Soy and Breast Cancer

I wanted to share this amazing information about soy and breast cancer recurrence:

First of all, some information about a 5-year study called The Shanghai Breast Cancer Study, in which over 5000 female breast cancer survivors in China, with diagnoses between March 2002 and April 2006, were recruited and followed up through June 2009.

The Objective was to evaluate the association of soy food intake after diagnosis of breast cancer with total mortality and cancer recurrence.

Context Soy foods are rich in isoflavones, a major group of phytoestrogens that have been hypothesized to reduce the risk of breast cancer. However, the estrogen-like effect of isoflavones and the potential interaction between isoflavones and tamoxifen have led to concern about soy food consumption among breast cancer patients.

Results During the median follow-up of 3.9 years (range, 0.5-6.2 years), 444 deaths and 534 recurrences or breast cancer–related deaths were documented in 5033 surgically treated breast cancer patients. Soy food intake, as measured by either soy protein or soy isoflavone intake, was inversely associated with mortality and recurrence. The hazard ratio associated with the highest quartile of soy protein intake was 0.71 (95% confidence interval [CI], 0.54-0.92) for total mortality and 0.68 (95% CI, 0.54-0.87) for recurrence compared with the lowest quartile of intake. The multivariate-adjusted 4-year mortality rates were 10.3% and 7.4%, and the 4-year recurrence rates were 11.2% and 8.0%, respectively, for women in the lowest and highest quartiles of soy protein intake. The inverse association was evident among women with either estrogen receptor–positive or –negative breast cancer and was present in both users and nonusers of tamoxifen.

Conclusion Among women with breast cancer, soy food consumption was significantly associated with decreased risk of death and recurrence.

A few other things that I've found as I've studied this subject:

"But in human studies, scientists have not found that diets high in soy increase breast cancer risk. In fact, most have found the reverse."

In this same article, it talks about the Shanghia study (the one I outlined above), but also another, more recent study:

"In a more recent multiyear study, published in May in The American Journal of Clinical Nutrition, scientists followed nearly 10,000 breast cancer survivors, many of them in the United States. They found that women who at the most soy had lower rated of cancer recurrence and mortality.

Though the findings reflect only a correlation, they suggest that the concerns about soy and breast cancer may be unfounded."
http://well.blogs.nytimes.com/2012/06/25/really-eating-soy-increases-the-risk-of-breast-cancer/

"Fears that the isoflavone chemicals found in soy -- which have estrogen-like properties -- might raise the risk of cancer recurrence seem unfounded. The conclusion comes from a large study compiling data from more than 18,000 women diagnosed with invasive breast cancer; an average of nine years after diagnosis, no statistical difference was seen between groups of women who ate a lot of soy and those who ate very little, both with regard to either recurrence of the cancers or death.
http://articles.latimes.com/2011/apr/06/news/la-heb-soy-breast-cancer-survivors-20110406

The following comes from a soy overview done by Take Shape for Life and Medifast:
Breast cancer is the most common cancer among women in the United States and is the second leading cause of cancer death after lung cancer.  However, in many other countries outside the United
States, breast cancer rates are very low. In fact, the historically low rate of breast cancer in Japan, where soy foods are part of traditional meal plans, is what helped spark researchers’ curiosity about whether soy may play a protective role against this particular cancer.

Soy’s proposed benefits for breast cancer...

In Japan, deaths from breast cancer are only about one-third of those in the United States. Many cultural and dietary differences exist between Asian and Western populations; however, over the last 40 years, as Japanese culture has become more “Westernized,” the number of deaths from breast cancer has increased dramatically.  Higher rates of cancer are also seen in Japanese-Americans compared to native Japanese and women who migrate from Japan to the United States.  What could be driving these changes in the rates of breast cancer development and death? An analysis by researchers at the University of Southern California suggests that soy may have a protective role: Among Asian women, those who eat the most soy were about 30% less likely to develop breast cancer compared to those who eat little soy. The protective effects of soy are especially compelling
when eaten early in life. Studies show that eating a modest amount of soy as a child and/or teen can help reduce adult breast cancer risk between 28% and 60%.  Less certainty exists about whether these protective effects are extended to those who begin eating soy foods in their adult years. Women with a history of breast cancer can safely eat and may even benefit from choosing soy foods. Recent research, using data from the Women’s Healthy Eating and Living (WHEL) study, found that women who eat the highest level of isoflavones (>16.3 mg/day) had a non-significant 54% reduction in risk of death compared to those eating the least. Furthermore, a study published in the Journal of the
American Medical Association of over 5,000 Chinese breast cancer survivors found that those who eat the highest amount of soy protein (about 2 ½ servings/day) were about 30% less likely to suffer a recurrence or die of their disease. The beneficial effects of soy protein for reducing recurrence and death from breast cancer were seen in both estrogen receptor-positive and estrogen receptor-negative breast cancer and in both users and non-users of the breast cancer drug tamoxifen. A 2009 study of almost 2,000 United States breast cancer survivors reported similar findings. Evidence continues to accumulate supporting the safety and possible benefit of choosing soy foods for breast cancer survivors—and is especially important, as this has been an area of much debate. Although it’s probably too soon for physicians to recommend soy foods to breast cancer patients as a way to improve their prognosis, evidence indicates that soy foods can be safely eaten by women with a history of breast cancer. This position is supported by the ACS, which states that moderate amounts of soy foods are safe for breast cancer survivors.

I'm happy to send you the full Soy Overview, with all of the references.  Email me at yourroadtohealthy@gmail.com

-Kara