Cooking your carrots whole can boost the vegetable's anti-cancer properties by 25 per cent, new research shows, writes MICHAEL KELLY
A RECENTLY published study in Britain has found that leaving your carrots whole while cooking them can boost the vegetable’s anti-cancer properties by 25 per cent.
The study, carried out by Newcastle University’s School of Agriculture, Food and Rural Development, found that “boiled-before-cut” carrots contained significantly more of an anti-cancer polyacetylene compound called falcarinol than those that were chopped up first.
As part of the FIRM project, Teagasc and the University of Limerick have also been researching the impact of “processing” on the antioxidant levels in food including the impact on falcarinol levels in carrots. Recent research has indicated that the compound may have a more significant contribution towards the anti-cancer properties of carrots than well-known contributors such as beta-carotene.
The Teagasc research has highlighted, however, that we know little about what happens to falcarinol during storage, preparation and cooking.
“We have always assumed that when you cook vegetables, the heat degrades the nutrients,” says Dr Nigel Brunton from Teagasc, “but the Newcastle research is an example of where the compounds are enriched by cooking.
“In a way it’s easy to understand, because these compounds are not soluble in water and therefore do not leach away.”
Falcarinol is a phytochemical that protects carrots from fungal diseases – it is also thought to be a potent anti-tumour agent.
It is one of a range of “non-nutrient” chemicals found in plants that are now believed to have a role in the fight against chronic diseases.
Scientists are currently grappling with the implications of a strange anomaly – vegetables such as carrots lose vitamins and minerals in the cooking process, but at the same time see increased levels of beneficial phytochemicals.
A similar situation arises with tomatoes – researchers from Cornell University in the US found that cooking tomatoes reduces the amount of vitamin C, but increases the level of the phytochemical lycopene.
According to Margot Brennan, spokeswoman for the Irish Nutrition and Dietetic Institute (INDI), there are discoveries being made almost on a daily basis about the antioxidants contained in fruit and vegetables.
“It points to the fact that some of the non-nutritive properties of fruit and vegetables are extremely important in their own right,” she says.
“That is why it is so important to eat plenty of fresh fruit and vegetables as opposed to trying to get vitamins and minerals from supplements.
“We believe the most sensible approach is to eat a variety of fresh fruit and vegetables and to vary the way that you cook and consume them.”
The INDI also recommends saving the water left over after boiling vegetables such as carrots to recoup some of the “leached” vitamins and minerals.
“The old approach that our grandparents would have used – keeping the water and using it to make gravy or soup – is a very good one,” according to Brennan.
The Newcastle researchers believe that cooking carrots whole maintains nutritional value but also ensures that they taste better – the naturally occurring sugars which are responsible for giving the carrot its distinctively sweet flavour were also found in higher concentrations in the carrot that had been cooked whole.
In a blind taste test carried out for the research, 100 people were asked to compare the taste of “boiled-before-cut” versus “cut-before-boiled” – nearly 80 per cent preferred the carrots that were cooked whole.
“Chopping up your carrots increases the surface area so more of the nutrients leach out into the water while they are being cooked,” according to Dr Kirsten Brandt of Newcastle University.
“By cooking them whole and chopping them up afterwards, you are locking in both taste and nutrients so the carrot is better for you all round.
“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 you,” she says. “All you need is a bigger saucepan.”
The health benefits of falcarinol in carrots were first discovered four years ago by Brandt and colleagues at Newcastle University and the University of Southern Denmark.
They found that rats being fed on a diet containing carrots or on isolated falcarinol were a third less likely to develop full-scale tumours than those in a control group.
Since these early experiments were carried out on raw carrots, the team has since investigated the impact of cooking on falcarinol.
The simple act of boiling a carrot has a profound effect on its composition, the study shows.
According to the report, the heat kills the cells in the carrot so they lose the ability to hold on to the water inside them – this actually increases the concentration of falcarinol in the carrot.
However, the heat also softens the cell walls, allowing water-soluble compounds such as sugar and vitamin C to be lost via the surface of the tissue.
The impact is heightened if the carrot is cut before being boiled, since the surface area becomes much greater and so the loss of nutrients is increased.