Light and Fertility

by Ann Douglas


Light is a fertility all-star, playing a make-it-or-break-it role in the functioning of the reproductive systems of both women and men.

It’s what keeps the circadian pacemaker (the body’s master clock) in synch 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 synch with the world around us at a rate of roughly 10 minutes each day. And, even worse, in terms of our reproductive health, our body systems fall out of synch with the body’s 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. 

Here’s the thing. To keep functioning as it should from day to day, the master clock needs to re-synch itself using a very simple signal: a period of bright light followed by a period of darkness. That light-dark signal reaches the master clock in the brain via the retina. A century ago, it was (literally) a no-brainer for the pineal gland in the brain to obtain the feedback it is so desperately seeking. Today, it’s not that easy.

Circadian darkness (a lack of exposure to suitable sources of light during the day, typically as a result of working indoors) and light pollution (being exposed to overly bright sources of light at night) can make it difficult for the master clock to distinguish between real light and real darkness and manmade facsimiles. If it falls for the lookalikes, the body’s circadian rhythm gets thrown for a loop, leading to all kinds of unpleasant fallout. 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 body fights off disease to how well the orchestra of reproductive hormones is conducted).

You get the picture. 


So just how powerfully does light impact on fertility? 

It’s a question that has been fascinating researchers for the past few decades.

The study of circadian rhythms is still a brand new science (about 50 years old) 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 multi-disciplinary effort, with contributions to the growing body of knowledge about light and fertility coming from experts in gynecology, physics, biology, nursing, astrophysics, psychiatry, and andrology, among others. And what scientists in all these fields have been discovering has exciting implications for both men and women.

Some of the earliest research about light and fertility focused on the use of light as a means of regulating the menstrual cycle. 

In 1967, astrophysicist E.M. Dewan, PhD; obstetrician-gynecologist, John Rock, MD; and a third researcher published a study in the American Journal of Obstetrics and Gynecology that proved that it was possible to regulate women’s menstrual cycles using light. (The women slept under complete darkness during Days 1 to 13 of their cycle; next to a 100-watt light-bulb under a lampshade in their bedroom on days 14 to 17); and then slept in complete darkness for the remainder of their cycle.) (Related article.)

Then, in 1975, Louise Lacey, author of Lunaception: A Feminine Odyssey into Fertility and Contraception, experimented with lower levels of light in an attempt to mimic the effects of moonlight from a full moon. 

The August 1990 issue of Psychiatry Research published a study (“Night Light Alters Menstrual Cycles”) replicating Dewan and Rock’s earlier research and reporting that that sleeping with a 100-watt bulb beside them from days 13 to 17 of their menstrual cycles shortened the menstrual cycles of women with long and irregular cycle patterns from a mean of 45.7 days to 33.1 days; and helped to regulate their cycles. 

And, in a study published in The Journal of Alternative and Complementary Medicine in Winter 1997, Scientists at the University of California, San Diego, Sleep Lab, reported on their successes in altering the length of women’s menstrual cycles by exposing women to artificial light around the middle of their cycles. The light was administered at night, while they slept, using two different sleep treatment methods: a lighted sleep mask and a bedside lamp. (Related article.)

Other groups of scientists chose to focus their efforts on the flip side of the equation: the effects of daytime light exposure on the menstrual cycle. 

A 2000 study by Wright, Myers, Plenzler, Drake, and Badia found that a combination of light and caffeine could be used to reduce melatonin in the luteal (post-ovulatory) phase of the menstrual cycle. A 2007 study published by Danilenko in Psychiatry Research reported that women receiving light therapy for seasonal affective disorder (SAD) started their periods 1.2 days earlier on average. And a study published by Danilenko and Saoilova of the Centre for Chronobiology, Institute of Internal Medicine, Siberian Branch of the Russian Academy of Medical Sciences, Novosibirsk, Russia, in 2007, reported that morning exposure to bright light in the follicular (pre-ovulatory) phase of the reproductive cycle could be used to stimulate the secretion of reproductive hormones prolactin, LH, and FSH; to promote ovary follicle growth, and to increase ovulation rates in women with “slightly lengthened” menstrual cycles. (The researchers noted that women with “very long” menstrual cycles are only slightly responsive to light exposure, a finding that suggested that “significant hormonal abnormalities are not subject to a relatively subtle intervention such as light therapy.”) The researchers highlighted the significance of their findings: “The study...shows conclusively, to our knowledge for the first time, that ovulation may be successfully potentiated by morning artificial bright light. This might be a promising method to overcome infertility in some women.” These and other similar studies led Mary Lee Barron, ARPN, BC, to conclude, in her 2007 review of the research on light and female reproductive function in the July 2007 issue of Biological Research for Nursing, “There is evidence of a relationship between light exposure and melatonin secretion and irregular menstrual cycles, menstrual cycle symptoms, and disordered ovarian function.”

These findings make perfect sense to obstetrician Robert Greene, MD, medical director of the Sher Institute for Reproductive Medicine of Northern California and author of Perfect Hormone Balance for Fertility: The Ultimate Guide to Getting Pregnant. Think of it as if your hormones were different elements on a mobile. When everything is working properly, your hormones are in a state of balance. When you have too much of any one hormone, your body functions shift as well.” The period of darkness -- when melatonin rules -- is a significant time for reproductive hormones as well, Greene adds. “The LH surge that triggers ovulation happens during this period of sleep. And 80 percent or more of women ovulate between midnight and 6 am.”

In recent years, one of the key areas of focus in light-and-fertility research has been on the hormone of darkness, melatonin.

An April 2008 study published in the Journal of Pineal Research reported that researchers at Japan’s Yamaguchi School of Medicine had discovered that melatonin had the potential to improve egg quality and fertilization rates. (Oxidative stress interferes with egg maturation; and melatonin protects eggs from oxidative stress.)

A 1999 study from the Department of Psychiatry at the University of Helsinki in Finland noted that “melatonin considered essential or both spermatogenesis [the creation of sperm] and folliculogenesis [the creation of the egg follicle].” Other studies reported that men with low sperm counts or the inability to produce sperm tended to have slow-moving sperm and higher levels of melatonin than other men; and that these high levels of melatonin could be the result of either hormonal imbalances or melatonin wearing away at the lining of the tubules that transport sperm in the testes.” The researchers concluded that bright light therapy may have a role to play in treating what is being called melatonin-dependent infertility in men.

If a man’s melatonin levels are running on empty, odds are his libido and testosterone levels may be lagging, too. Light therapy has a cure for that, as well. A 2003 study reported in Neuroscience Letters found that treating healthy men with 1000 lux (light units) of light via bright light therapy from 5 am to 6 am for five consecutive days boosted luteinizing hormone (LH) levels by 69.5 percent. LH raises testosterone levels in men and triggers ovulation in women.

Laser treatments have also proven to be a promising treatment for infertility in men. Researchers with the Queensland Fertility Group, in Brisbane, Australia, have discovered that treating prepared sperm with lasers prior to intrauterine insemination or in vitro fertilization may improve the odds of achieving a pregnancy. And, what’s more, men with discouraging sperm test results may benefit from in vivo (direct testicular) laser treatments. There’s just one small caveat: while these low-level laser therapy treatments appear to improve sperm motility, it may be at the cost of sperm longevity.

While it may seem that we’ve already entered a world of high-tech light treatments for infertility, in reality, the science is still in its infancy.

As the science of light therapy evolves evolves, fertility patients can look forward to light treatment recommendations that have been tailored to their specific needs.

“We can tailor the intensity, spectrum, timing, duration, and distribution of light,” explains Mariana Figueiro, PhD, an assistant professor at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute and the director of the Light and Health Program at the LRC. “Light has great potential to serve as a non-pharmacological treatment tool.”

It’s a treatment method whose time as come. We are, after all, living in an era when complementary and alternative therapies have gained mainstream acceptance and people are seeking holistic, less invasive treatments wherever possible.

“People are more willing to accept alternative therapies now than they were back in the 1970s,” notes Peter Breining, whose company is in the process of bringing the light therapy product Lunesse to market. (Lunesse is designed to provide the exact right dose at a particular time on a particular schedule, replicating the natural rhythm of moonlight.) “They've moved beyond a mindset of wanting a pill for everything. And many have benefited from other recent advances having to do with the study of light.”

Healthcare practitioners are also eager to discover how light can work in conjunction with traditional treatments, he adds. “Light therapies can be layered on top of other therapies.”

* * * 

So what does the new science of light and fertility mean to you? Plenty, both in terms of practical lifestyle changes you can make, starting today (or tonight); and new products you may wish to investigate as a fertility consumer.

Leading a light-friendly lifestyle

There are plenty of ways you can make the science of light (and darkness) to work for — not against — your fertility.

While you can’t turn back the clock to a time when the night skies were pitch black, and you had the time to linger in the morning sunshine for as long as your body required, there are plenty of ways you can make the science of light (and darkness) to work for  -- not against -- your fertility.

Keep your body in synch with the solar day. In practical terms, that means getting out in the daylight each morning. “Taking a half-hour walk in the morning after daybreak is a great way to cue your body that morning has arrived,” says Mariana Figueiro, PhD, an assistant professor at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute and the director of the Light and Health Program at the LRC. Here’s why: Your body doesn’t call a halt to the suppression of melatonin until approximately 10 minutes after your retina is first exposed to daylight.

Celebrate the sun. Sunlight is a free source of daylight, it’s readily available, and full of other good things (it contains an active form of vitamin D that is now believed to govern at least 1000 different genes governing virtually every tissue in the body), exposing your body to daylight (as opposed to an artificial form of light) is most fertility-enhancing. Just how powerful is the impact of sunshine on fertility? A woman’s chances of conceiving with IVF are roughly twice as high during the summer (15.7 summer vs 7.5 percent winter). Researchers at the Countess of Chester Hospital and Liverpool Women’s hospital stated that melatonin may act directly on reproductive tissues, making women more fertile during times of year when there is maximum daylight.

Get the word out: guys need sunshine, too -- and not just because they need to keep the body’s master clock in synch. A 2008 Australian study found that almost one-third of 800 men with fertility problems had lower-than-normal levels of vitamin D. The researchers concluded that concerns about sun exposure could be contributing to vitamin D deficiencies among men.

Ban blue light late at night. Can’t get yourself out of bed in the morning for that early morning walk? Being exposed to blue light late in the evening can delay the flow of melatonin, resulting in excessive sleepiness come morning. Limit your late-evening exposure to blue light (computers, TV, fluorescent light, and to a lesser degree, incandescent light). According to researchers at Researchers at John Carroll University’s Lighting Innovations Studio found that wearing blue-light blocking sunglasses during the two hours before bed allows melatonin to start flowing a little sooner. Once melatonin starts flowing, it continues to flow for approximately seven to eight hours, until the retina is exposed to enough blue light (typically in daylight) to suppress melatonin. You’ll also want to ensure that your room is dark enough to prevent unwanted light from striking your retina in the middle of the night, sending melatonin-blocking messages to your brain. See for a variety of products designed to block blue light.

If you’re working shift, pop on a pair of blue light-blocking sunglasses while you’re on your way home from work. This will prevent the early-morning light from blocking the flow of melatonin (something that would make it difficult for you to fall asleep when you arrive home from work). Unwanted encounters with bright light may help to explain why women tend to sleep approximately one hour less when working night shifts. They consistently report that it takes them longer to fall asleep. It’s worth doing anything you can to tilt the reproductive odds in your favor, if you’re working shift. 53% of women report menstrual irregularities while on shift; and sleep disturbances are known to lead to menstrual irregularities.

Give your circadian clock a break. “Avoid a lot of travel that will take you across time zones and throw your circadian clock off schedule while you’re trying to conceive,” says Figueiro.

if you have an extra-long menstrual cycle that makes it extra challenging to predict the timing of ovulation, consider purchasing Lunesse, a patented medical device that is designed to reduce the length and variability of the menstrual cycle. (“There’s a natural rhythm of light and darkness,” explains Peter Breining, whose company is bringing Lunesse to market. “But that rhythm has been interrupted by artificial light.”) Lunesse is roughly the size of a computer mouse and features a light on top. You press the light on the first night of your menstrual cycle. Each night the amount of light the product emits changes, mimicking the light emitted during the various phases of the moon. The product is based on clinical trials dating back to 1967. The initial trial was conducted by the same scientist who is credited with inventing the birth control pill. Cycle lengths of women who are exposed to light stimulation at mid-cycle at night have been found to be shorter and less variable than those not are not exposed to such light stimulation. There is a tendency for cycles to regulate at a length of 29 days (the length of the lunar cycle).

Consider purchasing a light box so that you can keep the sunshine in your life regardless of the season or your schedule and avoid what researchers call “circadian darkness” (basically living in a cave, as far as your body’s master clock is concerned). 
You might also consider such a purchase if your menstrual cycles are irregular. A 2007 study by Danilenko and Samoilova (2007) concluded that administering 4300 lux 45 minutes after wakening led to an increase in the number of ovulatory (as opposed to anovulatory) cycles. Bright light therapy is well established as a treatment for seasonal affective disorder (SAD). Prices vary according to make and model. According to the non-profit Center for Environmental Therapies, it’s important to choose a light box that has been tested successfully in peer-reviewed clinical trials; that provides 10,000 lux of illumination at a comfortable sitting distance; that features a smooth diffusing screen that filters out ultraviolet (UV) rays; that gives off white light rather than colored light; that projects light downward rather than at an angle to minimize glare; and that is large enough to do the job properly. 

Light Matters in IVF Labs, Too

Germicidal ultraviolet C (UVC) lights have a significant impact on clinical pregnancy rates. Rates increased by 18.2 percent during the test period, the 2009 annual meeting of the American Society for Reproductive Medicine (ASRM) heard. UVC degrades and abates the proliferation of airborne and surface embryotoxic organics. 

An earlier study conducted at the University of Hawaii found that even a few minutes of  exposure to the blue light in sunlight and fluorescent lighting is harmful to mice embryos. Researchers involved in the study advise clinics to use warm-white lights (which are yellow-white in color and designed to block blue light) and to keep clinic lighting at a minimum during egg collection and insemination; and while fertilized eggs are being examined prior to uterine transfer.