Eating citrus fruits, especially oranges and grapefruit, because of the flavonone they contain, may lower women's risk of developing clot-associated or ischemic stroke, according to a new study led by Norwich Medical School of the University of East Anglia in the UK that was published online in Stroke: Journal of the American Heart Association on Thursday.
The researchers wanted to examine more closely how consumption of foods containing different classes of flavonoids affected the risk of stroke.
Flavonoids are a group of compounds found in fruits, vegetables, dark chocolate and red wine.
Study lead author and professor of nutrition at Norwich Medical School, Dr Aedín Cassidy, told the press:
"Studies have shown higher fruit, vegetable and specifically vitamin C intake is associated with reduced stroke risk."
A stroke is where part of the brain shuts down because of loss of blood supply, caused either by a blockage or embolism that stops the blood flow (ischemia), or due to leakage caused by a hemorrhage.
Cassidy said flavonoids are thought to provide some protection against stroke by improving blood vessel function and reducing inflammation, among other things.
For their study, Cassidy and colleagues examined data from the Nurse's Health Study. Based in the US, this is one of the largest and longest running investigations of factors that influence women's health. It started in 1976 and expanded in 1989.
The researchers looked at 14 years of follow-up data completed by 69,622 female participants who every four years had reported their dietary intake, including details of the fruits and vegetables they consumed.
They looked for links between the six major subclasses of flavonoids commonly present in the American diet and risk of ischemic, hemorrhagic and total stroke.
The six major subclasses they examined were: flavonones, anthocyanins, flavon-3-ols, flavonoid polymers, flavonols and flavones.
Since we already know that each subclass has a different biological effect, the researchers did not expect to find any strong beneficial links between total flavonoid consumption and stroke risk.
But they did find a strong link between high consumption of flavonones in citrus fruits and reduced stroke risk: women who consumed the most showed a 19% lower risk of ischemic stroke compared to women who ate the least amounts of flavonones in citrus fruits.
In this study, oranges and orange juice (82%) and grapefruit and grapefruit juice (14%) had the highest amounts of flavonones. But the researchers said if you are looking to increase your intake, then go for the fruit rather than the juice, because the latter tends to be accompanied by high amounts of sugar.
While previous studies have shown links between various foods and protection against both kinds of stroke, and this study further informs the field, the researchers said we still need to get a better understanding about why the link occurs, and that has to come from further research.