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Estrogen: Too Much, Too Little or Just Right?

Updated: Apr 29

Hormones are complex and explanations of their role are often oversimplified. Nevertheless, some basic knowledge on estrogen and steps you can take to metabolize it properly are important.

Eating reasonable quantities of plants that contain phytoestrogens can help in balancing this hormone

Known primarily as a sex hormone, estrogen actually serves over 300 functions in the body from protecting our bones to preserving the integrity of our tissues. Throughout most of a woman's life, estrogen levels will be high but nearing menopause, production starts to decline. Older men, on average, will have higher levels than post-menopausal women and having adequate amounts helps both men and women in keeping fat off the waistline and preserving muscle mass. Estrogen can have major implications for our health and wellbeing and many women will experience balance, excess and decline throughout their lifespan. Understanding how to support the body while inevitable imbalances occur can improve our wellbeing.

It's important to understand that there are several forms of estrogen and this matters when looking at its role in the development of breast cancer. There are 3 main types of estrogen: estrone (predominant after menopause), estradiol (predominant in women who are still cycling) and estriol (highest during pregnancy). In the liver, estradiol (active estrogen) and estrone can be converted to a variety of estrogen metabolites. One specific metabolite, the 4-OH-estrone is an active carcinogenic form and has been studied for its role in breast cancer development . Another area of interest is the 2:16 ratio of 2-OH-estriol to 16-alpha-OH-estrone, which is associated with low breast cancer rates. (This will come up later with food recommendations!)

Excesses and Deficiencies

When estrogen is balanced women will have regular periods, tissues will feel well lubricated, they will react better to stress and their mood is stable throughout the cycle. When women enter perimenopause, usually in their 40s, progesterone will decline first and they will likely experience some estrogen dominance which brings with it a variety of uncomfortable symptoms. Estrogen dominance is a term you might have heard before but it is not a generally accepted condition in mainstream medicine and is a term primarily used in the research literature and by those practicing/using alternative and integrative medicine. However, the term "unopposed estrogen" where there is not enough progesterone to counter the effects of estrogen, is an accepted term in standard medicine. The symptoms of having an excess of estrogen are the following:

  • premenstrual headaches/migraines

  • fluid retention

  • weight gain

  • anxiety

  • panic attacks

  • low libido

  • PMS

  • breast tenderness

  • depression

  • fibrocystic breast disease

  • uterine fibroids

  • ovarian cysts,

  • menorrhagia (heavy, painful menstrual periods)

Whether it is simply a lack of progesterone that causes these symptoms is arguable since there are other well-known factors involved in estrogen levels. One example of this is the estrabolome, the healthy estrogen-converting bacteria in the gut, is involved in metabolizing and eliminating circulating estrogens from the body. Xenoestrogens are also known to add to the problem. These endocrine disrupters found in some waters, cosmetics, plastics, construction materials, pesticides and conventionally-raised meat and they are everywhere and difficult to avoid and can affect both males and females in childhood and beyond. In fact, xenoestrogens are believed to be responsible for current and continuous decline in male fertility rates.

In menopause, estrogen levels will drop and women will likely experience some changes like hot flashes, mood changes, tissue changes, a slower metabolism, brain fog and issues with recall.. For many women, the hot flashes and mood changes are the most obvious and problematic issues and eating plants with natural estrogen-like compounds may ease those symptoms somewhat.


Whether it's an excess or a decline in estrogen that is the issue, phytoestrogens can help in balancing estrogen levels. Phytoestrogens are not estrogen, the are like estrogen and bind weakly to the estrogen receptors, thereby blocking estradiol. When estrogen is high, they have an anti-estrogen effect in the body. When estrogen is low, they have a mild pro-estrogen effect. They were once thought to be endocrine disruptors and this is likely the case if they are eaten beyond reasonable amounts. Red clover is a phytoestrogen-rich plant loved by cows and it was noticed by farmers that cows that grazed in clover-laden fields tended to reproduce at lower rates. It is believed that the phytoestrogens were part of the plant's defence system and by maintaining lower levels of grazing animals, the plant would have a better chance of survival. But humans are said to have adapted to phytoestrogens in the diet and in most cases these estrogen-like compounds are health supportive.

Some phytoestrogen-rich foods include:

  • Beans and legumes, especially soy

  • Cruciferous vegetables like cabbage and broccoli

  • Nuts and seeds, especially flax and sesame

  • Garlic

  • Fruits

  • Red wine (but...)

Of all the phytoestrogens, none has received as much attention as the isoflavones that are found primarily in soy. Isoflavones are particularly good at mimicking the effects of estrogen and some believe that this makes it dangerous. But more and more, research is showing that isoflavones actually decreases the risk of breast cancer for most women and provide many health benefits. Isoflavones have been shown to support cardiovascular health, reduce symptoms of menopause and protect against cancer. Because of its pro-estrogenic quality, it might promote breast cancer in some women who metabolize it differently but even this is being disputed now for it is believed that the amount of isoflavones in the diet are not enough to have an affect. Whether soy has a more protective or harmful effect in the body has been heavily researched and results have been inconsistent which has led to a lot of confusion.

So why is there so much conflicting research on soy?

Genetic background: The protective benefits of soy are more cut and dry in Asian populations where soy has been eaten for thousands of years. Asian women have far lower incidence of breast cancer than women in Western countries. It is still not clear exactly why this is, it may be due to genetic differences in how isoflavones are metabolized, but factors like age of exposure to soy products and differences in the microbiomes likely are involved as well. But there does seem to be a genetic component, Asians who move to the the US are found to have higher rates of breast cancer by the second generation, though even after adopting a Western diet, they remain lower risk than the general US population.

Individual differences in how estrogen is metabolized in the body: While most women will metabolize estrogen to a protective form, some women seem to metabolize it into its genotoxic form. Studies looking at isoflavones and cancer risk indicate that the type of estrogen receptor that is stimulated by phytoestrogens can vary from person to person- in most people it will attach to beta-receptors while those with higher cancer risk are more likely to stimulate the alpha-receptors.

Forms of soy: Studies on soy have been inconsistent with regards to the form of soya products used. Some have argued that the reason North American women did not see the same benefits as Asian women who have lower rates of breast cancer, is in how the soy was delivered. In Asia, traditionally processed soy is a big part of the diet, while in the West it is eaten in industrially processed foods and in many studies the isoflavones were taken as supplements with differences in the ratio of isoflavone types.

Differences in the microbiomes: Our ability to metabolize soy products into health-promoting metabolites depends on the presence of certain bacteria. Some gut bacteria are known to produce a non-steroidal form of a phytoestrogenic metabolite called equol. The amount of equol in the urine indicates that presence of these bacteria in the gut. Equol has been found in 25-30% of people in the Western countries and in 50-60% in Asian countries.

Age at consumption: In order to see some of the benefits of eating soy, particularly for breast cancer prevention, it likely has to be consumed in adolescence.

Politics: Soy is a cheap protein and is now a major part of our diet and food chain. It is fed to livestock, it is added to processed foods and with many people reducing meat consumption, it is increasingly becoming a staple protein. North American governments have subsidized soy production and the US now produces more soy than China. Powerful companies stand to gain a lot from soy's popularity and would have a lot to lose if it were associated with poor health outcomes. With this kind of money at stake, there is bound to be some research bias.

A recent meta-analysis on the benefits of soy isoflavones found that there were vast discrepancies between studies, but concluded the following in regards to isoflavones:

  • they are likely beneficial when it comes to bone health

  • they do not provide any meaningful protection for cardiovascular disease risk

  • they could be useful in reducing the risk of certain cancers, including breast cancer

  • they could be useful in reducing hot flashes

So should we be eating soy?

In general, research supports eating soy and there is growing consensus that it has a small protective effect. Having soy along with other phytoestrogen-rich foods can help balance estrogen levels. I encourage my clients to eat soy products that are organic and traditionally fermented like miso or tempeh. In fact, one study found that the beneficial effects on bone health were found only for those consuming fermented isoflavones. For tofu, again, organic is good, and organic and sprouted is even better as this reduces some of the anti-nutrients contained in most legumes. The negative effects of soy consumption can be seen in the rare individuals who are eating soy as their main source of nourishment. If you drink litres of soya milk every day, this could pose some problems.

If you have a family history of breast cancer you can boost healthy estrogenic metabolites (2OH-estrogen) with:

  • Moderate exercise

  • Cruciferous vegetables like cabbage and broccoli

  • Flax

  • Omega-3-fatty acids

  • Nutrients that support methylation

  • Rosemary

  • Turmeric

  • Weight loss

  • High protein diet

  • Reducing catecholamine production by decreasing stress

It's also possible to decrease estrogen metabolism to toxic 4-Catechol estrogens by ensuring you're eating iodine-rich foods like seaweed, selenium-rich foods found in meat proteins and nuts, plenty of the antioxidants found in turmeric, dark chocolate and berries.

(from Dr. Pam Smith's ZRT presentation: Breast Cancer Risks Can They Be Mitigated?)

The best way to ensure that your levels are balanced without the use of chemical hormones is to:

  • Eat plenty of fibre to help eliminate any excesses

  • Support your microbiome

  • Be careful with alcohol as it impairs estrogen metabolism

  • Avoid xenoestrogens from conventionally-raised meat, cosmetics, unfiltered water, and plastics

  • Include foods with phytoestrogen in your diet, especially fermented soy

Eating healthy is one way of supporting your hormonal health. Using a combination of approaches like botanicals, supplements and exercise along with a healthy diet will likely be more effective, get in touch for more information. For more problematic issues, it can be helpful to speak to your doctor about hormone therapy which has evolved over the years and is considered not only much safer but can provide many health benefits too.


Hormone Repair Manual: Every woman's guide to healthy hormones after 40 by Lara Briden, ND

The Hormone Cure by Sara Gottfried, MD

Dr. Pam Smith's ZRT presentation: Breast Cancer Risks Can They Be Mitigated? March, 2021

Soy and isoflavones consumption and breast cancer survival and recurrence: a systematic review and meta-analysis

Scientific Evidence Supporting the Beneficial Effects of Isoflavones on Human Health

Estrogen-gut microbiome axis: Physiological and clinical implications

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