Sept. 28, 2005
Bolstering the diet with fruits, vegetables and legumes rich in plant-based estrogens tends to protect against lung cancer, according to a study to be released today.
Conducted by a team of cancer-prevention researchers at M.D. Anderson Cancer Center in Houston, the analysis marks the largest study to date to examine dietary effects on the development of lung tumors. Lung cancer is the most common cause of cancer-related deaths in men and women in the United States.
Plant-based estrogens, or phytoestrogens, come in three main classes:
isoflavones, lignans and cumestrans, with isoflavones and lignans the most widely seen in nature. All act as weak estrogens with varying capacities to influence the life and death of cells. Isoflavones, the most common, are found in a range of foods, especially soybeans, chickpeas, yams and red clover. Lignan sources include spinach, broccoli, tea, carrots and rye grains. Cumestrans are found in beans, peas, spinach and sprouts.
“Basically, we found that people with lung cancer were less likely to consume these foods,” said Matthew Schabath, a postdoctoral fellow specializing in cancer prevention. “What we saw was quite interesting in terms of protective effects in ‘never smokers’ and former smokers,” Schabath said.
Schabath and colleagues studied 1,674 people with lung cancer and 1,735 people without the disease from July 1995 to October 2003. Participants answered questionnaires on food frequency. Researchers were particularly interested in quantifying dietary intake of specific phytoestrogens.
“Phytoestrogens have a variety of protective effects that have been shown in experimental models (lab animals) and lab models (Petri dishes) to have various chemo-effects,” Schabath said. Some of those effects have been as antioxidants, which means they can inhibit the prevalence of rogue oxygen molecules called free radicals. Schabath defined other effects of weak estrogens as limiting angiogenesis, the growth of blood vessels required by tumors and inducing programmed cell death.
Schabath pointed to Asians who consume robust quantities of phytoestrogens, especially in the form of soy-based foods, as having lower rates of cancer.