Breast microbe elevated in women with obesity after menopause
One bacterium’s average share of breast bacteria was 5.6% in postmenopausal women with obesity versus 0.054% in premenopausal women without obesity; all had breast cancer.
Limit: Only 20 women per group contributed to the main breast tissue comparison
Edited by Boris Djordjevic · AgingResearch.News
Women undergoing mastectomy for breast cancer provided noncancerous breast tissue for an observational study, with 20 women per group defined by menopause and obesity status. Researchers analyzed bacterial DNA. Postmenopausal women with obesity had different bacterial communities and more Akkermansia muciniphila, a bacterial species, than all other groups. In a separate cohort of 63 women undergoing breast reduction surgery, body mass index—a measure of weight relative to height—was linked to this bacterium’s abundance.
In separate animal experiments, injecting the bacterium into mammary glands increased tumor formation in female mice prone to breast cancer and fed a high-fat Western diet.
Why it matters
Obesity is a modifiable risk factor for breast cancer after menopause. The work addresses whether bacteria living in breast tissue may help connect obesity, aging and cancer risk.
Caveats
The human comparisons were observational and cannot show that the bacterium caused cancer; tumor-promoting effects came from mice. The main cohort already had breast cancer and excluded women who used antibiotics within four weeks of surgery.
The paper
Wake Forest University Health Sciences; Atrium Health Wake Forest Baptist
Cancer Research, Jul 9, 2026, Open access
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