30th of January 2015

Full Moon Sex and New Moon Blood

Did you know that humans, orangutans, and possums are the only mammals that have an average menstrual cycle length of approximately 28 days? We can all agree that humans are somewhat similar to orangutans, but possums?

What the hell do we have in common with possums? Aside from the 28 day menstrual cycle, not much really. The fact that we share this trait with only two other species indicates that the menstrual cycle length is not fixed to cyclic external pressure, such as the moon’s gravitational influence. We often think menstrual cycle length is somehow related to the lunar cycle, but is this really true?


There has been some evidence that the menstrual cycle is influenced by moon’s phases. According to a study on 826 women, 28.3% menstruated around the new moon, more than at any other time of the lunar cycle. Similarly, the levels of the sleep hormone melatonin were significantly higher during menstruation than during the ovulation (full moon). The levels of melatonin decrease in response to nocturnal light exposure.


What if the menstrual cycle of women could really be regulated by light? Have you ever felt restless during the full moon? Do you sleep best on the dark new moon nights?


Evolutionarily speaking, this makes sense. While you’ll menstruate during the peaceful phase of new moon, your fertile days will occur during the full moon, when it is shining bright all night. Make the best of this time by getting busy and procreating under glowing moonlight.


Our ancestors seemed to be aware of this connection between the moon and fertility. There are a number of traditional fertility rites around the world that were celebrated almost exclusively during full moon. Often these rites were in conjunction with summer solstice, such as Beltane, Kupala (Slavic), and many more. Perhaps our ancestors knew what they were doing after all! Picking a mate under the moonshine could at least help to avoid the sobering experience of waking beside the wrong bedmate.


Today we are ready to embrace more romantic explanations, enjoying yet another rediscovered piece of our inner nature.  In the ‘60s however, this question was studied with a different aim in mind. The moonshine was unceremoniously replaced by a light bulb in the scientific studies, “On the possibility of a perfect rhythm method of birth control by periodic light stimulation” and “Light regulation of the menstrual cycle”.  The possibility of synchronizing the menstrual cycle in women by light was considered to be of an interest for the U.S. Air Force and there has been even a U.S. patent granted on a method of synchronizing the menstrual period by light as late as 2002.


But does the synchronization of the menstrual cycle by light really work? Try it for yourselves. The basics are easy, just keep the light on in your bedroom around the 14th to 17th days of your cycle and it should return to the normal length of 28 days.


And if by any chance you decide to use this approach as a method of natural contraception, it will be as easy as always - leave the lights on, watch TV or play games all night during your fertile days and you will have no time for sex. If you are one of those that really cannot resist the pull of the full moon, than the unfashionable pill might do the trick for you. And don’t forget to check for blood under your fingernails in the morning!


Author: Martin Lukan, PhD




Devan E.M. “On the possibility of a perfect rhythm method of birth control by periodic light stimulation.”Am J Obstet Gynecol.1967 1;99(7):1016-9.


Knott C. (2003)."Orangutans: Reproduction and Life History". Gunung Palung Orangutan Project. Harvard University. Archived on 04/21/2008


Kripke D. F. "Light regulation of the menstrual cycle.” Wenner Gren International Series 1993: 305-305.


Law  S.P. “The regulation of menstrual cycle and its relationship to themoon.” Acta Obstet. Gynecol. Scand., 1986; 65: 45–48US Patent No.: US 6,497,718 B1, Date: 12/24/2002


Zimecki M. “The lunar cycle: Effects on human and animal behaviour and physiology.” Postepy Hig Med Dosw. 2006;60:1–7