Part 1: Overcoming the Taboo of Menstrual Blood
Discussing periods, especially period blood, has long been considered a no-no in everyday conversation, but this taboo is not only silly, it's preventing us from learning
Quick Note: When I use the term “woman” in this article, I’m referring to anyone who menstruates, but I acknowledge that not all people who menstruate identify as women and not all people who identify as women menstruate.
Hiya!
I told you that I fell down some rabbit holes about women’s health and to expect additional articles about what I learned. Well, this is one of them. While researching the gender disparities regarding statins and heart disease, I stumbled upon some incredible research about menstrual blood.
If your initial reaction to my mention of menstrual blood is disgust, then you’ll probably benefit from reading this and its sequel because while society poo-poos any mention of menstruation, some courageous researchers are discovering that period blood could revolutionize science in ways that benefit everyone.
Yet, scientists trying to study menstrual blood today say our deep-rooted cultural taboos about the natural process hinder researchers’ ability to study it. Something physician Sara Naseri learned firsthand.
The Curiosity
I came across an impressive, in-depth feature by Maddie Oatman in Mother Jones that inspired this entire menstrual rabbit hole I tumbled down.
In it, Naseri, who was raised in Denmark but now lives in the US, told Oatman she remembers noticing that most of her medical school training focused on reactive care, such as diagnosing problems and deciding on treatments after an ailment arose, rather than preventive methods like detecting ailments before they became serious.
Naseri wondered how people might learn information about their bodies early on, outside of the doctor’s office, and before severe symptoms present. She figured that medical professionals typically monitor a person’s health through bodily fluids, particularly blood. However, blood draws require puncturing the skin, and Naseri wondered whether there was a way to access it more conveniently.
Then, while sitting in class one day, she had an epiphany. Naseri told Oatman she realized:
“Hold on a minute, women bleed every single month. Why has nobody looked at that?”
It didn’t take long before she realized that a large part of the answer was because her fellow researchers thought menstrual blood was too gross to study.
But before I continue with Naseri’s story, let’s review some menstrual basics and a bit of history that likely contributes to the general response Naseri received.
The Mysterious Menstrual Cycle
Around half of the world’s population is female, and in 2019, it was estimated that about 24 percent of females were of reproductive age (between 15 and 49 years old). This means that roughly 350 million females menstruate on any given day.
However, the number is likely much higher considering the average age at which girls begin their periods is actually around 12 years old, and it’s happening younger and younger, including many who begin menstruating as young as 8 years old.
Unfortunately, education about menstruation is lacking.
A 2021 survey discovered that while over three-quarters (77 percent) of teens reported that “periods are regularly discussed at home,” a similar percentage (78 percent) agreed that they “were taught more about the biology of frogs than of the human female body at school,” and a third (35 percent) said their “health teacher appears uncomfortable discussing menstruation.”
Similarly, a 2023 survey of teens found that the vast majority say there needs to be more in-depth education about menstrual health (81 percent) and that it should be part of the core curriculum at school (78 percent).
One look at history and modern global culture makes it easy to see why education about menstruation is limited — it’s a taboo topic. A fact anyone who menstruates knows because they’ve experienced period-related drama firsthand. People who menstruate avoid pool parties, dates, and white pants when on their periods.
We’ve spent hours curled on the couch with heating pads on our stomachs and tracked our periods when hoping to avoid, or trying for, a pregnancy. People who menstruate spend untold amounts of money, time, and energy thinking about and preparing for their periods over decades.
Yet, the female reproductive system, including menstruation, remains a relatively uncharted field of research. In fact, scientists can’t even entirely agree on why female humans menstruate at all, let alone at such regular intervals.
In her 2024 book Blood: The Science, Medicine, and Mythology of Menstruation, Canadian-American gynecologist and New York Times columnist Jennifer Gunter discusses the current theory about why menstruation typically occurs monthly. She says that regular bleeding is just a byproduct of the menstrual cycle, “not the point” of it.
This theory makes sense, considering what scientists know about the menstruation cycle:
Seven to ten days after the ovaries release an egg, the hormone progesterone tells the uterus to prepare for a possible pregnancy. In response, the uterus thickens its lining (called the endometrium) and begins a process called decidualization, which is when some of the uterine endometrial cells transform to store fats and sugar and provide nutrients for a potential embryo.
Gunter compares the process to baking a soufflé because there are precise steps and measurements to follow. More importantly, once your soufflé is baked, it “can’t be turned back into a bowl of egg whites and another of egg yolks.”
Similarly, when the endometrium has completed its transformation to prepare for pregnancy, its cells can’t return to their original states to be broken down and reabsorbed by the body. Instead, the uterus sheds the endometrium every month and starts the whole process over.
On average, a menstruating person experiences this cycle roughly 400 times in their lives.
Yet the fact that humans menstruate at all is extraordinary and practically as big a mystery as the cycle itself. After all, less than 2 percent, or around 85 species, of the mammals on Earth experience menstruation.
Unlike humans and other menstruating mammals, the uterine lining for the other 98 percent of mammals that don’t menstruate doesn’t change until an embryo implants.
So, there must be some evolutionary advantage to menstruation. Otherwise, why undergo this inconvenient, often painful, monthly process instead of doing what the other over 6,000 mammalian species on Earth do?
Indeed, researchers identified some possible evolutionary advantages to a monthly menstrual cycle. A big one is that having a period encourages the endometrium to grow extra thick, which helps the mother fend off the invasive human placenta. (I’ve written about the placenta before. It’s an extraordinary, temporary organ created by a mother and her fetus that attaches to the uterine wall and provides nutrients and oxygen to the fetus via the umbilical cord.)
Or, as Columbia University researcher Cat Bohannon puts it in her 2023 book, Eve: How the Female Body Drove 200 Million Years of Human Evolution, the placenta is an organ with “one side that’s always hungry, and one side that’s trying to protect itself from that hunger.” As for why human females menstruate, she writes,
“Human women menstruate because it’s part of how we manage to survive our bloodsucking demon fetuses.”
Yet, even though hundreds of millions of humans menstruate every day, discussing the menstrual cycle is often faced with immediate discomfort and even disgust. But why?
Religious & Philosophical Menstrual Ick Factors
Of all our bodily fluids, including urine, spit, phlegm, feces, sweat, vomit, and blood — menstrual blood, specifically, tends to evoke an unusually strong repulsive reaction from people.
Feeling grossed out, ashamed, or embarrassed about menstruation is something people, regardless of sex or gender, have experienced throughout history. There have been, and still are, countless historical, religious, and cultural taboos around menstruation that shape our narratives and perceptions of it — often for the worse.
In most major religious texts, there are references to menstruation or the women who experience it as shame, impure, and to be avoided and shunned. The contempt for this natural cycle is so widespread and resilient that it’s leaked into scientific research. But let’s start with some of the oldest references.