Results of a recent study build further evidence for the cancer-fighting power of blueberries. The so-called “super food” showed significant activity against breast tumors, according to City of Hope scientists who reported their research in the October issue of The Journal of Nutrition.

Shiuan Chen (Photo by Walter Urie)

Blueberries have long been deemed a potent part of the diet because of the brightly colored compounds called flavonoids and proanthocyanidins they contain.

Previous studies have shown that these compounds can affect growth and death in healthy cells as well as fight damaging chemical byproducts called free radicals. Scientists have speculated that these abilities might mean the compounds could be effective against cancer cells.

Shiuan Chen, Ph.D., director of the Division of Tumor Cell Biology at City of Hope and senior author on the paper, has shown in past studies that blueberry juice could inhibit cancer cell survival and growth in the lab.

The latest research went one step further and tested concentrated blueberry powder against aggressive cancer cells in mice.

Chen and the team performed two studies. In the first study, the scientists fed three groups of mice a diet that contained either no blueberry powder, low levels of blueberry powder or high levels of it.

They found that tumor size decreased significantly in mice fed blueberry powder compared to similar mice that ate no blueberry. Importantly, molecular analysis showed that blueberry consumption altered expression of genes important to inflammation, cancer and metastasis (spread of cancer) in ways that would lower cancer risk.

The second study compared cancer metastasis among mice fed blueberry to metastasis in mice that ate no blueberry. The results jibed with the first study, showing a significant decrease in metastasis in mice that ate blueberry powder compared to those that did not.

“The results show that, at least in mice, blueberry consumption can greatly reduce the growth and spread of an aggressive form of breast cancer,” said Chen. This is especially important because few drugs are effective against so-called “triple-negative” breast cancer — the particular type of breast cancer the researchers studied, according to the team. Triple negative breast cancers do not respond to common hormone therapies or to the powerful drug Herceptin.

“And what’s really exciting is that the amount of blueberry powder we used is one that could reasonably be consumed by women,” Chen added. “It’s equivalent to about two cups of fresh blueberries per day.”

The team cautioned that more research is needed to confirm the effect in humans.

Other researchers on the study include first author Lynn Adams, Ph.D., Noriko Kanaya, Ph.D., Sheryl Phung and Zheng Liu, Ph.D.

The study was funded by the U.S. Highbush Blueberry Council and the National Institutes of Health.