You know that what you eat can affect your fertility, as can your exercise habits, your weight, whether you drink or smoke, etc. But you may not realize that the light your body is exposed to—both natural and artificial—also plays a big role in regulating your body’s reproductive system.
Light is what keeps the circadian pacemaker (the body’s master clock—called the suprachiasmatic nucleus—in the brain) in sync with the solar (24-hour) day. If we aren’t exposed to enough of the right kinds of light at the right times of day, the master clock starts falling out of sync with the world around us at a rate of roughly 10 minutes each day. Even worse in terms of our reproductive health, our body systems fall out of sync with the master clock. Depending on how far out of whack things are allowed to get, the result can range from a missed period to reproductive anarchy.
Getting out of sync is surprisingly easy to do. Many of us work indoors all year, and aren’t exposed to much natural sunlight during the work week. On the other hand, artificial lighting illuminates the night sky, meaning we don’t experience a full period of natural darkness either. It can be difficult for the body’s master clock to distinguish between real light, real darkness, and man-made facsimiles. Is it any wonder our bodies are confused?
When that happens, the body’s master clock loses control over the timing of the secondary clocks that govern everything from how we think and behave to how the body functions . . . (everything from when we sleep and eat to how well the orchestra of reproductive hormones is conducted).
To keep functioning as it should, the master clock needs to re-sync itself all the time using a very simple signal: a period of bright light followed by a period of darkness, i.e., day and night. That light-dark signal reaches the master clock in the brain via the ocular nerve, which relays the signal to the brain’s pineal gland. A century ago, before the widespread use of artificial lights, the pineal gland (which produces the hormone melatonin) had no problem obtaining the feedback it so desperately seeks. Today it’s not that easy. But once you understand how your body responds to light, you can take steps to make sure that you get the light you need to keep your reproductive system functioning like clockwork.
Light and the Menstrual Cycle
The study of circadian (24-hour) rhythms is still a relatively new science, so it’s not surprising that the research demonstrating a link between light and fertility is still fairly new as well. What makes it so exciting is that it’s a multidisciplinary effort, with contributions coming from experts in gynecology, physics, biology, nursing, astrophysics, psychiatry, and andrology, among others.
Women’s menstrual cycles follow an approximately 28-day pattern based on the 29-day cycle of the moon. The moon’s light ebbs and flows over the course of the 29 days, with the days surrounding a full moon being the brightest. Back in the 1960s and 1970s, researchers started to focus on using light exposure that mimicked moonlight as a means of regulating the menstrual cycle.
Then in 1990, Psychiatry Research published a study (“Night Light Alters Menstrual Cycles”) reporting that women with long and irregular menstrual cycles who slept with a 100-watt bulb beside them from days 13 to 17 of their cycles succeeded in regulating and shortening those cycles from a mean of 45.7 days to 33.1 days.
More recently, scientists have focused on daylight as well as moonlight, and how daylight exposure affects the menstrual cycle. A 2007 study published in Psychiatry Research reported that women receiving light therapy for seasonal affective disorder (SAD) started their periods 1.2 days earlier on average.
That same year, a Russian study reported that “ovulation may be successfully potentiated by morning artificial bright light. This might be a promising method to overcome infertility in some women.”
Light therapy can help regulate men’s reproductive functions, too. A 2003 study reported in Neuroscience Letters found that treating healthy men with 1,000 lux (light units; a measure of light exposure) of light via bright light therapy from 5 a.m. to 6 a.m. for five consecutive days boosted luteinizing hormone (LH) levels by 69.5 percent. LH raises testosterone levels in men (and triggers ovulation in women).
- 1
- 2
