red light or blue light: it makes a difference to your health


Blu Light Disease

Three short weeks ago a group of 10 researchers from the Institute of Vision at Paris’s Sorbonne University published a study in Free Radical Biology & Medicine titled Blue Light Exposure in Vitro Causes Toxicity to Trigeminal Neurons and Glia Through Increased Superoxide and Hydrogen Peroxide Generation.  Allow me to break down the abstract for you.

The authors spoke of the “noxiousness of blue light from… particularly artificial (fluorescent tubes, LED panels, visual displays)” sources, and the fact that it (blue light) is usually “discussed in the context of various ocular diseases” that have “neurologic and painful” components.  Even though the second cranial nerve (the Optic Nerve) is responsible for vision, if there is any pain in the eye, those nerve impulses are carried to the brain by the Trigeminal Nerve (Cranial Nerve Five).  Thus, the purpose of this study was to look at the “cytotoxic effects” of blue light on both the Trigeminal Nerve and supporting GLIAL CELLS.  After exposing mice to a mere three hours of blue light, they were sacrificed so that these tissues could be studied.

“Three-hour exposure to narrow wavebands of blue light… provoked cell death, altered cell morphology [structure] and induced oxidative stress and inflammation.  We observed that neurons and glial cells processed the light signal in different manner, in terms of resulting superoxide and hydrogen peroxide generation, inflammatory biomarkers expression and phototoxic mitochondrial damage….. These effects were not observed for other tested visible wavebands.Taken together, our results give some insight into the circuit of tangled pain and photosensitivity frequently observed in patients consulting for these ocular symptoms.”

What I want you to grasp is that the production of CANCER-CAUSING FREE RADICALS (the “oxides“) along with various biomarkers that are classified as INFLAMMATION, not to mention light-induced damage to the part of the cell that makes energy (THE MITOCHONDRIA), go far beyond simply causing pain.  The scariest part of this is that there are slews of similar studies hitting the journals as we speak.  Take for instance the October issue of Free Radical Biology and Medicine (Blue Light Phototoxicity Toward Human Corneal and Conjunctival Epithelial Cells in Basal and Hyperosmolar Conditions), which dealt with cancer-causing free radicals (ROS or Reactive Oxygen Species) induced by specific frequencies of blue light.  A team of seven researchers concluded thusly….

“We worked either in basal conditions or under hyperosmolar stress, in order to mimic dry eye disease (DED) that is the most common disease involving the ocular surface.  Exposure to blue wavebands significantly decreased cellular viability, impacted on cellular morphology and provoked reactive oxygen species (ROS) over-production. Conjunctival epithelial cell line had a greater photosensitivity than the corneal epithelial one. Hyperosmolar stress potentiated the blue light phototoxicity, increasing inflammation, altering mitochondrial membrane potential, and triggering the glutathione-based antioxidant system.  Blue light induced cell death and significant ROS production, and altered the expression of inflammatory genes and operation of the cellular defensive system.”

This made me curious to see how common DED is?  According to Dr Kathleen Kenny who was writing for a 2017 issue of the Pharmacy Times (Dry Eye Disease: Higher Rates in View), “A 2012 Gallup poll estimated that 26 million Americans suffer from dry eye, and this number is projected to increase by 3 million by 2022.”  She went on to say that almost half of American adults “regularly experience dry eye symptoms” as well as the fact that women have almost double the number of cases of DED as men.  Knowing that women are far more likely than men to develop AUTOIMMUNITY, we can’t be surprised at the conclusions of a 2014 issue of Eye Contact Lens (The Core Mechanism of Dry Eye Disease (DED) Is Inflammation).  “Recent progress on human DED inflammation reveal that both innate and adaptive immunity are critical to DED pathogenesis and progression, and reports strongly indicate that DED is an autoimmune disease of the ocular surface and that inflammation plays the key role in determining its progression.

A Japanese study from earlier this month in the journal Experimental Eye Research (Exposure to Excessive Blue LED Light Damages Retinal Pigment Epithelium and Photoreceptors of Pigmented Mice) looked at what LED exposure did to the light receptors of the retina.  “Ophthalmoscopy showed that blue LED exposure for 3 days induced white spots on the retina…  Exposure of pigmented mice to 3 consecutive days of blue LED light will cause RPE and photoreceptor damage. The damage led to an accumulation of macrophages and drusen-like materials around the outer segments of the photoreceptors.”  The authors concluded that this might be a factor in the number one reason for vision loss in America — macular degeneration (the macula is part of the retina). Allow me to take a few moments to show you some recent studies (past few months) on the adverse effects of too much artificial blue light, not enough red light, or getting the wrong frequency of light at the wrong time of the circadian cycle.


When it comes to overexposure to blue light (particularly later in the day), one of the chief things it does is mess up the normal sleep / wake cycles we refer to as circadian rhythms; the chief reason you’ll see numerous health-related issues related to something that the scientific literature refers to as ALAN (artificial light at night).  I’ve previously shown you how the predominance of insomnia (ONE THIRD OF AMERICAN ADULTS) is related to an over-dominance of the sympathetic (fight-or-flight) nervous system (HERE).  Today we are going to look at how it’s related to ALAN (for the record, there are numerous studies on ALAN and sympathetic activation / hyper-activation).

What are circadian rhythms (CR’s)?  Sometimes referred to as diurnal rhythms, they make up the normal 24 hour cycle of sleep and wakefulness that humans live by.  CR’s, however, are sensitive and can be disrupted by either too much or too little light, light at the wrong times, or the wrong kinds of light.  When I plugged the term “circadian rhythm” into the huge government database of biomedical research, PubMed, I came up with just shy of 75,000 studies.  One of the first things that I saw was that when it comes to circadian rhythms and health, it cuts both ways — a fact shown in last week’s study from the European Journal of Neuroscience (Circadian Disruption and Human Health:  A Bidirectional Relationship).  In other words, ill health can cause disruption of the CR, or disruption in the CR can cause ill health.

Circadian rhythm disorders have been classically associated with disorders of abnormal timing of the sleep-wake cycle, however circadian dysfunction can play a role in a wide range of pathology, ranging from the increased risk for cardiometabolic disease and malignancy in shift workers, prompting the need for a new field focused on the larger concept of circadian medicine. The relationship between circadian disruption and human health is bidirectional, with changes in circadian amplitude often preceding the classical symptoms of neurodegenerative disorders.”

In September, Chronobiology International published an overview of 128 studies on CR’s as related to MELATONIN (the ‘sleep hormone’) titled Systematic Review of Light Exposure Impact on Human Circadian Rhythm that concluded, “There is an increasing concern of the potential health and environmental impacts of light. Findings from a number of studies suggest that mistimed light exposure disrupts the circadian rhythm in humans, potentially causing further health impacts.”  Not surprisingly, too much blue light or mistimed blue light had the greatest effects on melatonin.  In another similar study (Ocular and Systemic Melatonin and the Influence of Light Exposure), this one from August’s issue of Clinical & Experimental Optometry, we saw similarities, as well as an extremely brief definition of this hormone.

“Melatonin is a neurohormone known to modulate a wide range of circadian functions, including sleep. The synthesis and release of melatonin from the pineal gland is heavily influenced by light stimulation of the retina… Melatonin is also synthesised within the eye, although to a much lesser extent than in the pineal gland. Melatonin acts directly on ocular structures to mediate a variety of diurnal rhythms and physiological processes within the eye.”

The truth is, melatonin does way more than this (look for an upcoming post on the topic).  For those who are interested, below are highlighted and cherry-picked portions from several studies on light as related to health.  Please note that blue light is not bad in and of itself, and when used at the right time of day, can be extremely beneficial.  After browsing hundreds of abstracts, my biggest takeaway was that being bombarded with blue light from a variety of artificial sources later in the day carried with it an almost unlimited number of adverse health consequences.

  • “Beyond its essential visual role, light, and particularly blue light, has numerous non-visual effects, including stimulating cognitive functions and alertness.  Analyses reveal that blue light modulates executive brain responses in both young and older individuals. These findings show that, although its impact decreases, light can stimulate cognitive brain activity in aging.”  From the November 2018 issue of Frontiers in Physiology (Plasticity in the Sensitivity to Light in Aging: Decreased Non-visual Impact of Light on Cognitive Brain Activity in Older Individuals but No Impact of Lens Replacement)


  • “Blue-enriched light caused significantly greater suppression of melatonin than standard light.  Blue-enriched light significantly improved subjective alertness.”  From the January 2019 issue of Physiology & Behavior (Randomized Trial of Polychromatic Blue-Enriched Light for Circadian Phase Shifting, Melatonin Suppression, and Alerting Responses)


  • “Differential effects of blue- and red-enriched light on attention and sleep have been primarily described in adults. In our cross-over study in adolescents (11-17 years old), we found attention enhancing effects of blue- compared to red-enriched light in the morning in two of three attention tasks: e.g. better performance in math tests and reduced reaction time variability in a computerized attention test.  Actigraphy measures of sleep indicated slight benefits for red- compared to blue-enriched light in the evening.”  From October’s issue of Physiology and Behavior (Effects of Blue- and Red-Enriched Light on Attention and Sleep in Typically Developing Adolescents)


  • “In this study, we investigated the effects of different colors of LED lighting on children’s melatonin secretion during the night.  In children, blue-enriched LED lighting has a greater impact on melatonin suppression and it inhibits the increase in sleepiness during night.”  From this month’s issue of Physiological Reports (Melatonin Suppression and Sleepiness in Children Exposed to Blue-Enriched White LED Lighting at Night)


  • “Liver cancer is the second leading cause of cancer death worldwide. Metabolic pathways within the liver and liver cancers are highly regulated by the central circadian clock in the suprachiasmatic nuclei (SCN). Daily light and dark cycles regulate the SCN-driven pineal production of the circadian anticancer hormone melatonin and temporally coordinate circadian rhythms of metabolism and physiology in mammals. In previous studies, we demonstrated that melatonin suppresses linoleic acid metabolism and the WARBURG EFFECT in human breast cancer and that blue-enriched light at daytime (bLAD) amplifies nighttime circadian melatonin levels in rats by 7-fold over cool white fluorescent (CWF) lighting. Compared with rats housed under a 12:12-h light:dark cycle in CWF light, rats in bLAD light evinced a 7-fold higher peak plasma melatonin level at the mid-dark phase; in addition, high melatonin levels were prolonged until 4 h into the light phase. After implantation of tissue-isolated hepatoma, tumor growth rates were markedly delayed, and tumor cAMP levels, LA metabolism, the Warburg effect, and growth signaling activities were decreased in rats in bLAD compared with CWF daytime lighting. These data show that the increased nighttime circadian melatonin levels due to bLAD exposure decreases hepatoma metabolic, signaling, and proliferative activities beyond what occurs after normal melatonin signaling under CWF light.”  From August’s issue of Comparative Medicine (Effect of Daytime Blue-enriched LED Light on the Nighttime Circadian Melatonin Inhibition of Hepatoma 7288CTC Warburg Effect and Progression)


  • “Several population-level studies revealed a positive association between breast cancer (BC) incidence and ALAN exposure. We investigated a possible link between BC and ALAN of different subspectra using a multi-spectral year-2011 satellite image, taken from the International Space Station, and superimposing it with year-2013 BC incidence data available for the Great Haifa Metropolitan Area in Israel. Spatial dependency models confirmed only a positive association between BC incidence and short-wavelength (blue) ALAN subspectrum while reporting insignificant associations between BC and either green or red subspectra. The obtained result is in line with the results of laboratory- and small-scale cohort studies linking short-wavelength nighttime illumination with circadian disruption and melatonin suppression.”  From September’s issue of Chronobiology International (Population-Level Study Links Short-Wavelength Nighttime Illumination with Breast Cancer Incidence in a Major Metropolitan Area)


  • “Lesion to the retinal pigment epithelium (RPE) is a crucial event in the development of age-related macular degeneration (AMD), the leading cause of blindness in industrialized countries. Tobacco smoking and high-energy visible blue (HEV; 400-500 nm) light exposure are major environmental risk factors for AMD. Individually, they have been shown to cause damage to the RPE. Tobacco smoke contains toxic polycyclic aromatic hydrocarbons (PAH) that can accumulate in RPE and which absorb HEV light.  Using mitochondrial network morphology changes and key features of AMD-related RPE defects such as cell death and oxidative stress, we demonstrate that a synergistic phototoxicity is generated when nanomolar concentrations of IcdP interact with HEV light. Indeed, we found IcdP to be at least 3,000 times more toxic for RPE cells when irradiated with HEV light.”  From Last month’s issue of Archives of Toxicology (Absorption of Blue Light by Cigarette Smoke Components is Highly Toxic for Retinal Pigmented Epithelial Cells)


  • “Sleep is crucial for recovery and skill acquisition in athletes. Paradoxically, athletes often encounter difficulties initiating and maintaining sleep.  Blue (short-wavelength) light as emitted by electronic screens is considered a potential sleep thief, as it suppresses melatonin secretion. Fifteen recreational athletes, between 18 and 32 years (12 females, 3 males), were randomly assigned to start the intervention period with either the light restriction condition (LR; amber-lens glasses), or the no-light restriction condition (nLR; transparent glasses). Results indicate that blocking short-wavelength light in the evening, as compared to habitual light exposure, significantly shortened subjective sleep onset latency, improved sleep quality, and increased alertness the following morning.  Blocking short-wavelength light in the evening by means of amber-lens glasses is a cost-efficient and promising means to improve subjective sleep estimates among recreational athletes in their home environment.”  From the November issue of the European Journal of Sports Science (Restricting Short-Wavelength Light in the Evening to Improve Sleep in Recreational Athletes – A Pilot Study)

With over a hundred thousand studies on light, melatonin, and circadian rhythms as related to health, I could keep going into the next century and still never get to the end.  Honestly, pick a topic and I can almost guarantee that someone did a study to see if it was affected by light.  There were numerous studies on nutrition as related to light (mostly what you would expect).  I found studies using light to kill off the BIOFILMS of various INFECTIONS, including CANDIDA.  I even found a study linking too much electronic blue light exposure to advanced aging of one’s skin.  And while the study using an electric toothbrush outfitted with LED’s to better-fight tartar and plaque buildup was certainly cool, I would guess this could likewise foul the ORAL MICROBIOME.

The real question on the table is what can the average person do to combat light-related problems?   Prior to the advent of artificial light, this was a non-issue (unless you were a miner) — no artificial lights and nothing but SUN EXPOSURE during the day.  Unfortunately, the amount of blue light the average person is being exposed to today — especially during the latter part of the day and evening —- is both crazy and probably increasing.  Fortunately there are some steps you can take to tip the balance in your favor. 

For one, get out and get in the sun when you can (see previous link) because there are benefits that go far beyond Vitamin D.  Secondly, although it’s cliche, limit screen time — especially in the evening.  Thirdly, when we choose to ignore the previous sentence, inexpensive blue-blocking filters are readily available for your TV, computer, phone, I-pad, etc.  And lastly (and maybe most importantly), as seen in the study in the last bullet point above, wearing blue-blocking glasses at certain times and for certain portions of the day can have huge positive impacts.  Highly rated glasses range in price from eight bucks on Amazon to in excess of 200 dollars.  Which one is the best?  Depends on who you ask.

Sleep is critical for the proper function of virtually every bodily function; especially anything to do with healing, repair, or regeneration.  Face it; if you are not sleeping, you are going to have a tougher row to hoe as far as solving chronic illnesses and / or chronic pain are concerned. This is why using light to your advantage is an integral portion of the protocol I give many of my patients for the express purpose of helping them diminish high levels of systemic inflammation (HERE).  Also; if you are enjoying our site, be sure and tell others about it so that they can enjoy it as well.  FACEBOOK is still a great way to reach those you love and care about most.

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