Poor gut health may be an underestimated trigger for breast cancer in women.

A tremendous body of research shows how poor gut health, especially chronic constipation, slow digestion and an imbalance of the gut microbiome, not only lowers performance and increases discomfort in the body but also increases the risk of various of cancers; e.g. breast cancer


Although it is very hard to demonstrate a causal relationship, the link is obvious.


I condensed 3 ways from the scientific literature how poor gut health can be related to breast cancer development or tumor growth:

Poor digestion accumulates carcinogens and increases cancer risk

Bile acids, toxic sulfur compounds, nitrosamines and other harmful molecules produced during digestion of certain foods need to be flushed out through regular bowel movements as soon as possible – or ideally prevented from being produced in the first place (I share more on that in my books and course seminar series the Microbiome Academy)

Otherwise, these compounds do not only act mutagenic and pro-inflammatory to gut cells – but to other organs, too.

That is suspected to be one of the reasons why irregular and slower digestion is associated with a higher risk of breast cancer in women, as a prospective study on 28000 women showed and breast tumor tissue reveals.

A disrupted gut microbiome produces toxic molecules that cause inflammation and mutations promoting breast cancer development

Certain lifestyle factors and a poor diet affect gut health negatively, specifically the gut microbiome.

A disrupted gut microbiome produces toxic molecules that act carcinogenic to gut cells and that enter the blood circulation causing inflammation and uncontrolled cell growth in other tissues.

For example, a high concentration of toxic gut microbial molecules accumulating in the gut is shown to promote breast cancer cell growth.

Interestingly, cellular receptors for inflammatory gut bacterial molecules are detected in around 80 % or ER+ breast cancer patients. Researchers also detected the gut molecules in breast cyst fluid of women. (Javitt et al., 1994)

A disrupted gut microbiome influences estrogen levels triggering breast cancer cell growth

Especially, estrogen dependent breast cancers may partially be triggered indirectly via the Gut Microbiome.

You can read more details about this complex connection in my other article Why gut health is so important for women

There is an abundance of scientific evidence showing the importance of gut health and microbiome health to lower all sorts of cancer risk, including breast cancer.

Although more research is needed, the science recommends considering microbiome and gut health for promoting health, treatment and disease prevention.

Learn all the science-based details HOW to support the gut microbiome best in my upcoming science-based Microbiome Academy online seminar series (Launch January 2024) and also my upcoming book (more info soon)

P.s. Receive weekly actionable science for gut & microbiome health and support healthy aging by subscribing to the Longevity Microbiome Journal.

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Dr. Sarah-Schwitalla
Dr. Sarah Schwitalla

PhD in molekularer Medizin und Biochemie 10 Jahre biomedizinische Krebs-Forschung und Pharmaindustrie Erfahrung TU München, Harvard Medical School, University of Cambridge.


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Maruti SS, Lampe JW, Potter JD, Ready A, White E. A prospective study of bowel motility and related factors on breast cancer risk. Cancer Epidemiol Biomarkers Prev. 2008;17(7):1746-1750. doi:10.1158/1055-9965.EPI-07-2850

Javitt NB, Budai K, Miller DG, Cahan AC, Raju U, Levitz M. Breast-gut connection: origin of chenodeoxycholic acid in breast cyst fluid. Lancet. 1994 Mar 12;343(8898):633-5. doi: 10.1016/s0140-6736(94)92635-2. Erratum in: Lancet 1994 Apr 16;343(8903):986. PMID: 7906811.

The crosstalk of the human microbiome in breast and colon cancer: A metabolomics analysis

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Dr. Sarah Schwitalla

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