Black Raspberries A Potentially Powerful Agent In Fight Against Colon Cancer

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http://www.sciencedaily.com/releases/2002/05/020502072053.htm

Source: Ohio State University (http://www.acs.ohio-state.edu/)

Date: Posted 5/2/2002

Black Raspberries A Potentially Powerful Agent In Fight Against Colon Cancer

COLUMBUS, Ohio -- There is a potentially powerful biological weapon for health

-- a mix of compounds suspected of

thwarting colon cancer -- hiding deep inside the juicy sweetness of a black

raspberry. And if it can be harnessed, it

could play a major role in preventing the second leading cause of cancer deaths

in the United States.

In a recent study, rats that were injected with a cancer-causing agent and then

fed a berry-rich diet had 80 percent

fewer malignant tumors compared to rats that had no berries in their diet.

For years, scientists have touted the health benefits of eating fruits and

vegetables. They’re only now starting to gain

an understanding of what compounds give certain foods a healthful edge. Black

raspberries are rich in several substances

thought to have cancer-preventing properties, said Stoner, a study

co-author and a professor of public health at

Ohio State University. Stoner is also a researcher at the university’s

Comprehensive Cancer Center.

Such substances are called antioxidants. The researchers also compared the

antioxidant activity of black raspberries to

that of blueberries and strawberries, two fruits with suspected chemopreventive

effects. Black raspberries prevailed in

the comparison by as much as 40 percent.

“We were surprised by how much difference there was between the antioxidant

activity of the raspberries vs. the other

fruits,” Stoner said.

The research appears in the current issue of the journal Nutrition and Cancer.

Rats were injected with azoxymethane (AOM), a carcinogen that causes colon

tumors. After two weeks of exposure to AOM,

the animals were placed into four groups and fed diets mixed with 0, 2.5, 5 or

10 percent freeze-dried black

raspberries. Two additional groups of rats, which did not receive AOM, served as

controls. The two latter groups were

fed a diet containing 0 or 5 percent freeze-dried black raspberries,

respectively.

Nine weeks after the final injection of AOM, researchers looked for the

development of tiny lesions in the colon called

aberrant crypt foci (ACF). Although ACF rarely occur in humans, the lesions can

develop into polyps in rats. In humans,

polyps are benign masses of tissue which, if left untreated, could develop into

malignant tumors.

Every rat injected with the carcinogen AOM developed the ACF lesions. While most

of these lesions go away on their own,

Stoner said, some may eventually develop into malignant tumors. In rats fed

diets supplemented with black raspberries,

the number of malignant tumors seemed to correspond with the amount of

freeze-dried berries fed to a rat -- the more

berries a rat ate, the fewer tumors it had.

At the end of the study, the prevalence of adenocarcinomas or malignant tumors

was reduced by 80 percent in the rats

that ate the most black raspberries in their diets. “That’s a much higher

reduction than I thought we'd see,” Stoner

said.

Adenocarcinomas were reduced by 28 and 35 percent, respectively, in the groups

eating diets of 2.5 and 5 percent black

raspberries. This reduction is based on the average number of tumors found in

rats that had been injected with AOM and

fed a berry-free diet.

The tumors were smaller in the rats that ate freeze-dried berries -- diets of

2.5, 5 and 10 percent yielded reductions

in tumor size of 28, 42 and 75 percent, respectively, when compared to the

animals not fed the berries.

The researchers also measured urinary levels of 8-OHdG -- a compound that is

related to the degree of oxidative damage

in the body. The process of oxidation produces free radicals, which can damage

cells as well as genetic material. Free

radicals are thought to play a role in the onset of cancer.

Berries reduced the level of 8-OHdG in the urine by 73, 81 and 83 percent in the

2.5, 5 and 10 percent berry diets,

respectively. “This suggests that berries bind up a good portion of free

radicals, preventing them from causing damage

in the body,” Stoner said.

In addition to measuring the levels of some of these chemopreventive compounds,

Stoner and his colleagues compared the

antioxidant activity of the black raspberries to that of strawberries and

blueberries. Previous studies suggested that

these two fruits had antioxidant activity superior to that of other fruits

commonly eaten in the United States, but

researchers had not studied black raspberries.

Using a device that measured each fruit’s ability to absorb free radicals, the

researchers found that black raspberries

topped the charts: these berries exhibited 11 percent more antioxidant activity

than did blueberries and 40 percent more

than strawberries.

One reason for the raspberries' seemingly stellar health advantage may be their

richness in compounds such as

anthocyanins, which give berries their almost-black pigment; phenols, such as

ellagic, coumaric and ferulic acid;

calcium; and vitamins such as A, C, E and folic acid. All of these substances

are known chemopreventive agents, Stoner

said.

Fresh black raspberries are undoubtedly beneficial, but they are also expensive

and can be hard to come by. Freeze-dried

berries have as much nutritional content as fresh berries do, but the

freeze-dried version isn't readily available to

consumers, Stoner said. He tells people to hold off on getting discouraged,

though.

“The results of this study would translate in humans to eating two large bowls

-- or four cups -- of fresh black

raspberries each day,” he said. “That may seem a bit extreme. People need to

know that these animals are given whopping

doses of a carcinogen. It’s conceivable that a much lower dose would be

effective in humans.”

It’s also good to keep in mind that the National Cancer Institute continues to

recommend four to six helpings of fruits

and vegetables each day. “We’re just suggesting that people make one of those

helpings berries,” Stoner said.

The research was supported in part by a grant from the Ohio Department of

Agriculture.

Stoner conducted the research with Ashok Gupta, Nines, Kresty,

el, Suzy Habib, Krista La Perle

and professor of food science and nutrition Schwartz, all with Ohio

State; of the National

Institute of Occupational Safety and Health in town, W. Va.; and

Gallaher of the University of Minnesota,

Twin Cities.

Editor's Note: The original news release can be found at

http://www.osu.edu/researchnews/archive/brberry.htm

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Good health & long life,

Greg ,

http://optimalhealth.cia.com.au