My PhD Research: Gut Microbiome, Estrogen, and Women’s Health

Targeted Dietary Modulation of the Gut–Estrobolome:

Implications for Oestrogen Metabolism and Breast Cancer-Relevant Risk Pathways

I am currently completing my PhD at the University of Westminster, where I study how targeted dietary changes influence the gut microbiome and, in turn, estrogen metabolism in women.

At the centre of this research is something called the gut–estrobolome axis. Your gut is home to trillions of microorganisms, weighing close to two kilograms in total. These microbes do far more than help digest food. They interact with your immune system, regulate inflammation, and play a direct role in hormone metabolism.

The Estrobolome:

Within the gut microbiome exists the estrobolome, a group of microbes involved in processing estrogen. These bacteria help determine whether oestrogen is safely broken down and eliminated or reabsorbed back into circulation. When oestrogen is not metabolised efficiently, it may contribute to higher inflammatory tone and increased stimulation of oestrogen-sensitive tissues, which are biological pathways relevant to breast cancer risk.

Over the past decade, researchers have begun linking differences in gut microbial composition with differences in oestrogen metabolites and inflammatory markers. At the same time, diet has consistently been shown to shape the gut microbiome. What remains unclear is which specific dietary behaviours meaningfully influence this gut–hormone connection and how precise those changes need to be in order to produce measurable biological effects.

My research focuses on answering that question.

The Study:

The study examines how clearly defined, evidence-based dietary modifications affect gut microbial diversity and composition, and how those changes relate to urinary oestrogen metabolite profiles, including the 2:16-hydroxyestrone ratio. In practical terms, this means analysing stool samples to understand microbial patterns and urine samples to understand how estrogen is being metabolised. Looking at both together allows us to see whether changes in diet translate into changes in hormone processing.

A key part of this work involves building a structured, measurable intervention framework. Instead of vague advice about “eating healthier,” the study focuses on defined domains such as fermentable fibre intake, phytoestrogen consumption, polyphenol-rich foods, fermented foods, cruciferous vegetables, alcohol moderation, metabolic regulation, and reduction of ultra-processed foods. Each area is translated into measurable criteria so adherence can be evaluated alongside biological outcomes.

This research is deeply relevant to the shared terrain underlying many hormone-related conditions. PCOS, oestrogen dominance patterns, PMDD, endometriosis, and even some infertility challenges all involve interactions between inflammation, metabolic health, and hormone signalling. The gut microbiome sits at the centre of that terrain. It influences immune activity, insulin sensitivity, bile acid metabolism, and estrogen recycling. While these conditions are distinct, they overlap biologically in ways that often trace back to gut–hormone communication.‍

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Advancing Research in Women’s Hormone Health‍

Women remain underrepresented in microbiome intervention trials, despite the clear bidirectional relationship between reproductive hormones and gut microbial composition. Estrogen affects microbial community structure. The microbiome affects how estrogen is activated, detoxified, and recirculated. My research focuses on women in hormonally active life stages to better understand this dynamic interaction.

The broader aim of my research is to bring clarity and structure to the conversation around diet, hormones, and disease prevention. Precision nutrition requires more than general recommendations. It requires measurable intervention design, reproducible methodology, and biological validation.

By studying targeted dietary modulation of the gut–estrobolome axis, this work aims to strengthen the scientific foundation for hormone-informed nutrition strategies, with implications for breast cancer risk as well as broader hormone-related conditions affecting women.

Thank you for following and supporting my work!

Sarah Brandow, MSc

Current Doctoral Researcher, University of Westminster, London UK