Moon and Menstrual

Medical and biological text books will mostly say that the female cycles have a typical duration of 28 days, with a range of variation between 21 and 35 days. In practice there is however often a considerable variation between different women and also over the life-time of an individual woman. Yet, we may still ask what is the duration of the natural female cycles and what determines its duration. Most animals have estrus cycles of a very different length and so why would the human female be special in having a cycle paralleling the full moon?

Upon closer study, it turns out however that 28 days is not the true average of the natural female cycle. In ancient mythologies it is clearly related to the full moon, but in the modern world the female cycle is disturbed above all by the existence of artificial lights and the use of artificial hormones on a scale that has left no woman unaffected. It is thought that the many moon-mimicking light sources, probably including TV and computer screens, has perturbed the female cycle and generally shortened it. It is however obvious from these disturbances that it is the light of the moon, in other words the full moon cycle of 29.5 days, that the female body is responding to. Women desiring more regular menses are in fact sometimes recommended to sleep with lights on at certain days. Some also use this to attempt to precipitate ovulation. The point to realize is that the female cycle responds to light.

The above is anecdotal, but there is also scientific evidence to support that the natural female cycles of ovulation and menses are 29.5 days long. The most extensive studies that have been conducted to determine the period between menses in fact came up with mean values of 29.5 days for these2,3. A study of great relevance also measured the duration of menstrual periods in rural China, where artificial light was virtually non-existent4. This study confirmed the same duration for the female cycle, 29.5 days. What was especially interesting about this is that the urinary levels of hydroxymelatonin, an excretion product resulting from the activation of the light sensitive hormone melatonin, were in fact measured over the course of the full moon cycle and found to correlate with it. The case was thus closed and the relationships between the full moon cycle, a light sensitive hormone affecting the onset of menses and the duration of the menstrual cycle itself was established in a setting that was much closer to natural conditions than that of most of the modern world. Considering this, it is not really possible to argue that the natural female cycle is 28 days. The data instead favor the interpretation that it is linked to the full moon cycle of 29.5 days, and it makes sense that in many cultures, including Native American, women have gathered at full moons when their periods are believed to have been synchronized. This is supported by the more or less ubiquitous mythological evidence from ancient times that the female cycle was linked with the full moon. Almost all pre-patriarchal cultures had a goddess associated with it.

Also, the best measure of the average duration of a pregnancy is 265.80 days, almost exactly 265.77 days corresponding to nine full moon cycles of 29.53 days. This is hardly accidental. In a large study of 510,000 births it was further found that births were more common on days of full moons than on other days. The authors concluded: "Biological and medical scientists…would take a step forward in scientific thinking and teaching if they abandoned the use of the fictitious 28 day "lunar" month and if they adopted the view that human gestation is 9.00 0.01 synodic lunar months from conception (or ovulation)….and that the ovulatory or menstrual cycle is 1.00 0.01 such month in length". 5

This quote indicates that even before (1959) the duration of the female cycle had been seriously disturbed by the contraceptive pill and other hormonal preparations the idea was already around that the female cycle was 28 days although this was in direct conflict with the existing data. One might ask why. Leonard Shlain6 argues however that the exact correlation of menses and full moons in ancient times was the root of the first development of a marker of time. If nothing else, the words moon and menses have the same root. Very possibly there has later been an inclination on the part of males to deny the magical link between the female cycle and the full moon cycle and so in modern medicine the idea of a fictitious 28-day cycle came into existence.

Regardless, it seems clear that it is the period between full moons that is the natural female cycle. Since the erect woman of the human species could actually see the moon, and had a pineal gland that was affected by it, she came to be the only female with an ovulation cycle corresponding to the full moon. A calendar that would be an expression of the natural female cycle, unaffected by the artificial light and hormones of the modern world, would then really be the traditional Mayan way of counting moons. Their moons alternated in length between 29 and 30 days and went from full moon to full moon. A calendar of months alternating between 29 and 30 days, of course, would not be a prophetic calendar, but an endlessly repeated cycle. Yet, it is a natural female calendar related not only to ovulation, but also to gestation.

by
Carl Johan Calleman has a Ph.D. in Physical Biology from the University of Stockholm and is a noted toxicologist