Breast Cancer and Your GI Tract: Part 1

In order to have a meaningful discussion, we need to get into some of the details. I promise it won't be as difficult as my med school biochemistry course!
06/05/2013 04:20 pm ET Updated Aug 05, 2013

Well, I promised you that I'd get back to the breast cancer/gut association, so here goes. My disclaimer is that there is no way to evaluate you through this blog, so if this is something you are concerned about, I invite you to find a functional medicine practitioner in your area for a full, individualized consult.

All humans have a wide range of hormones in their body, and not just reproductive ones! But those are the ones on which we are going to focus.

In order to have a meaningful discussion, we need to get into some of the details. I promise it won't be as difficult as my med school biochemistry course! Your body has three types of estrogens: estradiol (the most potent), estriol and estrone. During this discussion, I'm going to refer to them all as "estrogen" for simplicity's sake. Women make estrogens from cholesterol in various places in their body, as well as from conversion of androgens (i.e., testosterone) in other places.

As your estrogens circulate through your body, they eventually encounter your liver, which is responsible for doing lots of cool things, including: storage and release of glucose, storage of vitamins A, D, E and K, and, most pertinent to this topic, processing your hormones. If you'll remember our discussion in a previous blog, the liver has two phases, phase one, and phase two. Once the estrogens are done circulating through your body, both liver phases are required to "process" and remove them.

In order to process estrogens, you have to go through these two steps. In phase one, your liver oxidizes the hormones, which often makes them more toxic. Phase two conjugates (think: adds) the oxidized hormone to a substance that renders it harmless, and then the conjugated hormone goes into your intestine or urinary system to be excreted.

An estradiol molecule has 18 carbon atoms. This is important because, depending on which of those carbon atoms gets hydroxylated (i.e., given an oxygen/hydrogen pair) during phase one, you will either wind up with a metabolite that can promote or protect against the development of breast cancer. Depending on your individual body, your diet, and how you metabolize your estrogens will determine whether you are someone who will make "good" estrogen (2-hydroxyestrone), or estrogens that increases the risk of breast cancer (16 alpha-hydroxyestrone and 4-hydroxyestrone).

After your liver alters the chemical shape of the estrogens, these metabolites then proceed onto phase two, which has two main ways to further alter these estrogens in order to make them ready for removal from your body through your feces or urine. Here is where I find it gets a little confusing. One of the major phase-two pathways is methylation. If 4-hydroxyestrone is methylated (i.e., given a methyl group), this may make it more cancer-promoting. If 2-hydroxyestrone is methylated, it may make it more cancer-preventing.

The other phase-two pathway is called glucuronidation, which means to add glucuronic acid to the estrogen molecule. When this is added, it makes it easier to get the molecule out of the body. Now here is where things get creepy.

Many of us have too little of the beneficial bacteria in our intestines, and an overabundance of bacteria that aren't acting in our best interests. Some of these bacteria secrete a substance that separates the estrogen molecule from the glucuronic acid. When this happens, the estrogen molecule is now back to being toxic, and is also recycled back into our bodies (through the liver -- go figure!). And guess what? Now your estrogen levels are not balanced, and you have an overabundance of toxic estrogens floating around.

This leads to a whole host of problems that may include acne, menstrual disorders, mood disorders, and... an increased risk of breast cancer.

So what's a girl to do? Stay tuned. We'll get to practical tools that can directly decrease your risk of breast cancer in my next blog post.


1. Willner, C. (2001). "Nutritional Influences on Estrogen Metabolism." Applied Nutritional Science Reports, 1, 1-8. Available online here.

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