Using Light (Sunlight, Blue Light & Red Light) to Optimize Health

Light in Physics and Biology

• Light is electromagnetic energy
• Wavelengths of light are measured in nanometers (nm)
• Different wavelengths (colors) of light have different effects on the body

Light for Skin Health, Appearance, and Longevity

• Red light therapy can improve skin health and appearance
• Red light can stimulate collagen production, reduce inflammation, and promote wound healing
• Blue light can kill acne-​​causing bacteria and improve skin clarity

Light for Hormone Balance and Sleep Regulation

• Exposure to natural sunlight during the day can help regulate sleep and hormone balance
• Blue light in the evening can disrupt sleep and hormone balance
• Red light in the evening can promote relaxation and sleep

Light for Brain Health and Dementia Prevention

• Exposure to specific wavelengths of light can improve brain function and potentially prevent dementia
• Red light therapy has been shown to improve age-​​related vision loss by increasing ATP production in eye cells
• Brief exposures to red light early in the day can offset vision loss in people 40 years or older

Using Light Therapy in Everyday Life

• Choose the appropriate wavelength (color) of light for the desired effect
• Follow specific protocols from peer-​​reviewed literature for safe and effective use of light therapy
• Be aware of the quality of light therapy products and choose those with a strong foundation in scientific research

Live Events with Andrew Huberman

• Seattle, Washington on May 17
• Portland, Oregon on May 18
• Lecture series titled “The Brain-​​Body Contract” discussing science and science-​​based tools for mental health, physical health, and performance
• Tickets available at Hubermanlab​.com/​t​our
  Understanding Light and Its Effects on the Body
• Light as energy 
  • Electromagnetic energy that can impact other things in its environment
  • Travels in wavelengths, like sound waves
• Different wavelengths of light 
  • Visible spectrum: red, orange, green, blue, purple
  • Invisible spectrum: infrared, ultraviolet 
    • Infrared: sensed by pit vipers, emitted as heat from our bodies
    • Ultraviolet: can burn our skin, but also has positive effects (e.g., reducing pain)
• Penetration of light into tissues 
  • Longer wavelengths (red, near-​​infrared) can penetrate deeper into tissues
  • Shorter wavelengths (blue, green, ultraviolet) do not penetrate as deeply
• Absorption of light energy 
  • Different pigments/​​colors absorb different wavelengths of light
  • Absorbance properties determine whether light energy stays at a location or bounces off

Light’s Impact on Cells and Organelles

• Different wavelengths of light can penetrate and access particular organelles within cells 
  • Mitochondria: responsible for generating ATP and energy
  • Nucleus: contains DNA
• Light can be used to stimulate the function of particular organelles within cells and organs 
  • No other form of energy (sound, chemical, touch) can target specific locations in cells, organs, and the body as precisely as light can

Absorption of Light Energy

• Absorbance properties of a surface determine whether light energy stays at a location or bounces off 
  • Example: A metal table reflects more light than a black table, while a red or green table is somewhere in between
  • The color of the surface affects how much light energy is absorbed or reflected
    Biological Functions of Light
• Light is absorbed, reflected, or passes through cells or compartments within cells 
• Light is converted into biological events

Photoreceptors in Eyes

• Rods and cones in the back of the eyes 
  • Rods: elongated, absorb light of any wavelength, sensitive to low light conditions
  • Cones: absorb specific wavelengths (red, green, blue), create perception of color
• Photopigments absorb light of different wavelengths

Skin Pigmentation

• Melanin in skin absorbs UV light 
  • Melanocytes in the epidermis create skin pigmentation
  • Tanning occurs due to increased melanocyte activity in response to UV light exposure

Light Impact on Cells

• Direct impact: light on skin or photoreceptors
• Indirect impact: light on photoreceptors informing other cell types 
  • Example: light signals spleen to activate immune response to protect skin from UV damage

Light as a Transducer

• Communicates environmental information to the body
• Direct and indirect signals impact organs and tissues
• Light can impact biology rapidly or slowly

Rapid Effects of Light

• Example: sudden exposure to bright light increases alertness and adrenaline release

Slow Integrating Effects of Light

• Circannual rhythms: internal calendar based on hormone release 
  • Melatonin release from the pineal gland
  • Light activates intrinsically photosensitive ganglion cells, which inhibit melatonin production
  • Shorter days (winter) have longer melatonin release duration
  • Longer days (summer) have shorter melatonin release duration
  • Melatonin acts as a transducer, communicating light information to determine position in the calendar year
    Melatonin and Its Effects
• Melatonin: hormone produced naturally in the body 
  • Regulates sleep, bone mass, gonad function, and more
  • Affected by light exposure
• Melatonin supplementation
  • Can have various effects on the body
  • Should be used cautiously and with a doctor’s guidance

Melatonin’s Regulatory and Protective Effects

• Regulatory effects
  • Positively impacts bone mass
  • Involved in maturation of gonads during puberty
  • Can suppress maturation of ovaries and testes
  • Modulates placental development in pregnant individuals
  • Affects central nervous system, regulating sleep and wakefulness
• Protective effects
  • Activates the immune system
  • Acts as a potent antioxidant
  • Has anticancer properties

Light’s Impact on Melatonin

• Light inhibits melatonin production 
  • Bright light exposure at night can disrupt melatonin levels
  • Avoid bright light exposure during sleep cycle
  • Use dim, long-​​wavelength (red or amber) light at night to minimize melatonin disruption

Melatonin Supplementation

• Can have various effects on the body
• Should be used cautiously and with a doctor’s guidance
• Natural melatonin production varies according to time of year and light exposure
• Supplementation may not mimic natural melatonin fluctuations
  Melatonin Supplementation and Effects on Mating Behavior
• Melatonin supplementation can change the total amount and normal rhythms of melatonin release 
• Melatonin is a hormone available without prescription, which raises concerns about its use
• Melatonin suppresses the gonadal axis, inhibiting testosterone and estrogen output from testes and ovaries 
  • Both testosterone and estrogen are critical for the desire to mate and mating behavior
• Light inhibits melatonin, leading to more hormone output from the gonads during longer days

UVB Light Exposure and Hormone Production

• Study published in Cell Reports (2021) titled “Skin exposure to UVB light induces a Skin, Brain gonad Axis and Sexual Behavior”
• UVB exposure increased sex steroid levels (testosterone and estrogen) in mice and humans
• UVB exposure enhanced female attractiveness, receptiveness to mate, and fertility (follicle growth)
• Study protocol: 20–30 minutes of midday sun exposure, 2–3 times a week for 10–12 treatments 
  • Subjects wore minimal clothing, no hat or sunglasses, and were outside engaging in various activities

Psychological Changes from UVB Light Exposure

• Significant increases in hormones were observed after 10–12 UVB light exposure treatments
• Psychological changes included increased aggressiveness, passionate feelings, and perception of others
  Effects of Sunlight on Hormones and Pain Tolerance
• Sunlight exposure impacts hormones and desire to mate 
  • Study found increased testosterone and estrogen levels with sunlight exposure
  • Levels were higher during summer months (June, July, August, September)
  • Both males and females reported increased romantic passion after UV treatment
• Sunlight exposure affects pain tolerance 
  • Pain tolerance increases in longer day conditions
  • UVB exposure to skin and eyes plays a role in this effect
• Study: Skin exposure to Ultraviolet B rapidly activates systemic neuroendocrine and immunosuppressive responses 
  • One exposure to UVB light changed hormone and neurochemical output
  • Increased levels of corticotropin hormone and beta endorphins (endogenous opioids)
  • Suggests sunlight exposure may have a natural pain-​​relieving effect

Sunlight Exposure Protocol

• Aim for 2–3 exposures per week, minimum of 20–30 minutes of sunlight exposure on as much of the body as possible
• Prioritize skin health and avoid sunburn
• Sunscreen may block some effects, but its use should be balanced with the need for sun protection
• Individual tolerance for sun exposure varies; some people are more prone to skin cancers and should take precautions accordingly
  Effects of UVB Light on Endorphins and Pain Relief
• Exposure to UVB light increases the release of beta-endorphins 
  • Beta-​​endorphins are endogenous painkillers that counter physical and emotional pain
• Recent study in the journal Neuron shows that light landing on the eyes triggers anti-​​pain pathways 
  • Melanopsin cells in the eyes absorb UVB light and communicate with brain areas like the ventral lateral geniculate nucleus and the intrageniculate leaflet
  • These brain areas then communicate with the periaqueductal gray area, which releases endogenous opioids that reduce pain perception
• Previous studies showed that light exposure to the skin also reduces pain perception, but this new study shows that light exposure to the eyes plays a significant role as well

Recommendations for UVB Exposure

• Aim for 20–30 minutes of sunlight exposure 2–3 times per week 
  • Be cautious of skin sensitivity and sun intensity in different areas
• Even on cloudy days, outdoor light is more beneficial than indoor light sources 
  • Avoid looking directly at bright light sources
  • Wearing eyeglasses or contact lenses is fine, but avoid sunglasses or blue light blocking glasses during the day
• Consider clothing choices for maximizing skin exposure to sunlight
• UVB exposure throughout the year may be beneficial, especially for those with seasonal affective disorder (SAD)
  • SAD lamps or LED lighting panels can be used as an alternative light source during winter months or in areas with limited sunlight

Alternative UVB Exposure Sources

• Tanning salons provide UVB exposure to the skin, but not the eyes 
  • High UVB intensities may pose risks to skin health
    Effects of UVB Light on Eyes, Skin, and Immune Function
• UVB exposure beneficial for mood, hormone pathways, and pain reduction 
• Caution for those with retinitis pigmentosa, macular degeneration, glaucoma, or prone to skin cancers — consult with ophthalmologists and dermatologists before increasing UVB exposure
• UVB light can enhance immune function by activating spleen and immune cells 
  • Fewer colds and flus in summer months due to better immune response
  • UVB exposure important for maintaining immune system during winter months
• Wound healing is faster with sufficient UVB exposure
• Hair, skin, and nails grow faster and look better with sufficient UVB exposure to eyes and skin

Light Therapies for Skin and Mood

• Localized light therapies can help with skin issues, but systemic activation across large areas of skin and eyes is more effective
• Caution with high-​​intensity light therapies — can damage skin if intensity is too high
• Systemic effects through broad scale illumination and illumination to the eye, combined with local treatments, are likely to have the most success

Effects of Light on Mood

• Getting as much UVB light in eyes and on skin in the early day and throughout the day as safely possible is beneficial for mood
• Another time of night in which UVB can be leveraged to improve mood is the inverse of everything discussed so far
  Effects of Light on Mood and Sleep
• Neural circuit involving melanopsin cells in the eye and perihabenular nucleus in the brain 
  • Related to sleep, wakefulness, and release of dopamine, serotonin, and endogenous opioids
• UVB light exposure in the morning and throughout the day can elevate and maintain mood 
  • Avoiding UVB light at night can prevent activation of the eye to perihabenular pathway, which can cause depression
  • Avoid exposure to UVB light from artificial sources between 10:00 PM and 4:00 AM
  • Those with depression should be cautious about UVB exposure in the late evening (8:00 PM to 4:00 AM)

Light Exposure During Sleep

• Study in Proceedings of the National Academy of Sciences 
  • Human subjects slept in rooms with different lighting conditions (dim light or slightly bright light)
  • Melatonin levels not altered in either case
  • One night of sleeping in a moderately lit environment (100 lux) caused: 
    • Increases in nighttime heart rate
    • Decreases in heart rate variability
    • Increases in next morning insulin resistance
  • Light exposure during sleep disrupts autonomic nervous system function and metabolism

Low-​​Level Light Therapy (LLLT)

• Involves the use of red light and near-​​infrared light 
  • Effective for various biological phenomena and medical treatments
• Infrared light LLLT shown to be effective for treating acne and skin lesions 
  • Reduces scars and acne cysts
  • Can pass through skin layers and change metabolic function of cells
  • Initial improvement may be followed by resistance to treatment
    Sebaceous Glands and Skin Health
• Sebaceous glands produce oil in the skin 
  • Located near hair follicles
  • Can lead to acne lesions
• Melanocytes and stem cells also found in the dermis 
  • Stem cells can activate to repair damaged skin

Red Light Therapy for Skin

• Red light or near-​​infrared light can stimulate skin repair 
  • Penetrates deep into the skin without burning
  • Triggers biological pathways in sebaceous glands and stem cells
• Can help with wound healing, scar reduction, and pigmentation issues 
  • Works by activating mitochondria, increasing ATP, and reducing reactive oxygen species (ROS)

Retinoic Acid and Vitamin A

• Retinoic acid, a derivative of vitamin A, is used in acne treatments 
  • Similar biological pathway to photopigments in the eye

Red Light Therapy for Neuronal Function

• Dr. Glenn Jeffrey’s research at University College London 
  • Explores red light and near-​​infrared light for restoration of neuronal function as we age
• Red light can penetrate cells and access mitochondria 
  • Increases ATP and reduces ROS
  • Can help preserve or reverse neuronal function

Red Light Therapy Studies

• Two human studies by the Jeffrey Lab 
  • Examined how red light and near-​​infrared light can improve visual function
  • Based on the understanding of mitochondria, ATP, and ROS
• Subjects exposed to red light of about 670 nm wavelength 
  • Found improvements in visual function and reduced age-​​related decline
    Red Light Therapy for Vision Improvement
• Two studies by the Jeffrey Lab explored the effects of red light therapy on vision 
• Participants aged 40–72 years old exposed their eyes to red light for 2–3 minutes per day
• Exposure occurred at a safe distance (about a foot away) and at a low intensity that did not damage the eyes
• One study lasted 12 weeks, the other lasted a couple of weeks
• Results showed a 22% improvement in visual acuity in the 40–72 age group, specifically in the triton exam (measures short wavelength cone function)
• Red light therapy reduced reactive oxygen species and cholesterol deposits (Druzen) in the eye
• Exposure to red light needed to happen within the first 3 hours of waking
• Red light sources should be safe to look at and not too bright
• Wavelengths of 670 nm (red light) and 790 nm (near-​​infrared light) were found to be effective

Precautions and Recommendations

• Consult an optometrist or ophthalmologist before starting any red light therapy protocols
• Make sure the red light source is not too bright or painful to look at
• Commercially available red light panels may be too bright for direct eye exposure; use caution and follow manufacturer guidelines
• More research is needed to confirm the long-​​term effects and safety of red light therapy for vision improvement
  Red Light for Enhancing Neuronal Function
• Use red light within 3 hours of waking to improve neuronal function 
• Red light can also be beneficial late in the day and during the night for shift workers
• Red light does not inhibit melatonin production or increase cortisol at night

Photic Avoidance Pathway

• Protects us from too much light, which can damage our eyes and body
• Bright light triggers a headache and squint reflex, signaling us to turn away

Red Light for Shift Workers

• Study: “Red Light: A Novel Nonpharmacological Intervention to Promote Alertness in Shift Workers”
• Red light is the best choice for staying awake late at night without affecting melatonin or cortisol levels
• Use red light as dim as possible while still being able to perform necessary activities

Gamma Entrainment for Brain Health

• Gamma waves: a pattern of electrical activity in the brain that can be restorative for learning, memory, and clearing debris
• Leeway PSI and colleagues at MIT found that delivering certain patterns of light flicker (40 Hz) to the eyes can induce gamma oscillations in the brain
• This gamma entrainment can reduce amyloid plaques and phosphorylated tau, which are associated with Alzheimer’s and age-​​related cognitive decline
  Phototherapy for Cognitive Decline and Alzheimer’s
• Flashing light patterns delivered to the eyes create neuronal firing patterns in the brain 
  • Triggers molecular pathways that reduce markers and causes of age-​​related cognitive decline and Alzheimer’s
  • Upregulates biological pathways that enhance neuronal function and maintain synapses
• Non-​​invasive treatment with potential for various stimulation frequencies and wavelengths 
  • Currently being explored in clinical trials for Alzheimer’s, dementia, and other forms of neuronal degeneration
• Caution for those prone to epilepsy, as flickering lights can induce seizures

Future Phototherapy Research

• Interest in red light and other wavelength therapies for ovarian and testicular health 
  • Current rodent studies not easily translated to humans
  • Human studies hold potential but data not yet clear
• UVB light on the skin has shown promising results in increasing hormone output (testosterone and estrogen) in both men and women