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Eating a Wide Variety of Vegetables Is Key to Reducing Risk of Prostate Cancer, Reports Seattle Study
PRNewswire/NEWSdesk -- Move over, tomatoes! All vegetables -- especially broccoli, cabbage and their cruciferous cousins -- may substantially reduce the risk of prostate cancer, according researchers at the Fred Hutchinson Cancer Research Center.
Eating just three servings of vegetables a day can cut a man's risk of prostate cancer nearly in half. While carrots, beans, greens and cooked tomatoes all were found to decrease risk, the strongest effect was for cruciferous vegetables. These findings will appeared in the Jan. 5 issue of the Journal of the National Cancer Institute.
"The bottom line is that if you eat a lot of vegetables, you can cut your risk of prostate cancer by about 45 percent," says Alan Kristal, Dr.P.H., co-investigator of the study. "And, if some of those vegetables are from the cruciferous family, like broccoli and cabbage, you may reduce your risk even further."
The study looked at the associations of total fruit and vegetable consumption, as well as specific types of fruits and vegetables, on prostate-cancer risk in 1,230 Seattle-area men. Half of the men had been diagnosed with prostate cancer and the other half were randomly selected men living in the Puget Sound region.
Funded by the National Cancer Institute, this study was unique because it examined risks for prostate cancer in younger men (ages 40-64). By focusing on men who are at a very low risk of prostate cancer, the researchers were better able to assess the impact of lifestyle factors, such as diet, on cancer risk. The men were interviewed about their dietary habits three to five years prior to diagnosis (or an equivalent time frame among the control group). They also completed a detailed dietary questionnaire that asked how much and how often they ate 99 foods. Men who ate three or more servings of vegetables a day (about 15 percent of the sample) had a 48 percent lower risk of prostate cancer, compared to men who ate fewer than one serving a day (also about 15 percent of the sample). This association was independent of other dietary factors, such as fat intake, and for medical factors, such as history of prostate cancer in a father or brother.
The strongest effect was for cruciferous vegetables, which include broccoli, cauliflower, brussels sprouts, and cabbage-based dishes such as sauerkraut and coleslaw. Men who ate three or more half-cup servings of cruciferous vegetables per week had a 41 percent decreased risk for prostate cancer, compared to men who ate fewer than one serving per week.
"At any given level of total vegetable consumption, as the percent of cruciferous vegetables increased, the prostate-cancer risk decreased," Kristal says.
Fruit, on the other hand, was a different story. When measuring the impact of total fruit intake as well as that of specific fruits, such as citrus, the researchers found no associations with reduced risk of prostate cancer. The researchers also found no special benefits for cooked tomatoes. This finding contradicts much-publicized research extolling the prostate-cancer-fighting properties of cooked tomato products, an effect attributed to a carotenoid called lycopene, a pigment that gives the fruit its red color.
"We found no association between lycopene and decreased prostate-cancer risk," Kristal says. "We also looked at foods that were good sources of lycopene, such as spaghetti sauce and pizza. These were not related to cancer risk at all." These results support four earlier studies that found no association between either tomato consumption or lycopene intake and risk of prostate cancer. The handful of studies to date that have shown protective effects have not controlled for total vegetable consumption, a flaw in study design, Kristal believes, that makes it difficult to accurately assess the cancer-fighting role of specific types of vegetables.
Scientists believe that vegetables protect against cancer because they contain a wide variety of phytochemicals. Many phytochemicals increase the activity of enzymes that can detoxify cancer-promoting compounds in the body.