A study published in the Journal of Clinical Oncology shows that soy intake may have a favorable effect on lung cancer survival in women.
“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,” said lead study author Gong Yang, Research Associate Professor at Vanderbilt University Medical Center. “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.”
The study assessed the impact of soy intake on lung cancer survival among participants of the Shanghai Women’s Health Study, which tracked cancer incidence in 74,941 Shanghai women. Information on usual dietary intake of soy food (soy milk, tofu, fresh and dry soybeans, soy sprouts, and other soy products) was collected in-person at study enrollment and again two years later. Soy food and isoflavone content of various food products was calculated based on the Chinese Food Composition tables. During the course of the study, 444 women were diagnosed with lung cancer. The median time between the first dietary assessment and cancer diagnosis was 5.8 years.
In this analysis, patients were divided into three groups according to soy food intake prior to lung cancer diagnosis. The highest and lowest intake levels were equivalent to approximately 4 oz or more and 2 oz or less tofu per day, respectively. The researchers found that patients with the highest soy food intake had markedly better overall survival compared with those with the lowest intake—60% of patients in the highest intake group and 50% in the lowest intake group were alive at 12 months after diagnosis.
The risk of death decreased with increasing soy intake until the intake reached a level equivalent to about 4 oz of tofu per day. Researchers found no additional survival benefit from consuming higher amounts of soy. Similar trends were observed when dietary isoflavone intake was evaluated. The findings may not necessarily apply beyond this study’s population, which has a very low prevalence of cigarette smoking, a known risk factor for the development of lung cancer, and postmenopausal hormone replacement therapy use, a factor that may negatively affect lung cancer prognosis. In addition, the overall soy food intake is higher in Chinese women than in Western women.