According to a new study published in the Journal of the National Cancer Institute, soy protein may enhance gene activity that is associated with breast cancer growth in women who already have breast cancer. Jacqueline Bromberg, MD, PhD, from Memorial Sloan Kettering Cancer Center in New York, New York, and her colleagues assigned 140 women with newly diagnosed, early-stage breast cancer to either take a soy protein supplement every day for up to 4 weeks or milk powder.
The researchers found that about 20% of those who took the soy supplement had increased blood concentrations of genistein, a soy phytoestrogen, and some of those women had increased gene activity that promotes breast cancer proliferation and metastasis; however, the study did not show that those women's breast cancers had increased proliferation.
The researchers suggest that women with breast cancer consume food containing soy in moderation and avoid soy-containing supplements to be safe. The benefits and harms from eating soy may depend on how old a woman is. Women in their 60's that consume soy may have more breast cancer death than younger women.
Soy protein may increase activity in genes linked to breast cancer growth — at least in certain women who already have the disease, a new study suggests.
Experts said the findings, reported in the Sept. 4 Journal of the National Cancer Institute, shouldn’t scare women off from eating tofu. But to be safe, the researchers suggest women with breast cancer eat soy foods only in moderation and avoid supplements. And for women who don’t have breast cancer?
“This study doesn’t tell us anything about whether soy raises the risk of developing breast cancer,” said researcher Dr. Jacqueline Bromberg, a breast cancer specialist at Memorial Sloan Kettering Cancer Center in New York City.