- Posted by jdavis on August 24, 2011
Smokers, Non-Smokers Benefit From Certain Foods
Foods containing chemicals with weak estrogen-like activity appear to reduce the risk of developing lung cancer in smokers and non-smokers, according to new study results.
M. D. Anderson investigators reported in the Sept. 28 issue of the Journal of the American Medical Association that participants who ate the highest amount of foods with dietary “phytoestrogens” had a 46% reduced risk of developing lung cancer, compared to those who ate the lowest quantity.
Phytoestrogens are plant chemicals (such as soy, grains, legumes and vegetables) that bind to the estrogen receptors present in normal and malignant lung tissue, and that could play a role in the regulation or deregulation of cancer growth.
Men and women benefit from different foods
The study also found the following gender-specific benefits:
- Men & soy Men who ate the highest amount of soy-isoflavones (a type of phytoestrogen found in soymilk, soy, miso) lowered their risk of developing lung cancer by 72%.
- Women & fruit Women who ate certain lignans (a type of phytoestrogen found in fruits, vegetables, seeds, berries and teas) lowered their risk of developing lung cancer by 41%. For those women who also used hormone replacement therapy, this protective effect was further enhanced.
The type of lignans found effective in the study include broccoli, carrots, lettuce, onions and flaxseed.
Reliability of participant memory may weaken study results
More than 3,500 people participated in the research, making it the largest case-control study to examine dietary phytoestrogens and lung cancer risk in the United States, researchers say. Between 1995 and 2003, the research team enrolled 1,674 patients treated for lung cancer at M. D. Anderson, and 1,735 healthy “control” volunteers from private clinics in the Houston area.
The participants were asked detailed questions about their diet for the year prior to their enrollment or to their cancer diagnosis, with the assumption that what they ate that year reflected their general eating pattern over a number of years, says the study’s lead author, Matthew Schabath, Ph.D., a postdoctoral researcher in M. D. Anderson’s Department of Epidemiology.
“What we’ve found is intriguing and supports a small but growing body of evidence that suggests estrogenic-like compounds in food may help protect against development of lung and other cancers,” Schabath says. “But these kinds of studies, which rely on a person’s recall of the food they’ve eaten months before, have known limitations and require more investigation.”
Non-smokers’ lung cancer risk reduced by foods
One of the most intriguing findings, Schabath says, is that people who never smoked had a reduced chance of developing the disease if they ate large quantities of phytoestrogen-rich food.
“About 15% of lung cancers occur in those who have never smoked. Besides exposure to second-hand smoke, other risk factors for these cancers are yet to be determined,” Schabath says.
Previous hormone replacement research leads to study
The study builds on the group’s 2004 finding that women who used hormone replacement therapy (medication that restores estrogen to postmenopausal women) had a lower risk of developing lung cancer than women who didn’t use these agents, given a similar history of cigarette use.
If estrogen drugs could protect against lung cancer, the researchers wondered if the same is true of foods that have naturally occurring low levels of estrogens. Several epidemiological studies of phytoestrogenic foods had suggested that might be the case for breast, endometrial and prostate cancers.
Results don’t mean smoking should continue
As promising as the study findings are, they shouldn’t be seen as a license for smokers to continue smoking while increasing consumption of vegetables, cautions the study’s principal investigator, Margaret Spitz, M.D., chair of M. D. Anderson’s Department of Epidemiology.
“The best cancer prevention advice continues to be to stop smoking, and it is clear that all of us can benefit from healthy eating and exercising,” Spitz says. “Still, our results generally show that higher intake of these foods resulted in lower lung cancer risk, and that is certainly a tantalizing preliminary finding.”