The medical properties of carrots – including the boost they provide to night vision, which led to them being fed to RAF pilots during the second world war – can be enhanced by the way in which they are cooked, researchers say.
Food chemists at Newcastle University have found that boiling the vegetables whole rather than slicing them up increases the supply of healthy ingredients by a quarter.
Dicing carrots – still the commonest way of cooking them in Britain – resulted in the loss of 25% of their compound falcarinol, a series of experiments using laboratory rats revealed.
The naturally occurring sugars have anti-cancer properties and also give carrots their slightly sweet taste.
Dr Kirsten Brandt, of the university's school of agriculture, food and rural development, said pre-cut carrots presented a larger surface area, allowing more falcarinol to come out.
Helped by researcher Ahlam Rashed, Brandt found that more sugar and vitamin C was also lost through slicing because more carrot cells heated up and lost their ability to keep out the boiling water.
Presenting her findings to a conference in Lille yesterday, Brandt said: "By cooking carrots whole and chopping them up afterwards, you are locking in both taste and nutrients so the carrot is better for you all round."
A blind tasting carried out by just under 100 volunteers found that 80% considered carrots cooked whole to be tastier.
"We all want to try to improve our health and diet by getting the right nutrients and eating our five a day," Brandt said.
"The great thing about this is it's a simple way for people to increase their uptake of a compound we know is good for us. All you need is a bigger saucepan."
The online World Carrot Museum has yet to add the findings to its food and recipe section, but suggests adding whole carrots to fried onions in the carrot and lentil soup in its recipe section.
Brandt's team, working with colleagues from the University of Southern Denmark, discovered the health benefits of falcarinol in a series of experiments with rats four years ago.
