The Prostate Puzzle

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Is diet the missing piece?

When Robert Pruett was growing up in the East Texas oil town of Tyler, he didn't give a second thought to his long-term health prospects--even the year he turned 16, when his father was diagnosed with prostate cancer. "I guess I was like a lot of kids at that age," Pruett says. "I was concerned about my father, of course, but that such a thing might happen to me someday didn't rely register."

You live and learn. Even by the time Pruett was in his 30s and had begun to experience irritating prostate infections, doctors told him he didn't have too much to worry about. "They said there wasn't really a connection between prostate infections and prostate cancer," he recalls. "Even then people didn't know a whole lot about prostate cancer--they still don't so there wasn't a whole lot I could do, anyway."

This fatalism, however rooted in the medical realities of the day, did not serve him well. In Pruett's 40s, blood tests showed rising levels of prostate-specific antigen (PSA), indicating a higher risk for prostate cancer. In May 2001, Pruett was diagnosed with cancer of the prostate, the walnut-sized gland below the bladder that secretes semen. Six months later, his prostate was removed, and two and a half years after that, he is keeping his fingers crossed and having his PSA levels monitored to ensure he avoids a recurrence of the cancer.

He also engages, from time to time, in a bit of rueful recollection. "I did everything I could to educate myself once I learned that family history was one of the risk factors," he says. Unfortunately, given existing levels of medical knowledge at that time, there was only so much he could do. Back when Pruett's father was diagnosed with prostate cancer, doctors not only were unaware of the importance of family history, they also knew next to nothing about the role of diet.

Risky Business
Today, the National Cancer Institute (NCI) in Bethesda, Maryland, says that a diet high in saturated fats, primarily from meats and dairy products, increases the risk of prostate cancer. In addition to diet, risk factors for prostate cancer include age (men 55 and older are at highest risk), family history and race (African-American men are more likely to develop prostate cancer than white, Asian or Native American)--meaning Pruett already had age and family history working against him.

"I wasn't really well educated about prevention," Pruett admits. "My doctors were telling me to drink lots of beer and have frequent sex" to flush out the prostate. A study published in August 2003 in the medical journal BJU International suggested that men who ejaculate frequently have lower risks of prostate cancer. As for the beer, several studies--such as one reported in the September 2001 issue of Cancer Causes and Control suggest that alcohol may be harmful to prostate health.

The Power of Food
Howard Parnes, MD, chief of the Prostate and Urologic Cancer Research Group of the NCI, says that nutrients such as isoflavones (found in soy), lycopene (found in tomatoes and tomato-based products), vitamin E and selenium have been shown in some clinical trials to reduce the risk of prostate cancer. Vitamin E is found in plant foods rich in healthful fats such as nuts and sunflower seeds, green vegetables, wheat germ, whole grains and vegetable oils.

Isoflavones are phytoestrogens--plant compounds with estrogen-like effects. Mitchell Gaynor, MD, assistant clinical professor of medicine at Weill-Cornell Medical College in New York, says that those effects include inhibiting the growth and proliferation of prostate cancer cells.

Isoflavones, lycopene, vitamin E and selenium also have antioxidant properties. Antioxidants protect the cells from free radicals--harmful ions that damage cells which may trigger the cell mutations that lead to cancer. And onion-like vegetables such as garlic, leeks, scallions, shallots and chives are important sources of antioxidants. Cabbage, broccoli, cauliflower and Brussels sprouts are good sources of some antioxidant compounds, though they don't contain selenium.

Other potentially useful compounds in the fight against prostate cancer include vitamin D and omega-3 fatty acids--heart-healthy essential fats. Saw palmetto has been frequently promoted as an aid against prostate cancer, but clinical tests of products made from the plant have been inconclusive.

Information Overload
Once Pruett was diagnosed with prostate cancer, he was quickly overwhelmed by the profusion of conflicting information about foods that might help prevent the disease. Even though he had been eating a wholesome diet rich in fruits and vegetables before his diagnosis, as his prostate problems worsened, he began making some changes, such as taking zinc supplements--based on unsubstantiated claims that zinc may help prostate health--but he had little confidence in the usefulness of his efforts. "You have so much information from so many sources, it's hard to know what to believe anymore," he says. Pruett spoke with a number of physicians about prevention and treatment options, but they gave him conflicting opinions.

While patients may be confused about which foods may help prevent prostate cancer, researchers face a lot of uncertainty as well. "We do not have sufficient evidence on which to base firm recommendations on diet and lifestyle modifications for prostate cancer prevention," says Parnes, whose research is focused on vitamin E and selenium.

Other scientists emphasize a different list of beneficial nutrients. "I think the best data at this time in the field supports lycopene, omega-3 fatty acids from fish oil, and a low-fat, high-fiber diet combined with exercise," says William Aronson, MD, associate clinical professor in the Department of Urology at the University of California-Los Angeles. Flaxseed, which is rich in omega-3 fatty acids, may also help prevent prostate cancer, says Wendy Demark-Wahnefried, PhD, director of the Cancer Prevention, Detection & Control Research program at Duke University Medical Center in Durham, North Carolina. Other vegetarian sources of omega-3s include flaxseed oil, walnuts, walnut oil, pumpkin seeds, pumpkin-seed oil, canola oil, purslane and soy.

Trial and Error
Some of the confusion facing patients lies in the very nature of past studies on the relationship of nutrition to prostate cancer prevention. Most of these studies are from correlation or epidemiological studies, which can show a statistical relationship between two phenomena but cannot establish cause and effect. Only clinical trials--experiments that involve comparisons between treatment groups (those receiving an experimental drug, for example) and control groups (those receiving placebos)--test the effectiveness of possible preventatives or treatments. No matter how promising a drug or dietary supplement looks in correlation or epidemiological studies, says Parnes, the results need to be confirmed in clinical trials.

Despite the confusion over the effectiveness of specific nutrients for prostate cancer prevention, Aronson, Demark-Wahnefried and Parnes agree that diets rich in fruits and vegetables are worthwhile. Pruett agrees.

"If I had eaten a lot of soy, or eaten a lot of tomatoes, maybe I could have prevented [the cancer]," he says. "You really have to weigh all the data and educate yourself and talk to as many people as you can, because the more informed you are, the better a [treatment] decision you will make." Even though there's no certainty that the changes in his diet will keep cancer at bay, Pruett feels they have improved his health overall.

What he is encouraged by is the fact that his father, diagnosed in middle age, lived well into his eighties. Here, at last, Pruett has family history working for him.

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By David Lawrence

Just the Facts
The American Cancer Society estimates that more than 230,000 men in the United States will be diagnosed with prostate cancer this year. About 29,000 men will die from the disease. Lung cancer is the only cancer that kills more men than prostate cancer. One in six men are diagnosed with prostate cancer over the course of their lives.

Join a SELECT Group
The National Cancer Institute (NCI) of the National Institutes of Health is conducting a long-term clinical trial--SELECT, or the Selenium and Vitamin E Cancer Prevention Trial--to examine whether selenium and vitamin E, used alone or in combination, are effective at reducing the incidence of prostate cancer.

NCI hopes to enroll 32,400 men in the study by 2006. Men aged 55 and older (or African-American men aged 50 or older) are eligible to enroll. As of August 2003, more than 24,000 men had signed up.

For more information about the study, go to the NCI Web site at www.nci.nih.gov/clinicaltrialsldigestpage/SELECT or call 800.4.CANCER.

World Wide Web of Information
If you're interested in learning more about nutrition and prostate cancer prevention, you have a bounty of sources to choose from on the Internet. Here is a selective list of some useful sites:

• National Cancer Institute: www.cancer.gov
The main page for prostate cancer can be found at: www.cancer.gov/cancer%5finformation/cancer%5ftype/prostate/

• Association of Cancer Online Resources (ACOR): www.acor.org
This site hosts the Prostate Problems Mailing List. For more information about subscribing, go to: http://listserv.acor.org/archives/prostate.html

• The Prostate Centre: www.library.utoronto.ca/medicine/prostate/
The booklet Eating Right for Life: Prostate Cancer Nutrition & You is a recent summary of research into nutrition and prostate cancer prevention--and it includes recipes. Download it for free from: www.library.utoronto.ca/medicine/prostate/prevention%5fdiet.html

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