New Links Detailed Between Diet, Cancer Risk

By Rick Ansorge
HealthDay Reporter
Thursday, November 16, 2006; 12:00 AM

THURSDAY, Nov. 16 (HealthDay News) -- What you choose to eat might determine your risk of developing some common cancers.

That's the conclusion of several new studies presented this week at an American Association for Cancer Research meeting in Boston.

Women who eat high amounts of soy, especially as children, may have a significantly lower risk of breast cancer, according to one study. Other studies show that men who eat a fish-rich diet may have a decreased risk of colorectal cancer and that male smokers who eat foods containing high amounts of vitamin E -- such as nuts, whole grains and green leafy vegetables -- may have a decreased risk of developing tobacco-related cancers.

Together, this research offers some of the strongest evidence to date of a link between diet and cancer, the study authors said.

"This is the first study to look at childhood soy exposure and the later risk of breast cancer. It suggests that there really is a biologic effect for soy, and we're excited about that," said lead researcher Dr. Larissa Korde, of the U.S. National Cancer Institute.

"The more we know about cancer, the more it's clear that diet is related to cancer," added Dr. Alan Kristal, of the Fred Hutchinson Cancer Research Center in Seattle, who moderated the meeting's diet and cancer session but was not connected with the three studies. "But the relationship is complex. Diet and cardiovascular disease is simple compared to diet and cancer because the risk factors differ for different cancers."

In their study, Korde's team examined diet and lifestyle factors in 1,563 Asian-American women, 597 of whom had breast cancer and 966 of whom did not.

The researchers found a 58 percent lower risk of breast cancer in women who ate the most soy as children -- an average of a little over two servings per week -- compared to women who ate the least soy -- an average one-quarter serving per week. They also found a 25 percent lower risk of breast cancer in women who ate the most soy as adolescents and adults.

A recent review of 18 epidemiological studies showed a more modest overall reduction in risk: 14 percent.

However, the new study looked at women of Chinese, Japanese and Filipino ancestry because "it is a population that has a very different diet and lifestyle than most Americans," Korde explained.

Asians consume much more soy than Americans do and breast cancer rates in Asian countries are four to seven times lower than they are in the United States, she said. But after Asians migrate to the United States, it usually takes only three generations for their breast cancer rates to catch up to those of American white women.

Korde's team used food-frequency questionnaires to study the women's diets. They also interviewed the women about other lifestyle factors, such as whether or not they lived in mostly Asian or non-Asian neighborhoods, shopped in Asian or non-Asian grocery stores and read Asian or non-Asian newspapers. They also interviewed 255 of their mothers to get additional information about their daughters' childhood exposures.

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