WASHINGTON (Reuters) - Just three servings a month of raw broccoli or cabbage can reduce the risk of bladder cancer by as much as 40 percent, researchers reported this week.
Other studies show that dark-colored berries can reduce the risk of cancer too -- adding more evidence to a growing body of research that shows fruits and vegetables, especially richly colored varieties, can reduce the risk of cancer.
Researchers at the Roswell Park Cancer Institute in Buffalo, New York, surveyed 275 people who had bladder cancer and 825 people without cancer. They asked especially about cruciferous vegetables such as broccoli and cabbage.
These foods are rich in compounds called isothiocyanates, which are known to lower cancer risk.
The effects were most striking in nonsmokers, the researchers told a meeting being held this week of the American Association of Cancer Research in Philadelphia.
Compared to smokers who ate fewer than three servings of raw cruciferous vegetables, nonsmokers who ate at least three servings a month were almost 73 percent less likely to be in the bladder cancer group, they found.
Among both smokers and nonsmokers, those who ate this minimal amount of raw veggies had a 40 percent lower risk. But the team did not find the same effect for cooked vegetables.
“Cooking can reduce 60 to 90 percent of ITCs, (isothiocyanates),” Dr. Li Tang, who led the study, said in a statement.
A second team of researchers from Roswell Park tested broccoli sprouts in rats.
They used rats engineered to develop bladder cancer and fed some of them a freeze-dried extract of broccoli sprouts. The more they ate, the less likely they were to develop bladder cancer, said Dr. Yuesheng Zhang, who led the research.
They found the compounds were processed and excreted within 12 hours of feeding. That suggests the idea that compounds are protecting the bladder from the inside, said Zhang.
“The bladder is like a storage bag, and cancers in the bladder occur almost entirely along the inner surface, the epithelium, that faces the urine, presumably because this tissue is assaulted all the time by noxious materials in the urine,” Zhang said.
In a third study, a team at The Ohio State University fed black raspberries to patients with Barrett’s esophagus, a condition that can lead to esophageal cancer.
Black raspberries, sometimes called blackberries or blackcaps, are also rich in cancer-fighting compounds.
Ohio State’s Laura Kresty and colleagues fed 1.1 ounces (32 grams) of freeze-dried black raspberries to women with Barrett’s esophagus and 1.6 ounces (45 grams) to men every day for six months.
They measured urine levels of levels of two compounds -- 8-isoprostane and GSTpi -- that indicate whether cancer-causing processes are going on in the body.
Kresty said 58 percent of patients had marked declines of 8-isoprostane levels, suggesting less damage, and 37 percent had higher levels of GSTpi, which can help interfere with cancer causing damage and which is usually low in patients with Barrett‘s.
Reporting by Maggie Fox, editing by Julie Steenhuysen and Vicki Allen