Soy and processed tomatoes help fight prostate cancer, research shows

(CP) - Prostate cancer survivor Grant Cooper was never a fan of soy products until he found out they are a good source of low-fat protein.

They also contain a special ingredient called isoflavones - including genistein and daidzein - which are compounds likely to play an important role in holding off the growth of prostate tumours, says Barbie Casselman, a Toronto nutritionist who works with several doctors who care for patients with prostate cancer.

"The fact is, in Asian countries the men consume a low-fat diet filled with lots of tofu, tempeh and soy milk, which are all excellent sources of soy protein, and they are free from prostate cancer," she said in an interview. "Researchers are supposing it has to do with their high soy intake."

Blood and urine analyses from Asian men have revealed that the samples contain anywhere from seven to 100 times more isoflavones than the samples from North American men. Plus, lab tests on genistein, the type of isoflavone found abundantly in soy foods, show that it's a potent inhibitor of cancer cells, including prostate cancer.

"Soy is a phytoestrogen and researchers believe there is some connection between that blocking the man's testosterone from feeding a prostate tumour," says Casselman.

In the booklet Eating Right for Life: Prostate Cancer Nutrition and You (Parkhurst), which deals with diet and prostate cancer, the authors also point to a low-fat diet being the first step to prostate health.

Recent studies have shown that fat and fatty foods are associated with the development of prostate cancer, which the Prostate Cancer Research Foundation of Canada says is the No. 1 cancer threat to the lives and health of men, afflicting one man in seven. At least one study suggests that prostate cancer is more likely to progress in men whose diet has a high fat content.

At New York's Sloan-Kettering Cancer Center, even men without established prostate cancer managed to reduce their prostate-specific antigen (PSA) values by eating a low-fat diet.

Cooper, 69, of Kitchener, Ont., was diagnosed in 1999 with an elevated PSA and had surgery to remove a tumour. Now, with regular checkups and a change in his diet, he is able to live a normal life, he says.

"I have changed my diet to a certain extent," he says. "Instead of eating a big slab of roast beef, I prefer fresh fish and lots of vegetables."

He also says he is consuming tomato juice, which contains lycopenes, a kind of antioxidant found particularly in tomatoes (it is what makes them red), as well as papaya and watermelon.

Researchers have found that men with prostate cancer have low levels of lycopenes in their blood and prostate tissue.

Processed tomatoes (in sauces and juices) are better than fresh because lycopenes are fat soluble, which means your body will absorb more of them when they're processed with a little bit of oil.

Cooking tomatoes is also preferred, since heat releases the lycopenes from inside the cells.

To access the book and other information, go to the Prostate Cancer Research Foundation of Canada website at www.prostatecancer.ca. For a copy of the cookbook, go to www.prostatecentre.ca/downloads/cookbook.pdf.

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Judy Creighton welcomes letters at 9 Kinnell St., Hamilton, Ont. L8R 2J8, but cannot promise to answer all correspondence personally. She can also be reached by e-mail at jcreighton(at)golden.net

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Some facts about prostate cancer and diet:

-Prostate cancer is the most commonly diagnosed cancer among men living in the western world such as Canada, the United States, Northern Europe and Australia.

-In Pacific Rim countries (Japan, China, Taiwan and Thailand), several Middle Eastern countries and Northern Africa, prostate cancer is rarely diagnosed.

-Recent studies have shown that fat or fatty foods are associated with the development of prostate cancer.

-Although inherited factors are important in some prostate cancers, the overwhelming majority are related to the environment - and diet seems to be the key.

Source: Eating Right for Life: Prostate Cancer Nutrition & You.