Wearing bras regularly impairs proper lymph flow and may greatly increase the chance of developing breast cancer. 

Researcher David Moth has conducted an experiment where he measured the actual pressure exerted by bras. He says, “The results suggest that the lightest possible bras will still exert pressures in excess of that found within the lymphatic vessels.”  

There are studies which confirm the link between bra wearing and breast cancer. In 1991, Hsieh & Trichopoulos studied breast size and left/right handedness as risk factors, and noted in the findings that premenopausal women who do not wear bras had less than half the risk of breast cancer compared with bra wearers. The study was published in the European Journal of Cancer, 1991;27(2):131-5.

Another more recent study (2000), published in Chronobiology International (the journal of biological and medical rhythm research), found that wearing a bra decreased melatonin production and increased the core body temperature.  Melatonin is a powerful antioxidant and hormone that promotes good sleep, fights aging, boosts immune system, and slows the growth of certain types of cancer, including breast cancer.

The most comprehensive studies on this subject were performed by medical researcher Sydney Singer. Singers found that the Maoris of New Zealand who integrated into white culture had the same rate of breast cancer, while the marginalized aboriginals of Australia had practically no breast cancer. The same was true for ‘Westernized’ Japanese, Fijians and other bra-converted cultures.

In the early 1990s Singers studied 4,500 women in 5 cities across the U.S. about their bra-wearing habits. He found that 3 out of 4 women who wore their bras 24 hours per day developed breast cancer. Furthermore, 1 out of 7 women who wore bras more than 12 hour per day but not to bed developed breast cancer. By comparison, merely 1 out of 152 women who wore their bras less than 12 hours per day had breast cancer, and only 1 out of 168 women who wore bras rarely or never developed breast cancer. In other words, the difference between 24 hour wearing of a bra and not at all was 125-fold.