Although adhering to current diet recommendations could lead to small benefits in coronary heart disease risk factors, a randomized study in Canada found that changing eating habits proved difficult.

Lead researcher David J.A. Jenkins, MD, of the University of Toronto, and colleagues published their results online in the Journal of the American College of Cardiology on Feb. 27.

“These data demonstrate the difficulty in effectively promoting fruit, vegetable, and whole grain cereals to the general population, using recommendations that, when followed, decrease risk factors for chronic disease,” the researchers wrote. “They indicate an urgent need for innovative approaches to support the implementation of current dietary advice.”

Previous research from cohort studies suggested that changes in diet and lifestyle could help prevent 82 percent of cardiovascular disease and 91 percent of diabetes risk, according to the researchers.

They added that the U.S. Dietary Guidelines Advisory committee recommends the healthy American diet, the Mediterranean diet and a vegetarian diet to prevent chronic disease. Those diets emphasize eating more fruit, vegetables, whole grain cereals and cholesterol-lowering functional foods such as oats, barley, nuts and plant protein foods.

For this study, the researchers enrolled 919 healthy residents of Toronto who were at least 18 years old, spoke English and had a body mass index (BMI) of 25 kg/m² or higher. Approximately 77 percent of participants were women, while the mean age was 44.7 years old and the mean BMI was 32.4 kg/m².

Between November 2005 and August 2009, the participants were randomized to receive Health Canada’s food guide or one of three interventions: dietary advice consistent with DASH and dietary portfolio principles, weekly food provision reflecting this advice or food delivery plus advice. The interventions lasted six months, and patients were followed-up at 12 months. They also completed food frequency questionnaires at baseline, six months and 18 months.

Overall, 685 participants completed six months of the interventions for a 75 percent retention rate. The retention rates were 91 percent for participants with food provision and 67 percent for those without food provision, which represented a statistically significant difference.

From baseline to six months, there were small increases in fruit intake (0.3 to 1.1 servings per day), vegetable intake (0.4 to 1.3 servings daily) and whole grains (0 to 1 serving per day). Compared with the control group, only participants in the food provision plus advice group had consistent increases in fruit, vegetables and whole grain cereals.

At six months, the participants had a mean reduction of 1 kg in body weight, 1.4 cm in waist circumference, 0.8 mm Hg in diastolic blood pressure and 0.7 mm Hg in arterial pressure. Participants in the three test groups had statistically significant reductions in body weight and waist circumference compared with the control group.

At 18 months, the retention rates were 65 percent for the overall group, 81 percent for those provided with food and 57 percent for those who did not have food provision. From baseline to 18 months, there were small increases in fruit intake (0.4 to 0.6 servings per day), vegetable intake (0.3 to 0.6 servings per day) and whole grain cereals (0 to 0.6 servings per day). The fruit, vegetable and whole grain cereals intakes were significantly reduced at 18 months compared with six months.

The reductions in body weight, BMI and waist circumference were maintained from six to 18 months. Further, there were 24 adverse events during the study, but the differences between groups were not statistically significant.

The researchers cited a few limitations of the study, including that there were significant differences in dropout rates between the food delivery groups and the no food delivery group. They also mentioned the provision of Canada’s Food Guide could have led to the control group having an increasing intake of desired foods. In addition, the participants were generally healthy at baseline, so the researchers noted it might have been more difficult to detect changes in risk factors.

“Increasing the intake of not only fruit, vegetables, and whole grain cereals but also functional foods proved difficult, even when these foods were provided weekly and despite the known effectiveness of such foods in managing [coronary heart disease] risk factors,” the researchers wrote. “Healthy shifts in diet among generally well populations is likely to require a range of sustained approaches and multiple forms of communication in a process measured in decades rather than months.”