Conducted by the US National Cancer Institute, researchers found that people who consumed three or more servings of vegetables per day (not including potatoes) had a 40 per cent lower risk of developing non-Hodgkin's lymphoma (NHL), a form of cancer of the lymphoid tissue that hits some 54,000 Americans each year, compared to people who ate less than one serving per day.
The findings were particularly strong for one or more servings per day of green leafy vegetables and just one half or more servings per day of vegetables from the broccoli and cabbage family, including cauliflower and Brussels sprouts.
Findings from the study carried out by the US cancer institute and four academic centres in Iowa, Seattle, Los Angeles and Detroit build on mounting evidence that suggests compounds found in fruit and vegetables, and notably green leafy vegetables, could help the body fight a raft of diseases.
Building on the research, the food industry is still enjoying strong growth for food formulations that absorb health-fighting compounds and has sparked new dynamics in the fruit and vegetable extracts market. The €819.9 million European and US fruit and vegetable extracts and powders market is on course to grow 4.5 per cent annually, reaching €1.07 billion by 2009, estimate market analysts Frost & Sullivan.
But food makers might want to opt for broccoli or cabbage family extracts as the study, confirming previous studies, shows that this range possesses particularly strong anti-cancer fighting properties.
More than 125 scientific papers have been published on sulphoraphane, abundant in broccoli, brussels sprouts and kale, with many of them focusing on sulphoraphane's anti-cancer activity, as well as its benefits for heart health. Since its discovery by a John Hopkins team in 1992, a company called Brassica Protection Products has been marketing patented concentrated forms of broccoli sprouts - three-day-old broccoli plants said to provide 20 times the concentration of sulphoraphane glucosinolate as found in adult broccoli and currently sold in the US, Japan and New Zealand.
In this latest study researchers investigated the relationship between cancer prevention and fruit and vegetable intake based on the results of a dietary questionnaire given to more than 450 men and women with NHL between the ages of 20 to 74 years.
Lower risks were also found, although not significantly, with higher intakes of whole fruits (excluding juices), yellow/orange/red vegetables and processed tomato products such as tomato sauce and tomato juice. For specific nutrients, higher intakes of both selenium and zinc were also associated with lower risk of NHL. The researchers found no strong link to increased intakes of the individual vitamins A, C, or E, or individual carotenoids or retinol.
The study participants were matched to approximately 400 individuals without cancer who were similar in age, sex, race and lived in the same geographical region.
"This type of study design has some limitations because we are asking people who already developed cancer to remember how often they ate fruits and vegetables in the year prior to cancer diagnosis," said Dr Linda Kelemen, Mayo Clinic College of Medicine, and lead investigator of the study. "However, even after taking into account other possible risk factors like smoking, our results are consistent with those of studies where diet was assessed in healthy people who were followed forward in time to see if they develop cancer."
Although specific links between individual antioxidants such as vitamins C and E were not found with NHL in this study, the scientists suggest that vegetables and fruits contain many other nutrients that may explain the association with NHL, and a reason for the public to take fruit consumption on board.
"Dietary modifications such as eating more vegetables and fruits are within the public's grasp to lower their risk of cancer and other diseases. We hope that these findings, in conjunction with continued research and reporting, will help to favourably change the public's eating behaviour," said Dr Kelemen.