Diabetes Forecast September 2004

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FOR TYPE 2

Research Profile

Carbs And Fats
How Much Of Each?
by Terri Kordella

Bonnie J. Brehm, PhD, RD, is comparing high-carb diets to diets high in monounsaturated fatty acids to see which have greater benefits for people with type 2.	Bonnie J. Brehm, PhD, RD Occupation Assistant Professor University of Cincinnati College of Nursing Professional Focus Nutrition, type 2 diabetes Outside Interests Travel, golfing, movies Research Funding ADA Clinical Research Award

Nutrition plays a major role in controlling type 2 diabetes and maintaining cardiovascular health. Yet conflicting recommendations abound: Watch your carbs. Watch your fats. No, watch your carbs. No, watch your fats.

The truth is that dietary recommendations for people with type 2 have changed over the years, and the recommendations are still evolving.

"Nutritional recommendations for people with type 2 have ranged from low-carb years ago to the current, most commonly used low-fat, moderately high-carbohydrate diet," says Bonnie Brehm, PhD, RD, assistant professor at the University of Cincinnati College of Nursing. "The current regimen gained popularity because of the goal of decreasing cardiovascular risk and lipids in people with type 2."

It turns out that all fats are not created equal, however. There are less healthy fats, such as saturated fats and trans fats, that are thought to contribute to your risk of cardiovascular disease by raising your LDL (bad) cholesterol and lowering your HDL (good) cholesterol. It makes sense to limit your intake of those.

But then there are healthier fats, such as monounsaturated fatty acids (MUFAs), which are thought to do just the opposite: They help lower your LDL and raise your HDL. By adhering to a low-fat diet in which you lump all fats together, you may be depriving yourself of the cardiovascular benefits of MUFAs.

To help you maintain proper weight, control your blood glucose, and lower your risk of cardiovascular disease, the American Diabetes Association currently recommends that 60 to 70 percent of your calories come from carbs and monounsaturated fats (MUFAs).

But even that leaves you and your dietitian a lot of leeway in determining exactly how much of your diet should come from carbs and how much should come from MUFAs. It's possible to eat within those recommendations and have your diet qualify as either high-carb or high-MUFA.

"There's a debate about which diet is more effective," Brehm says. "Small clinical studies indicate that a MUFA diet may have some advantages over a high-carb diet in that it can provide blood glucose control without the detrimental rise in triglycerides and the decrease in HDL cholesterol that has been seen with high-carbohydrate diets.

"However, one of the concerns in clinical practice is that high-MUFA diets have the potential to increase calorie intake and promote weight gain," she adds.

A Long-Term Study

Brehm wants to find out which ratio of carbs and MUFAs would be most beneficial for people with type 2. She is using her funds from an American Diabetes Association Clinical Research Award to clear up some of the controversy and try to pinpoint whether the currently recommended way of eating for people with type 2 should emphasize carbs or MUFAs. She, along with collaborator David D'Alessio, MD, and study coordinator Barbara Lattin, RD, will lead a study involving 120 people with type 2 diabetes to compare a high-carb diet to a high-MUFA diet and see which has the greater effect on weight, cholesterol, body composition, and blood glucose levels.

The study participants will be overweight, with A1Cs between 6.5 percent (well-controlled) and 9.0 percent (needs improvement). Diabetes treatments for the participants will range from diet and exercise to oral medications as prescribed by their doctors. People with type 2 who use insulin will be excluded from the study.

At the beginning of the study, the researchers will record the participants' weight, waist circumference, body mass index, and body composition, including body fat. Participants will have blood tests for their A1Cs, fasting insulin and blood glucose, HDL cholesterol, LDL cholesterol, triglycerides, and inflammatory markers like c-reactive protein. (High amounts of c-reactive protein in the blood have been linked to increased cardiovascular risk.)

Then the participants will be divided at random into two groups, the high-carb group and the high-MUFA group. Dietitians Suzanne Spang, RD, and Jane Boback, RD, will devise either high-carb or high-MUFA eating plans for each participant according to each participant's caloric needs. The high-carb eating plans will emphasize fruit, vegetables, skim or low-fat dairy products, whole grains, and lean meat, fish, and poultry. The high-MUFA eating plans will emphasize whole grains, fruits, vegetables, nuts, and oils such as peanut oil, olive oil, and canola oil. These foods are traditionally part of a Mediterranean diet, says Brehm.

The participants will attend counseling sessions with the dietitians. At first, they will come to the university once a week for either group counseling with others in their dietary group or for individual counseling. The sessions will alternate and gradually taper off until everyone is coming in only once a month for individual counseling. The participants will be advised on nutrition, weight loss, goals, and motivation.

They will also keep food journals on the days leading up to their counseling sessions. On the days they record their food intake, they will also record their physical activity.

"We encourage participants to adopt a walking program and then maintain that level of activity throughout the year of the study," Brehm says. "The activity level should be consistent throughout the study so we can see the effect of diet on their health."

At four months, eight months, and one year, participants will undergo the same tests and measurements they did when they enrolled: weight, waist circumference, body mass index, body composition, A1Cs, fasting insulin and blood glucose, HDL cholesterol, LDL cholesterol, triglycerides, and inflammatory markers. Then the research team will compare the results from the high-carb group to those of the high-MUFA group and see which way of eating had the more beneficial impact on these measurements.

Brehm is enthusiastic about the study and the insights she hopes it will provide. "So far, the studies we've seen about these diets have been shorter studies involving either a brief stay in the hospital or tracking for a few weeks. We needed a long-term study," she says. "I looked in the literature and thought 'someone must have done this,' but no, no one had looked at it over the long term.

"This will have real clinical significance," she says. "We know that diet is one of the cornerstones of treatment for people with type 2, so it's very important to find out which diet is more effective."