#286 ‒ Journal club with Andrew Huberman: the impact of light exposure on mental health and an immunotherapy breakthrough for cancer treatment
Peter Attia and Andrew Huberman, professor of neurobiology at Stanford University, discuss how light exposure impacts mental health and the groundbreaking role of immune checkpoint inhibitors in cancer therapy. They also share insights on critically evaluating scientific research.
Deep Dive Analysis
18 Topic Outline
Introduction to Journal Club and Reading Scientific Papers
Andrew Huberman's Paper: Light Exposure and Mental Health
Seasonal Affective Disorder and Bright Light Therapy
Biological Mechanisms of Light Perception and Mood Regulation
Types of Light Exposure for Optimal Health
The Importance of Dark Exposure at Night
Study Findings: Day and Night Light Exposure and Psychiatric Disorders
Statistical Analysis and Clinical Relevance of Findings
Practicalities of Optimizing Light Exposure and Minimizing Nighttime Light
Limitations of Observational Studies: Reverse Causality
Peter Attia's Paper: Immune Checkpoint Inhibitors in Cancer Therapy
Primer on the Immune System and Cancer Evasion
Mechanism of Immune Checkpoint Inhibitor Therapy
Clinical Trial Design and Patient Population for Ipilimumab
Results of the Ipilimumab Trial: Overall Survival and Subgroup Analysis
Adverse Effects of Immune Checkpoint Inhibitors
Why Melanoma Responds to Immunotherapy and Future Hopes
Preventing Melanoma: Sunburn and Sunscreen Considerations
9 Key Concepts
Melanopsin Retinal Ganglion Cells
These are intrinsically photosensitive cells in the neural retina that respond to two types of light input (bright light and color contrast) and send signals to the master circadian clock in the hypothalamus, as well as directly to brain areas controlling mood. They are low-resolution, interested in ambient light, and primarily gather light from above.
Circadian Dead Zone
This refers to the middle of the day and the middle of the night when bright light exposure cannot effectively shift the circadian clock. While bright light in the middle of the day can still increase mood, it won't anchor the sleep-wake cycle, and light at night can still provide a wake-up signal despite not shifting the clock.
Odds Ratio
A statistical measure representing the probability of an event occurring in one group divided by the probability of it occurring in another group. It typically refers to a lifetime exposure and indicates the increased or decreased chance of an outcome in the affected group compared to the reference group.
Hawthorne Effect
This phenomenon describes how people change their behavior when they know they are being observed. It suggests that tracking devices or monitoring can influence individuals to modify their actions, such as eating habits or sleep patterns, to achieve better outcomes.
Reverse Causality
In observational studies, reverse causality occurs when the assumed cause-and-effect relationship is actually inverted. For example, instead of diet soda causing obesity, obesity might lead to the choice of diet soda, making it difficult to determine the true direction of influence.
MHC Class Receptors
Major Histocompatibility Complex (MHC) receptors are proteins on cell surfaces that present small peptides (antigens) to T cells. MHC Class I presents endogenous peptides (from inside the cell, like viral proteins or cancer mutations) to CD8 killer T cells, while MHC Class II presents exogenous peptides (from outside the cell).
Immune Checkpoint Inhibitors
These are a class of drugs that block 'brakes' on the immune system, such as CTLA-4 or PD-1 receptors on T cells. By blocking these checkpoints, the drugs 'unleash' the T cells, allowing them to more effectively recognize and attack cancer cells that present foreign antigens.
Kaplan-Meier Survival Curve
A graph used in medical research to estimate the survival probability over time for a group of patients. The x-axis represents time (e.g., in months), and the y-axis represents the overall survival percentage, with curves monotonically decreasing as patients die or are censored from the study.
Warburg Effect
This describes the phenomenon where cancer cells primarily use glycolysis for energy production, even in the presence of oxygen. While initially thought to be due to defective mitochondria, it is now understood that cancer cells prioritize generating cellular building blocks for rapid division over energy efficiency, and also that the resulting lower pH can help cloak them from the immune system.
8 Questions Answered
On a sunny day at noon with minimal cloud cover, the sun can provide over 100,000 lux, potentially up to 300,000 lux. Most brightly lit indoor environments, even department stores, are only around 4,000 to 6,000 lux maximum.
In general, unless light is coming directly through the window, most of the relevant wavelengths are filtered out by glass. The neurons in the eye that signal the circadian clock primarily gather light from above and require direct exposure.
Viewing low solar angle sunlight at sunrise phase advances the clock, making one want to go to bed and wake up earlier. Viewing low solar angle sunlight in the evening phase delays the clock, making one stay up and wake up later. Both are important to keep the clock stable.
It is generally better to get morning light, as the retina is less sensitive to light early in the day and requires more photons to trigger the mechanism. Evening light exposure can partially offset negative effects of artificial light at night.
For people with bipolar disorder, light exposure at night is especially problematic for exacerbating symptoms, independent of daytime sunlight. Darkness for eight hours every night is suggested as a beneficial practice for managing bipolar symptoms.
A brightly lit full moon night is typically less than 100 lux. Candlelight ranges from 50 to 400 lux. A phone screen at maximum brightness, held at a typical distance, can be around 500 to 1000 lux.
Cancer cells employ various strategies to trick the immune system, including secreting inhibitory factors (like IL-10, TGF-beta), creating an acidic microenvironment through glycolysis (Warburg effect) that deters immune cells, and leveraging immune checkpoints to tamp down T cell responses.
Melanoma is one of the cancers with a significantly higher number of genetic mutations compared to most other solid tumors. This increased mutation load means there's a greater likelihood of producing antigens recognizable by the immune system, making it particularly responsive to immunotherapies like checkpoint inhibitors.
28 Actionable Insights
1. Prioritize Nighttime Dark Exposure
Make a point to get dark exposure at night (absence of light), as this is important for mental health outcomes, even if daytime sunlight exposure is insufficient. This practice is especially beneficial for individuals with certain mental health issues.
2. Optimize Daily Light Exposure
Strive to view low solar angle sunlight early in the day and again later in the day, and get as much bright light from sunlight as safely possible throughout the day. If natural sunlight is not consistently available, consider investing in a high-quality sunrise/evening simulator.
3. Get Morning Sunlight Exposure
On non-cloudy days, aim for at least 10 minutes of sunlight in your eyes in the early part of the day. This practice helps set your circadian clock and is correlated with elevated mood.
4. View Evening Low-Angle Sunlight
View low solar angle sunlight in the evening as often as possible to phase delay your circadian clock, which helps you stay up a little later and wake up a little later. This can also partially offset the negative effects of artificial light exposure at night.
5. Dim Evening Lights, Lower Fixtures
In the evening, dim your lights and ideally use lights that are set lower in your environment, avoiding overhead lights. This helps minimize disruptive light exposure and supports your circadian rhythm.
6. Avoid Sunglasses Early/Late
Avoid wearing sunglasses in the early and later parts of the day, unless driving into the sun for safety reasons. This allows sufficient photons to reach your eyes, which is crucial for circadian rhythm regulation.
7. Avoid Daytime Blue Blockers
Do not wear blue blockers in the middle of the day, as this is considered detrimental. Necessary daytime light signaling is interfered with by blocking blue light during these hours.
8. Darkness as Bipolar Treatment
For individuals with bipolar disorder, ensure eight hours of darkness every night. This is considered a crucial treatment, as nighttime light exposure significantly exacerbates bipolar symptoms, independent of daytime light.
9. Manage Nighttime Screen Content
Be mindful of the content you consume on screens at night, as the emotional or mental stimulation from stressful content can be more disruptive to sleep and well-being than the light itself. Prioritize relaxing content if using screens before bed.
10. Don’t Check Time at Night
If you wake up in the middle of the night, avoid looking at what time it is. This can be very disruptive to your ability to fall back asleep and negatively impact your perceived energy levels the next day.
11. Boost Morning Cortisol Spike
View bright sunlight in the morning to increase the amplitude of your morning cortisol spike, which is beneficial. A higher morning spike is inversely related to evening cortisol, reducing middle-of-the-night waking.
12. Outdoor Light Over Window Light
Do not rely on light coming through standard windows for circadian rhythm regulation, as most relevant wavelengths are filtered out unless the sun is directly visible. Skylights are an exception as they allow more effective light exposure from above.
13. Prioritize Morning Low-Angle Light
If you have to choose between viewing low solar angle light early or later in the day, prioritize the morning light. If you miss a day, aim to get twice as much light the next morning, as it’s a slow, integrative mechanism.
14. Evening Sun Offsets Night Light
Viewing afternoon and evening sunlight can partially offset the negative effects of artificial light exposure at night, halving melatonin suppression. Consider this a ‘Netflix inoculation’ to mitigate harm from evening screen time.
15. Use Red Light Bulbs
Replace evening light bulbs with red light bulbs or use red party lights to minimize disruptive light exposure at night. This can help maintain a natural circadian rhythm without needing expensive red light units.
16. Midday Sun for Mood, Not Clock
While bright midday sun is great for increasing mood and feelings of well-being, it will not help anchor your sleep-wake cycle. Focus on early morning and late evening low solar angle sunlight for circadian rhythm regulation.
17. Treat SAD with Bright Light
For Seasonal Affective Disorder (SAD), use a SAD lamp providing more than 10,000 lux of bright light, especially in the morning. This treatment has proven fairly effective in alleviating SAD symptoms.
18. Avoid Sunburn for Melanoma
To prevent melanoma, focus on avoiding sunburn, especially repeated sunburns early in life, rather than merely limiting all sun exposure. Differentiate between healthy sun exposure for vitamin D and damaging UV exposure that causes scorching.
19. Use Mineral Sunscreens
Use traditional mineral sunscreens for sun protection, as they are considered perfectly safe. These types of sunscreens are not associated with endocrine disruption, unlike some other formulations.
20. Limit Artificial Sweetener Intake
Exercise caution and use artificial sweeteners in limited amounts only, as they can potentially disrupt brain chemistry, gut chemistry, and metabolism. While not linked to cancer, their long-term metabolic effects warrant prudence.
21. Choose Xylitol and Allulose
If consuming sweeteners, consider xylitol (for chewing gum) and allulose (as an additive) as potentially safer alternatives. These are the only two the speaker will consume due to their perceived safety profile.
22. Track Calories for Awareness
Utilize calorie tracking apps (like Carbon) to gain awareness of your caloric intake and consumption patterns. The act of tracking can help manage intake and gamify healthy eating behaviors.
23. Mindful Sleep Tracker Use
Use sleep trackers as a tool for insight and behavioral change, but be mindful of their psychological impact. A poor sleep score should be an indication to adjust habits, not a reason to decide you’ll have a terrible day, and focus on averages rather than daily fluctuations.
24. Measure Light with App
Download and use a free ‘Light Meter’ app to measure lux levels in your environment. This helps you understand the actual brightness of light sources, including natural and artificial ones.
25. Learn to Read Scientific Papers
To avoid misrepresentation by news media, learn to read scientific papers yourself by practicing. Review papers before listening to discussions to identify key points and questions, which helps in understanding research and what is truly reported.
26. Modulate Immunity with Age
Consider strategies to modulate immunity as you age, such as potentially using rapamycin (if taken correctly), which has shown to enhance cellular immunity and vaccine response in short-term human experiments. This could be a significant factor in cancer prevention, though more research is needed.
27. Support Ad-Free Health Content
Subscribe to Peter Attia’s premium membership for exclusive content and benefits to deepen knowledge in health and wellness. This supports ad-free content and aims to provide value exceeding the subscription cost.
28. Minimize Night Phone Light
When using phones or tablets at night, minimize screen brightness and consider using built-in features to eliminate blue light. The amount of direct light exposure you get at night, and its duration, significantly impacts your circadian rhythm.
7 Key Quotes
Avoiding night at light and seeking light during the day... may be a simple and effective non-pharmacologic means for broadly improving mental health.
Andrew Huberman
The amount of melatonin suppression from nighttime light exposure is halved by viewing evening setting sun.
Andrew Huberman
If you're going to wear blue blockers, and I don't think they're necessary, but if you're going to wear them, you'd want to wear them at night.
Andrew Huberman
People spend 90% of their time indoors. Now their daytime environments are too dim. Their nighttime environments are too bright.
Andrew Huberman
More than 80% of those cancers have antigens that are recognized by the host's immune system.
Peter Attia
The overall survival for metastatic melanoma is zero with the exception of people who respond to interleukin-2, high dose interleukin-2, and that will boost the overall survival rate to somewhere between eight and 10%.
Peter Attia
I still believe that immunotherapy is probably the most important hope we have for treating cancer.
Peter Attia
1 Protocols
Optimal Daily Light Exposure for Mental and Physical Health
Andrew Huberman- View low solar angle sunlight in the early part of the day (e.g., 10 minutes or more on non-cloudy days, longer on cloudy days), ideally without sunglasses.
- View low solar angle sunlight in the later part of the day (e.g., 10 minutes or more), ideally without sunglasses.
- Get as much bright light in your eyes as safely possible throughout the day, ideally from sunlight.
- Minimize light exposure at night, aiming for dark exposure, especially avoiding bright, extensive artificial light.