Using Light to Optimize Health

These are my notes from The Huberman Lab Podcast episode #68. I am a BIG fan of Dr. Huberman and his podcast.

I thought this was going to be the classic “get sunlight in the day and avoid lights at night” but, as always, Dr. Huberman did an excellent episode explaining the Neurobiology of Light, how it affects our mood, our sleep, our sexual behavior, our tolerance for pain and much more.

There are very useful tools that can enhance immune system, delay cognitive decline and even help protect the cells responsible for vision.

Physics of Light

• Light is electromagnetic energy. Energy has an impact on other things in its environment: it causes reactions.
• Light travels in wavelengths, and there’s energy at all these wavelengths.

Different wavelengths can penetrate tissues to different depths.

• Longer ones (red light) have the ability to penetrate thru tissue.
• Short ones don’t penetrate tissue.

Light would be the sharpest and precise surgical tool to modulate our biology.

Absorption of light energy.

Certain pigments in the thing that is receiving the light energy are going to absorb particular wavelengths of light.

The absorbance properties of a given surface will determine whether or not light energy goes and stays at that location or it bounces.

In the back of our eyes we have Photoreceptors. Two types of photoreceptors reside in the retina: cones and rods. The cones are responsible for daytime vision, while the rods respond under dark conditions. Rods absorb light of any wavelength and are very sensitive. The cones come in three varieties: L, M, and S types (for long, middle, and short wavelength).

Skin has pigment too (melanin). In the epidermis we have melanocytes (cells that create pigmentation with the skin).

The ways in which light can impact the body can be direct or indirect. But in every case it starts with how the different wavelengths of light are absorbed.

Light communicates what’s going around us. The signals arrive at the surface of the body (photoreceptors and melanocytes) and pass that information to other organs of the body.

Circannual Rhythms and Melatonin

Melatonin is a hormone that your brain produces in response to darkness. It helps with the timing of your circadian rhythms (24-hour internal clock) and with sleep. It has two type of effects:

Regulatory effects: melatonin impacts bone mass and reduces gonads. High levels of melatonin tend to reduce testicle volume and suppress the maturation of eggs in women. Melatonin impacts how wake or asleep we are.

Protective effects: melatonin is a potent antioxidant. It can activate the immune system. (Not meaning that we want more melatonin. The rise and fall of melatonin is what causes this immune effect).

Light activates a cell that shuts down the production of melatonin.

In short days, the duration of melatonin release will be much longer.

In long days, we receive more light so the duration of melatonin release will be shorter.

Dr. Huberman is skeptical about melatonin supplementation. They can change the rhythms in the release of melatonin throughout the cycle.

Get Sunlight

Get outside as much as possible in summer days.

Changes in melatonin across the year are normal and healthy.

Light powerfully inhibits melatonin. Don’t turn on bright lights at night.

If you are going to use light at night, use long wavelength lights (red light, dim red light). The photosensitive cells within the retina that convey the signal about bright light that shut down melatonin respond to short wavelengths of light.

Light and Sexual Behavior

There is more mating behavior in longer days of the year. Why and How?

• Via the way of Melatonin, which inhibits testosterone and estrogen output, which are critical for the desire to mate.
• Via the way of Exposure to UV Blue light in the skin, which increases testosterone and estrogen and the desire to mate. The skin is an endocrine organ, meaning it influences and produces hormones. UVB can also increase female attractiveness and can change female fertility, by enhancing maturation of the follicle (more healthy eggs produced).

Study: humans doing 20–30 minutes of Mid-day UVB light exposure 2 or 3 times a week showed:

• Increases in testosterone and estrogen, desire to mate, and romantic passion.

Tool: Skin Exposure

2–3 exposures a week of 20–30 minutes a day with minimum clothing.

Light to Increase Tolerance for Pain

Tolerance for pain increases in longer day conditions.

The periaqueductal gray releases endogenous opioids.

Light landing on the eyes communicate with particular brain areas and then it communicates with the periaqueductal gray which releases opioids and reduces pain and increases our tolerance.

Light to Enhance Immune function

With more UVB exposure, spleen and immune function are enhanced.

UVB light arriving on the eyes activates the sympathetic nervous system and our spleen deploys immune cells.

So during the winter months we need the UVB light exposure to avoid colds and infections.

Light & Mood

Perivenular nucleus gets input from the cells that receive light, and if it is activated in the wrong times mood gets worse.

UVB exposure in the day enhances mood, but during night is detrimental. Specially between 10pm and 4am. It can turn on depression.

Study: Even just one night of dimly lit environment caused changes in Heart Rate, decreases in Heart Rate Variability (which is good) and increases in next morning insulin resistance (glucose management worsens). Even if you are asleep, because light can impact you with your eye lids closed! So light at night disrupts cardiac function and metabolism.

Red Lights and Infrared lights

Low-level light therapies: use of red lights and infrared lights.

LLLT is effective for ACNE and skin lesions. How?

Red light can pass into the deeper layers of the skin where it can change the metabolic function of particular cells. By shining red light in the appropriate amount the top layers of the skin are burned off and the cells in the deeper layers start to churn out new cells which go and rescue the lesion and replace it with healthy skin cells.

Long wavelength light can get deep into the skin and into individual cells and access the organelles (the mitochondria responsible for producing ATP). As cells age, they accumulate ROS (reactive oxygen species) & ATP tends to go down.

Red light passes into the deeper layers of the skin, activates mitochondria, increases ATP, and reduces ROS (which cause cellular death).

Infrared sauna don’t get hot enough to trigger the positive effects of Saunas, and it is not clear at all that they are beneficial.

Infrared Light for Vision Loss

In the neural retina we don’t generate any new cells after the time in which we are born. So it is essential to keep those cells healthy.

The goal of any treatment is going to increase ATP and reduce ROS.

Study: red light showed improvement in visual function (acuity).

As we age we lose certain neurons, but not cones.

Because rods and cones are the most metabolically active cells in the body, these cells tend to accumulate a lot of ROS. Red light is able to reduce the amount of ROS of rods and cones.

Viewing red light for a couple of minute can reverse aging of these neurons.

If you are under 40 it’s unlikely that this will be helpful.

TOOL: Exposure to red light

Exposure to red light need to happen early in the day.

How to do this?

Red Light panel or create your own red light source.

Rule of thumb: if it’s painful to look, it’s too bright. Don’t do it.

Look at these panels for 2–3 minutes.

The studies show that approx. 700 nanometers enhance neuronal function.

Red Light at Night

For shift workers red light can be very beneficial. If you need to be awake, red light is going to be your best choice. Useful for shift workers or for pulling an all-nighter. It does not alter melatonin or cortisol production.

Light Flicker Phototherapy

Light can be delivered in the eyes to change global patterns of firing of neurons in the brain.

Gamma activity: wavelength activity in the brain that can be restorative of certain aspects of learning and memory and help create molecular changes in neurons that lead to clearance of debris and reductions in age-related cognitive decline.

TOOL: How to induce gamma oscillations? By delivering certain patterns of light flicker the brain as a whole starts to match the patterns of that flicker, even though the brain areas are not directly within the visual pathway.

Frequency: 40 hertz

GENUS (Gamma entrainment using sensory stimulation) effects: reduce amyloid plaques and phosphorylated tau, which are related to Alzheimer's and cognitive decline.

I hope you found this useful, but I still highly recommend watching the entire episode.

I post these notes for every Huberman Lab episode. If you liked it, please feel free check out the ones that are already published as well.

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