Double serving of evidence underscores power of plant-based Portfolio Diet for heart health

Two new studies by researchers at Unity Health Toronto and the University of Toronto suggest that the plant-based Portfolio Diet can reduce the risk of cardiovascular disease and mortality, improving heart health across diverse groups of people. 

The first study, published in BMC Medicine, analyzed data from nearly 15,000 Americans and found that adherence to the Portfolio Diet was associated with a major reduction in the risk of death from cardiovascular disease, coronary heart disease and all causes. 

It is the first study to link the diet – developed in 2003 by Professor David Jenkins of U of T’s Temerty Faculty of Medicine – with lower cardiovascular disease mortality and all-cause mortality. 

“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 researcher in the department of nutritional sciences in U of T’s Temerty Faculty of Medicine. “You don't need to follow a strict diet to make a positive difference.” 

Participants earned points for consuming foods from each of the categories in the Portfolio Diet:

• nuts
• plant-based proteins such as beans or tofu
• viscous fibre sources from foods such as apples or oatmeal
• foods 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 adhered most closely to the diet showed fewer risk factors, including blood lipids, inflammation and high blood sugar. They also had a 16 per cent lower risk of cardiovascular disease and 18 per cent lower risk of coronary heart disease – and a 14 per cent reduction in all-cause mortality.  

Even moderate adherence 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 reduction in deaths from all causes. 

The study was led by John Sievenpiper, a staff physician and scientist at St. Michael’s Hospital, Unity Health Toronto, and a professor of nutritional sciences and medicine in U of T’s Temerty Faculty of Medicine. It drew on data from the U.S. National Health and Nutrition Examination Survey and included populations not previously reflected in Portfolio Diet research.

The team examined eating habits using a 24-hour dietary recall survey and food frequency questionnaires from earlier studies.  

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

“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 of the existing research on the Portfolio Diet 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 20s, 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 in U of T’s Temerty Faculty of 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 that adopting these eating habits early may help limit lifetime exposure to LDL cholesterol and delay the onset of cardiovascular disease risk. 

“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.” 

Adhering to 50 per cent of the Portfolio Diet beginning in young adulthood may delay the rise in cardiovascular disease risk later in life by an estimated six years. Full adherence could delay it by up to 13 years. 

Chen and her colleagues emphasize that dietary interventions in young adulthood are especially important as common life transitions – such as moving away from home for the first time or finishing school – have previously been linked with negative impacts on diet quality.  

“When we think of therapeutic diets, people in their 20s 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.”