Eating fruits and vegetables has proved helpful in preventing various chronic illnesses. (Bigstock)

THE QUESTION Eating fruits and vegetables, known for their nutrient and fiber content, has proved helpful in preventing various chronic illnesses. Does that mean the more the better?

THIS STUDY analyzed data from 16 studies, involving more than 833,234 adults. During the span of the studies, which ranged from five to 26 years, 56,423 participants died. Overall, the more fruits and vegetables people consumed, the less likely they were to have died during the study period. For every additional serving eaten, up to four a day, the chance of dying for any reason fell by 5 percent, and the chance of dying from cardiovascular disease dropped by 4 percent. Those who ate four servings a day were 24 percent less likely to have died than those who ate none at all. However, eating five or more daily servings conferred no added benefit. Higher consumption of fruits and vegetables also showed essentially no effect on the chance of dying from cancer.

WHO MAY BE AFFECTED? Adults, who most health experts say do not eat enough fruits and vegetables. Although dietary recommendations vary by age, health status and other criteria, current guidelines call for most adults to fill half their plate with fruits and vegetables; the food pyramid model suggested that adults eat three to five servings of vegetables and two to four servings of fruit daily.

CAVEATS In most of the studies, data on fruit and vegetable consumption came from the participants’ responses on questionnaires. The study did not determine whether certain fruits or vegetables were more or less beneficial than others.

LEARN MORE ABOUT the nutritional benefits of fruits and vegetables at www.cdc.gov (search for “fruitsvegetables” — all one word). Learn more about the Dietary Guidelines for Americans at www.dietaryguidelines.gov (click on 2010 guidelines).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment\'s effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.

www.washingtonpost.com/national/health-science/theres-a-limit-to-how-much-fruit-and-vegetables-are-good-for-you/2014/08/01/7283e53e-18c4-11e4-9349-84d4a85be981_story.html