Gwyneth Paltrow under fire for recirculating breast cancer bra myth

Gwyneth Paltrow attends Goop Pop-Up Shop on May 6, 2014, in Los Angeles.

Michael Buckner/Getty Images for Goop

Actress Gwyneth Paltrow is no stranger to controversy over some of the questionable health advice featured on her widely read lifestyle blog Goop.com. Now, a recent post is under fire for disseminating the long-discredited claim that wearing a too-tight bra may increase risk of breast cancer.

"Among those who acknowledge the bra/breast cancer risk connection, it's widely held that a tight-fitting bra restricts the lymph nodes around the breast and underarm area, preventing toxins from being processed through them and flushed out of the body," the post's author, Dr. Habib Sadeghi, writes. "Accumulated toxins anywhere in the body increase the risk for cancer."

But major medical organizations, including the American Cancer Society (ACS), have denounced these claims as false. "We do not know of any epidemiologic studies published in scientific journals that suggest bras directly contribute to breast cancer risk or that lymphatic compression by bras might cause breast cancer," the organization states on its website.

The theory circulated on the Internet last year, which is when the ACS pointed out that it stemmed from the writings of a husband and wife team of medical anthropologists who link breast cancer to wearing a bra. But according to the ACS, their research -- which Sadeghi points to in his post as evidence -- "was not conducted according to standard principles of epidemiological research" and did not take other variables into account, including known risk factors for breast cancer.

A 1991 Harvard study suggested an association between breast cancer and wearing bras, but again experts say other factors were most likely at play.

"One of the biggest variables in a woman not wearing a bra is that she is thinner and has smaller breasts and may not need the support of a bra. We know that having a leaner body mass does not put a woman at an increased risk of breast cancer," Dr. Therese Bevers, Medical Director of the Cancer Prevention Center at the University of Texas MD Anderson Cancer Center, told CBS News. "Conversely, a woman who is overweight or obese is much more likely to have larger breasts that are heavy and she needs the support of a bra. But it's not the bra that's increasing her risk of breast cancer, it's the weight."

This isn't the first time Paltrow's website has doled out unsound medical advice. Earlier this year, experts scoffed after she touted the benefits of a steam treatment for women's private parts available at a West Coast spa. "It is an energetic release -- not just a steam douche -- that balances female hormone levels," she wrote on Goop.

But doctors discourage douching, as it disturbs the natural flora of the female reproductive system, increasing the risk of urinary tract infections and yeast overgrowth.

"Like so many people she's susceptible to this pseudoscience that's permeating our society right now. I think part of it is people are becoming more disconnected from science, which is ironic because science has never been a bigger part of lives." Tim Caulfield, a professor at the Faculty of Law & School of Public Health at the University of Alberta in Canada and author of "Is Gwyneth Paltrow Wrong About Everything? When Celebrity Culture and Science Clash," told CBS News in February.

Caulfield went on to say that skepticism of mainstream medicine may make people more susceptible to believing misguided celebrity health claims. "There's a growing distrust ... people are worried about big pharma and big food," he said. "There's some justification of that. I think that growing distrust creates a space for people like Gwyneth."

A 2013 study published in the journal BMJ looked at how celebrities attain an aura of credibility as medical advisers.

"There are deeply rooted biological, psychological and social forces that make celebrity health advice influential. Our brains, psyches and societies appear to be hard-wired to give celebrities influence over our health decisions," lead study author Steven J. Hoffman, an assistant professor of clinical epidemiology and biostatistics at McMaster's Michael G. DeGroote School of Medicine, said in a statement. He pointed out that some celebrities use that credibility in a responsible way, citing Michael J. Fox's work against Parkinson's disease as an example.

While the latest Goop post in question wasn't written by Paltrow herself, its presence on her site represents her stamp of approval. Experts say its content is concerning, as it may lead to the spread of misinformation about breast cancer prevention and may cause psychological distress among breast cancer survivors who blame themselves for their disease.

"I would never want a woman to feel guilty because she has worn bras," Bevers said, "because again, there is no research we can reliably depend on linking the wearing of bras and breast cancer."

In terms of prevention, Bevers suggests focusing on the factors that we do know affects breast cancer risk, like weight, diet, exercise and alcohol use. "Pay attention to where we know the evidence is," she said. "I would encourage women to focus on maintaining a healthy body weight, being physically active, eating a healthy diet and limiting alcohol intake. All of these things we know can reduce a woman's risk of cancer."

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    Ashley Welch covers health and wellness for CBSNews.com