An apple a day keeps the doctor away. If you didn't believe that old adage before, you may want to take a look at a new study that finds that eating a lot of apples, pears and other produce with white flesh might protect against stroke.

While previous studies have linked high consumption of fruits and vegetables with lower stroke risk, this new study, published in the journal Stroke, is the first to examine the effects of different fruits and vegetable based on their colour.

For the study, researchers recruited about 20,000 adults with an average age of 41 who were free of any signs of cardiovascular disease. They asked them to fill out a questionnaire detailing what they regularly eat.

They then kept track of the volunteers over the next 10 years and recorded how many of them had strokes, noting 233 strokes among the group.

When the researchers looked at what the participants had eaten, they noted that people who had a high intake of white fruits and vegetables had a stroke incidence that was 52 per cent lower than those people with a low intake.

Each 25 gram per day increase in white fruits and vegetable consumption – a large slice of apple, for example -- was associated with a 9 per cent lower risk of stroke. (An average apple weighs about 120 grams.)

Interestingly, the amount of green vegetables the participants ate didn't seem to affect their stroke risk. Neither did their intake of orange, yellow, red or purple fruits and vegetables.

Why white-fleshed fruits and veggies might be beneficial isn't known. The authors note that apples and pears are high in dietary fibre and a flavonoid called quercetin.

Other foods in the white category were bananas, cauliflower, chicory and cucumber. (Potatoes were classified as a starch, not a vegetable.)

Dr. David Jenkins, with the Department of Nutritional Sciences at the University of Toronto, thinks it might be the fibre in apples in pears, or their antioxidants, that may be lowering blood pressure or cholesterol that can possibly protect brain blood vessels or prevent clots from forming.

"These results tell us there is something about fruit – low glycemic fruit – that do have beneficial effects," he tells CTV News.

While the study found only a link between white fruit and stroke, and the results are preliminary, the authors suggest it's not a bad idea to stock up on white fruits and veg.

"To prevent stroke, it may be useful to consume considerable amounts of white fruits and vegetables," said Linda M. Oude Griep, lead author of the study and a postdoctoral fellow in human nutrition at Wageningen University in the Netherlands.

"For example, eating one apple a day is an easy way to increase white fruits and vegetable intake."

She notes that doesn't mean one should skimp on other vegetables, because other fruit and vegetable colour groups might offer protecting against other diseases.

"Therefore, it remains of importance to consume a lot of fruits and vegetables," she says.

An accompanying editorial notes that the findings should be interpreted with caution because food frequency questionnaires may not be reliable.

As well, it's also possible that the lower stroke risk in those who ate white fruit and veggies might have a lot to do with a generally healthier lifestyle of those people who eat a lot of fruits and veggies as a whole.

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip