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Oestrogen Dominance

by Penny Crowther(more info)

listed in women's health, originally published in issue 151 - October 2008

Attending a recent seminar by hormone expert Lyra Heller, it hit home to me just how exposed we are to oestrogen in the modern age. A ‘normal’ monthly female hormone pattern will show oestrogen as the dominant hormone in the first half of the cycle, followed by a predominance of progesterone in the second half. However if, as commonly happens, oestrogen is too high overall in relation to progesterone, this is known as oestrogen dominance. Conditions associated with it are PMS, fibroids, fibrocystic breasts, PCOS, endometriosis, systemic lupus erythematosis, cervical dysplasia, breast cancer and premature bone loss.

A standard hormone test via your GP will involve measuring levels of bound sex hormones such as testosterone, oestrogen and progesterone in the blood. Unless a hormone imbalance is pronounced, the results of such a test will often come back normal. Much hormone imbalance is more subtle than this and is outside the scope of a blood test. A more sensitive means of testing is to use saliva which measures free circulating hormones rather than bound ones. Multiple samples can be taken at different times of the day and month, making it possible to track the hormonal pattern over an entire cycle, rather than simply spot checking on a certain day as is the case with conventional blood tests. The accuracy of saliva testing is well documented by specialists in the field of steroid hormones,[1] but it is not used by the NHS currently.

Why does oestrogen have a tendency to become dominant? Aside from the oestrogen produced by the ovaries, oestrogen comes from many other sources, whilst progesterone does not. Oestrogen has to be very carefully balanced and managed in the body. The tiniest increase in oestrogen can have a significant effect.

Sources of Oestrogen

  • Oestrogen is produced by fat cells so it will increase in proportion to body fat. Aromatase is the enzyme in fat tissue that triggers oestrogen production;
  • When oestrogen is high, it increases immune activity including inflammation, which stimulates even more oestrogen production. Oestrogen is pro-inflammatory when there is too much of it so the cycle continues. This activity can take place in the ovaries, breast and joints which act as local oestrogen factories;
  • Insulin resistance leads to increased oestrogen production;
  • Poor oestrogen metabolism is a major contributor to oestrogen dominance. Oestrogen has to be broken down by the liver. Methylation is the principle way in which oestrogen is deactivated, and for this process, folic acid is essential. It is thought that as many as 30% of women have a functional folic acid deficiency. An excellent way of checking for functional folic acid deficiency is to do live blood microscopy. If there is a marked increase in nuclear segmentation of the neutrophils, this is a good indicator of impaired folic acid metabolism;
  • Oestrogen may be re-absorbed into the gut. The health of the gut flora is critical in this respect. Oestrogen undergoes de-conjugation in the liver by the process of glucuronidation and is then excreted in the bile, leaving the body through the stool. Pathogenic bacteria produce the enzyme Beta glucuronidase which will interrupt the process by reactivating the oestrogen in the bile, so that it is then released as free oestrogen and re-absorbed into the bowel;
  • Our exposure to synthetic oestrogens is now widespread. For example, plastic food storage containers, cling film, pesticides, non organic meat and dairy products, fish from polluted water, the contraceptive pill and HRT are all sources.


Oestrogen dominance is very amenable to nutritional treatment. A good starting point is to adopt a low GI (glycaemic index) diet with plenty of protein (a good proportion of which should be from non animal sources), which will stabilize insulin levels. A study found that vegetarian women had half the levels of free circulating oestrogen of omnivores.[2]

Good digestion is the key to the efficient excretion of oestrogen metabolites. Low stomach acid is a common cause of poor digestion, and this can be topped up with an HCl and Pepsin supplement, or by taking a tablespoon of cider vinegar and lemon juice before meals. Vinegar and lemon juice, along with beetroot and artichoke, help stimulate bile flow which assist the breakdown of oestrogen.  Low stomach acid can be assessed with a home string test, or by live blood microscopy.

A probiotic, together with a vegetable fibre rich diet, will help balance the gut flora in favour of the beneficial bacteria and decrease the activity of beta-glucuronidase. Production of this enzyme will be increased by a diet high in saturated fat and a gut environment that is too alkaline. Some anti-bacterial herbs in the form of oregano, golden seal, thyme, berberis, clove, curcumin may also be of value.

Liquorice lowers oestrogen and increases progesterone by inhibiting the enzyme responsible for the breakdown of progesterone. Vitamin B6 shouldn’t be ignored either, as it increases oestrogen detoxification.

Plant oestrogens from beans, soya foods, seeds, lentils and peas are weakly oestrogenic, and will be taken up by the oestrogen receptors in the cells in place of the stronger oestrogens.

Oestrogen is broken down into different types of metabolites, some of which are beneficial (the 2 series) and others (the 16 series) are pro-breast cancer. Soya favours the metabolism of oestrogen into the 2 series, which is anti-cancer and decreases the amount of oestradiol in circulation.[3] Soya is very beneficial in its whole food form, such as green soya beans, tofu, tempeh and organic soya milk. Raw soya is not recommended.

Cruciferous vegetables such as cabbage, cauliflower and Brussels sprouts also favour the beneficial oestrogen metabolites. Finally, milled flaxseeds should definitely be a daily addition to the diet, as they contain lignans which are converted by gut microbes into substances similar in structure to oestrogen. Flax also inhibits aromatase activity.


1.    Riad-Fahamy D, Read GF and Walker RF. Salivary Steroid Assays for Assessing Variation in Endocrine Activity. J Steroid Biochem. (1A): 265-72. 1983. July 19.
2.    Goldin BR et al. Estrogen Patterns and Plasma Levels in Vegetarian and Omnivorous Women. NEJM. 307: 1542-7. 1982.
3.    Xu X, Duncan AM, Merz BE and Kurzer MS. Effect of Soy Isoflavones on Oestrogen and Phytooestrogen Metabolism in Pre-Menopausal Women. Cancer Epidemiol Biomarkers. 7 (12): 1101-08. Prev 1998.


  1. Anne Mitchell said..

    excellent article, very well written, clear facts, clear instructions.
    Thank you

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About Penny Crowther

Penny Crowther DN Med BANT NTCC qualified as a nutritional therapist in 1997 and has seen hundreds of clients at her practices in SW15. She has written for Positive Health, Families, Green Farm, Health Matters, The Health Times and contributed to articles for the Daily Telegraph, The Times Literary supplement, Pregnancy & Birth, Marie Claire, has been featured in the Daily Express, Daily Mirror and on local radio. She is a current member of the BANT (British Association for Applied Nutrition and Nutritional Therapy) and formerly sat on their ethics committee.

Experienced London nutritionist Penny Crowther has been in clinical practice for 20 years. Penny has been featured in the national press (including the Daily Express and the Daily Mirror) for her work with nutrition for fertility and is the author of many nutrition articles.

Penny’s approach to health is holistic, and takes into account emotional, mental and environmental factors as well as nutrition. She studied many complementary therapies before training as a nutritionist which provides a broad foundation of knowledge. She is dedicated to personal and professional development and frequently attends lectures and seminars to keep up to date with the latest scientific nutrition research. Penny may be contacted on Tel: 07761 768 754;

Please note that nutritional advice is not a substitute for medical advice and treatment or visiting your GP or Health Professional.

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