Researchers with the Agricultural Research Service are breeding different colour carrots with added health-promoting properties.

The conventionally-bred carrots come in colours such as yellow, dark orange, bright red and purple. But the unusual colours are not just for the sake of appearances. Each colour pigment contains an added health benefit.

Xanthophylls give the yellow carrots their hue and have been linked with good eye health. Red carrots contain lycopene, a type of carotene also found in tomatoes, which is believed to guard against heart disease and some cancers.

Purple carrots owe their colour to anthocyanins, which are believed to be powerful antioxidants that can guard the body's cells from the destructive effects of unstable molecules known as free radicals.

At first, researcher Philipp Simon from the ARS Vegetable Crops Research Unit in Madison, Wisconsin was unsure if such vegetables could provide nutrients in a form that the human body can use.

But in studies with nutritionist Sherry Tanumihardjo from the University of Wisconsin, Simon found that yellow carrots' lutein was 65% as bioavailable as it is from a lutein supplement. The two also discovered that lycopene from red-pigmented carrots is 40% as bioavailable as it is from tomato paste.

The Agricultural Research Service is the chief scientific research agency of the US Department of Agriculture. This research was funded in part by the Initiative for Future Agriculture and Food Systems, a programme of the USDA's Cooperative State Research, Education and Extension Service.