For generations, moms have been telling kids that if they want to grow up healthy and strong they need to eat their fruits and vegetables. And moms are right — a decade ago, the Dietary Guidelines for Americans 2010 recommended that fruits and vegetables should make up one-half of what’s on your plate. But the idea is much older: in the 4th century B.C. the Greek philosopher Plato advocated a diet light on meat and alcohol and heavy on fruits, vegetables, and cereals — and Plato lived to be 80!
But even though the benefits of fruits and vegetables are established, many questions remain. How much? How often? What kinds? Recently, however, two large observational studies using data from nearly two million people have thrown some light on these questions. The results were published in the journal Circulation, which is published by the American Heart Association.
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The authors, led by Doug Wang, MD, of Brigham and Women’s Hospital and Harvard Medical School, first analyzed data from two long-time ongoing studies: the Nurses’ Health Study and the Health Professionals Follow-Up Study, both of which have collected health data for over 30 years. Both of these studies contain comprehensive dietary information collected every two to four years. From the Nurses’ Health Study the researchers gathered information on 66,719 women and from the Health Professionals Follow-Up Study they got data on 42,016 men. In addition to the information from the Nurses’ Health Study and the Health Professionals Follow-Up Study, the researchers also included data on fruit and vegetable consumption from 26 separate studies that included nearly 2 million people around the world — 29 countries and territories in Europe, North and South America, Asia, Australia and Africa.
Fruits and vegetables not all equal
The researchers concluded that fruit and vegetables are indeed beneficial and are associated with lower death rates, but they also found there was a limit on how much good they could do and that not all fruits and vegetables are equal.
First, the researchers determined that the recommendation of “five-a-day,” which has been getting a lot of media attention, really is better than two servings a day. Eating about five servings of fruits and vegetables daily was associated with the lowest risk of death, or, as Dr. Wang put it, “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.” The data showed that the subjects who ate five portions of fruits and vegetables every day 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 an impressive 35% lower risk of death from respiratory disease. But the data also showed that more is not necessarily better — eating more than five servings of fruits and vegetables was not associated with any additional benefits.
Beyond these findings, the researchers were able to fine-tune the “five-a-day” advice. For example, they determined that vegetables might be more slightly important than fruit — consuming about two servings of fruit and three servings of vegetables every day was associated with the longest life spans. Also, not all fruits and vegetables are equally valuable. Green leafy vegetables, including spinach, lettuce and kale, were determined to be healthful, and so were citrus fruits, berries and carrots, while fruit juices were not found to be as beneficial as whole fruit. Finally, starchy vegetables like peas, corn, and potatoes were not associated with a lower risk of death.
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