ANN ARBOR, Mich. -- In a new study led by the University of Michigan Health System, women more than doubled their fruit and vegetable intakes and dramatically increased their consumption of "good" fats when they were counseled by registered dietitians and provided with a list of guidelines on the amount of certain foods they should eat each day.
The six-month study of 69 women divided the participants into two groups. In one group, registered dietitians used an "exchange list" of foods that are common in a Mediterranean diet to make a plan for each participant. The new plan maintained the caloric and total fat intakes that the participants consumed at the beginning of the study.
The list included suggested servings, or exchanges, of several categories of foods--such as dark green vegetables, such as spinach, or high-monounsaturated fats, such olive oil. The dietitians also provided counseling on the telephone to help the participants to make the dietary changes, as well as in-person sessions at the start of the study and three months later.
Women in the comparison group continued their usual diet and did not receive any dietary counseling, though they were offered one free dietary counseling session after they completed their part in the study. If their intake of any vitamin or mineral was less than two-thirds of the recommended levels, they were given a list of foods that are rich in that nutrient. They also were given the National Cancer Institute's "Action Guide to Healthy Eating."
Researchers found that the group that followed the exchange-list plan reached the goals of the Mediterranean diet within three months, and maintained the change for the six-month duration of the study. But the comparison group that did not use the exchange list or receive dietary counseling made few dietary changes.
"That tells us that the exchange list was helpful in assisting women to make major changes in their diet, without changes in their caloric or total fat intake," says lead author Zora Djuric, Ph.D., research professor of Family Medicine at the U-M Medical School. The study appears in the December issue of the Journal of the American Dietetic Association.
Djuric--a member of the U-M Comprehensive Cancer Center--is also leading a study called Healthy Eating for Colon Cancer Prevention, in which she and colleagues are examining whether a Mediterranean diet can have preventive effects in the colon in persons at increased colon cancer risk. The diet used in the newly published study also should be applicable to prevention of many cancers, such as , breast cancer, Djuric says. More information on the current study, and how to participate in it, can be found at the University of Mcihigan Engage Web site.
Mediterranean diets have been associated with health benefits such as lower risks for cardiovascular disease and cancer, Djuric notes. Recent studies also have suggested that such a diet can increase longevity, but this data is from observational studies of Europeans who followed a traditional Mediterranean dietary pattern. The new research is the first time a method has been devised to achieve the major Mediterranean nutrient intakes using American foods, and American women were able to follow this diet.
Eating patterns in Greece and other Mediterranean countries traditionally have been high in monounsaturated fats, compared with the saturated fats and polyunsaturated fats that are more common in the United States. The Mediterranean diet is also rich in fruits and vegetables.
In this new study, specific suggestions in the exchange list included:
- 8-10 servings (or exchanges) each day of high monounsaturated fatty acid (MUFA), such as olive or hazelnut oil, avocado and macadamia nuts
- Limits on fats that are low in MUFA, such as corn oil, margarine, tahini, pine nuts and sesame seeds.
- One or more servings a day of dark green vegetables, such as broccoli, peas and spinach
- At least one exchange per day of garlic, onions and leeks
- One tablespoon or more per day of green herbs, such as basil, cilantro, peppermint and sage
- One or more servings a day of red vegetables, such as tomatoes, tomato sauce and salsa
- One or more servings a day of yellow or orange vegetables, such as carrots, red bell peppers and pumpkin
- One or more servings a day of other vegetables, such as artichokes, cucumber, green beans and sugar snap peas
- One or more servings a day of vitamin C fruits, such as oranges, mangoes and strawberries
- One or more servings a day of other fruits, such as apples, bananas and grapes
Authors: In addition to Djuric, authors of the paper were: senior author Ananda Sen, Ph.D., associate professor at the U-M Department of Family Medicine; Glee van Loon, R.D., who was a research dietitian at U-M; and from the Karmanos Cancer Institute: Katherine Radakovich, M.D., R.D., Nora M. DiLaura, M.S., R.D., and Lance K. Heilbrun, Ph.D.
Funding: American Institute for Cancer Research; National Institutes of Health Cancer Center Support Grants; and the chemistry laboratory of the Michigan Diabetes Research and Training Center and the General Clinical Research Center at U-M.
Reference: Journal of the American Dietetic Association, Dec. 2008, Vol. 108 Number 12, "Design of a Mediterranean Exchange List Diet Implemented by Telephone Counseling."