Their study is thought to be the first to demonstrate the impact of carotenoids on protecting against oxidative damage, which has been linked to increased potential for disease.
It also suggests that a combination of carotenoids, such as is found naturally in the diet, may offer greater benefits than a single carotenoid.
Lead investigator Kyung-Jin Yeum from the Human Nutrition Research Center on Aging at Tufts University in Boston, said that the study was designed to add new information to the evidence that fruit and vegetables can help fight off disease.
Fruit and vegetables contain numerous different chemical compounds making it difficult to assess which of these are acting against disease.
However carotenoids are the main source of pigments in fruit and vegetables and have already been linked to decreased risk of cancer and other diseases in which oxidative damage is thought to play a role.
The researchers supplemented 37 healthy, postmenopausal women with either a combination of 4mg each of lycopene, beta-carotene and lutein, 12mg of a single carotenoid or a placebo for eight weeks.
The carotenoids were provided by German group BASF, which funded the study.
The scientists assessed oxidative damage to lymphocytes (white blood cells) at certain points during the study.
"Both the single and mixed carotenoid groups showed significantly increased plasma total carotenoid levels within 15 days of supplementation and significantly decreased damage at day 57," write the researchers in the study abstract.
The mixed carotenoids supplemented group showed significantly decreased DNA damage as early as day 15 (by around 22 per cent) and this further decreased at days 29 and 43. By day 57, it had been reduced by 36 per cent.
There were no significant changes in the placebo group.
"We wanted to combine three different carotenoids as we know they have a different structure and are located in different positions in the membrane. This means they have different functions so could have a synergistic effect when combined," Dr Yeum told NutraIngredients.com.
She added that 4mg of lutein can be gained from a quarter of a cup of cooked spinach, while the same dose of beta-carotene can be found in a third of a carrot. A medium-sized tomato offers 4mg lycopene.
"What is really important is that we have used a physiologic dose. We do not want to use pharmacological levels as increasingly research is showing that high doses of nutrients like vitamin E or beta-carotene can have side effects," she added.
"Our findings emphasise the importance of a balanced diet. If fruit and vegetable intake is low, supplements could be helpful although the study did not intend to promote supplements," continued Dr Yeum.
The researcher explained that while there is no study showing a direct connection between DNA and disease, several have shown that heart disease and breast cancer patients have higher DNA damage compared to controls.
The study was presented at the Nutrition, Oxygen Biology and Medicine conference at the Societe De Recherches Sur Les Radicaux Libres in Paris from 2-4 March 2005. It will shortly be submitted for publication in a scientific journal.