Does soy prevent breast cancer or increase the risk? The debate heats up this month as part of Breast Cancer Awareness Month.

“It's a myth that soy prevents breast cancer,” says Kaayla T. Daniel, PhD, author of The Whole Soy Story: The Dark Side of America's Favorite Health Food. “Numerous studies show that soy can cause, contribute to or even accelerate the growth of cancer.”

In spite of the most recent research showing the association between soy products and breast cancer women are still being urged to purposefully increase their consumption of soy milk and soy foods in the mistaken belief that soy will prevent or even cure breast cancer.

Dr. Daniel explains, “The truth is that soy protein contains dangerous levels of plant estrogens. Although not identical to human estrogens, these have been proven to increase breast cell proliferation, a widely accepted marker of breast cancer risk.”

“The soy industry consistently plays down the evidence that soy can promote breast cancer,” says Dr. Daniel. “It is even using Breast Cancer Awareness Month as an excuse to push its products on unsuspecting women.”

Companies using Breast Cancer Awareness Month as part of their marketing efforts include Vitasoy, which has launched a breast health education initiative that includes giving away soy milk in bright pink containers – called “Pinkies” - to women attending Breast Cancer Awareness Month activities such as the upcoming Komen Races for the Cure in Boston and Miami.

“The soy industry also heavily promotes the myth that Asians have lower rates of breast cancer because of soy consumption,” says Dr. Daniel. “In fact, Asians eat soy in very small quantities, as a condiment in the diet and not as a staple food. What's more, they eat old-fashioned, whole soybean products such as miso, tempeh, natto and tofu, not the new heavily processed products marketed by the soy industry such as soy milk, veggie burgers and 'energy bars.'”

Dr Daniel points to a Japanese study published this month in the journal, Cancer Causes and Control, in which researchers at Nagoya University showed that soy consumption offers no protection and has no effect on breast cancer risk.

“The researchers were curious as to whether Asians enjoy lower rates of breast cancer because of their soy consumption,” she says. “Using data from the Japan Collaborative Cohort (JACC) they examined whether soy foods really have a protective effect. They found that Asians on high soy diets did not have a lower incidence of breast cancer. Clearly it's time to credit other dietary and lifestyle factors for their lower rates of breast cancer.”

Leading scientists and government agencies share Dr. Daniel's concern. The Israeli Health Ministry has advised women to “exercise caution” when it comes to soy consumption because of increased breast cancer risk.

The French Food Agency will soon require warning labels on soy milk and other soy foods because of the risks to women who've been diagnosed with – or have a family history of - breast cancer.

In the U.S., Cornell University's Center for Breast Cancer and Environmental Risk Factors has examined the evidence on soy and phytoestrogen-containing herbs such as black cohosh and warned women not to self medicate with soy foods or soy supplements.

“The risks are well established. Soy is clearly not the answer for breast cancer prevention,” concludes Dr. Daniel. “The evidence is mounting that soy may even be part of the problem.”