The estrogen-poop connection

Debunking the myth about a daily bowel movement and your hormones

There are many fragments of distorted science masquerading as “hormonal truths” in the corner of the Internet dedicated to so-called wellness. One that is especially pervasive is the myth that women must have a bowel movement every day to balance their hormones. Typically, this “hormone balancing” refers to estrogen levels.

This myth festers because it has been promoted by popular websites and self-styled hormone experts, many of whom have large social media footprints. It surfaced recently on an account on TikTok with over 45k followers and can also be found on mindbodygreen dot com, a site that claims to have over 15 million unique visitors each month. On mindbodygreen dot com, Jolene Brighten, a naturopath who wrote the unfortunately popular book Beyond the Pill, is quoted as follows, "If your bowels aren't moving, your estrogen sticks around longer than it should and goes back into circulation in the body."

There is a nugget of truth here, albeit misused (we’ll get to that, so hang on). This makes it sound science-ish and hence believable. In addition, most of us are bloated when we are constipated and of course, many women feel bloated in response to changing hormone levels with their menstrual cycle, so that only makes it seem even more truthful. But before I get into the details, let me state now in no uncertain terms, that this is not just an oversimplification it’s wrong. 

Estrogen metabolism is more complex than the incorrect concept that it hangs around on the mean streets of your intestines waiting to jump back into your bloodstream to cause mayhem because the poop bus is behind schedule. Because of this complexity, most people don't have the background to say, “Hey, I’m calling bullshit” when they see this floating around TikTok or Instagram.

So let’s discuss estrogen metabolism, because it is super cool.

Before menopause, the estrogen circulating in the blood is made by the follicles (eggs) in the ovaries. As all blood passes through the liver, so does the estrogen that it contains. Many people like to think of the liver as a filter, but a better analogy is a factory that does a combination of manufacturing and waste removal. Part of this waste removal involves hormones. It is here in the liver where the estrogen in the blood is metabolized, meaning it is converted to inactive forms by various enzymes. These inactive estrogens enter the bile and are sent to the intestine for elimination. Some of these inactivated estrogens also enter the blood and are then eliminated by the kidneys in the urine. 

But the story of estrogen metabolism doesn’t stop in the bowel. It is here, courtesy of the gut bacteria, that the inactive estrogens can be returned to an active state by an enzyme called beta-glucuronidase. When this happens, the estrogen that once was inactive, and had been sent to the intestine for removal, can be reabsorbed back into the bloodstream and get back in action. A healthy gut microbiome has lower levels of the enzyme reactivating beta-glucuronidase, meaning a healthy gut microbiome helps to limit estrogen reabsorption. 

But there is even more going on! I know right? Not all of the estrogen that is reactivated is reabsorbed because it sticks to the fiber in the stool, basically hitching a ride to the toilet. Whether you go three times a day or once every three days (the range of normal for bowel movement frequency), doesn’t matter.

One study took a deep dive into the stool-fiber connection. Women who ate a low fiber diet had about half the amount of estrogen in their stool as women who ate a high fiber diet. But this was due to the amount of stool, as the women who ate more fiber had almost twice the amount of stool by weight (fiber gives the stool bulk, among other things). The concentration of estrogen in the stool, meaning the amount per gram of stool, was the same. As women who ate less fiber likely had fewer bowel movements, it was clear that going less often didn’t affect how the estrogen bound to the fiber in the stool. More poop, regardless of timing, meant more estrogen out. 

The interaction between dietary fiber and hormones is very complex. While part of it is this regulation of estrogen metabolism in the gut and removal of estrogen, some data suggests that fiber decreases levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH), these are hormones released by the brain that are integral in regulating ovulation. This effect appears to be independent of fiber’s impact on estrogen levels, so it is possible that the brain gets feedback from the gut microbiome and ways we don’t yet understand. Another study tells us that when women have a low fiber diet and consequently more estrogen is absorbed back into the bloodstream, the amount of estrogen removed by the kidneys may increase to compensate. In addition, some studies suggest that fat intake may be a modulating factor in how estrogen is metabolized in the bowel and reabsorbed. 

The association between a high fiber diet and lower levels of circulating estrogens isn’t new. It’s actually one mechanism that is proposed for explaining a lower risk of breast cancer — a hormonally responsive cancer — among women with high fiber diets. But there is a lot going on here and we don’t understand all the reasons why this association exists. The most accurate summary is the gut microbiome plays an active role in estrogen metabolism and there are all kinds of symbiotic relationships between what is happening in the gut and what is happening hormonally in the body. But as a high fiber diet is often lower saturated fat, that may also play an important role.

The detailed explanation I just provided about what we know about estrogen metabolism and the gut and the fact that there are still unknowns is harder to explain, and may even sound less plausible, than the incorrect assertion that a bowel movement once a day is needed to regulate hormones. Oversimplifications are seductive because we like simple explanations, but science isn’t always simple. 

Now think of how we share information? How do you explain what we know and what we don’t know about estrogen and the gut in 59 seconds on TikTok? I’m not sure it’s possible (although I am going to give it a try!). And sadly, even if it is possible will people watch it as it won’t provide the satisfaction of a simple and tidy (yet incorrect) answer? After all, it’s easy to make something sound simple when facts aren’t a consideration.

Focusing on the number of bowel movements a day is the wrong health metric. A high fiber diet is good for you, and it seems to have a role in estrogen metabolism, but it is also beneficial for many other reasons, for example, lowering the risk of heart disease. A high fiber diet may also make you poop more often, but it’s not how often you go that impacts your estrogen levels. So please don’t worry about how often you have a poop and your “hormonal balance,” because it really is a story that is full of shit.