In a word: Nothing. The myth of moon phases and their connection to the menstrual cycle is one that has passed down through the ages, influencing ideas of menstruation across the world. Here, we take a deeper dive into how the myth came about in the first place.
Scientists have indeed found a link between animal behaviour and lunar phases but although the moon may have an impact on the behaviour of many animals, such as gerbils and fiddler crabs, humans aren’t as affected by the lunar cycle. In the past, the human menstrual cycle has also been compared to the ebb and flow of tides with claims that menstruators ovulate around the full moon and have their periods near the new moon. Adding to the lunar connection, the terms “menstruation” and “menses” come from Latin and Greek words meaning moon (mene) and month (menses).
Perhaps the strongest correlation that healers have used in the past to prove the link between menstrual and lunar cycles is their similar length, with the global average menstrual cycle length being 29 days long and the lunar cycle 29.5 days. This can seem like a compelling argument, but menstrual cycle lengths vary greatly between menstruators, lasting anywhere from 21 to 35 days. Furthermore, period tracking app Clue’s data science team analysed 7.5 million cycles, but found no connection between the lunar phases and the menstrual cycle or period start date.
Nonetheless, some menstruators find that synchronising their menstrual cycle to the moon’s lunar phases gives them comfort, peace, harmony, or an overall sense of well-being. Even without any scientific basis, creating a connection between the phases of the moon and your menstrual cycle can be helpful if you’re looking to build an attachment to the earth or find a sense of tranquillity during your period.