Apparently, you can tell whether a fruit is rich in phytochemicals by the color of its edible portion. Phytochemicals are naturally-occurring compounds that are found in plants. Generally, phytochemicals refers to plant compounds that may have an impact on human health although they are not established essential nutrients. Examples include carotenoids and flavonoids.
Linda M. Oude Griep, M.Sc. and team set out to determine whether there might be a link between vegetable and fruit color group consumption and 10-year stroke incidence. Their study involved 20,069 adults, with an average age of 41 years. None of them had any cardiovascular disease when the study began - they had all filled in a 178-item food frequency questionnaire for the previous year.
They classified the fruits and vegetables into the following color groups:
- Cabbages, lettuces and other dark green leafy vegetables
- Orange and yellow colors, most of which were citrus fruits
- Red and purple colors, most of which were red vegetables
- White colors, apples and pears made up 55% of them
There was a 9% reduced risk of stroke for every 25 gram increase in daily white fruit and vegetable consumption. An average sized apple weighs about 120 grams.
Linda M. Oude Griep, M.Sc., said:
"To prevent stroke, it may be useful to consume considerable amounts of white fruits and vegetables. For example, eating one apple a day is an easy way to increase white fruits and vegetable intake.
However, other fruits and vegetable color groups may protect against other chronic diseases. Therefore, it remains of importance to consume a lot of fruits and vegetables."
Pears and apples are rich in quercetin, a flavonoid, as well as dietary fiber. The authors wrote that white category fruit and vegetables include cucumber, chicory, cauliflower and banana. Potatoes were classed as starch.
Current US federal dietary guidelines recommend picking varying vegetables from five subgroups: starchy, legume, red/orange, dark/green and other vegetables.
The authors say their study should be confirmed by further research before it is adopted into everyday practice.
Oude Griep said:
"It may be too early for physicians to advise patients to change their dietary habits based on these initial findings."
As food frequency questionnaires are sometimes unreliable, an Accompanying Editorial in the same journal advises readers to interpret the findings with caution.
Heike Wersching, M.D., M.Sc., of the Institute of Epidemiology and Social Medicine at the University of Münster, Germany, wrote:
"The observed reduction in stroke risk might further be due to a generally healthier lifestyle of individuals consuming a diet rich in fruits and vegetables."