2 New Studies Show CVD Benefit of Portfolio Diet

Two new Canadian studies suggest that the plant-based Portfolio Diet, which features cholesterol-lowering food choices, can reduce the risk for cardiovascular disease (CVD) and mortality across diverse groups. The diet previously had been evaluated mostly among older, White participants.

The first study found an association between the diet, which was developed in 2003 by David J.A. Jenkins, MD, PhD, DSc, a researcher at the University of Toronto, Toronto, and a lower risk for CVD mortality and all-cause mortality. It was published last month in BMC Medicine.

Researchers analyzed data of 14,835 US adults from the National Health and Nutrition Examination Survey (1988-1994) and found that adhering to the Portfolio Diet was associated with a significant reduction in the risk for death from CVD, coronary heart disease (CHD), and all causes.

Points for Foods

Participants’ diets were evaluated by 24-hour dietary recall and a food frequency questionnaire (FFQ) at baseline using the Portfolio Diet Score (PDS). Patients were assigned positive points for the four focus groups of the diet: Nuts, plant protein (eg, beans or tofu), viscous fiber (eg, apples, oatmeal, and eggplant), and phytosterols and plant monounsaturated fatty acid sources (eg, enriched margarine or oils). Patients received negative points for foods high in saturated fat and cholesterol. The primary outcome was CVD mortality.

For all participants, an 8-point increase in PDS was associated with a 12% lower risk for CVD mortality. Other mortality outcomes included CHD, stroke, and all-cause mortality.

Examining 22 years of follow-up, the researchers found that higher adherence to the diet was associated with lower risk factors, including blood lipids, glycemia, and inflammation. An increase in PDS of 8 points was associated with a 12% lower risk, 14% lower risk, and 12% lower risk for CVD, CHD, and all-cause mortality, respectively, after adjustments for known CVD risk factors.

“We know that it works,” study author Meaghan E. Kavanagh, PhD, of the Department of Nutritional Sciences at the University of Toronto’s Temerty Faculty of Medicine, told Medscape Medical News. It has been clear since early clinical trials that the diet can lower the level of low-density lipoprotein (LDL) cholesterol substantially, she said. “It’s the same effect as a first-generation statin.” The current research is the next step, she explained, and the studies demonstrate that the diet can reduce people’s risk for dying from these factors. They also broaden the diversity of the cohort.

Younger, Diverse Group

The focus of the related trial, which was published last month in BMC Public Health and written by many of the same researchers, “was to look at [the diet] in a younger population to see if we could find associations with LDL cholesterol in such a healthy, young population. We’re trying to show it works in all groups,” Kavanaugh said.

The trial, led by Victoria Chen, a student at the University of Toronto, included 1507 ethnoculturally diverse people in their 20s using data from the Toronto Nutrigenomics and Health Study.

In that study, diet was assessed by a validated Toronto-modified Harvard 196-item FFQ. Participants were instructed on how to complete the FFQ using visual aids of portion sizes. Adherence to the Portfolio Diet was measured using the PDS, and data analysis was adjusted for potential confounders.

Researchers studied the association of the PDS with LDL and other established CV risk factors in young people.

In this group, “an 8-point higher PDS was associated with 3% lower LDL-C, the primary outcome,” the authors wrote. “Our findings are also in agreement with cross-sectional analyses of other dietary patterns that share some similar components (legumes, whole grains, nuts, plant oils, fruits, and vegetables) to the Portfolio Diet, including the Dietary Approaches to Stop Hypertension (DASH) and Mediterranean diets, which have been associated with more favorable lipid, blood pressure, and/or adiposity markers in young adults who are predominantly university students.”

According to the study, 50% adherence to the Portfolio Diet beginning in young adulthood may delay increases in CVD risk later in life by about 6 years. Strict adherence could delay it by up to 13 years.

“This diet reinforces that patterns of eating are important over and above any one nutrient or food group,” said Jodi Heshka, MD, director of the Guideline-Directed Medical Therapy Clinic at the University of Ottawa Heart Institute, Ottawa. “These new data show the Portfolio Diet also works in a variety of patients, ages, different backgrounds.” Heshka did not participate in the study.

Low Adherence Beneficial

Heshka, who recommends the diet to her patients, said another benefit is that even low adherence improves outcomes. “You don’t have to go crazy following the Portfolio Diet to a tee,” she pointed out. “Simply by incorporating more of these foods and by default reducing other foods — even that alone can add benefit.”

Michele Blanchet, RD, a registered dietitian with Vancouver Coastal Health, Vancouver, told Medscape Medical News that she’s been recommending the Portfolio Diet to patients since she started specializing in CV health 14 years ago.

“It’s been the crux of me helping individuals lower cholesterol,” she said, but she also combines it with parts of the Mediterranean diet, particularly the visual representations of proportions of food groups.

She said she was particularly glad to see the finding that the diet can reduce the risk even in young, healthy people. “We’re seeing in our cardiac rehab program younger and younger individuals coming in needing bypass surgeries, having heart attacks,” Blanchet said.

To work with young adults to follow the diet, she takes a diet history and looks at where they can make small changes: Adding vegetables and legumes and sprinkling flaxseed on foods, for instance.

“By making small changes throughout the day, they can have this synergistic effect of lowering their cholesterol and seeing the heart health benefits of this diet,” she said.

The study led by Kavanaugh was funded by the Canadian Institutes of Health Research (CIHR). The study led by Chen was funded by a Toronto 3D Research Fellowship Award, CIHR, and a University of Toronto fellowship. Kavanaugh, Chen, Heshka, and Blanchet reported having no relevant financial relationships.

Marcia Frellick is a Chicago-based healthcare journalist and a regular contributor to Medscape Medical News.