Can Periods Really Sync Up? (McGill OSS)

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The idea that periods can synchronize was first investigated in a 1970’s paper by Martha McClintock, who examined the menstrual cycles of women living together in dorms. McClintock found that after 7 months of living together, the women’s periods had gone from an average of 6.5 days apart to 4.6 days apart, leading to the idea that proximity caused the periods of these women to synchronize due to some chemical signal.

However, studies since then have been largely unable to replicate these findings. McClintock’s results are now largely believed to have occurred by chance or poor experimental design, with many researchers calling menstrual synchrony a methodological artifact.

While it may appear that periods are synchronizing, it is important to remember that not everyone has a 28-day cycle, as some range from 21-35 days. This variability allows synchronicity to vary and periods to occur at the same, or different times. 

This article was originally posted here:

Why do we Poop More on Our Periods?

Originally published here:

The menstrual cycle of humans is complicated. It consists of a luteal and follicular phase, follows a roughly 21 day cycle, and has many effects beyond the shedding of the uterine lining. In addition to the cramps, bloating, hunger, exhaustion or nausea that some people deal with, many people also experience period related poop problems. Menstrual cycles are regulated by changing hormone levels, namely progesterone and estradiol (an estrogen), with some minor inputs from other biologically active molecules. One of these molecules is a prostaglandin that is released by the cells of the uterine lining when they die, that triggers the uterine contractions that expel the lining. The problem is that some of these prostaglandins escape the uterus and are detected by the smooth muscle cells of the large intestine, which are then triggered to contract. This results in, predictable, more frequent bowel movements during your period. It also turns out that the progesterone regulating your period can also effect your intestines, though contrarily to prostaglandins- by relaxing smooth muscle. This often manifests as fewer trips to the bathroom, or even constipation, during the luteal phase (from ovulation to just pre-menstruation) of the menstrual cycle.