NEW YORK (Reuters Health) — Experiments in rats show that eating both tomatoes and broccoli is better than eating either vegetable alone, or lycopene supplements, for slowing prostate tumor growth, researchers report in the journal Cancer Research.The findings show that men hoping to beat or prevent prostate cancer should stick with whole foods, rather than dietary supplements, Kirstie Canene-Adams, a doctoral candidate at the University of Illinois and the study’s lead author, told Reuters Health. They also back up public health guidelines that recommend people eat a variety of fruits and vegetables to cut their cancer risk, she added.

The human equivalent of the study rats’ diet would be 2.5 cups of cherry tomatoes, two 3-inch tomatoes, or one cup of tomato sauce daily along with 1.5 cups of broccoli every day, Canene-Adams said. Moreover, she noted, epidemiological studies have shown that men who consume that much broccoli and tomato three to five times weekly cut their prostate cancer risk by 30 percent.

In their study, Canene-Adams and her team fed rats a variety of diets: food supplemented with different concentrations of lycopene, a phytochemical contained in tomatoes; tomato powder; broccoli powder; 5 percent broccoli powder plus 5 percent tomato powder; or ten percent broccoli plus ten percent tomato. The animals stayed on their allotted diet for one month before being implanted with prostate tumour tissue.

Other tumour-implanted rats were fed a normal diet but were given the drug finasteride, which is used to treat benign prostate enlargement, while others were castrated.

Tumour growth was slowest in the castrated animals, followed by those given the ten percent tomato and ten percent broccoli diet. Microscopic studies showed that the most concentrated veggie combination enhanced destruction of tumour cells and slowed their growth.

However, animals given only lycopene did not show a significant reduction in tumor growth. “Lycopene alone may have some anti-prostate cancer activity, but the whole tomato and its array of phytochemicals clearly shows anticancer potential that exceeds the pure carotenoid,” Canene-Adams and her colleagues write.

She pointed out that many men with slow-growing prostate cancers will be treated with “watchful waiting,” in which their physician carefully observes them to see if the tumour growth has accelerated, making treatment with drugs, radiation or surgery necessary.

“Diet is maybe something very simple with no side effects — certainly a lot less expensive than surgery or drugs — that they can do during this period that will slow the growth of their cancer,” Canene-Adams concluded.