How to Get the Right Kind of Light

Back on the podcast, today is sleep, nutrition, and metabolism expert, Greg Potter, PhD. Through his academic research, public speaking, consulting and writing, Greg empowers people to make simple and sustainable lifestyle changes that add years to their lives and life to their years. His work has been featured in dozens of international media outlets, including Reuters, TIME, and The Washington Post, and he regularly contributes to popular websites, blogs, and podcasts.

In this podcast, Greg is talking about light, including the importance of getting out in the sun and also modern problems with artificial light. He discusses the impact of light on the circadian system along with up-to-date recommendations related to light hygiene. We discuss practical tips for reducing light at night (not all of which involve putting away your device), and why not getting the right kind of light might be keeping you from achieving your body composition goals.

Here’s the outline of this episode with Greg Potter: 

[00:02:14] Wellics Corporate Wellness Software.

[00:06:49] The importance of light.

[00:08:30] The introduction of electric light.

[00:09:55] myLuxRecorder (Satchin Panda's app, no longer available); Podcast: How to Use Time-Restricted Eating to Reverse Disease and Optimize Health, with Satchin Panda.

[00:10:37] How light influences the circadian system.

[00:15:34] Consensus paper with recommendations related to light hygiene; Study: Brown, Timothy M., et al. "Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults." PLoS biology 20.3 (2022): e3001571.

[00:19:13] Practical tips for reducing light at night.

[00:22:44] Increasing prevalence of myopia.

[00:23:46] Podcast: Getting Stronger, with Todd Becker.

[00:26:01] Vitamin D synthesis; Podcast: The Pleiotropic Effects of Sunlight, with Megan Hall.

[00:26:15] Effects of light on mood and cognition.

[00:27:24] Effect of light exposure patterns on cognitive performance; Study: Grant, Leilah K., et al. "Daytime exposure to short wavelength-enriched light improves cognitive performance in sleep-restricted college-aged adults." Frontiers in neurology (2021): 197.

[00:28:14] Effects of light on metabolic health.

[00:28:20] Dan Pardi podcast featuring Peter Light: Sunlight And Fat Metabolism: A New Discovery.

[00:28:52] Effect of bright and dim light on metabolism (Netherlands); Study: Harmsen, Jan-Frieder, et al. "The influence of bright and dim light on substrate metabolism, energy expenditure and thermoregulation in insulin-resistant individuals depends on time of day." Diabetologia 65.4 (2022): 721-732.

[00:30:53] Effects of light on skin and immune function.

[00:31:57] Highlights #15 (topics: Sun avoidance & exposure, increasing testosterone, Robert Sapolsky).

[00:35:14] Skyglow.

[00:36:48] Light at night and endocrine disruption.

[00:37:45] Light at night and quality/duration of sleep.

[00:38:19] Blue light in the evening interferes with sleep homeostasis; Study: Cajochen, Christian, et al. "Evidence that homeostatic sleep regulation depends on ambient lighting conditions during wakefulness." Clocks & Sleep 1.4 (2019): 517-531.

[00:38:53] Effects of light at night on sympathetic nervous system/cortisol; Study: Rahman, Shadab A., et al. "Characterizing the temporal dynamics of melatonin and cortisol changes in response to nocturnal light exposure." Scientific reports 9.1 (2019): 1-12.

[00:39:26] Effects of light at night on heart rate, HRV, insulin resistance; Study: Mason, Ivy C., et al. "Light exposure during sleep impairs cardiometabolic function." Proceedings of the National Academy of Sciences 119.12 (2022): e2113290119.

[00:41:34] Effects of moon phases on sleep; Study: Casiraghi, Leandro, et al. "Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions." Science advances 7.5 (2021): eabe0465.

[00:45:40] Effects of individual sensitivity to light; Study: Phillips, Andrew JK, et al. "High sensitivity and interindividual variability in the response of the human circadian system to evening light." Proceedings of the National Academy of Sciences 116.24 (2019): 12019-12024.

[00:47:55] Camping and melatonin synthesis across seasons; Study: Stothard, Ellen R., et al. "Circadian entrainment to the natural light-dark cycle across seasons and the weekend." Current Biology 27.4 (2017): 508-513.

[00:48:40] Seasonal changes in thyroid hormones (meta-analysis): Kuzmenko, N. V., et al. "Seasonal variations in levels of human thyroid-stimulating hormone and thyroid hormones: a meta-analysis." Chronobiology International 38.3 (2021): 301-317.

[00:53:24] Effect of location in the world; Podcast: Morning Larks and Night Owls: the Biology of Chronotypes, with Greg Potter, PhD.

[00:54:30] Daylight Savings Time transition and  traffic accidents in the US; Study: Fritz, Josef, et al. "A chronobiological evaluation of the acute effects of daylight saving time on traffic accident risk." Current biology 30.4 (2020): 729-735.

[00:56:08] Effects of Daylight Savings Time on cardiac events.

[00:56:48] Daylight Savings Time and cyberloafing; Study: Wagner, David T., et al. "Lost sleep and cyberloafing: Evidence from the laboratory and a daylight saving time quasi-experiment." Journal of Applied psychology 97.5 (2012): 1068. 

[00:57:26] Circadian clock disrupted by Daylight Savings Time; Study: Kantermann, Thomas, et al. "The human circadian clock's seasonal adjustment is disrupted by daylight saving time." Current Biology 17.22 (2007): 1996-2000. 

[01:00:44] Implications of permanent daylight savings time.

[01:03:37] Effects of light at night in animals; Study: Sanders, Dirk, et al. "A meta-analysis of biological impacts of artificial light at night." Nature Ecology & Evolution 5.1 (2021): 74-81.

[01:09:14] Minimizing the impact of light at night on wildlife.

[01:13:50] Human-centric lighting at hospitals; Study: Giménez, Marina C., et al. "Patient room lighting influences on sleep, appraisal and mood in hospitalized people." Journal of sleep research 26.2 (2017): 236-246.

[01:14:51] Babies in a neonatal unit did better with light/dark cycle; Study: Vásquez-Ruiz, Samuel, et al. "A light/dark cycle in the NICU accelerates body weight gain and shortens time to discharge in preterm infants." Early human development 90.9 (2014): 535-540.

[01:17:59] Effects of light at night on plants; Study: Ffrench-Constant, Richard H., et al. "Light pollution is associated with earlier tree budburst across the United Kingdom." Proceedings of the Royal Society B: Biological Sciences 283.1833 (2016): 20160813.

[01:18:50] Maturation of soybeans shifted with  artificial light at night; Study: Palmer, Matthew, et al. Roadway lighting’s impact on altering soybean growth. No. FHWA-ICT-17-010. 2017.

[01:19:44] How to optimise your light environment.

[01:19:54] Incandescent vs compact fluorescent bulbs.

[01:21:58] LED lights.

[01:25:33] Light-emitting devices with screens; metamerism.

[01:26:20] Using metamerism to regulate impact of digital devices; Study: Allen, Annette E., et al. "Exploiting metamerism to regulate the impact of a visual display on alertness and melatonin suppression independent of visual appearance." Sleep 41.8 (2018): zsy100.

[01:26:51] Software that reduces your exposure to short wavelengths: Nightshift (iPhone), Night Light/Blue Light Filter (Android), f.lux.

[01:27:23] Apps to prevent short-wavelength light emissions do help; Study: Gringras, Paul, et al. "Bigger, brighter, bluer-better? Current light-emitting devices–adverse sleep properties and preventative strategies." Frontiers in public health 3 (2015): 233.

[01:27:31] Blue-light blocking app did not improve sleep; Study: Smidt, Alec M., et al. "Effects of Automated Diurnal Variation in Electronic Screen Temperature on Sleep Quality in Young Adults: A Randomized Controlled Trial." Behavioral Sleep Medicine (2021): 1-17.

[01:28:31] Blue-blockers.

[01:31:31] Recommendations for shift workers. Greg’s paper on this topic: Potter, Gregory DM, and Thomas R. Wood. "The future of shift work: Circadian biology meets personalised medicine and behavioural science." Frontiers in Nutrition 7 (2020): 116.

[01:33:34] Jet lag: Jet Lag Rooster.

[01:37:27] Find Greg on Instagram, TikTok; gregpotterphd.com

[01:37:56] Book: When Brains Dream: Understanding the Science and Mystery of Our Dreaming Minds, by Antonio Zadra.

[01:38:08] Book: The Beginning of Infinity: Explanations That Transform the World, by David Deutsch.

[01:38:32] Book: The Precipice by Toby Ord.