The results of this study, conducted by the National Cancer Institute and four academic centers in Iowa, Seattle, Los Angeles and Detroit, show that individuals who consumed three or more servings of vegetables per day (not including potatoes) had a 40 percent lower risk of developing NHL 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 one half or more servings per day of vegetables from the broccoli and cabbage family (including cauliflower and Brussels sprouts).
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 researchers investigated this relationship based on the results of a dietary questionnaire administered to more than 450 men and women with NHL between the ages of 20 to 74 years, who were identified from four large cancer registries across the country. These 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, RD, ScD, of 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 to those of studies where diet was assessed in healthy people who were followed forward in time to see if they develop cancer.
A novel finding was the lower risk observed with selenium and zinc, and confirmation of this observation by other researchers will be an important area of future research."
Although specific links between individual antioxidants such as vitamins C and E were not found with NHL in this study, vegetables and fruits contain many other nutrients that may explain the association with NHL.
"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 favorably change the public's eating behavior," said Dr. Kelemen.
According to the American Cancer Society, there will be more than 54,000 new cases of NHL in this country in 2004, and more than 19,000 people will die of the disease. Although some types of NHL are among the most common childhood cancers, more than 9 out of 10 cases occur in adults.
Founded in 1907, the American Association for Cancer Research is a professional society of more than 24,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's Annual Meetings attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.