Cancer experts say men who eat at least 1.5 cups a week of cruciferous veggies, such as broccoli, cabbage and cauliflower, can cut their risk of prostate cancer by more than 40 percent.
The finding, which appears in the latest issue of the Journal of the National Cancer Society, suggests that eating a variety of vegetables is just as important for cancer protection as eating any vegetables at all.
Researchers have long known that fruits and vegetables guard against cancers and other diseases. These foods contain naturally occurring chemicals that stimulate the body to break down tumour-causing compounds.
In the latest study, Dr Alan Kristal and colleagues at the Fred Hutchinson Cancer Research Centre asked more than 1 200 men, 628 of whom had prostate cancer, to detail their eating habits in recent years. The men questioned were under 65, putting them at particularly low risk of prostate disease.
Men who reported eating four servings of vegetables a day for at least three years prior to the study were about 48 percent less likely to have prostate cancer as those who ate two or fewer daily servings over the same period.
Those who said they ate three or more half-cup servings a week of cruciferous vegetables cut their prostate cancer risk by 41 percent, compared with men who ate only a serving or less a week.
In contrast with earlier research, Kristal's group did not find that high fruit intake protected against prostate cancer. Nor did they see any special benefit from tomatoes. Tomatoes are rich in lycopene, a powerful antioxidant, and previous studies suggested that tomatoes and tomato products were particularly strong cancer shields.
It's not clear why cruciferous vegetables reduce the risk of prostate cancer. But Kristal says the plants are high in chemicals called glucosinolates, which the body converts to trigger the production of enzymes that destroy cancer-causing chemicals, and thus protect vulnerable cells, he says.
What to do
Although prostate cancer does have a genetic component, Kristal says good nutrition can overcome a family history of the disease. What's more, it's never too late to start adding vegetables to your diet. Some studies suggest that even men with diagnosed prostate cancer survive longer if they eat healthily.
"My advice to men, regardless of their age, is they should start taking responsibility for the food on their plates," says Kristal. If you're tepid on vegetables, find ways to make them taste good, he says.
And don't try to take the supplement shortcut, he says. "These [cancer fighting] compounds aren't in multi-vitamins. There are hundreds if not thousands of bioactive compounds in vegetables. We can only guess how they work and which work."