Is Your Nightlight Making You Fat and Unhealthy?

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Is Your Nightlight Making You Fat and Unhealthy?

30 April 2014 by VRP Staff in Sleep Newsletter 2014 Newsletter 2014 May Newsletter - No Comments

By Chris D. Meletis, N.D.

Electric lighting is both a blessing and a curse. It allows us to be more productive after sunset. But it also has a darker side. Exposure to light at night may have a role to play in the health concerns you’re battling at this very moment—not to mention make you more likely to develop other diseases in the future.

Most life on earth evolved under bright days and dark nights. So we have developed circadian rhythms synchronized to this daily light/dark cycle. However, in the last 100 years, humans have shifted away from the naturally occurring solar light cycle in favor of artificial lighting at night. Artificial lighting at night suppresses your nocturnal production of the hormone melatonin—and when melatonin levels plunge, your health may suffer.

For starters, nighttime light exposure has been linked to several forms of cancer. That means flipping the switch in the middle of the night may prove to be a deadly habit.

But cancer isn’t the only disease linked to light at night. In fact, light at night may be the reason why your weight loss efforts haven’t born fruit no matter how much sugar or fat you cut from your diet.

In this article, I’ll also touch upon the many ways nighttime light exposure may harm your health. And I’ll offer some suggestions on how you can keep yourself and your loved ones “in the dark.”

Accelerating Aging

In animal studies, exposure to light at night sped up the aging process at the same time as it triggered the development of other diseases such as cancer. Exposure to constant light shortened life span both in male and female rats as compared to rodents that were not exposed to light at night. The constant light also accelerated development of metabolic syndrome—a cluster of risk factors for heart disease—and increased the spontaneous development of tumors.¹

Another study by some of the same researchers using mice instead of rats also found that constant artificial and natural light accelerated the age-related switch-off of reproductive function in the female animals. Melatonin given in nocturnal drinking water prevented the damage done by constant illumination.²

Boosting Breast Cancer Risk

Exposure to light at night also increases your risk of many forms of cancer. The research is strong enough that the International Agency for Research on Cancer classified shift work as a “probable human carcinogen, 2A.”³

Some of the most convincing research exists on how nighttime light affects breast cancer development. Studies have documented an increased breast cancer risk among female night-shift workers.⁴ There’s also strong evidence from rodent studies connecting light at night to breast cancer.⁴

Two reviews of the medical literature published in 2004 and 2008 found a 36 to 60 percent higher rate of breast cancer risk in night-shift workers.^5-6

And the disturbing news keeps pouring in. A more recent study published in April 2013 investigated the incidence of breast cancer in Georgia. The researchers conducted the study among 34,053 breast cancer cases and 14,458 lung cancer patients. The scientists used satellite images to estimate light-at-night levels.

High exposure to light at night was associated with overall breast cancer incidence. When the researchers separated their results by race, light-at-night exposure was associated with increased breast cancer risk among whites—but not among blacks.⁷

In another study published later that same year, scientists explored whether night-shift work was associated with either estrogen-receptor positive or estrogen-receptor negative breast cancer. Exposure to light at night depletes melatonin—a hormone that has anti-estrogenic properties—and the researchers theorized that the drop in melatonin that occurs after exposure to light at night might alter the estrogen receptor.

The study found that night work for 20 years or more was associated with a significantly elevated risk of estrogen-receptor negative breast cancer.⁸

In a 2012 policy statement on the harmful effects of light at night, the American Medical Association wrote, “The human evidence is also accumulating, with the strongest epidemiologic support for a link of circadian disruption from light at night to breast cancer.”⁹

Not only does exposure to light at night impact estrogen levels by reducing the nocturnal melatonin surge—it also may increase breast cancer risk by disrupting the expression of genes involved in breast cancer.¹⁰

One of these genes is called Period2 (Per2). Exposure to light at night reduces the expression of Per2, which increases breast cancer tumor growth rates. On the other hand, overexpression of Per2 is thought to suppress tumors.^11-13

Men Are at Risk Too

Light at night may boost a man’s chances of developing prostate conditions. For example, expression levels of Per2 are significantly lower in all prostate diseases compared with normal prostate tissue.¹⁴

Several studies also specifically have linked light at night with prostate cancer. One study compared incidence rates of prostate, lung and colon cancer among men residing in 164 different countries. Only prostate cancer was significantly linked to light-at-night exposure and per capita electricity consumption. Exposure to light at night was associated with a 30 to 80 percent increase in prostate cancer, depending on the intensity of light exposure.¹⁵

Researchers also have found an increased risk of prostate cancer—anywhere from 10 to 50 percent—among men who make their living in occupations associated with nighttime light exposure including public safety workers, waiters, firefighters and policemen.^16-19

The Skin Cancer Connection

By reducing melatonin levels, exposure to light at night could also increase your risk of skin cancer. Melatonin reduced the development of tumors both in animal experiments and in cell culture studies.^20-22

Animal experiments have shown that melatonin also plays some roles in skin health such as hair growth, fur pigmentation and melanoma control. Melatonin protects against ultraviolet (UV) damage to skin cells and acts as a strong antioxidant on UV-exposed cells.²³

The story is much the same in humans. In 70 patients with skin cancer (55 with basal cell carcinoma and 15 with squamous cell carcinoma) and 70 healthy controls, researchers measured the mean level of 24-hour urine 6-sulfatoxymelatonin, which is the principal breakdown product of melatonin. 6-sulfatoxymelatonin was significantly higher in the control group.²⁴

The researchers concluded, “It seems that a low level of 24-hour urinary 6-sulfatoxymelatonin renders human beings prone to skin cancer. This association, however, requires further investigation.”

Do Night Owls Weigh More Than Morning Doves?

Light at night may be belly fat’s best friend. Exposure to light at night is strongly linked to weight gain, as well as the development of metabolic syndrome, a cluster of risk factors for heart disease including the build up of visceral fat in your abdomen.

One study looked at 528 elderly people. Researchers measured the intensity of light at night in the bedroom at one-minute intervals during two consecutive nights. They also measured overnight urinary melatonin excretion.

Compared to the subjects whose rooms were the darkest, the subjects who were exposed to the most light at night had significantly higher body weight, body mass index, waist circumference, triglyceride levels and low-density lipoprotein (LDL) cholesterol levels. The subjects exposed to the most light also had significantly lower levels of the “good” cholesterol, high-density lipoprotein (HDL). The cholesterol levels seemed to have nothing to do with the urinary melatonin excretion, which means light at night may damage our health by other means beyond lowering melatonin.²⁵

What’s more, exposure to light at night makes the harmful effects of a high-fat diet even worse.²⁶ Plus, melatonin regulates brown fat tissue,²⁷ which snatches calories away from normal fat and helps burn off the calories.

Another reason why the glow from the streetlight spilling into your bedroom window may not help you look your best in your swimsuit has to do with imbalanced cortisol levels.²⁸ Cortisol is a stress hormone also linked to weight gain. Nighttime light wreaks havoc on other hormones too. Levels of the hunger hormone leptin become imbalanced, meaning you’re more likely to crave unhealthy food.²⁹

Another Danger of Shift Work

The news isn’t good for diabetes either. Some studies have reported diabetes occurs more often in shift workers. In a study of shift work in female nurses, diabetes occurred more often in the women who had worked rotating night shifts the longest. The subjects who had worked rotating night shifts for 15 or more years had a 5.6 percent prevalence of diabetes compared to 3.2 percent in subjects who worked rotating night shifts for one to two years.³⁰

Damaging the Immune System

Exposure to light at night does as much damage to your immune system as it does to your weight loss goals. In one study, researchers exposed Siberian hamsters to dim light (5 lux) throughout the night for four weeks. This level of lighting is approximately five times brighter than bright moonlight and is comparable to light levels in areas surrounding urban centers. This level of light also has been found to lower melatonin in hamsters.

Four weeks of exposure to light at night was enough to reduce immunity and the ability to kill bacteria.³¹

Other studies have shown light at night suppresses immune function in Japanese quail,³² cockerels³³ and rats.³⁴

The pineal gland in the brain and melatonin play an important role in immunity. Evidence from the last few decades shows the immune system can make melatonin.³⁵ Melatonin is found in a variety of immune tissues, organs and cells from rats, mice and humans, including the thymus, spleen and immune cells known as natural killer cells.³⁵

Bright Lights, Dark Moods

Exposure to nighttime light may be one of the reasons why so many people are suffering from depression. Many animal and human studies have confirmed the connection between bright lights at night and dark moods.^36-38

For example, researchers measured the intensities of nighttime bedroom light and daytime light along with overnight urinary melatonin excretion in 516 elderly people (mean age, 72.8). The scientists measured depressive symptoms using the Geriatric Depression Scale. Of the total subjects, 101 were depressed.

Light-at-night exposure (average intensity, 5 or more lux) was significantly more common in the depressed group compared with the non-depressed group. More of the depressed group was exposed to light that was 10 lux or more for 30 minutes or more per night compared to the non-depressed group. Urinary melatonin excretion was not significantly associated with depressive symptoms.³⁹

Nighttime Light and Your Heart

Melatonin secreted by the pineal gland of the brain plays an important role in the regulation of blood pressure (BP), and melatonin administration reduces hypertension both in animals and humans. Continuous 24-hour exposure to light is known to cause melatonin-deficient hypertension as well as cardiovascular and kidney dysfunction.⁴⁰

In humans, the nighttime rise in circulating melatonin levels may reduce nighttime blood pressure. Some hypertension patients have a much greater reduction in blood pressure at night. These patients are called “extreme dippers” and “dippers.”

In other patients with high blood pressure—the “non-dippers” and “inverted dippers”—there is only a slight fall in nighttime systolic and diastolic pressure. Studies of these patients show that inverted dippers and non-dippers die at a faster rate than do dippers and extreme dippers.

The nightly administration of melatonin to hypertension patients causes a measurable drop in nighttime systolic and diastolic blood pressure. Additionally, the higher the nighttime level of naturally occurring melatonin in the body, the greater the reduction in arterial blood pressure at night.⁴¹

The researchers concluded, “The implication of these findings is that melatonin may have utility as an antihypertensive agent.”

Furthermore, night-shift work is related to cardiovascular disease overall. In one review of the medical literature that evaluated 17 studies on shift work and cardiovascular disease, researchers concluded that shift workers had a 40 percent greater risk for cardiovascular disease compared with day workers.³⁰

Light-at-Night and Sleep Apnea: A Destructive Combination

Obstructive sleep apnea (OSA) and exposure to light at night are both destructive in their own right. But when people who have sleep apnea expose themselves to light late at night, the combined effect might be even more destructive.

People who have obstructive sleep apnea stop breathing in their sleep, which causes their oxygen levels to drop. OSA is linked to both high blood pressure and cardiovascular disease. Researchers studied the additive effects of OSA and exposure to dim light at night in rats exposed to low oxygen levels (hypoxia). Exposure to both dim light at night and intermittent hypoxia for three weeks increased anxiety-like behaviors in the animals.

Dim light at night and intermittent hypoxia also caused the animals to behave in a depressed way. In addition, intermittent hypoxia reduced learning and memory performance. Hypoxia combined with dim light at night resulted in damage to the brain region known as the hippocampus.⁴²

The researchers believe these results suggest that if you have sleep apnea, limiting nighttime exposure to light in combination with other established treatments may be especially effective.

Other Ways Light at Night Damages Health

Research has linked light-at-night exposure to Alzheimer’s disease,⁴³ gastrointestinal disorders such as peptic ulcer disease in shift workers³⁰ and altered menstrual cycles in nurses working night shifts.⁴⁴ Researchers also have linked shift work with pre-term births and low birth weights.³⁰

Dangers of Blue Light

In our modern society, we are exposed to many sources of blue light well into the night. Cell phones, computers, e-readers and CFL light bulbs are all sources of blue light. White light also contains blue wavelengths. Cells in our eyes are highly sensitive to blue light and less sensitive to red light.³⁷

Looking at sources of blue light just before bed or in the middle of the night is especially harmful—and very likely to cause many of the health problems mentioned in this article.

In fact, as this report from WBTV News in Charlotte, NC shows, the use of devices before bedtime is especially concerning when it comes to our children.

Keeping Yourself “In the Dark”

Obviously, the best solution would be to sleep in total darkness and avoid nightlights in the bathroom. If you have insomnia or are a shift worker, this isn’t always possible.

If you have insomnia, it’s critical to have your doctor test you for sleep apnea. This is even more important if you have hypertension, due to the strong link between hypertension and sleep apnea.

If you do have sleep apnea, proper treatment with a continuous positive airway pressure (CPAP) device may help you sleep through the night.

Relaxation CDs/MP3s can also help you get reacquainted with the sandman. The relaxation CDs from the Immrama Institute are a good choice.

For insomniacs and shift workers, melatonin supplementation can help resynchronize your body after disruptions to your circadian clock.⁴⁵ It’s also been shown to improve sleep in human subjects, including a group of hypertensive patients on beta blockers, blood pressure drugs known to cause insomnia.⁴⁶

Valerian is another option. Studies in humans have shown valerian can improve the quality of sleep.⁴⁷

Shift workers also may benefit from a nap during their shifts. One study in premenopausal nurses working the night shift found that nurses who took a nap during their shift experienced less of a disruption of estrogen levels compared to night-shift nurses who didn’t nap.⁴⁸

If you’re not a shift worker, try to go to bed by 10 p.m. on most nights. If that seems impossible, shoot for 11 p.m. An hour before bed, avoid using your cell phone, computer and e-reader.

When you do go to bed, keep your room as dark as possible at night. If there is any light spilling into the room from outdoors, try a facial mask or blackout curtains. When you get up to go the bathroom in the middle of the night, try to keep the lights off.

Finally, you may want to use a grounding pad on your bed. Grounding is based on the concept that electrons in the earth can act as antioxidants. Most people have no contact to the earth, since we no longer walk barefoot or sleep on the ground. Studies where patients have used a grounding pad to ground them to the earth have noted improved sleep in the subjects and a reduction in sleep apnea.⁴⁹

A Dark Bedroom Equals a Healthy Body

Exposure to light at night is something we take for granted. In this fast-paced world, sometimes night is the only time we’re able to get our chores done. It’s not easy to go to bed early. But with all the research connecting nighttime light exposure to some of the worst diseases of our time, flipping off the lights as early as possible may be one of the most important actions you can take to achieve vibrant health and well-being.

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