Plant-Based Diets Protective Against CVD in Two Studies

A pair of new studies are adding strength to the long-term health benefits of a plant-based diet by showing that individuals who have better adherence to that way of eating have lower risks of developing CVD over time.

In one, focused on postmenopausal women enrolled in the Women’s Health Initiative who were free of CVD and followed for 15 years, high adherence to plant-based eating was associated with not only less CVD but also less coronary disease and heart failure compared with low levels of adherence. 

In the second, researchers found that following a plant-focused diet from a young-adult age led to a 52% decrease in incident CVD by mid-life. Of note, participants in the study were not told what to eat. Instead, their diets were assessed periodically for quality.

“From a clinical and public health perspective, our findings support a recommendation of eating primarily nutritionally rich plant foods, but allowing small amounts of animal products (eg, low-fat dairy products, nonfried fish, and nonfried poultry), to prevent early cardiovascular disease,” write the authors of the latter study, led by Yuni Choi, PhD (University of Minnesota Twin Cities, St Paul).

In an interview with TCTMD, senior author on the Choi paper, David R. Jacobs Jr, PhD (University of Minnesota Twin Cities), said despite not being randomized, cohort studies like this one, which tracked eating patterns of young adults enrolled in CARDIA, should be seen as encouraging: they show that trying to eat as well as possible the majority of the time has future rewards without being a burden.

“What we can say is that those things that are centered on nutritionally-rich plant foods, excluding refined grains, excluding sugar . . . are not a guarantee [of less CVD], but people who eat them in general did better,” he noted. 

Both studies were published online in the Journal of the American Heart Association.

Emphasis on Plant-Centered Eating

For the CARDIA analysis, researchers followed 4,946 adults ages 18 to 30 who were free of CVD at baseline. Information on diet, including specific types of food and amounts eaten, was collected at the start of the study and again at year 7 and year 20. An index was created that consisted of 46 food groups. Plant-based diet quality was assessed using the A Priori Diet Quality Score (APDQS), which gives higher scores to nutritionally-rich plant foods and lower scores to consumption of high-fat meat products and unhealthy plant foods. 

Compared with lower scores, higher APDQS scores were associated with being older and female, having a higher level of education, being more physically active, consuming more alcohol, and consuming fewer total calories.

In addition to the lower risk of CVD associated with long-term adherence to a plant-centered diet, individuals whose APDQS scores increased during the study—reflecting that they made changes from year 7 to year 20 to include more-frequent consumption of beneficial plant-based foods—also saw a lower subsequent risk of CVD (HR 0.39; 95% CI 0.19-0.81).

Jacobs said that point in particular is important for consumers to note. “I try to think of this from the perspective of individual flexibility,” he added. “The emphasis is not low fat, low carbs despite all the noise that is out there. The emphasis really should be on plant centering and on maintaining a full and balanced diet.” Given that most physicians have limited education on nutrition and how to discuss it with patients, he said the importance of food as a social experience and as an enjoyable part of life should be incorporated into advice about adhering to a plant-based diet while also being realistic that no one will be 100% compliant at all times. The authors write that “it appears that the complete exclusion of animal foods from diet is not necessary.”

More Nutrition Outreach and Education Needed

Similarly, in the 123,330-person Women’s Health Initiative cohort study in which higher Portfolio Diet scores were correlated with better CVD outcomes, no participants actually attained the highest adherence score possible on the plant-based diet, though those who were most compliant saw reductions in total CVD, CAD, and HF. 

Portfolio groups food items into six components: plant protein, nuts, viscous fiber, phytosterols, monounsaturated fatty acids, and saturated fat/cholesterol sources, with each component being scored from 1 (unhealthy) to 5 (healthiest). Scores ranged from 20.5 to 30 for those in the top quartile of adherence to plant-rich foods and from 6 to 14 for those in the lowest quartile. The researchers, led by Andrea J. Glenn, MSc, RD (University of Toronto, Ontario, Canada), say the true benefits of the diet on CVD risk reduction are likely underestimated due to the study’s self-reported nature, how infrequently the dietary data were collected, and overall uncertainty about adherence rates. 

“This would suggest that as long as you can adhere to the Portfolio Diet to the extent possible, you still could get the benefits,” co-author Simin Liu, MD, PhD (Brown University, Providence, RI), said in an email. “It is certainly not ‘all or nothing adherence.’”

Liu added that while he considers this the best choice for those who want to commit to a plant-based diet, “more outreach and education would be necessary if the Portfolio Diet is to be adopted by the majority of populations in the United States.”

Asked if cardiologists should be recommending the Portfolio Diet to their postmenopausal patients, Liu said yes. “Data from this large national prospective cohort provide the best evidence to date in support of such a recommendation,” he said. “The Portfolio Diet is clearly one of the best, if not the best, therapeutic dietary approaches for managing CVD risk in postmenopausal women.”