Some studies have shown isoflavones, a class of phytoestrogens, or plant-derived compounds, found in soy could impact a woman’s estrogen levels and increase the risk of cancer recurrence among some breast cancer patients. Estrogen is known to promote the growth of breast cancer cells.
“We looked at data among many breast cancer survivors both from the United States and Asia,” says Chen. “We found that women who ate a large amount of soy had a similar or decreased risk of breast cancer recurrence compared to women who didn’t eat soy.”
Dr. Chen adds if women with breast cancer want to make soy a regular part of their diet, it should be dietary or food-based soy.
She doesn’t recommend people use soy exclusively in their diet or that they use forms of processed soy or soy in pill form.
“It’s very easy to find soy products in neighborhood grocery stores now,” says Chen. “Besides the more common ones like soybeans, soy sauce and tofu, now you can easily buy food-based soy products like miso soup, soy milk and soy nuts. Also, many of the dark green, leafy vegetables like spinach, kale, and broccoli are rich in isoflavones.”
Besides eating a healthy diet, Chen says there are other things breast cancer survivors can do to reduce their risk of the disease returning.
“Exercising regularly, limiting alcohol consumption, quitting smoking and maintaining a healthy weight have been shown to be very helpful in improving survival,” she says.