The problem with bras, according to medical anthropologists Sydney Ross Singer and Soma Grismaijer, is that they restrict the flow of lymphatic fluid, thereby retaining toxins in the breast that have nowhere to go. They compare it to the feet and ankle swelling that occurs on long flights, because the lymphatic fluid pools in the lower extremities and isn’t allowed to circulate.
Singer and Grismaijer, co-authors of Dressed To Kill: The Link Between Breast Cancer and Bras, say that wearing a bra more than 12 hours a day dramatically increases the risk of getting breast cancer. A woman who wears a bra 24/7 is 125 times more likely to develop breast cancer than a woman who rarely or never wears a bra. Those who sleep in their bra, they found, have a 75% chance of developing breast cancer at some point in their lives.
Harvard did a study in 1991 that showed greatly increased incidence in breast cancer in those who wear bras over those who don’t.
This research has been shown to the Susan G. Komen Foundation as well as the American Cancer Society, and they have been aware of the research for at least 20 years. There are no studies that refute this. Yet nowhere in their information about breast cancer is there as much as a mention that taking off one’s bra at the end of the day can make a difference. [emphasis mine]
Wait, this is a thing? I didn't think that anyone slept in their bra. How common is that? Sounds horribly constricting.
From the Komen website,
A 1991 case-control study found that premenopausal women who did not wear bras had a lower risk of breast cancer than women who did wear bras. However, the authors stated this link was likely due to factors related to wearing a bra rather than the bra itself. The women in the study who did not wear a bra were more likely to be lean, which the authors concluded might account for the lower risk
"Women, you must smoke cigarettes when you're in public." Are most cultures indoctrinating women with the equivalent?
"It's best to take off your bra when you're at home." Komen and the ACS could easily give that advice!
Or better yet, change our cultures so women can safely be with or without bras in public!
From the study's abstract (the full paper is behind a paywall): "Premenopausal women who do not wear bras had half the risk of breast cancer compared with bra users (P about 0.09), possibly because they are thinner and likely to have smaller breasts."
Also from Singer and Grismaijer: "Droop Phobia, The Bra, and Breast Cancer". It lists two other studies, in addition to their own, linking bras with breast cancer much more strongly than the Harvard study. Both there and in their article Ruth linked to in the original post, they mention their follow-up study in Fiji, where about half the women wear bras.
"We discovered that — given the same village, with the same genetics and diet — the women getting breast cancer were the working women who had to wear bras for work. We also discovered that bra-free cultures were relatively free of breast cancer, and their rates of developing this disease increased as the bra became adopted as essential clothing. We also discovered that women who had stopped wearing bras after learning about our research experienced an end to breast pain and cysts."
(Speculating, I'd attribute the reluctance of mainstream authorities to give such advice to the strength of cultural norms about women's bodies and image, rather than ill will on the part of the "cancer detection and treatment industry".)
I agree about them bowing to cultural norms, specifically norms of women's sexuality being controlled (how shameful) unless it's being exploited for male enjoyment.
I haven't seen any real science behind it, and the explanation that it's lean women - usually very lean - who don't wear bras, makes sense. Obesity is a known risk factor for breast cancer.
To give credibility to the idea, they would have to do a lot more work to show there's an effect when you account for the influence of body weight on breast camcer.