Prostate cancer: more questions than answers

HARRY BELAFONTE, Colin Powell, John Kerry, Bob Dole, Arnold Palmer, Norman Schwarzkopf, and Robert Goulet chose surgery. Rudolph Guiliani, Nelson Mandela, Richard Riordan, Charlton Heston, and Rupert Murdoch went with radiation. Gregory Hines, Linus Pauling, Frank Zappa, Telly Savalas, and Timothy Leary died of the disease.

Anyone who's past middle age can add the names of friends, fathers, brothers, and others who have or had prostate cancer. That's what happens when a disease hits one in six men.

Death rates are down 20 percent since the peak in the early 1990s. But prostate cancer is still expected to strike 230,100 men and claim 29,900 lives this year.

Here's the latest on what may--or may not-keep your name off the list.

It's not the worst cancer you can get. The odds of surviving prostate cancer for five years are 98 percent, up from 67 percent in the mid-1970s. That's a higher survival rate than for any common cancer (except non-melanoma skin). After ten years, 84 percent of patients are still alive.

Nevertheless, prostate cancer is a source of immeasurable suffering and loss. And while researchers have stepped up their efforts to find foods or supplements that might keep tumors from starting or spreading, their findings have yet to yield a slam dunk. Here's an A-to-Z guide to what they've learned so far.

Alpha-Llnolenic Acid & Flaxseed

It seems contradictory.

In studies of thousands of men, the risk of prostate cancer is 70 percent higher in those who consume more alpha-linolenic acid, or ALA--an omega-3 fat found in meat, vegetable oils, and other foods. (1) (The body may convert ALA to the longer-chain omega-3s that are found in fish oil.)

"At first we thought that ALA was associated with a higher risk of prostate cancer because men who consumed more ALA also consumed more meat," says Walter Willett, who chairs the nutrition department at the Harvard School of Public Health in Boston. "But now it looks like the ALA in oils like soy and canola are also linked to prostate cancer."

So it seems surprising that flaxseed, one of the richest sources of alphalinolenic acid, lowered PSA levels (from 8.5 to 5.7, on average) in a pilot study of 15 men who were scheduled to have a repeat biopsy. (2) (The men added an ounce a day of ground flaxseed to a lower-fat diet for six months.)

"The findings are conflicting, but people don't eat isolated nutrients--they eat foods," says researcher Wendy Demark-Wahnefried of Duke University in Durham, North Carolina. "We tested the whole flaxseed, which has a host of nutrients--not just ALA, but lignans, which are fiber-rich plant estrogens."

A recent study at the University of Michigan found that ALA promoted prostate cell growth, she notes. "But that was a study done in cell lines, not in people or even animals. And they used purified ALA, which is devoid of antioxidants and is kept at high temperatures, not ALA as it is found in the body."

Demark-Wahnefried's studies have found that flaxseed slows the growth of prostate tumors in mice. (3) "Those results, plus the slower cancer growth and the drop in PSA we found in men who are flaxseed during the month before surgery, are compelling," she says. "But I wouldn't stand on a soapbox and tell men to eat flaxseed. We first need well-controlled trials to find out if it can help."

She has now started a clinical trial that will give a low-fat diet supplemented with flaxseed to cancer patients who are scheduled to have their prostate glands removed. (Most weeks before the surgery can be performed.)

"Then when the prostate comes out, we can measure the cell proliferation rate," she says. "That's more reliable than measuring PSA."

Demark-Wahnefried suggests several mechanisms to explain why flaxseed might work. "The lignans could be acting like estrogen," which slows prostate cell growth. "Or they could bind to testosterone in the GI tract, just as the beta-glucan fiber in oat bran binds to cholesterol. That would enhance testosterone excretion."

But until more research results are in, it makes sense to avoid too much ALA, especially from concentrated sources like flaxseed oil supplements.

"We found an increased risk of prostate cancer in men who consumed 1.5 grams of ALA a day compared to those who got 0.7 grams," says Ed Giovannucci of the Harvard School of Public Health. Every 1,000 mg of flaxseed in a typical supplement contains roughly 500 mg (0.5 grams) of alpha-linolenic acid.

His advice: "ALA is a tough one because we have good evidence that it's beneficial for heart disease, but men can certainly reduce the ALA they consume by eating less red meat." That might protect the prostate without jeopardizing the heart.

Calcium

Calcium is everywhere--fruit juices, breakfast cereals, pancake mixes, and dozens of other foods. You'd never guess that too much calcium may raise a man's risk of prostate cancer. Yet that's what several studies show. (4)