Breast Cancer Basics: Reducing Estrogen Receptor Stimulation (Without Drugs)

Seventy-to-eighty percent of all breast cancers have estrogen receptors (“ER-positive”.) When estrogen binds to these receptors, it leads to their activation and stimulation of cancer cell growth. Breast cancer medications are often prescribed to inhibit either the stimulation of the estrogen receptor (selective estrogen receptor modulator or “SERM”: Tamoxifen, Raloxifene) or the production of estrogen (aromatase inhibitors or “AI”: Anastrozole, Letrozole, Exemestane.)

Researchers have found that many plant compounds possess SERM and/or AI activity. Here are some examples of these phytochemical:

Natural SERMs:

  • Daidzein
  • Ellagic acid
  • Epigallocatechin-3-gallate (EGCG)
  • Genistein
  • Kaempferol
  • Naringenin
  • Phloretin
  • Ursolic acid

Use this search feature to find food sources for these compounds.

Natural AIs:

  • Apigenin
  • Chrysin
  • DIM
  • Galangin
  • Genistein
  • Hesperitin
  • Kaempferol
  • Luteolin
  • Naringenin
  • Oleuropein
  • Pinocembrin
  • Quercetin
  • Resveratrol
  • Sakuranetin
  • Tectochrysin
  •  White button mushroom (species Agaricus bisporus)
  • Zinc

Use this search feature to find food sources for these compounds.

Can you take natural compounds that have SERM or AI activity instead of the pharmaceutical versions to reduce your breast cancer risks?

  • Maybe…but we simply don’t know because the prospective studies have not been done.

What amount (dose) of natural SERM or AI compounds should one consume each day?

  • Again, we don’t know.

Is it safe to consume soy?

The safety of high intakes of soy isoflavones and other phytoestrogens for breast cancer survivors is an area of controversy. Soy isoflavones are known to have weak estrogenic activity due to their structural similarity with 17-β-estradiol. Soy isoflavones preferentially bind to and activate estrogen receptor-β (ER-β) — rather than ER-α. In many breast cancers, ER-α activation by estrogens is generally considered responsible for enhanced proliferation, whereas this is counteracted by activation of ERβ, which exerts an antiproliferative effect.

A meta-analysis of four prospective cohort studies suggested that high versus low isoflavone intakes might be associated with a 16% reduction in risk of recurrence in breast cancer survivors. A pooled analysis of data from 9,514 breast cancer survivors from large prospective studies found a 25% reduced risk of recurrence with soy isoflavone intakes ≥10 mg/day (compared to intakes of <4 mg/day).

Based on these data and others, there are no compelling evidence to discourage breast cancer survivors from consuming soy foods in moderation.

What other strategies can reduce the amount of estrogen in the body?

  • Improve estrogen break down into healthy metabolites (DIM, cruciferous vegetables, exercise)
    • Diindolylmethane (DIM, in short) is the principal breakdown product of indole 3-carbinol (I3C), the phytochemical found in cruciferous vegetables like cabbage, cauliflower, broccoli, brussel sprouts, kale, collards, mustard greens, radishes, watercress, and turnips. DIM, has been shown in studies to reduce the risk of estrogen-driven cancers cancer by helping the body to make a better balance of the “good estrogen” (2-hydroxy-estrone, 2-OHE1) compared to the “bad estrogen” (16-alpha-hydroxy-estrone, 16α-OHE1). Increases in this ratio (2-OHE1/16α-OHE) have been associated with a significant reduction in breast cancer risk.
    • Exercise has been shown to significantly change estrogen metabolism, leading to increases in 2-OHE1 and possible decreases in 16α-OHE1 ultimately resulting in significant increases in the 2-OHE1/16α-OHE1 ratio.
  • Decrease exposure to xenoestrogens:
    • Xenoestrogens, such as PCBs, phthalates, pesticides and DDT, cause estrogenic effects. It is critical to incorporate a diet consisting of organic foods whenever possible and purchase personal care and household cleaning products that do not contain these estrogen-like chemical compounds. My favorite resource is
  • Increase estrogen excretion:
    • A low-fiber diet causes estrogen levels to be higher, while a diet high in fiber results in decreased estrogen levels in the bloodstream. Why? Excess estrogen is excreted in the bowel. When stool remains in the bowel for a longer time, as in constipation, the estrogen is reabsorbed. Studies have shown that women on a high-fiber diet have lower levels of circulating estrogen
  • Lose weight:
    • Your body produces estrogen in the adrenal glands, brain, and in your ovaries or testes. Another place both men and women produce estrogen is in adipose (fat) tissues. The more fat cells you have, the more estrogen you will make.

What to do about “estrogen dominance?”

Nothing. While this is a very hot topic on the internet, it is not a condition that is legitimately recognized by mainstream medicine.

I recommend checking your ratio of estrogen metabolites:

Estrogen is metabolized (primarily by the liver) down three phase I pathways. The 2-OH pathway is considered the safest because of the anti-cancer properties of 2-OH metabolites. Conversely, the 4-OH pathway is considered the most carcinogenic as its metabolites can create reactive products that damage DNA. The third pathway, 16-OH creates the most estrogenic (promotes growth of estrogen sensitive cells) of the metabolites – 16-OH-E1.

My favorite lab test to check your ratio of these estrogen metabolites is the DUTCH Test (I usually order the DUTCH Complete.) You want your 2-OH percentage to be between 60-80% to have a less promotional (anticancer) estrogen state.

The DUTCH test also checks your methylation status. This is part of the second phase of detoxification that occurs in the liver that eventually leads to the elimination of estrogen from the body. If you methylate well (higher methylation), you will have lower levels of systemic estrogen metabolites due to better excretion of estrogens (more favorable). If you don’t methylate well (lower methylation), you will build up more systemic estrogen metabolites (less favorable).