein B; and small, dense LDL-C, as well as postprandial levels of remnant lipoprotein (RLP)-triglycerides and RLP-cholesterol, were all significantly increased ( P < .01) in the fructose group. By comparison, these levels remained unchanged in the glucose group.

Fructose-consuming participants also demonstrated increased plasma concentrations of the atherogenic risk factors oxidized LDL-C ( P < .0001) and intracellular adhesion molecule ( P < .05), but those consuming glucose did not.

"Consumption of sugar-sweetened beverages containing fructose has increased by 135% from 1977 to 2001 and may be a contributing factor to an increased incidence of metabolic syndrome," the authors note in their abstract.

According to Dr. Havel, most soft drinks in the United States are sweetened with high-fructose corn syrup, which is a mixture of about 55% fructose and 45% glucose.

"It is known that fructose, after being metabolized by the liver, is more likely to go into a lipogenic pathway than glucose," Dr. Havel noted. "So these results were not surprising to us, but the magnitude of some of the changes was striking," he added.

"While this is an interim report, the findings do suggest that persons at risk for cardiovascular disease, diabetes, or hyperlipidemia should limit consumption of fructose-sweetened beverages. It is unclear, however, whether a nonatherogenic level of fructose consumption exists, and what that might be."

According to Amy Hess-Fischl, MS, RD, LDN, BC-ADM, CDE, diabetes educator/coordinator from the Adolescent and Teen Diabetes Program, University of Chicago Comprehensive Diabetes Center, Chicago, Illinois, who moderated the session at the meeting, although this study was conducted in overweight and obese individuals, other studies indicate that the atherogenic effect of fructose may extend to normal-weight individuals as well.

However, Ms. Fischl told Medscape that controversy exists over the extent of atherogenicity associated with fructose consumption: "On the basis of these findings, fructose consumed at 25% of total energy had a negative effect, while another study found that 17% of total energy had a negative impact."

"Finding the safe limit will be key, and more research is needed to identify those persons most at risk," noted Ms. Fischl. "Until then, healthcare professionals can recommend that, based on several studies, limiting consumption of fructose-containing beverages is probably beneficial."

American Diabetes Association 67th Scientific Sessions: Abstract 0062-OR. Presented June 23, 2007.

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