Your Microbiome

Over thousands of years, our bodies have developed a symbiotic relationship with organisms living in and on our bodies, generally supporting each other’s health and well-being. Research links your microbiome—and changes in it—to several types of cancer and how well you respond to some conventional cancer treatments.

What is your microbiome?

Many trillions of microorganisms live in and on us, many of which are in our gut. In fact, the cells of microbes in our bodies outnumber our human cells. Over thousands of years, our bodies have developed a symbiotic relationship with these organisms, generally supporting each other’s health and well-being. In exchange for food and lodging, these microorganisms perform these essential functions:1Houghton D, Stewart CJ, Day CP, Trenell M. Gut microbiota and lifestyle interventions in NAFLD. International Journal of Molecular Sciences. 2016 Mar 25; 17(4):447; Dahiya DK, Renuka et al. Gut microbiota modulation and its relationship with obesity using prebiotic fibers and probiotics: a review. Frontiers in Microbiology. 2017 Apr 4;8:563; Mazzotti A, Caletti MT, Sasdelli AS, Brodosi L, Marchesini G. Pathophysiology of nonalcoholic fatty liver disease: lifestyle-gut-gene interaction. Digestive Diseases. 2016;34 Suppl 1:3-10; Tian S, Liu X, Lei P, Zhang X, Shan Y. Microbiota: a mediator to transform glucosinolate precursors in cruciferous vegetables to the active isothiocyanates. Journal of the Science of Food and Agriculture. 2018 Mar;98(4):1255-1260; Galland L. The gut microbiome and the brain. Journal of Medicinal Food. 2014 Dec;17(12):1261-72.

  • Help with digestion and produce essential nutrients
  • Support intestinal wall integrity
  • Influence these functions and systems:
    • Metabolism
    • Sleep cycles
    • Brain and nervous system
    • Immune system, including inflammation 

Your microbiome is influenced both by your genetics and by your environment.2Hall AB, Tolonen AC, Xavier RJ. Human genetic variation and the gut microbiome in disease. Nature Reviews Genetics. 2017 Nov;18(11):690-699. Contact with other people, soil, decaying materials, foods, animals, and waste (fecal material) can introduce both good and harmful microbes to your body.

What can contribute to an out-of-balance microbiome?


Some behaviors can affect your microbiome composition and balance:3Jewell T. What Causes Dysbiosis and How Is It Treated? Healthline. February 1, 2019. Viewed September 20, 2022; Pole L, Hepp N. How can Eating Well help me? What the research says. CancerChoices. September 24, 2022. Viewed September 30, 2022; Lewis JD, Chen EZ et al. Inflammation, antibiotics, and diet as environmental stressors of the gut microbiome in pediatric Crohn’s disease. Cell Host & Microbe. 2015 Oct 14;18(4):489-500; Salavrakos M, Leclercq S, De Timary P, Dom G. Microbiome and substances of abuse. Progress in Neuro-Psychopharmacology and Biological Psychiatry. 2021 Mar 8;105:110113; Yao ZW, Zhao BC et al. Relationships of sleep disturbance, intestinal microbiota, and postoperative pain in breast cancer patients: a prospective observational study. Sleep and Breathing. 2020 Nov 19.

  • Changing your diet to increase protein, fat, food additives, or sugar or other carbohydrates 
  • Drinking two or more alcoholic beverages per day
  • Poor dental hygiene, which allows bacteria in your mouth to grow out of balance
  • Unprotected sex, which can expose you to harmful bacteria
  • Use of stimulant drugs
  • Sleep disturbance

Medical conditions

  • Inflammation,4Shi N, Li N, Duan X, Niu H. Interaction between the gut microbiome and mucosal immune system. Military Medical Research. 2017 Apr 27;4:14; Lewis JD, Chen EZ et al. Inflammation, antibiotics, and diet as environmental stressors of the gut microbiome in pediatric Crohn’s disease. Cell Host & Microbe. 2015 Oct 14;18(4):489-500. including inflammation from high blood sugar5Daryabor G, Atashzar MR, Kabelitz D, Meri S, Kalantar K. The effects of type 2 diabetes mellitus on organ metabolism and the immune system. Frontiers in Immunology. 2020 Jul 22;11:1582. 
  • Obesity6Hepp N, Pole L. Body Weight. CancerChoices. January 27, 2023.
  • Diabetes or high blood sugar and insulin resistance7Pole L, Hepp N. High Blood Sugar and Insulin Resistance. CancerChoices. February 28, 2023.

Medical treatments

Environmental exposures

Pesticides or heavy metals: modest evidence of alterations in the microbiome leading to dysbiosis among people eating food contaminated with pesticides or heavy metals 

Risk factors for an imbalanced microbiome

  • Advanced age12Power SE, O’Toole PW, Stanton C, Ross RP, Fitzgerald GF. Intestinal microbiota, diet and health. British Journal of Nutrition. 2014 Feb;111(3):387-402.

The role of fiber and short-chain fatty acids

Intestinal bacteria ferment dietary fiber into the short-chain fatty acids (SCFAs) butyrate, acetate, and propionate. These SCFAs are absorbed in your intestine and play an important role in energy metabolism. Butyrate in particular provides energy for the epithelial cells in the colon. Butyrate also maintains intestinal integrity, inhibits inflammation and carcinogenesis, promotes a feeling of fullness after a meal (satiety), and decreases oxidative stressan imbalance between free radicals and antioxidants in your body; this imbalance can cause harmful oxidation reactions in your body chemistry.13Hartstra AV, Bouter KE, Bäckhed F, Nieuwdorp M. Insights into the role of the microbiome in obesity and type 2 diabetes. Diabetes Care. 2015 Jan;38(1):159-65; Hamer HM, Jonkers D et al. Review article: the role of butyrate on colonic function. Alimentary Pharmacology and Therapeutics. 2008 Jan 15;27(2):104-19. The other SCFAs enter the bloodstream (venous system). Short-chain fatty acids also affect immune cell function.14Alvarez-Curto E, Milligan G. Metabolism meets immunity: the role of free fatty acid receptors in the immune system. Biochemical Pharmacology. 2016 Aug 15;114:3-13.

Some evidence shows that a lack of these SCFAs or the microbes that produce them is linked to the development of intestinal disease, inflammatory bowel diseases, and colorectal cancer.15Hartstra AV, Bouter KE, Bäckhed F, Nieuwdorp M. Insights into the role of the microbiome in obesity and type 2 diabetes. Diabetes Care. 2015 Jan;38(1):159-65. 

Either too low or too high a concentration of SCFAs shows an imbalance and higher risk of poor health outcomes. High concentrations of SCFAs are linked to obesity, for example.16Scheithauer TP, Dallinga-Thie GM, de Vos WM, Nieuwdorp M, van Raalte DH. Causality of small and large intestinal microbiota in weight regulation and insulin resistance. Molecular Metabolism. 2016 Jun 10;5(9):759-70. 

Helpful links

Gacesa R, Kurilshikov A et al. Environmental factors shaping the gut microbiome in a Dutch population. Nature. 2022 Apr;604(7907):732-739.

Dill-McFarland KA, Tang ZZ et al. Close social relationships correlate with human gut microbiota composition. Scientific Reports. 2019 Jan 24;9(1):703.

Bai-Tong SS, Thoemmes MS et al. The impact of maternal asthma on the preterm infants’ gut metabolome and microbiome (MAP study). Scientific Reports. 2022 Apr 19;12(1):6437.

Ursell LK, Metcalf JL, Parfrey LW, Knight R. Defining the human microbiome. Nutrition Reviews. 2012 Aug;70 Suppl 1(Suppl 1):S38-44.


Laura Pole, MSN, RN, OCNS

Senior Clinical Consultant
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Laura Pole is senior clinical consultant for CancerChoices. Laura is an oncology clinical nurse specialist who has been providing integrative oncology clinical care, navigation, consultation, and education services for over 40 years. She is the co-creator and co-coordinator of the Integrative Oncology Navigation Training at Smith Center for Healing and the Arts in Washington, DC. Laura also manages the “Media Watch Cancer News That You Can Use” listserv for Smith Center/Commonweal. In her role as a palliative care educator and consultant, Laura has served as statewide Respecting Choices Faculty for the Virginia POST (Physician Orders for Scope of Treatment) Collaborative as well as provided statewide professional education on palliative and end-of-life care for the Virginia Association for Hospices and Palliative Care.

For CancerChoices, Laura curates content and research, networks with clinical and organizational partners, brings awareness and education of integrative oncology at professional and patient conferences and programs, and translates research into information relevant to the patient experience as well as clinical practice.

Laura sees her work with CancerChoices as a perfect alignment of all her passions, knowledge and skills in integrative oncology care. She is honored to serve you.

Laura Pole, MSN, RN, OCNS Senior Clinical Consultant

Nancy Hepp, MS

Lead Researcher
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Ms. Hepp is a researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. She serves as lead researcher and writer for CancerChoices and also served as the first program manager. Her graduate work in research and cognitive psychology, her master’s degree in instructional design, and her certificate in web design have all guided her in writing and presenting information for a wide variety of audiences and uses. Nancy’s service as faculty development coordinator in the Department of Family Medicine at Wright State University also provided experience in medical research, plus insights into medical education and medical care from the professional’s perspective.

Nancy Hepp, MS Lead Researcher

Andrew Jackson, ND

Research Associate
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Andrew Jackson, ND, serves as a CancerChoices research associate. As a naturopathic physician practicing in Kirkland, Washington, he teaches critical evaluation of the medical literture at Bastyr University in Kenmore, Washington. His great appreciation of scientific inquiry and the scientific process has led him to view research with a critical eye.

Andrew Jackson, ND Research Associate

Last update: April 21, 2024

Last full literature review: July 2021

CancerChoices provides information about integrativein cancer care, a patient-centered approach combining the best of conventional care, self care, and evidence-informed complementary care in an integrated plan cancer care. We review complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocialtherapy, and acupuncture therapies and self carelifestyle actions and behaviors that may impact cancer outcomes; examples include eating health-promoting foods, limiting alcohol, increasing physical activity, and managing stress practices to help patients and professionals explore and integrate the best combination of conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy and complementary therapies and practices for each person.

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