Soy and it’s potential link to breast cancer has been studied and debated for years. But I have a new study to tell you about that may somewhat ease your fears.

Soy’s Past Link with Breast Cancer

People have been concerned about soy because it contains “phytoestrogens”—natural plant compounds that can behave as weak estrogens in the body.

Researchers have been concerned that it could trigger estrogenic cancers like breast cancer and prostate cancer. Studies so far, however, have been confusing. Some showed that women could reduce their risk of cancer recurrence by eating more soy, and men could reduce their risk of prostate cancer the same way. Other studies, however found that phytoestrogens might actually increase the risk of tumors and stimulate breast cancer cell growth.

With all the confusion, I’ve been recommending that those concerned about estrogen-driven cancers avoid soy foods, soy supplements, and soy ingredients in personal care products. A new study, however, shows that we may be able to relax our concern a bit.

Study Shows Eating Soy May Reduce Recurrence of Disease

Researchers analyzed data from four large studies encompassing over 18,000 women. All had a history of breast cancer diagnosed between the ages of 20 and 83. They found that eating soy foods did not increase risk of recurrence, even among women who ate a lot of soy. (Note: The study looked only at foods, not supplements, so the conclusions apply only to soy foods.)

What’s more, the study found what seemed to be a health benefit for those eating more soy. Women who ate the most had a 9 percent lower risk of dying from any cause, and a 15 percent lower risk of breast cancer recurrence, compared to women who ate very little. The researchers cautioned against taking these percentages too seriously, however, as they were not statistically significant and could be due to chance.

“This is quite reassuring for women who were concerned that they might have to eliminate healthy soy foods from their diets,” said Leif Ellisen, M.D., Ph.D. of the Gilette Center for Breast Cancer.

My New Recommendation on Soy Intake

Though I still strongly recommend caution on soy supplements, I feel like after this study I can relax a little bit on soy foods. If a woman came up to me today wanting advice, I’d tell her that the evidence seems to show that eating soy foods is beneficial. I would still caution her, however, to read labels on her skin care products, and avoid the ones that contain soy, as we don’t have enough studies yet on how soy ingredients in personal care products may affect breast cancer recurrence.

Does this study put your mind more at ease concerning soy foods? Share your thoughts.

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In the study, women taking one of these three medications along with tamoxifen were about twice as likely to experience breast cancer a second time. (Celexa, Lexapro, and Luvox did not show the same results.)

It’s a bit of a shock, as antidepressants are often prescribed to ease depression caused by cancer, or to reduce the sometimes severe hot flashes caused by tamoxifen. In fact, over 25% of women experiencing hot flashes on tamoxifen are now prescribed antidepressants to manage the symptoms!  But the interaction is not a good one. Tamoxifen interacts with a liver enzyme to become a tumor-fighter, but antidepressants block that same enzyme, which reduces the effectiveness of the cancer drug. Antidepressants that are stronger enzyme blockers have the strongest effect, so that’s why Paxil, Prozac, and Zoloft were more detrimental than the weaker blockers.

The study involved about 1,300 women taking tamoxifen between 2003 and 2005. Women taking the antidepressant/tamoxifen combo had a breast cancer recurrence rate of 13.9% compared to 7.5% for women only on tamoxifen.

What to do? There have been few studies on the matter, so the results aren’t gospel, yet. (One smaller study reported little risk in the tamoxifen/antidepressant combo, though it looked at the effects for a shorter amount of time and didn’t compare results with women on tamoxifen alone.) Still, there’s enough evidence here to raise concern. If possible, avoid the antidepressants, or ask your doctor for those less likely to interfere with tamoxifen’s effectiveness. Judy Gralow, M.D., breast cancer specialist at the University of Washington in Seattle, recommends Effexor to her patients. In the study, it had the weakest affect on tamoxifen.

Bottom line: Don’t think you need to stop taking the breast cancer drug. “Tamoxifen is a very important drug,” says Dr. David Flockhart, director of the Division of Clinical Pharmacology at the Indiana University School of Medicine, “and we don’t think women should stop taking it because of this.”

Have you changed antidepressants as a result of this study? Please share your experience.

Photo courtesy of jen_m_stewart via Flickr.com.