More Evidence Fruit and Vegetables Cut Stroke Risk
For every 200 g per day increment of fruits and vegetables, the risk for stroke fell by 32% and 11%, respectively, across these studies, the study team found.
"The findings are consistent with the current knowledge that increasing consumption of fruits and vegetables should be encouraged to prevent stroke," Yan Qu, MD, the study's senior author, from Qingdao Municipal Hospital and Medical College of Qingdao University in Qingdao, China, told Medscape Medical News by email.
The study is published online May 8 in Stroke.
Positive and Negative Associations
In recent years, several prospective cohort studies have assessed the effect of fruits and vegetables consumption on the risk for stroke, yielding both positive and negative associations, Dr. Qu explained. The magnitude of association also varies among the previous publications on fruit and vegetable consumption and the risk for stroke, she noted.
To quantitatively assess the effect of fruits and vegetables consumption on the risk for stroke, Dr. Qu and colleagues did a meta-analytic review of 20 prospective cohort studies published to January 2014. The analysis included 16,981 stroke events among 760,629 adults.
Higher intake of fruits and vegetables (together and separately) were inversely related to stroke risk in multivariable analysis.
Table. Risk for Stroke With Highest vs Lowest Intake
|Intake||Odds Ratio (95% Confidence Interval)|
|Fruits and vegetables||0.79 (0.75 - 0.84)|
|Fruits||0.77 (0.71 - 0.84)|
|Vegetables||0.86 (0.79 - 0.93)|
The inverse association of total fruits and vegetables consumption with the risk for stroke was consistent in subgroup and meta-regression analysis, the researchers say.
The average serving was calculated as 77 g for vegetables and 80 g for fruits. "A linear dose-response relationship was found, the more consumption of fruit and vegetables, the better for stroke prevention," Dr. Qu told Medscape Medical News.
Stroke risk decreased by 32% (relative risk, 0.68; 95% confidence interval, 0.56 - 0.82) and 11% (0.89; 0.81 - 0.98) for every 200-g increment in daily fruits and vegetables, respectively.
Apples and Oranges
Asked for comment on these findings, Gustavo Saposnik, MD, director, Stroke Outcomes Research Center, St. Michael's Hospital, University of Toronto, Ontario, Canada, who wasn't involved in the study, called the study "interesting," and said the benefits seen are consistent with previous studies. A limitation is that in most of the studies vegetable/fruit consumption is self-reported, he noted.
"Two hundred grams of fruit per day may sound a lot, but this would represent 2 medium-size apples or a large 1 and a half," he told Medscape Medical News.
Dr. Qu noted that "citrus fruits, leafy vegetables and apples/pears were found inversely associated with risk of stroke. However, the effect of other types of fruit and vegetables on stroke risk still needs to be confirmed."
A recent bulletin from the World Health Organization (WHO) estimates that increasing individual fruit and vegetable consumption to at least 600 g daily could cut the burden of ischemic stroke by 19% worldwide.
Dr. Qu and colleagues say several biological mechanisms might explain the inverse association. "Both short-term controlled intervention trials and prospective cohort studies have shown that an increase in fruits and vegetables consumption can lower blood pressure and also improve microvascular function," they point out. Favorable effects on other cardiovascular risk factors, including body mass index, cholesterol, inflammation, and oxidative stress, were also seen.
"Higher fruits and vegetables consumption increases micronutrient, carbohydrate, and fiber intakes, and possibly reduces fat intake. Nutrients such as potassium, folate, antioxidants (vitamin C, β-carotene, and flavonoids), and fiber have been shown to be significantly associated with a reduced risk for stroke," they note.
The study was funded by the Qingdao Municipal Hospital. The authors have disclosed no relevant financial relationships.