Moon Phase and the Menstrual Cycle

TEAM KNIX / YOUR BODY

Throughout history, many cultures and civilizations believed there was a relationship between the phases of the moon (aka lunar cycle) and the phases of a woman’s cycle. Evidence suggests this belief goes as far back as Ancient Rome and Ancient Greece. The word “menstruation” and “menses” comes from the Latin and Greek words that mean month (mensis) and moon (mene).  

A big reason it was so widely accepted is the fact that both cycles are approximately 28-days long. BBC’s Science Focus suggests Charles Darwin also perpetuated this belief, claiming it proved our ancestors lived near the ocean and needed to sync with the tides. 

Since then, many studies have been done to explore if there is, in fact, a link between the moon cycle and the human menstrual cycle. 

Does the Moon Affect Menstrual Cycles?

According to modern science, there is no direct correlation between the phases of the moon or the lunar month and human cycles. While it’s true the moon’s gravitational pull is powerful enough to control the ocean’s tides, there is no scientific evidence that proves lunar phases have an impact on the human menstrual cycle, as stated by The Cleveland Clinic

However, the importance of linking the lunar cycle to the phases of menstruation has cultural and spiritual importance that cannot be ignored.

Cultural and Spiritual Significance of the Moon Cycle and Menstrual Cycles

There’s no denying many people find cultural and spiritual significance by linking the moon cycles to a woman's cycle. Many women find comfort, empowerment, and spiritual meaning by mapping their cycles to the moon phases. 

This often plays off the traditional beliefs that ovulation and fertility are linked to a full moon. No one knows exactly why these beliefs exist, but some suggest it’s because the full moon resembles a pregnant belly. 

There’s also a powerful significance in the fact that many ancient mythologies have female lunar deities. For example the Greek goddess Selene, the Roman goddess Luna, and the Chinese goddess Chang'e. 

While the link between moon and menstruation can be meaningful from a cultural and spiritual perspective, the scientific connection is not as clear.

Busting the Moon Myth

In the 1980s, some studies were done that looked into the link between the lunar month and a woman's cycle; however, they ended up with contradictory results:

So, which is it? The above studies ran over the course of 12-14 weeks. More long-term, comprehensive studies suggest that neither claim is correct. 

In 2013, a journal called Endocrine Regulations published a study that tracked the periods of 74 women over an entire calendar year. It states that “in defiance of traditional beliefs and contrary to what some researchers have argued with short-term research work, in this long-term study we did not find any synchrony of lunar phases with the menstrual cycles.” 

Even more recently, the Clue app ran the largest study of this nature. They analyzed a whopping 7.5 million cycles and also concluded there is no correlation between the phases of the moon and menstrual phases and/or fertility.

There is certainly something to be said for the power of numbers and results of such large-scale studies can’t be ignored. So, what does control your cycle if not the lunar cycle? 

Hormones and the 4 Phases of Your Cycle

A woman’s cycle consists of four main phases:

  • Menstrual 
  • Follicular 
  • Ovulation
  • Luteal 

Each stage is driven by the rise and fall of certain hormones. Hormones are chemical messengers found in the body and released by various glands. Depending on which hormones are present determines which menstrual phase you’re in and how you feel mentally, emotionally, and physically at any given time of the month. 

The following chart shows which hormones are present during each stage of your cycle:

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Phase

Main Hormone(s) Involved

Menstruation

Estrogen and progesterone

Follicular

Follicle Stimulating Hormone (FSH), estrogen, and progesterone

Ovulation

Luteinizing Hormone (LH)

Luteal 

Progesterone and Human Chorionic Gonadotropin (if fertilization occurs)


An average cycle is 28 days; however, women can experience cycles as long as 35 or as short as 21 days. Let’s take a look at what’s happening in your body during each stage of your cycle. 

Menstruation

During menstruation (aka your period), estrogen and progesterone levels drop causing your uterine lining to break down and for uterine contractions to begin. During menstruation, your uterus sheds its lining (endometrium) along with the unfertilized egg from the previous cycle. Menstruation lasts approximately 5-7 days.

The Follicular Phase

The follicular phase begins in the ovaries at the same time menstruation is happening in the uterus. It continues until around day 13 to 14 of the cycle. Follicle Stimulating Hormone (FSH) triggers a cluster of about 15-20 follicles to collect on an ovary’s surface. Each follicle contains a single immature egg. One of those eggs will mature into an oocyte and will be released during ovulation.

Ovulation

Ovulation is the stage of the cycle when you’re most fertile—and you have Luteinizing Hormone (LH) to thank for that! 

LH is released by the brain’s pituitary gland in the days leading up to ovulation. The surge of LH causes an ovarian follicle to burst from the ovary, travel down the fallopian tube, and become an ovum (or egg).  At that point, one of two things can happen: either the egg gets fertilized by a sperm or it does not.

The Luteal Phase

After the egg bursts from its follicle during ovulation, the ruptured follicle stays on the surface of the ovary and slowly transforms into a structure called the corpus luteum. The corpus luteum releases progesterone (along with small amounts of estrogen). 

These hormones make sure your uterine lining stays thick and healthy in preparation for the implantation of a fertilized egg. If the egg is fertilized, then pregnancy will occur. If it isn’t, then the corpus luteum withers and dies. As that happens progesterone levels begin to drop and the uterine wall starts to break down. At approximately day 28, the body enters the menstrual phase and the cycle begins again.

Scientifically Proven Factors That Affect Your Menstrual Cycle

Your menstrual cycle is a very delicate process and fluctuations in hormone levels can easily disrupt it. So if your menstrual cycle doesn’t work like clockwork, don’t sweat it! It’s totally normal to experience different signs and symptoms month-to-month. And it’s also totally normal if the length of your menstrual cycle fluctuates one month to the next.

Having said that, some factors that can disrupt your menstrual cycle are cause for medical concern. Be mindful of the following conditions and consult your doctor if you think any of these apply to you:

  • Lifestyle factors including stress, anxiety, exhaustion, insomnia, diet, and eating disorders.
  • Pregnancy obviously stops your monthly cycle as fertilization and implantation stop your period. If you think you’re pregnant, visit your doctor for a check-up!
  • Polycystic ovary syndrome (PCOS) is a medical condition that can lead to infrequent or prolonged menstrual periods or excess male hormone levels. 
  • Uterine fibroids or polyps are benign growths that can cause heavy bleeding and disrupt your cycle (they are also pretty painful).
  • Birth control & other medications interrupt your natural menstrual cycle in order to prevent pregnancy (that’s their main purpose). 
  • Perimenopause happens just before menopause (when periods stop completely) and is usually characterized by an irregular menstrual cycle as periods gradually stop. Menopause is diagnosed when you go 12 months without a period.

In Summary

While there's a scientific explanation behind your menstrual cycle, it doesn’t negate the fact that many women find value in tying their cycles to nature. I mean, think about it: The menstrual cycle has been around since the beginning of time and is nature’s way of preparing the female body for the miracle of pregnancy and birth—pretty powerful, right?

It’s no wonder that so many cultures and civilizations find strength and comfort in ritualizing its cyclical nature. So, don’t forget to establish your own personal rituals. Whether that means following the lunar cycle in relation to your period or simply taking a hot bath or meditating to combat the emotional and physical symptoms of premenstrual syndrome (PMS). 

You can read all the peer-reviewed journals in the world but, at the end of the day, you know what your mind and body needs at any given time. So, when it comes to you and your menstrual cycle, you do you! You can check out other moon-related myths and legends at History.com.