Eating blueberries may inhibit breast cancer tumor growth, according to a recent study by researchers at the City of Hope in Los Angeles that is published in the October 2011 issue of The Journal Of Nutrition. The study found that the oral intake of whole blueberry powder could reduce the growth and metastasis of a very aggressive form of breast cancer (triple-negative cancer) – for which there are very few effective drugs.
"We searched fruits with the ability to suppress the proliferation and migration of triple-negative breast cancer cells. Blueberries were found to have such properties,” says Dr. Shiuan Chen, senior author of the publication.
"Super food" blueberries are known for being rich in flavonoids and proanthocyanidins, and these phytochemicals have been shown to both affect cell growth and fight free radicals with their antioxidant properties. To test the cancer-fighting qualities of blueberries, researchers conducted two studies on mice with tumors derived from aggressive cancer cells.
In the first study, mice were assigned to one of three treatment groups: a control diet, a low-blueberry diet (containing 5% blueberry powder), or a high-blueberry diet (containing 10% blueberry powder). In the second study, mice were divided into two experimental groups: control diet and low-blueberry diet. In the second study, factors related to metastasis were also studied.
Tumor size was reduced by 75% in mice fed the low-blueberry diet; tumor size was reduced by 60% in the high-blueberry diet. In addition, molecular analysis revealed that blueberry consumption altered the expression of genes that are important to metastasis, suggesting that cancer risk would likely decline from blueberry consumption. The blueberry dose required to achieve these results was equivalent to two cups of fresh blueberries per day, and could be reasonably consumed by women, says researchers. Also, consumption of blueberries at this level was found to be nontoxic and did not affect food intake, weight, or overall health of the mice studied.
The research suggests that the bioactive substances in berries inhibit different components of the extremely complex tumor invasion and metastasis system. The number one gene network affected by blueberry ingestion was inflammatory disease, cancer and cell morphology. And, interestingly, tumor growth was lower in the 5% diet versus the 10% diet, indicating that there may be an optimal level of blueberry intake.
"Many natural products do that. Since there are many phytochemicals in fruits like blueberries and these chemicals have different effects, the 5% dose may have the proper quantities to achieve best protection," says Chen.
Chen says that while we know that blueberries contain phytochemicals, which can help to suppress the proliferation and migration of cancer cells, we have not yet defined the active chemicals. What we do know, he says, is that blueberry ingestion mediates key processes such as inflammation, cell signaling, survival and migration, which in turn affect tumor growth and metastasis. Future studies using whole blueberry powder are recommended to determine the suitable human dose and future dietary strategies to help prevent breast cancer.
"We hope to evaluate in humans. We are working on funding and need to identify the proper patient population for the clinical trial. The laboratory findings are exciting, but further studies, especially clinical trials, are needed to confirm the observation before we can make a recommendation for human consumption. Our studies suggest that blueberries contain phytochemicals with anticancer properties. However, we do advise everyone to consume a diet with a wide variety of fruits and vegetables for overall health," says Chen.