American Institute for Cancer Research
Newsletter 86, Winter 2005

Mining New Sources of Phytochemicals

Thousands of cancer-fighting phytochemicals may remain to be discovered in plant-based foods. Scientists are now finding these natural compounds in the outer layers of whole grains, and are discovering how phytochemicals in other edible plants can be modified for more health protection.

Vegetables, fruits and beans are known to be rich sources of cancer-fighting phytochemicals. Now, scientists are discovering that phytochemicals in whole grains are likely to work together with similar substances in vegetables and fruits to fend off cancer development.

Bound to Be Healthful

Brown rice and whole wheat have plenty of antioxidants called orthophenols in their outer layers. These layers are removed when grains are processed into refined grains from their ?whole? states. Stripping a grain of its bran and germ removes up to 75 percent of the phytochemicals.

Dr. R.H. Liu has studied antioxidants in whole grains. In his laboratory at Cornell University, he analyzed corn, oats, wheat and rice. "We found out that antioxidant activity in whole grains was underestimated because scientists previously only looked at the phytochemicals that were not bound to the cell walls in the outer layer of the plant," Dr. Liu says. The outer layer is retained in whole grains and discarded when grains are refined.

The main phenolic antioxidant in the whole grains he studied was 85 percent bound in corn, 75 percent in whole oats and whole wheat, and 62 percent in rice. This is important, Dr. Liu points out, because bound phytochemicals remain intact throughout digestion in the stomach until they reach the colon. Then, in the fermentation process, the phytochemicals that may provide protection from colon cancer are released.

"Whole grains have a completely different phytochemical profile than do fruits and vegetables," Dr. Liu explained in his presentation at last July?s AICR International Research Conference on Food, Nutrition and Cancer. "The complex mixture of phytochemicals from fruits, vegetables and whole grains is what appears to prevent cancer. The take-home message is, to get the optimal benefits from these foods, eat a wide variety of them."

Modified Phytochemical May Fight Colon Cancer

Resveratrol is a potent phytochemical that has been studied for its possible tumor-inhibiting effects in many types of cancer. It is most closely associated with peanuts, grapes and red wine. But could it be engineered to provide cancer protection in other plant-based foods? AICR grantee Dr. Diane F. Birt had conducted studies showing that resveratrol in its pure form inhibits precancerous developments in the colon. She decided to see if another type of resveratrol, added to alfalfa crops for preserving them, could be converted to the form that inhibits cancer. Dr. Birt believes the conversion will enable living cells to absorb the cancer-fighting type of resveratrol that will result from her experiments.

"What makes alfalfa a good crop to study is that it is easily genetically modified. But we?re hoping our concept could eventually be transferred to other crops that are more commonly consumed - like corn, for example," Dr. Birt explains.

Whole grains also have phytic acid and other types of phytochemicals that may add to their cancer-fighting power. Overall, whole grain phytochemicals appear to be a fertile area for cancer prevention research.

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