Mmm, citrus. There’s nothing like a refreshing orange, a tangy tangerine or a sweet pink grapefruit. It really does taste like sunshine.

But these juicy fruits aren’t just delicious—they may actually help you ward off a stroke, according to new research.

And you may be surprised to hear that it’s not because of the vitamin C…

HONING IN ON FLAVONOIDS

A zillion studies have shown the health benefits of eating fruit, including studies that have shown that people who eat five or more servings of fruits and vegetables have a 25% lower risk for stroke (both ischemic and hemorrhagic) compared with those who eat three or fewer servings. Researchers have suspected that flavonoids, antioxidant compounds found in many fruits and vegetables, are one key to their power since they reduce inflammation and improve blood vessel function.

But there are six different types of flavonoids found in foods, and each has a subtly different chemical structure. Given the variety, researchers from England, Italy and the US wanted to learn which specific flavonoids and which fruits or vegetables, in particular, are most beneficial for preventing stroke.

To learn more about the study, I spoke to one of the authors—Kathryn M. Rexrode, MD, MPH, a physician in the division of preventive medicine at Brigham and Women’s Hospital and associate professor of medicine at Harvard Medical School, both in Boston.

THE FLAVONOID THAT CAME OUT ON TOP

The researchers used information from 70,000 women who were followed for 14 years as part of the Nurses’ Health Study. Every two years, the participants completed questionnaires that covered their medical histories and lifestyles. And every four years, the women completed food questionnaires, which asked how much of certain foods and drinks they consumed and how often they consumed them.

The women’s diets were analyzed for the six different types of flavonoids, and their medical histories were reviewed for the number and type of strokes that the women had. What they found was that high consumption—more than about 63 milligrams per day of a certain subclass of flavonoids called flavanones (the amount found in about one to two servings of citrus per day)—was associated with a 19% reduced risk for ischemic stroke (the type caused by a clot, not by a bleed), compared with low flavanone consumption (under 13.7 milligrams per day). And this was after adjusting for other stroke risk factors, such as smoking, age, body mass index and others. The other five flavonoids studied reduced stroke risk, too, but not by as much (only by 4% to 13%).

Dr. Rexrode said that one reason that the flavanones may have been associated with decreased risk for ischemic stroke is that flavanones may inhibit platelet function and clotting factors. The researchers didn’t study whether citrus affected risk for hemorrhagic stroke, but Dr. Rexrode said that it’s unlikely that eating citrus would lead to an increased risk for hemorrhagic stroke. She said that it takes a relatively small amount of clotting to cause an ischemic stroke, but, on the other hand, it takes a relatively large amount of excessive bleeding to cause a hemorrhagic stroke.

Although this study, which was published this past February in Stroke, looked only at women, Dr. Rexrode said that there is no reason to think that these findings wouldn’t apply to men, too.

PICK YOUR CITRUS

Dr. Rexrode said that you can get all the flavanones you need (about 63 milligrams) from eating one or two servings of citrus each day. Whole fruits are always better than juices or smoothies, she said, because the bulk of the flavanones are found in the inner membranes of the fruit and the pith or white part of the fruit. The pith is generally removed when the fruit is juiced or cleaned for smoothies.

The USDA provides information about the amount of flavanones in every 100 grams of edible fruit, so to save you the trouble of weighing your fruits, here are estimates of the flavanone content for some common citruses:

Grapefruit (one-half of a four-inch diameter) 47 milligrams
Orange (2? inch diameter) 42 milligrams
Tangerine (2½ inch diameter) 18 milligrams

Dr. Rexrode doesn’t recommend supplements—she said sticking to whole fruit is best. And don’t overdo it on citrus, or else your stomach or teeth might suffer from the acid. Just a serving or two a day is all you need!