One of the most exciting areas of research in the last 10 years has been the understanding of how the gut microbiome has an impact on a wide range of physiological functions, as well as our overall physical and mental health. We know that the gut microbiome can induce inflammatory and metabolic changes, modulate our immune system and mood, and much more. Interestingly, emerging research shows that the gut microbiome plays a key role in hormonal regulation, including oestrogen.
What is oestrogen and what is its role?
Oestrogen is a female sex hormone and has many fundamental physiological roles including maintenance of female reproductive health, regulating body composition, cardiovascular health and cognitive health. During perimenopause, the production of oestrogen falls until menopause has occurred. After the menopause, the ovaries produce estrone, a less potent form of oestrogen.
Introducing the estrobolome
The specific collection of bacteria (and their genes) within the gut microbiome that are thought to metabolise oestrogen and oestrogen-like metabolites has been coined the ‘estrobolome’. We know that the gut microbiome and oestrogen influence each other -- the gut microbiome has been shown to be affected by oestrogen, whilst also playing a role in modulating oestrogen levels. Studies have shown that the estrobolome regulates oestrogen levels through oestrogen-metabolising enzymes (beta-glucuronidases) which convert oestrogens into their active forms so that they can enter the blood circulation and reach other tissues in the body.
Menopause and the Gut Microbiome
During and post menopause, women experience a decline in oestrogen levels, which along with the normal ageing process alters the gut microbiome and reduces not only its diversity, but also that of the estrobolome. We know that as we age our hormone levels change and this can affect our risk for disease, particularly during and after menopause. This fall in oestrogen levels is also associated with an increased risk of changes to our metabolism, weight gain, cancers, (e.g. breast cancer) and other chronic disease states including heart disease and diabetes. The latest research suggests that the gut microbiome can potentially influence the development of disease through the changes to the estrobolome which metabolises oestrogen. Any diet or lifestyle change that can modify the estrobolome may be beneficial through menopause and beyond to reduce the risk of oestrogen-related disease.
Diet and Lifestyle
We know that certain lifestyle factors such as diet (e.g. high-fat/sugar/processed foods) and high levels of alcohol consumption and smoking are commonly associated with disruption to the gut microbiome, in addition to medication use such as antibiotics.
Maintaining a healthy gut microbiome with a plant-based diet focusing on dietary fibre through fruit and vegetables, whole grains, nuts, seeds, herbs, beans and pulses is recommended to support the gut microbiome, and therefore, the estrobolome too. Eating phyto-oestrogens, which are naturally abundant in soy
as well as linseeds, wholegrains and beans may impact the estrobolome as phytooestrogens are structurally similar to oestrogen. The estrobolome metabolises these phytooestrogens into a variety of different compounds depending on the composition of an individual’s gut microbiome Therefore, health effects of consumption of phytoestrogens are likely to vary significantly from person to person.
Emerging research in animals shows that probiotic supplementation with various strains of Lactobacillus probiotic may alter the gut microbiome and the estrobolome and potentially protect against low oestrogen conditions such osteoporosis. Lactobacilli supplementation could potentially be used to support breast cancer prevention as Lactobacilli has been shown to have anti-cancer effects in breast tissue. While we still require more research on the effects of probiotics on the estrobolome, it is plausible that in the future, supplementation may be considered a simple and effective approach to help reduce the risk of oestrogen-related health conditions, particularly after the menopause.
 Baker JM, Al-Nakkash L, Herbst-Kralovetz MM. Estrogen-gut microbiome axis: Physiological and clinical implications. Maturitas. 2017 Sep;103:45-53
 Baker L, Meldrum KK, Wang M, Sankula R, Vanam R, Raiesdana A, Tsai B, Hile K, Brown JW, Meldrum DR. The role of estrogen in cardiovascular disease. J Surg Res. 2003 Dec;115(2):325-44
 Pollet RM, D’Agostino EH, Walton WG, et al. An Atlas of β-Glucuronidases in the Human Intestinal Microbiome. Structure. 2017;25(7):967-977.
 Kwa M, Plottel CS, Blaser MJ, Adams S. The Intestinal Microbiome and Estrogen Receptor-Positive Female Breast Cancer. J Natl Cancer Inst. 2016 Apr 22;108(8
 Zhu J, Liao M, Yao Z, Liang W, Li Q, Liu J, Yang H, Ji Y, Wei W, Tan A, Liang S, Chen Y, Lin H, Zhu X, Huang S, Tian J, Tang R, Wang Q, Mo Z. Breast cancer in postmenopausal women is associated with an altered gut metagenome. Microbiome. 2018 Aug 6;6(1):136
 Britton RA, Irwin R, Quach D, Schaefer L, Zhang J, Lee T, Parameswaran N, McCabe LR. Probiotic L. reuteri treatment prevents bone loss in a menopausal ovariectomized mouse model. J Cell Physiol. 2014 Nov;229(11):1822-30
 Urbaniak C, Gloor GB, Brackstone M, Scott L, Tangney M, Reid G. The Microbiota of Breast Tissue and Its Association with Breast Cancer. Appl Environ Microbiol. 2016 Jul 29;82(16):5039-48