Growing up, we were always told to eat our vegetables, and now, new research provides some affirmation of this advice, as results from two new long-term studies show that eating more plant-based foods can reduce the risk of heart disease in both young adults and postmenopausal women.
The research studies, published in the Journal of the American Heart Association, reveal that young adults and postmenopausal women benefit from high plant-based food consumption. Both groups were found to have fewer heart attacks and were less likely to develop cardiovascular disease if they consumed more healthy plant-based foods.
One of the studies had a 30-year follow-up and showed that long-term consumption of plant-based foods, or a plant-centered diet, in young adulthood was associated with a lower risk of cardiovascular disease in midlife. The second study followed participants for 15 years and found that eating a cholesterol-lowering plant-rich diet, known as the “portfolio diet,” is associated with a lower risk of cardiovascular disease in postmenopausal women.
As part of a healthy diet, the American Heart Association Diet and Lifestyle Recommendations promote the consumption of fruits and vegetables; non-tropical vegetable oils; nuts and legumes; whole grains; low-fat dairy products; and skinless poultry and fish. It also advises people to limit the intake of saturated fat, trans fat, red meat, salts, sweets and sugary drinks.
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“Earlier research was focused on single nutrients or single foods, yet there is little data about a plant-centered diet and the long-term risk of cardiovascular disease,” said Yuni Choi, PhD, lead author on the young adult study and a postdoctoral researcher in the division of epidemiology and community health at the University of Minnesota School of Public Health in Minneapolis.
Young Adult Study
In the young adult study, Dr. Choi and his colleagues looked at diet and heart disease occurrence in 4,946 adults enrolled in the prospective Coronary Artery Risk Development in Young Adults (CARDIA) study. At the time of enrollment (1985 to 1986), participants were between 18 and 30 years of age, did not have cardiovascular disease and were followed for over 30 years until 2018. Women comprised 54.9 percent of all participants, which included 2,509 Black adults and 2,437 white adults who were assessed for various factors including education levels (based on completion of high school).
In addition to lab tests, physical measurements, medical histories and evaluation of lifestyle factors, detailed diet history interviews were conducted to record participants’ food consumption at years zero, seven and 20.
Diet quality was evaluated using the A Priori Diet Quality Score (APDQS), in which higher scores indicate higher intake of nutritious plant-based foods with limited consumption of high‐fat meat products and less healthy plant-based foods. The APDQS consists of 46 food groups classified into beneficial foods (such as fruits, vegetables, beans, nuts and whole grains); adverse foods (like salty snacks, fried potatoes, fatty red meat, pastries and soft drinks); and neutral foods (like potatoes, refined grains, lean meats and shellfish) based on their known association with cardiovascular disease.
Participants who achieved high scores (in the top 20 percent of scores) consumed a variety of beneficial foods representing a nutritionally-rich plant-centered diet, while people that had lower scores consumed more adverse, meat-heavy foods. The high scorers had a 52 percent reduced risk of developing cardiovascular disease after adjusting for factors such as age, sex, race, education, family history, smoking and physical activity among others.
Significantly, between year seven and 20 of the study when the age of the participants ranged from 25 to 50, individuals with the most improved diet quality were 61 percent less likely to develop cardiovascular disease when they got older, compared to participants whose diet quality worsened the most over the same period.
The effects of a strict vegetarian diet (which excludes all animal products including eggs and dairy) could not be evaluated as there were few vegetarians among the participants.
“A nutritionally rich, plant-centered diet is beneficial for cardiovascular health. A plant-centered diet is not necessarily vegetarian,” said Dr. Choi. “People can choose among plant foods that are as close to natural as possible, not highly processed. We think that individuals can include animal products in moderation from time to time, such as non-fried poultry, non-fried fish, eggs and low-fat dairy.”
Based on these findings, a cause-and-effect relationship between diet and heart disease cannot be established due to the observational nature of the study.
The Portfolio Diet and Cardiovascular Health in Postmenopausal Women
In the other study, consumption of foods based on the portfolio diet was evaluated by a team of researchers that included investigators on the Women’s Health Initiative (WHI) led by Simin Liu, MD, PhD, at Brown University.
The researchers assessed whether the Portfolio Diet, which consists of plant-based foods claimed to lower “bad” or low-density lipoprotein cholesterol (LDL-C) as per the US Food and Drug Administration (FDA), were associated with less cardiovascular disease events in a large group of postmenopausal women.
Portfolio diet foods include nuts; beans; tofu; soy-based plant protein; viscous soluble fiber from oats, barley, okra, eggplant, oranges, apples and berries; plant sterols from enriched foods and monounsaturated fats found in avocadoes as well as olive and canola oil; as well as limited consumption of saturated fats and dietary cholesterol.
Two randomized trials had previously demonstrated that meeting high target levels of portfolio diet foods led to significant lowering of LDL-C compared with a traditional low-saturated-fat National Cholesterol and Education Program diet in one of the studies, and was comparable to taking a cholesterol-lowering statin medication in the other study.
The WHI-based study included 123,330 women in the US. The WHI is a long-term national study evaluating risk factors in the prevention and early detection of serious health conditions in postmenopausal women. Women enrolled in the study between 1993 and 1998, at which time they were 50 to 79 years old (average age of 62) and did not have cardiovascular disease. The group was followed until 2017, with an average follow-up time of 15.3 years. Women were scored for their adherence to the portfolio diet based on data from self-reported food-frequency questionnaires.
Results of the study show that women that were in closest alignment with the portfolio diet were 11 percent less likely to develop any type of cardiovascular disease (14 percent less likely to develop coronary heart disease and 17 percent less likely to develop heart failure) compared with women who did not frequently adhere to the diet.
There was no association between closely following the portfolio diet and stroke or atrial fibrillation.
“These results present an important opportunity, as there is still room for people to incorporate more cholesterol-lowering plant foods into their diets. With even greater adherence to the Portfolio dietary pattern, one would expect an association with even less cardiovascular events, perhaps as much as cholesterol-lowering medications,” said John Sievenpiper, MD, PhD, senior author of the study at St. Michael’s Hospital, a site of Unity Health Toronto in Ontario, Canada, and associate professor of nutritional sciences and medicine at the University of Toronto.
“Still, an 11 percent reduction is clinically meaningful and would meet anyone’s minimum threshold for a benefit. The results indicate the portfolio diet yields heart-health benefits,” he added.
The researchers believe the results provide a strong rationale for people to incorporate more portfolio diet foods into their diets as a possible way to reduce their risk of heart disease.
Interestingly, and encouragingly, Andrea J. Glenn, MSc, RD, lead author on the study and a doctoral student in nutritional sciences at the University of Toronto, said, “We also found a dose response in our study, meaning that you can start small, adding one component of the portfolio diet at a time, and gain more heart-health benefits as you add more components.”
This study was also observational, and because of this, causal relationships cannot be established. Nevertheless, the researchers say that due to the study design that includes well-validated food frequency questionnaires administered at baseline and year three in a large population of highly dedicated participants, it provides a reliable estimate for the diet-heart connection to-date.
The researchers also say that the findings should be further investigated in other populations including men and younger women.
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