Harvard Study Calculates "Ideal" Fruit and Vegetable Intake for Heart Health

This article was originally published on PracticalCardiology.com.

Dong D. Wang, MD, ScD

A Harvard Medical School-led team purports their research has determined the "ideal" daily intake of fruits and vegetables for preventing cardiovascular events.

Investigators noted high amounts of inconsistency within dietary guidance can often cause confusion among patients and found consuming 2 servings of fruit and 3 servings of vegetables daily was linked to the greatest overall longevity and a 12% reduction in risk of death from cardiovascular disease.

“While groups like the American Heart Association recommend four to five servings each of fruits and vegetables daily, consumers likely get inconsistent messages about what defines optimal daily intake of fruits and vegetables such as the recommended amount, and which foods to include and avoid,” said lead study author Dong D. Wang, MD, ScD, an epidemiologist, nutritionist, and member of the medical faculty at Harvard Medical School and Brigham and Women’s Hospital, in a statement.

Few topics have been as exhaustively studied or debated as dietary science and the role of nutrition in cardiovascular and overall health. Spurred by an interest in describing the ideal diet, wang and a team of 10 colleagues designed the current study as a meta-analysis of cohort studies to assess the effects of diet on long-term mortality in patients free from cardiovascular disease, cancer, and diabetes at baseline.

Funded by the National Institutes of Health and the American Heart Association, investigators designed their study as an analysis of data from 66,719 women from the Nurses’ Healthy Study (NHS) and 42,016 men from the Health Professionals Follow-up Study (HFPS). Of note, the NHS cohort was enrolled between 1984-2014 while HPFS patients were enrolled from 1986-2014.

Patients enrolled in both of the studies completed semiquantitative food frequency questionaries at baseline and again every 2-4 years. Using this data and information from the National Death Index, investigators hoped to identify any dose-response relationships between intake of fruits and vegetables and mortality. With an interest in verifying the results of their initial analyses, investigators also conducted a dose-response meta-analysis using data from the aforementioned cohorts and 24 other prospective studies.

During the follow-up period, which lasted 2,855,065 person-years, a total of 33,898 deaths occurred within the NHS and HFPS cohorts. In adjusted analyses, results indicated nonlinear inverse associations of fruit and vegetable intake with total mortality and cause-specific mortality attributable to cancer, cardiovascular disease, and respiratory disease (P for all <.001). Further analysis indicated intake of 5 servings per day of fruit and vegetables or 2 servings of fruit and 3 servings of vegetables was associated with the lowest mortality and greater intake beyond that level was not associated with additional risk reduction.

Specifically, when compared to those consuming 2 servings per day, daily intake of 5 servings of fruits and vegetables was associated with a 13% reduction in risk of mortality (HR, 0.87; 95% CI, 0.85-0.90), a 12% reduction in risk of death from cardiovascular disease (HR, 0.88; 95% CI, 0.83-0.94), a 10% reduction in risk of death from cancer (HR, 0.90; 95% CI, and a 35% reduction in risk of death from respiratory disease (HR, 0.65; 95% CI, 0.59-0.72).

In their dose-response meta-analysis, which included more than 145,000 deaths and 1,892,885 participants, results pointed to a similar effect. Additional analysis suggested higher intakes of most subgroups of fruits and vegetables were associated with lower mortality, but investigators noted this did not extend to starchy vegetables. Furthermore, consumption of fruit juices and potatoes was not associated with total or cause-specific mortality.

“This amount likely offers the most benefit in terms of prevention of major chronic disease and is a relatively achievable intake for the general public,” Wang added. “We also found that not all fruits and vegetables offer the same degree of benefit, even though current dietary recommendations generally treat all types of fruits and vegetables, including starchy vegetables, fruit juices and potatoes, the same.”

This study, “Fruit and Vegetable Intake and Mortality: Results From 2 Prospective Cohort Studies of US Men and Women and a Meta-Analysis of 26 Cohort Studies,” was published in Circulation.