Men who eat vegetables from the cabbage family three times a week are probably a half less likely to develop prostate cancer than men who never eat these types of vegetables. We infer this from a study published by researchers at the American Fred Hutchinson Cancer Research Center in the Journal of the National Cancer Institute. The same publication also suggests that a diet that is rich in green leafy vegetables reduces the risk of prostate cancer.
When the researchers decided to carry out their study it was already known that fruit and vegetables in general reduce the likelihood of developing cancer, but not much was known about prostate cancer in particular. The researchers studied the diet of over six hundred men whose physicians had discovered that they had prostate cancer. The researchers compared these diets with those of an approximately equal-sized group of men without prostate cancer.
To start with the researchers found that fruit did not have a protective effect. The table with these data you can find here.
A diet that contained a lot of vegetables had more effect. The more vegetables men eat, the less likely they are to get prostate cancer. Men who eat 21 portions of vegetables per week have 35 percent less chance of developing prostate cancer than men who only eat 7 portions per week.
When the researchers started to break down their data further they noticed that cabbage-related vegetables had the strongest protective effect. Men who eat broccoli, cauliflower, sprouts or other brassicas three times a week or more nearly halve their risk of developing prostate cancer compared with the men who never ate cabbage-related vegetables.
When the researchers came to process their data they had just gained access to a database that indicates the amount of carotenoids in different foodstuffs. The researchers discovered that there was almost a correlation between the combined intake of lutein and zeaxanthin on the one hand and prostate cancer on the other.
The P value is 0.09. If that had been 0.05 or lower then there would have been a statistical relationship.
The researchers suspect that lutein and zeaxanthin probably have a positive effect, but that the men did not eat sufficient amounts of leafy vegetables for the effect to show up. Lutein and zeaxanthin are found in leafy vegetables.
Fruit and vegetable intakes and prostate cancer risk.
Cohen JH, Kristal AR, Stanford JL.
Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024, USA. firstname.lastname@example.org
There is extensive and consistent evidence that high fruit and vegetable intakes are associated with decreased risks of many cancers, but results for prostate cancer risk have been inconsistent. We studied the associations of fruit and vegetable intakes with prostate cancer risk in a population-based, case-control study of men under 65 years of age.
Case participants were 628 men from King County (Seattle area), WA, who were newly diagnosed with prostate cancer. Control participants were 602 men recruited from the same underlying population and frequency matched to case participants by age. Self-administered food-frequency questionnaires were used to assess diet over the 3- to 5-year period before diagnosis or recruitment. Daily nutrient intakes were calculated by use of a nutrient database with recently updated analytic values for carotenoids. Odds ratios for prostate cancer risk associated with foods and nutrients were calculated by use of unconditional logistic regression.
No associations were found between fruit intake and prostate cancer risk. The adjusted odds ratio (ORs) for the comparison of 28 or more servings of vegetables per week with fewer than 14 servings per week was 0.65 (95% confidence interval [CI] = 0.45-0.94), with a two-sided P for trend =.01. For cruciferous vegetable consumption, adjusted for covariates and total vegetable intake, the OR for comparison of three or more servings per week with less than one serving per week was 0.59 (95% CI = 0.39-0.90), with a two-sided P for trend =.02. The OR for daily intake of 2000 microg or more lutein plus zeaxanthin compared with an intake of less than 800 microg was 0.68 (95% CI = 0.45-1.00).
These results suggest that high consumption of vegetables, particularly cruciferous vegetables, is associated with a reduced risk of prostate cancer.
PMID: 10620635 [PubMed – indexed for MEDLINE]