A team of U.S. researchers has found an inverse association between fruit and vegetable intake and mortality in two large prospective cohorts, the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS), with detailed and repeated dietary measurements and long follow-up; the lowest risk of mortality was observed for approximately five daily servings of fruits and vegetables, eaten as two servings of fruit and three servings of vegetables, but above that level, the risk did not decrease further; an updated meta-analysis of 26 prospective cohort studies including the NHS and HPFS yielded similar results; the findings support current U.S. dietary recommendations to eat more fruits and vegetables and the simple public health message ‘5-a-day.’
Diets rich in fruits and vegetables help reduce risk for numerous chronic health conditions that are leading causes of death, including cardiovascular disease and cancer.
Despite recommendations in dietary guidelines to increase fruit and vegetable intake, 3-5 the current average intake among U.S. adults, 1 serving of fruit and 1.5 servings of vegetables per day, remains far from optimal.
“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 Dr. Dong Wang, a researcher at Harvard Medical School and Brigham and Women’s Hospital.
Dr. Wang and colleagues followed 66,719 women from the NHS study (from 1984 to 2014) and 42,016 men from the HPFS study (from 1986 to 2014) who were free from cardiovascular disease, cancer, and diabetes at baseline.
Diet was assessed using a validated semiquantitative food frequency questionnaire at baseline and updated every 2 to 4 years.
The researchers also conducted a dose-response meta-analysis, including results from NHS and HPFS cohorts and 24 other prospective cohort studies.
Intake of about five servings of fruits and vegetables daily was associated with the lowest risk of death. Eating more than five servings was not associated with additional benefit.
Eating about two servings daily of fruits and three servings daily of vegetables was associated with the greatest longevity.
Compared to those who consumed two servings of fruit and vegetables per day, participants who consumed five servings a day of fruits and vegetable had a 13% lower risk of death from all causes; a 12% lower risk of death from cardiovascular disease, including heart disease and stroke; a 10% lower risk of death from cancer; and a 35% lower risk of death from respiratory disease, such as chronic obstructive pulmonary disease.
Not all foods that one might consider to be fruits and vegetables offered the same benefits. For example: Starchy vegetables, such as peas and corn, fruit juices and potatoes were not associated with reduced risk of death from all causes or specific chronic diseases.
On the other hand, green leafy vegetables, including spinach, lettuce and kale, and fruit and vegetables rich in beta carotene and vitamin C, such as citrus fruits, berries and carrots, showed benefits.
“Our study identifies an optimal intake level of fruits and vegetables and supports the evidence-based, succinct public health message of ‘5-a-day,’ meaning people should ideally consume five servings of fruit and vegetable each day,” Dr. Wang said.
“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.”
“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.”
The study was published this week in the journal Circulation.
Dong D. Wang et al. 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. Circulation, published online March 1, 2021; doi: 10.1161/CIRCULATIONAHA.120.048996