A new study has discovered soy and tea may help protect men from prostate cancer.

Other studies have linked the foods to a reduced risk of breast cancer in women. This is the first study to make the same connections about prostate cancer.

The Harvard University study examined the power of soy and tea to inhibit the growth of prostate tumours in mice.

"I think the most important finding is that consumption of both soy and tea has a synergistic effect," says Jin-Rong Zhou, the study's lead author.

The report appears in The Journal of Nutrition.

Prostate cancer is the second most deadly form of cancer for men after lung cancer. One in eight men in Canada is expected to get the disease in their lifetime.

Zhou says he decided to test his idea when statistical data showed China had one of the lowest prostate cancer risk profiles in the world. He sensed diet may be the key and looked at the eating habits of Chinese men.

Zhou says tea and soy jumped out from the list because previous studies showed they may possess anti-cancer properties.

"Their bioactive components are more potent than other dietary components, we propose that they are dietary components...for prostate cancer prevention."

Researchers examined mice which had been engineered to grow prostate tumours. All the mice ate a diet of protein, carbohydrates, vitamins and minerals. Some were fed daily doses of soy compound in varying amounts. All had infusions of black and green tea.

Zhou says the mice ate an equivalent of about 250 mg a day of soy and six to eight cups of tea.

The researchers looked at the mice for the presence of tumours, the size of the tumours and the rate of growth.

They discovered:

• taken separately, the soy and the tea reduced the rate at which tumours developed
• when tumours grew, they were smaller if either tea or soy was consumed
• taken together, the foods inhibited tumour growth and controlled the spread of the cancer

While nutrition experts say the study shows promise, they don't think men should be ingesting soy or tea in large amounts.

"Many promising animal results never translate to human success," says Jyni Holland of the New York University Medical Center.

But Holland says adding the foods in moderate amounts could have positive results. "If you want of include these foods in your diet, then you may be well ahead of the game," says Holland.