Anthocyanins in Purple, Blue and Red Foods Fight Colon Cancer

A new study by researchers at Ohio State University proposes that the molecular structure of substances which give fruits and vegetables their rich colors may help find more powerful cancer fighting agents.

Experiments on rats and on human colon cancer cells suggest that anthocyanins, the compounds that give color to most red, purple and blue fruits and vegetables significantly slow the growth of colon cancer cells.
Professor Monica Giusti, lead author of the study and assistant professor of food science at Ohio State University says,

“These foods contain many compounds, and we’re just starting to figure out what they are and which ones provide the best health benefits.”

Wide Variety of Produce Tested

Researchers tested the anti-cancer effects of anthocyanin-rich extracts from a variety of fruits and vegetables.

They retrieved these anthocyanins from some relatively exotic fruits and other plants, including grapes, radishes, purple corn, chokeberries, bilberries, purple carrots and elderberries. These plants were chosen for their intense deep colors, and thus high anthocyanin content. Some of these plants are even used as a source for food coloring.

The researchers ascertained the level of extract required from each plant to slow the growth of human colon cancer cells to half the normal rate. Altering pigment structures only slightly, by adding an extra sugar or acid molecule changed biological activity profiles of these extracts.

The researchers then added the extracts to flasks containing colon cancer cells. Using high-performance liquid chromatography mass spectrometry they determined the precise chemical structure of each compound, then did biological testing to find the number of cancer cells left after anthocyanin treatment.

Purple Corn

The researchers found that the amount of anthocyanin extract needed to reduce cancer cell growth by 50 percent varied among the plants. Extract derived from purple corn was the most potent, in that it took the least amount of this extract (14 micrograms per milliliter of cell growth solution) to cut cell numbers in half. Chokeberry and bilberry extracts were nearly as potent as purple corn.

Radish extract proved the least potent, as it took nine times as much (131 µg/ml) of this compound to cut cell growth by 50 percent.

Black Raspberries

Other research at Ohio State has found that black raspberries may assist in reducing the growth of colon and esophageal cancer tumors.
Professor Giusti does not recommend one kind of fruit or vegetable over another.

“There are more than 600 different anthocyanins found in nature,” she said. “While we know that the concentration of anthocyanins in the GI tract is ultimately affected by their chemical structures, we’re just beginning to scratch the surface of understanding how the body absorbs and uses these different structures.”

She and her associates continue to study how chemical structures of anthocyanins contribute to the health benefits of food as well as how changes to these structures may affect the body’s ability to use the compounds.

“It is possible to use natural, anthocyanin-based food colorants instead of synthetic dyes,” Giusti said. “Doing so still maintains the wonderful colors of foods while enhancing their health-promoting properties.”

The findings were presented on August 19, 2007 at the national meeting of the American Chemical Society.

50 to 80% Reduction in Cell Growth

In other lab work, the team found that anthocyanin pigments from radish and black carrots slowed the growth of cancer cells anywhere from 50 to 80 percent. However, pigments from purple corn and chokeberries not only totally stopped the growth of cancer cells, but also killed roughly 20 percent of the cancer cells while having little effect on healthy cells.

In animal studies, rats induced with colon cancer cells were fed a daily diet of anthocyanin extracts either from bilberries and chokeberries, which are most often used as flavorings or to make jams and juices.

The dietary addition of the anthocyanin extracts reduced signs of colon tumors by 70 and 60 percent, respectively, when compared to control rats.

Giusti says the results suggest that anthocyanins may protect against certain gastrointestinal cancers.

“Very little anthocyanin is absorbed by the bloodstream,” Giusti said. “But a large proportion travels through the gastrointestinal tract, where those tissues absorb the compound.”