Double serving of evidence underscores power of portfolio diet for heart health

A pair of studies from the University of Toronto and Unity Health Toronto highlights the ability of the plant-based portfolio diet to lower cardiovascular disease risk and mortality. Together, the findings reinforce the diet’s potential to improve heart health across diverse groups of people. 

In the first study, published in BMC Medicine, researchers analyzed data from nearly 15,000 Americans. They found that following the portfolio diet was associated with a major reduction in risk for death from cardiovascular disease, coronary heart disease and all causes. 

“Even adding a small amount of these foods, like an ounce of nuts or half a cup of cooked beans, can have benefit,” says Meaghan Kavanagh, the study’s lead author and a postdoctoral fellow in the department of nutritional sciences at U of T’s Temerty Faculty of Medicine. “You don't need to follow a strict diet to make a positive difference.” 

Study participants earned points for eating foods from each of the categories in the portfolio diet: nuts; plant-based proteins like beans or tofu; viscous fibre sources from foods such as apples or oatmeal; and ingredients rich in phytosterols and monounsaturated fatty acid, for example enriched margarine or oils. Points were deducted for consuming foods high in saturated fat and cholesterol. 

Those who followed the diet most closely showed fewer risk factors including blood lipids, inflammation, and high blood sugar, and a 16 per cent lower risk for cardiovascular disease and 18 per cent lower risk for coronary heart disease. The researchers also observed 14 per cent lower all-cause mortality among this group.  

Moderate adherence to the diet less still yielded notable benefits, including a 12 per cent reduction in cardiovascular disease risk, 14 per cent fewer risk factors for coronary heart disease — and 12 per cent fewer deaths from all causes. 

The study was led by John Sievenpiper, a professor of nutritional sciences and medicine at Temerty Medicine, who is also a staff physician and scientist at St. Michael’s Hospital, Unity Health Toronto. The study is the first to connect the portfolio diet, developed in 2003 by Temerty Medicine Professor David Jenkins, with lower cardiovascular disease mortality and all-cause mortality. 

The study drew on data from the American National Health and Nutrition Examination Survey It included populations not previously reflected in portfolio diet research, such as non-hispanic Blacks and Mexican Americans, as well as non-hispanic Whites and seniors. 

The team examined eating habits using a 24-hour dietary recall survey as well as food frequency questionnaires used in previous studies.  

Many foods may have been missed in earlier research, says Kavanagh, who spent three months working at the U.S. Centres for Disease Control in Atlanta, Georgia as part of the research.  

“We were able to capture a more nuanced picture of how people were eating. In the past, we hadn’t distinguished between the various fats people may have been using,” she says. “While I was in Georgia, I observed that a lot of cooking there is done with lard. So, when people recorded cooking beans with fat, it was important to note which kind they used because lard has more saturated fat than olive oil, for example.” 

From aging hearts to young adults 

While much existing portfolio diet research has focused on older adults, a second study shifts attention to a younger, often overlooked demographic. Published in BMC Public Health, this study looked at approximately 1,500 ethnoculturally diverse people in their twenties, using data from the Toronto Nutrigenomics and Health Study. 

“We wanted to understand how these dietary patterns play out in younger, generally healthier populations,” says lead author Victoria Chen, who recently completed a master’s degree in nutritional sciences at Temerty Medicine.  

Even in this low-risk group, greater adherence to the portfolio diet was associated with lower LDL cholesterol and other cardiovascular risk factors including total cholesterol and blood pressure. Chen and her colleagues believe adopting these eating habits early may help limit lifetime exposure to LDL cholesterol and delay cardiovascular disease risk onset. 

“Because this cohort is low-risk and in good general health, their LDL cholesterol levels were quite low to begin with,” says Chen, who was also a member of Sievenpiper’s lab at the time of the study. “But we were still able to see significant favourable associations between the portfolio diet and people’s risk factors. Considering cumulative exposure to risk factors opened our eyes to the impact this way of eating can have in the long run.” 

A 50 per cent adherence to the portfolio diet beginning in young adulthood may delay a rise in cardiovascular disease risk later by an estimated six years. Following the diet completely was estimated to delay the risk onset by 13 years. 

Chen and her colleagues note that dietary interventions can play an important role in young adulthood because common life transitions, like moving away from home for the first time or finishing school, have previously been associated with negative impacts on diet quality.  

“When we think of therapeutic diets, people in their twenties aren’t the first demographic that comes to mind,” says Chen. “We found that some of the portfolio diet foods that are easy to ‘grab and go’ were already part of their eating habits. Things like nuts, fruits and berries can be easy for these populations to incorporate into their lifestyle and set the stage for better long-term health.”