Researchers from the Harvard School of Public Health in Boston have uncovered more evidence linking a diet with plenty of fruits and vegetables to better health outcomes.
The idea that fruits and veggies are good for you isn't new. What’s new in this study is that researchers saw a dose-response relationship: the more fruits and vegetables people ate, the less likely they were to have heart problems or die over the course of the study. The protective effects of fruits and veggies leveled out at five servings per day.
The findings are from a new analysis of 16 existing studies that involved more than 800,000 people. The studies lasted at least four years, and sometimes up to 26 years. Approximately 56,000 participants died during the studies.
Six studies included data on vegetables in the diet over time, six examined fruits, and four included both. The studies were conducted in the U.S., Asia and Europe.
Compared to people who ate no fruits or vegetables, those who ate one serving per day were roughly five percent less likely to die of any cause over the course of the studies. And with every additional serving, the risk of death decreased by another five percent, according to the combined analysis.
The risk of dying from heart disease decreased with more fruits and vegetables in a similar way, but the risk of dying from cancer did not appear to change.
More than five servings of fruits and vegetables daily didn't confer any additional benefit.
Most of the studies took into account people’s age, body mass index, smoking and alcohol consumption, which can all affect the risk of dying from heart disease or other problems. But since it only included observational studies, the review can't prove that these dietary habits will protect people from heart disease and death, only that the two are connected. People in the studies could have been making other lifestyle choices that would influence the results.
Randomized trials have, however, found a connection between a generally healthy diet and delayed onset of heart disease.
The vitamins, minerals, fibre and phytochemicals found in fruits and vegetables may improve blood cholesterol and blood pressure and reduce insulin resistance and chronic inflammation.
The study did not look at individual fruits and vegetables, and more research will be needed to examine the health effects of specific foods in this category..
Source: BMJ, July 29, 2014
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