Diet May Delay Prostrate Cancer

Diet may delay prostate disease, Sep. 18, 2006
ELVIRA CORDILEONE, STAFF REPORTER, The Toronto Star

A healthy diet over a lifetime didn't prevent Grant Cooper, 70, from getting prostate cancer. But it may have postponed its appearance and given him a better chance at surviving it.

Human bodies run best on a diet rich in lean protein, high fibre and an abundance of fruits and vegetables. Myriad recent studies point to a high correlation between the typical Western diet — with large amounts of foods from animal sources — and disease.

As the evidence linking diet and health accumulates, so does the medical research examining how diet can prevent cancer or slow its growth. Results have shown particular promise with prostate cancer.

"This field didn't exist until nine or 10 years ago, because medicine hasn't been geared toward prevention-related research," says Dr. Neil Fleshner, head of urology at the University Health Network and Princess Margaret Hospital.

Researchers found a link between a high-fat diet and cancer as far back as 1942, when tumours in animals fed a high-fat diet grew more quickly than in a control group, writes Stanley Brosman, a clinical professor in the urology department at the University of California, in Emedicine, an online medical database.

"The United States and Western Europe have the highest death rates from prostate cancer and the highest per capita fat consumption," writes Brosman. "In contrast, the Pacific Rim countries with the lowest death rates from prostate cancer have the lowest fat consumption."

However, he notes that when these people move to the West, they lose their edge. Americans born in China or Japan, for example, have an incidence of prostate cancer three to seven times higher than those still living in their homelands.

"Something to do with diet is going on here," says Barbie Casselman, a Toronto-area nutrition consultant.

But Casselman says scientists don't yet understand why. She says they're looking at whether fatty acids themselves contain carcinogens, whether men who eat a lot of meat consume too few fruits and vegetables (and thereby lose out on their protective effects), or whether it's that high-fat diets tend to lead to obesity, which itself carries a higher risk of cancer.

Cooper, a retired high school geography teacher who lives in Kitchener, grew up in Northern Ontario eating wild blueberries and vegetables grown in the family's garden.

He and his wife, Elizabeth, both weigh within a pound or two of what they did when they married 45 years ago. He considered his diet to be reasonable, he took supplements and went for a half-hour walk daily. Nevertheless, in 1999, he developed prostate cancer. Post-surgical tests showed it had already travelled to the margins of the excised tissue.

About a year after surgery, blood tests showed his PSA (prostate-specific antigen) had resumed its climb. His doctor prescribed hormone therapy and Cooper decided to further slash his consumption of dietary fats, particularly red meat. He also began drinking soy milk (which contains isoflavones thought to inhibit the growth of certain hormone-dependent cells) and eating plenty of dishes containing cooked tomatoes (a source of lycopene, which has been associated with a decreased cancer risk).

Cooper's recent blood tests show PSA levels so low they're virtually undetectable.

Dietary benefits may come not only from reducing fat intake, but also in eating foods rich in protective micronutrients. Fleshner recently completed a study of 50 men with early prostate cancer using vitamin E, lycopene and selenium. Six to eight weeks before surgery, each of five groups of 10 took either one of the micronutrients, a combination of all three, or a placebo. "To my surprise, and of my colleagues, there was a dramatic or total arrest of growth in those that took the combination of all three micronutrients," Fleshner says.

Dr. Vasundara Venkateswaran had similar results. The scientist at Sunnybrook hospital's urology department and assistant professor in the University of Toronto's surgical department added three micronutrients to the diets of mice. The incidence of cancer was reduced fourfold — even in the group fed a high-fat diet.

She cautions, however, that the mice were put on the diet as soon as they were weaned, which suggests that the later men begin a healthy diet, the smaller the beneficial effects may be.

Fleshner's advice to men wanting to start reducing their risk of cancer now? Eat more soy products, cut down on fat and take in fewer calories. And eat five to nine servings of fruit and vegetables a day, adds Casselman.