The connection between the menstrual cycle and lunar cycles is always the subject of controversial studies and theories. But now a research led by Julius-Maximilians-Universität Würzburg (Germany) seems to have found very convincing clues. According to the authors, in particular, it is highly probable that in the past the menstrual cycle was synchronized with the lunar cycles, but then artificial lights and human activities in general would have interrupted this balance.
That our satellite has a significant influence on the Earth is certainly not a recent discovery: it has long been known, for example, that its gravitational attraction interacts with our planet by moving the masses of water according to the daily rhythm of the tides.
Regarding this, it was also recently discovered that our satellite is moving further and further away from us, at a rate of almost 4 cm per year, a phenomenon that is modifying the tides and making our days longer, millimeter after millimetre.
But it is rather difficult to know whether the same gravitational force also influences life on Earth and in particular the human organism, such as women’s menstrual cycles. And the discussion gets even more complicated when it comes to how the Earth’s satellite’s fluctuating brightness between the full and new moons affects humans.
We demonstrate that synchronization with the moon has decreased significantly since the introduction of LEDs and the increasing use of smartphones and screens of all types
reports Charlotte Försterfirst author of the work
The study was conducted by analyzing long-term menstrual data from women over the past 50 years.
The results showed that the menstrual cycles of women whose data was recorded before the introduction of light-emitting diodes in 2010 and the widespread use of smartphones were significantly synchronized with the full and new moon cycle. After 2010, the cycles were mostly synchronized only in January, when the gravitational forces between the moon, sun and Earth are at their maximum
Scientists therefore hypothesize that humans have an internal lunar clock that can be synchronized with our satellite’s cycle thanks to natural night light and gravitational forces. However, the coupling of such a clock with the lunar cycle in humans is compromised by increased nighttime illumination due to artificial light.
Lunar clocks are widespread in marine organisms, but have not yet been demonstrated in humans – continues Förster – In fact, many species synchronize their reproductive behavior with a specific phase of the lunar cycle to increase reproductive success. The human menstrual cycle also has a similar duration to that of the lunar cycle, approximately 29.5 days, and recent studies also suggest at least temporary synchronicity between the menstrual and lunar cycles
This study, however, is not enough and the influence of the moon on the female cycle remains controversial.
It is not entirely clear how such a lunar clock could be synchronized by the small cyclic variations in gravity between the Earth and the Moon
But these findings are consistent with what has been demonstrated in sleep and psychiatry research.
For example, in 2013, work led by the University of Basel (Switzerland) showed that people sleep significantly less during the full and new moon than at other times.
But artificial light disrupts the synchronization, and this could in fact be another of the effects of light pollution, which has already been shown to be harmful to many living species.
Overall, the findings of the new research suggest that humans can react not only to moonlight, but also to gravitational cycles caused by the moon.
However, our study shows that increased exposure to artificial light severely impairs the synchrony between the menstrual cycle and the lunar cycle.
According to this study, in particular, artificial night light not only “eclipses” the natural lunar cycles, but also shortens the duration of the menstrual cycle. However, since continuous synchronization is only possible if the cycle duration is close to the lunar one, this shortening in turn reduces the probability of synchronization.
But why LEDs and the latest lighting sources in general?
LEDs have much higher energy than gas lamps and light bulbs. In addition, they contain a high proportion of blue light, to which our photoreceptors in the eye are particularly sensitive
Be careful though, the authors point out that, despite having clearly demonstrated that the synchronization of the female menstrual cycle with the moon is weakened by LEDs, smartphones and screens of all types, they were unable to demonstrate a causal link, which is essential to truly be able to state that this form of light pollution has caused the imbalance.
The research will continue, also because a significant potential application advantage emerges from the evaluation of the data.
Since menstrual cycle length appears to be a possible age-dependent indicator of female fertility, our findings could be relevant not only to human physiology and behavior, but also to fertility and contraception.
he concludes Charlotte Förster
The work was published on Science Advances.
Sources: Julius-Maximilians-Universität Würzburg / Science Advances
