Causes and Prevention of PCOS- The Microbiome - PCOS Diva
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Causes and Prevention of PCOS- The Microbiome

Guest Post by Dr. Shawna Darou, ND

The human microbiome refers to the bacteria, viruses, fungi and protozoa that live throughout your body, in the gut, nose, throat, mouth, skin and urogenital tract. These organisms support and perform many functions in the body – they fight pathogens, supply key vitamins and also affect weight and metabolism. These organisms are also key to your immune system function, and they affect how your genes express themselves.

The relevance with PCOS (polycystic ovarian syndrome) is that the health and balance of the gut microbiome is one of the key factors in the development of PCOS (1). So how does the microbiome get out of balance?

What affects our microbiome?

The gut microbiome begins to form in utero, and is impacted by mode of delivery, breastfeeding vs bottle feeding, the use of antibiotics, nutrition and more. Here are some of the biggest factors:

  • Mother’s weight pre-pregnancy: women with a high BMI pre-pregnancy have distinct bacterial flora which is linked to increased weight gain during pregnancy (2, 3); and also produce breastmilk with less bacterial diversity (4).
  • Baby’s delivery mode: during vaginal birth, babies are exposed to the largest load of healthy bacteria which are the primary colonizers of the baby’s gut microbiome. Babies born by caesarian have significantly less exposure to these strains of bacteria (5,6).
  • Breastfeeding: breastmilk contains more than 700 species of bacteria, which further colonize the gut, and support a healthy immune system (5,6).
  • Antibiotic use: the use of antibiotics in infancy and childhood can negatively impact the gut microbiome by killing off large amounts of healthy bacteria. Broad spectrum antibiotics such as macrolides have the biggest impact, and can affect the health of the microbiome for up to 2 years (7).
  • Genetically modified foods: GM plants are genetically engineered to withstand large amounts of a weed-killer called Roundup, with glyphosate as the main ingredient. Glyphosate kills plants by interfering with a biochemical pathway involved with synthesis of amino acids, called the shikimate pathway. The shikimate pathway is not found in humans, but is found in bacteria, hence glyphosate impacts the gut microbiome directly (8).

How your microbiome impacts PCOS

PCOS is characterized by both insulin resistance and inflammation as underlying causes which set off the cascade of hormone imbalance, including excess androgen production by the ovaries. Imbalances in the gut microbiome can impact the development of PCOS in the following ways:

1) Microbiome impacts insulin resistance

In a Danish study, having a relatively low diversity in the gut microbiome is correlated with higher overall inflammation, as well as greater insulin resistance and other markers of metabolic diseases. The chronic gut inflammation alone also promotes insulin resistance (9, 10).

2) Microbiome affects weight

Low bacterial richness in the gut is associated with higher body fat, insulin resistance and inflammation, compared to those with higher bacterial richness. What this means is having fewer numbers and variety of bacteria in the gut can lead to obesity (11, 12)

3) Microbiome affects intestinal permeability

Disturbances in the bowel bacterial flora increase irritation to the intestinal tract lining, leading to intestinal permeability (aka ‘leaky gut syndrome’). This activates the immune system and interferes with insulin receptor function and raising insulin levels (13,14).

Could we prevent PCOS in girls?

One of the most exciting parts of this association is that by supporting and rebalancing a healthy gut microbiome in infants and children, we may be able to actually prevent PCOS in young girls. Taking steps where possible for a vaginal birth, breastfeeding, minimizing antibiotics, avoiding GM foods, taking probiotic supplements and treating intestinal permeability can each positively impact the health of the gut microbiome. you have PCOS, what you can do NOW to support a healthy microbiome

As you can tell, a healthy and diverse microbiome is an essential component of your hormone balance with PCOS. It impacts your ability to lose weight, manage insulin resistance, and control inflammation, and may be a significant obstacle if you are struggling to achieve hormone balance with PCOS. The good news, is that there is lots you can do to rebalance your microbiome. Here are my top steps:

  • Take steps to kill off pathogenic bacteria, yeast and parasites with antimicrobials. Some of my favourites include olive leaf extract, oregano, berberine and garlic.
  • Take probiotics, preferably ones with multiple strains to support gut bacteria diversity. One large study from 2015 found that probiotic supplements alone lowered blood sugar levels and reduced insulin resistance in women with PCOS (15).
  • Repair intestinal permeability. Once you have rebalanced the organisms, taking steps to repair the gut lining will greatly reduce overall inflammation. Drinking bone broth soup, and supplements such as L-glutamine, DGL and slippery elm bark are all helpful for repair.
  • Avoid GM foods in your diet, as they have much higher amounts of glyphosate (which affects gut bacteria). The main foods to watch are corn, soy, canola, and sugar beet. You can further reduce your glyphosate ingestion by choosing organic.
  • Other steps to support a healthy microbiome include eating naturally fermented foods regularly (kefir, sauerkraut, miso and more), and minimizing your intake of sugar and simple carbohydrates.


Dr. Shawna DarouDr. Shawna Darou is a licensed and registered Naturopathic Doctor, who graduated from the Canadian College of Naturopathic Medicine ( at the top of her class and was the recipient of the prestigious Governor’s Medal of Excellence. Naturopathic medicine is her second career, her first being Engineering Chemistry from Queen’s University. She now uses her analytical brain and problem solving skills especially in the complicated arena of hormonal health, and in solving health puzzles.

Dr. Shawna Darou N.D. is a specialist in women’s health care and fertility who has treated thousands of women in her Toronto clinic since 2004. She is a dedicated and caring doctor with a gentle approach who is committed to the health of her patients. Dr. Darou’s is also an avid health writer, and her popular health blog can be found at

Outside of the office, Dr. Darou is the mother of two beautiful children who inspire her to evolve the medical model in order to reform healthcare for the next generation.




  1. Parker, Jim. Emerging concepts in the pathogenesis and treatment of polycystic ovary syndrome. Journal of the Australasian College of Nutritional and Environmental Medicine (2015) 34(1).
  2. Collardo, MC; Isolauri, E; Laitinen, K; and Salminen, S. Distinct composition of gut microbiota during pregnancy in overweight and normal-weight women Am J Clin Nutr (2008) 88(4): 894-899.
  3. Galley, JD; Bailey, M; Dush, CK; et al. Maternal Obesity Is Associated with Alterations in the Gut Microbiome in Toddlers. PLoS One (2014) 9(11): e113026.
  4. Collardo, MC; Isolauri, E; Laitinen, K; and Salminen, S, et al. The human milk microbiome changes over lactation and is shaped by maternal weight and mode of delivery. Am J Clin Nutr (2012) 96(3): 544-551.
  5. Madan, JC; Hoen, AG; Lundgren, SN, et al. Association of Cesarean Delivery and Formula Supplementation With the Intestinal Microbiome of 6-Week-Old Infants. JAMA Pediatr. (2016) 170(3):212-9.
  6. Bäckhed et al. Dynamics and Stabilization of the Human Gut Microbiome during the First Year of Life. Cell Host & Microbe, May 2015 DOI: 1016/j.chom.2015.04.004
  7. Korpela, K; Salonen, A; Virta, LJ, et al. Intestinal microbiome is related to lifetime antibiotic use in Finnish pre-school children. Nature Communications (2016) 7.
  8. Samsel, A; Seneff, S. Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases. Entropy (2013) 15(4): 1416-1463.
  9. Musso, G; Gambino, R; Cassader, M. Obesity, Diabetes, and Gut Microbiota. The hygiene hypothesis expanded? Diabetes Care October (2010) 33 (10): 2277-2284
  10. Esteve, Eduardo; Ricart, Wifredo; Fernández-Real, Jose-Manuel. Gut microbiota interactions with obesity, insulin resistance and type 2 diabetes: did gut microbiote co-evolve with insulin resistance? (2011) ,14(4): 483-490.
  11. Le Chatelier, E; Nielsen, T; Qin, J; Prifti, E, et al. Richness of human gut microbiome correlates with metabolic markers. Nature (2013) 500: 541-546.
  12. Caricilli, AM; Picardi, PK, de Abreu, LL, et al. Gut Microbiota Is a Key Modulator of Insulin Resistance in TLR 2 Knockout Mice. Pos Biology (2011).
  13. Tremellen K et al, Dysbiosis of Gut Microbiota (DOGMA)–a novel theory for the development of Polycystic Ovarian Syndrome. Med Hypotheses (2012) 79(1):104-12.
  14. Parker, J. A new hypothesis for the mechanism of glyphosate induced intestinal permeability in the pathogenesis of polycystic ovary syndrome. Journal of the Australasian College of Nutritional and Environmental Medicine (2015) 34(2).
  15. Shoaei, T; Heidari-Beni, M; Tehrani, HG, et al. Effects of Probiotic Supplementation on Pancreatic β-cell Function and C-reactive Protein in Women with Polycystic Ovary Syndrome: A Randomized Double-blind Placebo-controlled Clinical Trial. Int J Prev Med. (2015) 6: 27.
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