"It possibly could prevent the spread of the cancer," said City of Hope research fellow Lynn S. Adams, Ph.D.
And not just any cancer, but one that generally carries a poorer prognosis -- triple-negative breast cancers. Triple-negative tumors are not driven by estrogen, progesterone or HER2 proteins, so it can't be treated with latest targeted therapies.
"The feature of the cancer tends to be very aggressive," said Shiuan Chen, Ph.D., director of City of Hope's Division of Tumor Cell Biology.
But when researchers applied blueberry extracts to cancer cells in the laboratory it appeared to stop the growth and spread of a tumor.
"We actually believe that it's a combination of all the different phytochemicals in blueberries working together that aid in increasing its activity," said Adams.
While more research is needed to determine how many blueberries a person will need to eat to reap benefits, the animal studies do give us a clue.
"It comes out to be about two cups a day from what our animals were ingesting. But it is difficult to say that something that works in an animal study will work the same in a person," said Adams.
So how should you get your two cups of blueberries every day? Should you eat whole fruit, juice or supplements? Experts say many of the juices contain sugar and supplements vary in antioxidant activity.
"Turns out that their activity will be quite different from one brand to the other," said "In other words, at this point, there is no good quality control," said Dr. Chen.
The next step is to do human clinical trials on breast cancer patients.
"We want to give people every weapon in the arsenal that we can to help the prevention and reoccurrence," said Adams.
City of Hope researchers say if you are eating certain types of fruits and vegetables regularly, it's a good idea to alert your doctor because certain phytochemicals can interact with medication.