Jan. 29, 2003 COLUMBUS, Ohio – Supplementing the diet with a certain fatty acid may lead to better weight control and disease management in diabetics, a new study suggests.
Diabetics who added an essential fatty acid called conjugated linoleic acid (CLA) to their diets had lower body mass as well as lower blood sugar levels by the end of the eight-week study. Hyperglycemia, or high blood sugar, is a hallmark of diabetes.
Researchers also found that higher levels of this fatty acid in the bloodstream meant lower levels of leptin, a hormone thought to regulate fat levels. Scientists think that high leptin levels may play a role in obesity, one of the biggest risk factors for adult-onset diabetes.
"In previous work, we found that CLA delayed the onset of diabetes in rats," said Martha Belury, the senior author of the study and an associate professor of human nutrition at Ohio State University. "In this study, we found that it also helped improve the management of adult-onset diabetes in humans."
CLA is made up of various fatty acid isomers – compounds that share the same chemical formula but differ in chemical structure. Related isomers can have very different effects.
In the current study, the researchers found that one particular CLA isomer, t10c12-CLA, helped control both body weight and leptin levels. Nutritionists sometimes call this isomer the 10-12, isomer.
The research appears in the January issue of the Journal of Nutrition. Belury conducted the study while with the department of foods and nutrition at Purdue University. She is continuing the research at Ohio State.
The researchers asked 21 people with adult-onset diabetes to take either a supplement containing a mix of rumenic acid and 10-12 isomer or a safflower oil supplement as a control. The group was divided roughly in half. Rumenic acid is the predominant isomer in foods that contain CLA, while the 10-12 isomer is less abundant.
Participants were instructed to take their respective supplements every day for eight weeks.
"The amount of CLA, how long it's taken and the type taken all impact the fatty acid's ability to affect obesity in humans, and therefore help manage diabetes."
While CLA supplements are available to consumers, Belury encourages diabetics to get their CLA from food sources – primarily beef, lamb and dairy products.
"Not only does it taste better, it's also safer and more beneficial to get the nutrients from food," she said. "Besides, we don't yet know the long-term effects of taking CLA in supplement form."
At the end of the trial, the researchers took blood samples from each participant to check CLA levels. By then, fasting blood glucose levels had decreased in nine of the 11 people taking the CLA supplement, but only in two of the 10 taking safflower supplements, meaning that CLA was helping to control certain symptoms of diabetes.
Fasting blood glucose levels decreased nearly five-fold in patients taking CLA, compared to patients taking the safflower oil.
The researchers also studied the impact each isomer had on changes in body weight and levels of the hormone leptin.
It was the 10-12 isomer, and not rumenic acid, that was linked to a reduction in body weight and leptin levels. While the average weight loss among patients taking CLA supplements was small (about 3.5 pounds), they had been asked to not change their normal caloric intake during the study. The group taking safflower supplements neither lost nor gained weight. Leptin levels decreased in the CLA group, and rose slightly in the safflower group.
"The effect of the 10-12 isomer on reducing body mass and leptin levels was key," Belury said, adding that other researchers have shown the 10-12 isomer to be helpful in reducing body mass in animals.
"The amount of CLA, how long it's taken and the type taken all impact the fatty acid's ability to affect obesity in humans, and therefore help manage diabetes," Belury said.
A 2002 study conducted by the Diabetes Prevention Program Research Group found that a modest reduction in body weight resulted in a 58 percent reduction in the incidence of diabetes in a group of people at high risk for developing the disease.
Belury conducted the study with Annie Mahon of the department of foods and nutrition at Purdue University and Sebastiano Banni of the department of experimental biology at the University of Cagliari, Italy.
The research received support from Pharmanutrients, Inc., Lake Bluff, Ill., and Natural, Inc., Chicago. Although Belury has consulted for both companies in the past, she was not a paid consultant during the time of this study.
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