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Black raspberries may contain compounds
that prevent esophageal cancer and keep precancerous growths
from becoming malignant.
According to the report rats
injected with a cancer-causing compound were less likely to
develop cancer of the esophagus when black raspberries comprised
5% to 10% of their daily diet. The findings add
to a growing body of evidence linking berries with lower cancer
risk.
Raspberries contain many vitamins, minerals,
plant compounds and antioxidants known as anthocyanins that
may protect against cancer. While it is not clear how these
compounds fight off cancer, the researchers recommend that
individuals include a serving of fresh or frozen berries in
their daily diet.
In the study, researchers injected rats
with NMBA, a chemical that has been shown to cause esophageal
cancer. Some rats consumed a diet comprised of 5% to 10% black
raspberries before and/or after receiving injections, while
other rats were fed diets that did not include raspberries.
Rats that consumed the greatest amount
of black raspberries both 2 weeks before and up to 30 weeks
after NMBA injections had 49% fewer tumors than rats whose
diets did not include black raspberries, the researchers report.
Additionally,
tumors that had developed in rats fed raspberries only after
receiving the injections were found to decrease in size after
15 weeks.
After 25 weeks, rats fed diets of 5%
to 10% black raspberries saw the number of esophageal tumors
decrease by 43% to 62%. A diet containing 5% black raspberries
was more effective than a diet containing 10% black raspberries.
There may be a threshold over which protective
compounds such as antioxidants, which normally neutralize
disease-causing free radicals, actually damage DNA in the
presence of a carcinogen like NMBA.
Esophageal cancer is the fifth leading
cause of cancer death in the world, according to the report.
Just 8% to 12% of individuals will survive 5 years after being
diagnosed with the disease.
Cancer
Research 2001;61:6112-6119
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