Diets rich in fruits and vegetables have been linked with lower stroke risk in several studies, but researchers weren't sure why.
Flavonoids, a class of compounds present in fruits, vegetables, dark chocolate and red wine, are thought to provide some of that protection through several mechanisms, including improved blood vessel function and an anti-inflammatory effect. But which flavonoids are delivering these benefits? There are many types of flavonoids in fruits and vegetables.
Recent studies are beginning to narrow down which foods and specific compounds are responsible for specific health benefits like reducing stroke risk.
One of these studies was able isolate a specific sub-class of flavonoids called flavanones in citrus fruit that reduced the risk of stroke by as much as 19%.
The researchers were able to identify which of six main subclasses of flavonoids helped reduce the risk of stroke by analyzing detailed food diaries of participants in the U.S. Nurses' Health Study. This study followed nearly 70,000 women for 14 years.
Interestingly, total flavonoid intake did not reduce stroke risk, but intake of flavanones did. Women who ate the most flavanones had a 19% lower risk of blood-clot related stroke than those who ate the least. About 95 percent of the flavanones consumed came from citrus fruit and juice, mostly orange and grapefruit.
Women with the lowest intake of flavanones took in about 150 milligrams a day of flavonoids or less, compared to more than 470 milligrams a day in the highest group. A typical piece of citrus fruit contains 45 to 50 milligrams of flavanones.
For maximum benefit, whole fruits are preferable to juice because they contain more flavanones and no added sugar, said study authors.
Other Helpful Fruits
Last year another study found an association between white flesh fruits like apples and pears and a 52% reduction in stroke risk. This study followed the dietary habits of over 20,000 Dutch adults who were free of heart disease for over 10 years.
For every 25 g per day increase in white fruits and vegetables they found a 9% lower risk of stroke while no such association was found between green (dark leafy vegetables, cabbages and lettuces) orange/yellow (mostly citrus fruits) or red/purple (cherries, grapes and strawberries) fruits and vegetables.
Researchers in that study believe that another type of flavonoid, quercetin, is responsible. Quercetin promotes both histamine and inflammatory balance.
For overall good health, experts suggest that you consume a variety of fruits and vegetables to gain a full spectrum of flavonoids and other beneficial nutrients in your diet.