(RxWiki News) Foods made from soybeans have been controversial. That’s because soy products have a substance that’s very much like estrogen. A recent study showed that soy foods may help some cancer patients live longer.
Researchers reviewed previous studies looking at the outcomes of nearly 75,000 Chinese women with lung cancer.
The new observational study found that women who consumed larger amounts of soy prior to diagnosis lived longer than women who consumed lower levels of soy.
"If you've been diagnosed with cancer, work with a dietician."
Gong Yang, MD, MPH, a research associate professor at Vanderbilt University Medical Center, was the lead author of the study.
“To our knowledge, this is the first study to suggest an association between high soy consumption before a lung cancer diagnosis and better overall survival,” Dr. Yang said in a press release announcing the study results. “Although the findings are very promising, it’s too early to give any dietary recommendations for the general public on the basis of this single study.”
Female hormones – especially estrogens – are believed to have an impact on lung cancer survival. The authors explained that soy has isoflavones, which are estrogen-like substances that are known to affect tumor development and growth.
A previous study by this same research team found that high soy intake was associated with a 40 percent decreased risk of lung cancer.
For this study, researchers looked for associations between soy intake and lung cancer survival among 74,941 women in the Shanghai Women’s Health Study.
Upon enrollment and two years later, the women answered questions about how much soy food (tofu, soy milk, soybeans, soy sprouts, etc.) they consumed regularly.
During the study period, 444 women were diagnosed with lung cancer.
Study members were assigned to three different groups according to their soy intake prior to the lung cancer diagnosis.
The highest intake was equal to four ounces or more of tofu per day, while the lowest intake was two or less ounces of tofu per day.
Women who ate the highest amounts of soy prior to diagnosis lived substantially longer, the researchers found.
One year after diagnosis, 60 percent of those who ate the most soy were alive compared to 50 percent of women who ate the lowest amount of soy.
“This study suggests, to the best of our knowledge for the first time, that, among women with lung cancer, prediagnosis intake of soy food is associated with better overall survival,” the authors wrote.
The optimum level of soy was about four ounces of tofu a day. Survival benefits were not seen with consuming higher amounts.
The authors noted that these findings may apply only to Chinese women, who rarely smoke cigarettes or use postmenopausal hormone replacement therapy. Also, Chinese women are known to consume more soy foods than Western women.
Deborah Gordon, MD, an Integrative Medicine Practitioner, is not a proponent of soy foods. When asked to comment on this research, she told dailyRx News, "Of course primary prevention of lung cancer by smoke avoidance (either primary or secondary smoke), yields the maximum benefit of any lifestyle choice.
"However, some individuals have been exposed to secondary smoke beyond their control, and those individuals seeking a nutritional strategy for prevention and survival might include a limited amount of sprouted or fermented (miso, tempeh, tamari) soy in their diet, if tolerated," said Dr. Gordon who is who is Founder of DrDeborahMD.com
Dr. Yang pointed out that soy food is increasing in popularity in the US and elsewhere and more women who have never smoked are developing lung cancer. So results of this study may not be relevant beyond the study population.
Future research will look at effects of soy consumption following lung cancer diagnosis.
Results from this study were published March 25 in the Journal of Clinical Oncology. This research was supported by the US National Cancer Institute and conducted by investigators at Vanderbilt University in collaboration with those from the Shanghai Cancer Institute and NCI.