UI study finds two vegetables team up on cancer
Broccoli and tomatoes have shown cancer-fighting qualities in a number of studies, but a new University of Illinois study indicates that they work even better together in curtailing the growth of prostate cancer.
UI doctoral candidate Kirstie Canene-Adams, the lead author of the study, and food science and human nutrition professors John Erdman and Elizabeth Jeffery fed a mix of powder made from whole broccoli and tomatoes to rats given prostate cancer.
Other rats got either whole tomato or broccoli powder alone; lycopene, a cancer-fighting agent identified in tomatoes; or finasteride, a drug commonly given to men with enlarged prostates, which can be a precursor to prostate cancer. One group of rats also was castrated, which virtually halts the production of the hormones that drive prostate cancer growth.
At the end of 22 weeks, the UI researchers weighed the tumors. Canene-Adams also worked with scientists at Ohio State to image how actively tumor cells from the rats were growing.
In the end, the whole tomato and broccoli combination curtailed tumor growth more than any of the other treatments except castration, which wasn't better by much.
In addition, consuming broccoli and tomatoes obviously doesn't have the drawbacks presented by castration, including surgery and such side effects as weight gain, loss of muscle mass, fatigue and loss of sex drive.
Moreover, cancer tends to adapt to castration. Over time, it mutates to spread even in the absence of the hormones the surgical procedure cuts off the supply of, Erdman said.
He said previous studies already had indicated that three to five servings a week of broccoli or of tomatoes could benefit men with prostate cancer. The new UI study, published this month in the journal Cancer Research, seems to say that three to five servings of both would be even better.
Jeffery said the studies also indicate that the effect from the foods is amount-dependent, potentially meaning the more you eat the better still.
While the new study was done with rats, results from previous studies at the UI and elsewhere – including a Harvard men's health survey that linked broccoli and tomato consumption with lower prostate cancer incidence – makes the researchers "much more encouraged to say there's likely to be a translation to humans," Erdman said.
And given the overall health and nutrition benefits of the two foods, it doesn't hurt to eat more of them in any event, the researchers said.
"There really aren't any negative sides of this that we know of," Erdman said. "It's not gonna do harm."
Another significant aspect of the study, Jeffery said, is that whole foods turned out to be better than a cancer-fighting ingredient, lycopene, refined from the foods, as is done in the case of some health supplements on the market. The lycopene did have an effect, but the whole food powder was more effective.
One likely reason for the result is that whole broccoli and tomatoes contain more than just one beneficial, bioactive component, just as the benefits of oranges aren't limited to Vitamin C, Jeffery said.
Our bodies also seem to absorb the beneficial components of foods better when the foods are whole, probably because we've got eons of evolving to do so behind us.
Light cooking, steaming or stir frying for a few minutes, appears to make the bioactive components even more available to the body.
Jeffery has been turning up health benefits in broccoli, and Erdman in tomatoes, for years. So combining the two to see what happens came naturally. The new study was funded by the American Institute for Cancer Research and the U.S. Department of Agriculture.
Next, the UI researchers, with a grant from Illinois Council on Food and Agricultural Research, plan to look at other animal models and at sulforaphane, a major prostate cancer-fighting ingredient identified in broccoli.
They're also preparing a public education campaign with elements aimed especially at the Chicago area and at black men, the group with the highest known rate of prostate cancer.