Soy doesn’t harm – and may even help – breast cancer survivors, a new study has found.
Earlier research in animals had raised fears that soy foods might cause a recurrence of the cancer because soy can act like oestrogen. A new study of women finds just the opposite. Soy foods do not appear to increase the risk of breast cancer recurrence among survivors of the disease and may even confer some health benefits, new research suggests.
The study, published in the Journal of the American Medical Assn., should reassure breast cancer survivors that they need not scrupulously avoid soy foods.
Research in animals has indicated that soy might increase the chances of breast cancer recurrence because it can act like the hormone oestrogen, which promotes tumour growth. “Some doctors have advised women not to eat soy foods,” said Dr. Xiao Ou Shu, a professor of medicine at Vanderbilt University and lead author of the paper.
“But another school of physicians think it’s safe. So it has been controversial. Our findings are important because, nowadays, it’s very difficult to avoid soy exposure.” Shu and her colleagues analysed data from the Shanghai Breast Cancer Survival Study of 5,042 women in China. The breast cancer survivors were ages 20 to 75 and were followed for an average of four years. The study showed that the higher a woman’s intake of soy foods, the lower her chances of cancer recurrence and death. Soy food intake was measured by either soy protein or soy isoflavone intake. Isoflavones are hormones found in plants.
“Isoflavones can act as oestrogens and add to the circulating pool of oestrogen that is available and promote tumour growth. That is the concern,” said Bette J. Caan, a senior nutritional epidemiologist at Kaiser Permanente in Oakland, who was not involved in the current study. In research released earlier this year, Caan and colleagues at UC Berkeley also found that higher soy intake was linked to lower rates of breast cancer recurrence. That study, published in the journal Breast Cancer Research and Treatment, followed almost 2,000 U.S. breast cancer survivors.
The Los Angeles Times