Imbalances of the human gut microbiome may be involved in the development of polycystic ovarian syndrome (PCOS) and recent studies have demonstrated modulation of the gut microbiome may be useful in the management of this condition. The connection between the gut microbiome and the development of PCOS was first proposed in 2012  and, since then, numerous studies have shown a significant difference in the composition of the gut microbiome between healthy subjects and those with PCOS.
PCOS is a common cause of infertility in women and can lead to metabolic imbalances that are associated with obesity and insulin resistance, as well as an increased risk of Type 2 diabetes and cardiovascular disease. PCOS also presents with increased ovarian production of androgens and anovulation or absent periods. 
The role of the gut microbiome in the different features of PCOS
The human gut microbiome consists of up to 7000 different strains of bacteria, fungi, protozoa and viruses. It influences metabolism, nutrition, immune function and physiology. An imbalance within this microbiome can lead to the development of many diseases. Those with PCOS have changes to the diversity of their gut microbiota and to several bacterial species associated with metabolic disorders.
It is thought that insulin resistance (IR) and obesity are both closely linked to the gut microbiome. Imbalances of the gut microbiota cause increased permeability of the gut lining (leaky gut) which leads to low-grade persistent inflammation and immune activation. This inflammation interferes with insulin receptors and increases insulin levels in the body, leading to IR. Research studies have shown subjects with IR had marked differences in the abundance of different bacterial species within the gut compared to those with no IR and changes in the make-up of this gut bacteria has shown to have a clear relationship with the onset of IR.
IR increases the production of ovarian androgens and this prevents normal follicles from developing. It has also been suggested that androgens may also be involved in the development of PCOS as they can directly affect the gut microbiota. An animal study found that androgen-induced gut microbiota changes contributed to metabolic and endocrine malfunction in PCOS.
Altering the Gut Microbiome: a potential target in PCOS
When the gut microbiome is altered through the use of probiotics, prebiotics or Faecal Matter Transplant it has a positive effect on PCOS. This research has led to significant interest in manipulating the gut microbiome as a therapeutic strategy for those with PCOS. So how can the microbiome be changed? Exercise, dietary changes, and herbal medicine have all been observed to have a positive effect on changing the balance of the microbiome.
Avoid inactivity – A study of 40 women found that exercise three days per week for 30 minutes at moderate intensity modulates the microbial community of the gut and physical activity at a low dose but done regularly increased the abundance of health-promoting bacteria. Interestingly, this study found breaks in sedentary time and avoiding long periods of inactivity in your day also induces beneficial changes to gut microbiota.
Go Mediterranean – A 2020 international review of diet and the human gut microbiome found evidence from all regions of the world that the human microbiome can be modified by dietary changes both in adults and children. The Mediterranean diet is high in dietary fibre and unsaturated fats and is known to have a beneficial effect on metabolic syndrome, diabetes and cardiovascular health. Research has now found it modulates the gut microbiota and reduces inflammation  which would make it useful in the management of conditions such as PCOS.
Herbal medicine – A favourite culinary herb, Rosemary, was studied for its effect on depression and the mechanisms responsible for this. It was found that Rosemary rebalanced the gut microbiome in favour of beneficial bacteria and this change to the gut microbiome reduced inflammation and immune activation exerting a positive effect.
PCOS symptoms may develop due to an imbalance of the gut microbiome. Rebalancing the gut microbiome through diet, pre and probiotics, herbs and exercise may be an exciting new therapeutic target for those with this condition.