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MARCH / APRIL 2005

AROUND HARVARD

This article originally appeared in the January 2005 Harvard Health Letter and is provided courtesy of Harvard Health Publications.

Cancer: How not to go there
The secret to cancer prevention may be in the gym. Or in the spice rack. Let’s hope researchers find it soon.

The American Association for Cancer Research (AACR), a leading organization in that field, held a meeting on cancer prevention in 2003. The findings presented at this meeting are preliminary — shards of evidence designed to stir up further research, not settle debate or provide a solid basis for advice. Still, this kind of early science is intriguing. Here are some of the highlights.

Exercise
Physical activity lowers breast cancer risk, but nobody is sure why. A study led by a Yale researcher hints that exercise may reduce the density of breast tissue. Density, as measured by a mammogram, is a well-established risk factor for breast cancer. It’s an indication of a higher percentage of glandular tissue and possibly a sign of breast tissue having been exposed to higher levels of estrogen. In this study, women who exercised more had less dense breast tissue — but only if they were premenopausal and not obese. Physical activity had no bearing on breast density in postmenopausal or obese women.

Aspirin
Aspirin protects against colon cancer, lowering the risk of recurrence and of adenomas — abnormal growths (polyps) that can lead to cancer. Animal and test-tube experiments suggest that it should do the same for pancreatic cancer. But Harvard researchers analyzing data from the Nurses’ Health Study came to the conclusion that aspirin use increased pancreatic cancer risk, a truly surprising result given all other evidence. Nurses in the study who took aspirin regularly for 20 years or more had a 58% greater chance of developing pancreatic cancer. It’s possible that the cause is not aspirin but some other factor related to its use. The researchers who led this study speculate that aspirin might raise cancer risk in some tissues, like the pancreas, but lower it in others, like the colon.

Soy
A study of women in Shanghai, China, found that a higher intake of fruit and vegetables — especially fruit — correlated with a lower risk for breast cancer, but higher soy consumption, surprisingly, did not. Another study presented at the meeting, however, showed that soy consumption in adolescence had the expected protective effect. Researchers suggested that the divergent findings may be another indication that dietary and other choices we make — or have made for us — early in life may influence our health more than the habits we adopt as adults.

Ginger
In many parts of the world, ginger isn’t just a flavoring. It’s regarded as a powerful, all-purpose medicine for everything from nausea to cancer. To test its anticancer properties, University of Minnesota researchers fed the biologically active part of ginger to mice that had been injected with colon cancer cells. The mice given ginger developed tumors later than those fed an alternative, and the tumors that they eventually developed were considerably smaller.

Green tea
Studies have linked green tea to lower risk for breast, pancreatic, colon, esophageal, and lung cancers — and in humans, no less. One problem: The most active preventive chemical in green tea, epigallocatechin-3-gallate, is not only difficult to pronounce (use the initials, EGCG, instead) but hard to absorb. Researchers at SRI International, a Menlo Park, Calif., nonprofit research organization that was formerly part of Stanford University, may have found a way to get around the problem — a synthetic form of the most potent part of the EGCG molecule. In test-tube experiments, their chemical invention inhibited the division of breast cancer cells and frustrated growth factor proteins that spur cancer cells to proliferate. At this meeting, the scientists touted their version of EGCG as a research tool that might help scientists pinpoint the biochemical processes of cancer prevention. But they also dangled the prospect of a new generation of chemopreventive agents — the synthetic essence of green tea, if you will.

Other green tea findings included a study of smokers at the Arizona Cancer Center in Tucson showing that four cups of decaffeinated green tea every day for four months provided some protection against potentially carcinogenic damage to DNA, as measured by the amount of an enzyme in the urine. In a study measuring the same enzyme, researchers from Texas Tech showed that green tea polyphenols might inhibit cancer in people at high risk for liver cancer.

Pomegranates
Pomegranates (more precisely, the juice contained in the small sacs that hold the fruit’s seeds) are brimming with polyphenols and anthocyanins — compounds that seem to have anticancer properties. University of Wisconsin scientists tested a topical pomegranate extract on mice whose skin had been exposed to a tumor-causing chemical. All the exposed mice that weren’t treated with the pomegranate concoction developed skin tumors, while only 30% of those who got the treatment did. Don’t look for pomegranate juice in your sunscreen next summer, but pomegranates may eventually join green tea and ginger as natural cancer fighters.