🗃 Citations

Naturally Natural starts and ends with research. This is the living annotated bibliography.

Barolet, D., Christiaens, F., Hamblin, M. (2016). Infrared and skin: Friend or foe. Journal of Photochemistry & Photobiology, B: Biology, 155, 78-8.

This review of 61 papers concludes that the infrared light of early morning and late evening are both healing to the skin; the former produces a protective effect and the latter produces a restorative effect. The authors also show that studies on infrared light that used artificial light sources do not accurately reflect the effect of infrared light from the sun. TLDR: Getting unfiltered morning and evening light heals the skin.

Cited in Cool Weather Sunbathing.

Cain, S., McGlashan, E., Vidafar, P., et al. (2020). Evening home lighting adversely impacts the circadian system and sleep. Nature Research Scientific Reports, 10, 19110.

This report, which in turn references 40 additional studies, concludes that potential benefits of energy-efficient lighting may be outweighed by substantial disease-burden and lost productivity due to chronic light-induced sleep and circadian disruption. They highlight the need for consumer education and the hopeful potential for deploying biologically conscious lighting solutions at scale in the future. TLDR: Dimmer evening light is better for biology.

Cited in Circadian Coaching.

Demer, L., Hsu, J., Tintut, Y. (2018). Steroid Hormone Vitamin D: Implications for Cardiovascular Disease. Circulation Research, 122, 1576-1585.

This review of 146 papers concludes that the current models for dietary doses of vitamin D3 are dangerously flawed given vitamin D’s role as a steroid hormone in the body. They highlight that sunlight derived vitamin D has been the major source for humans for millennia, and that it travels in the body in a pathway that does not have the same cardiovascular risks as dietary vitamin D. TLDR: Getting solar Vitamin D is good but dietary Vitamin D is dangerous.

Cited in Useful Jargon.

Erdemir, I., Kizilet, A., Kizilet Bozdogan, T. (2013).Effects of Exercise on Circadian Rhythms of Cortisol. International Journal of Sports Science, 3(3): 68-73.

This small study (n=10), showed what has been shown many times over in research, that exercise effects circadian rhythms. They specifically show how how timing of exercise interacts with cortisol, and that recovery from high-intensity exercise happens faster if that exercise happens in the evening than in the morning. TLDR: Mild exercise is ok in the morning, but high intensity exercise should happen in the evening instead.

Cited in Circadian Coaching.

Fontana, J., Tserga, E., Sarlus, H., et al. (2019). Impact of noise exposure on the circadian clock in the auditory system. The Journal of the Acoustical Society of America, 146, 3960.

This review referencing over 50 additional studies concludes that noise is a significant influence on circadian rhythms and describes the auditory pathways for this to be so. TLDR: Quiet nights are better for sleep.

Froy, O. (2010). Metabolism and Circadian Rhythms—Implications for Obesity. Endocrine Reviews, 31, 1-24.

This review of 333 papers concludes that resetting the biological circadian clock by food components (such as a high-fat diet) or feeding time may lead to better functioning of the body as a whole, prevent metabolic disorders, promote well being and extend life span. Western metabolic problems are attributed to the lifestyle of high food consumption, inactivity during the active period, activity during the inactive period, and shortened sleep period. TLDR: There is every reason to adopt a more Circadian activity schedule.

Hatori, M., Gronfier, C., Van Gelder, R., Bernstein, P., et al. (2017). Global rise of potential health hazards caused by blue light-induced circadian disruption in modern aging societies. npj Aging and Mechanisms of Disease, 3:9.

This review of 23 papers concludes that light has a more powerful effect on human chronobiology than any available drug, and that personalized control over ambient lighting to enhance alertness during the active period and protect sleep during rest time may reduce the risk for health disorders including certain cancers, obesity, diabetes, and psychiatric disorders. They highlight the particular benefits of high-intensity blue light in the afternoon, and the particular dangers of the same lights at night. TLDR: No matter your sleep/work schedule, you need brighter days and darker nights.

Cited in Circadian Rhythmicity and Circadian Coaching.

Hotz Vitaterna, M., Takahashi, J., Turek, F., (2001). Overview of Circadian Rhythms. Institute on Alcohol Abuse and Alcoholism, 25, 85-93.

This review of 14 papers concludes that humans alone have the mind of their own to disobey their internal clock and that the increasing tendency toward a 24 hour lifestyle does not bode well for health and wellbeing, including alcohol consumption. Alcohol consumption is shown to affect circadian rhythm, but Circadian factors such as the light-dark cycle may also influence alcohol consumption. TLDR: Circadian rhythmicity is complicated and has profound social implications.

Lopez-Minguez, J., Gomez-Abellan, P., Garaulet, M. (2016). Circadian rhythms, food timing and obesity. Proceedings of the Nutrition Society, 75, 501-511.

This review of 39 papers concludes that what, how, and when we eat, exercise, sleep and expose ourselves to light can decrease obesity and increase weight loss. The effects come from the circadian lifestyle itself, as well as favorable changes to the genome that the lifestyle causes. TLDR: Living in a more Circadian way will improve your DNA.

Cited in Improve your genome and Circadian Coaching.

Mead, M. (2008).Benefits of Sunlight: A Bright Spot for Human Health. Environmental Health Perspectives, 116, 161-167.

This perspective tells the story of how sunlight went from hero to villain and now back again. TLDR: There are more benefits of sunbathing than just getting a tan and some Vitamin D.

Cited in Circadian Coaching.

Münzel, T., Kröller-Schön, S., Oelze, M., et al (2020). Adverse Cardiovascular Effects of Traffic Noise with a Focus on Nighttime Noise and the New WHO Noise Guidelines. Annual Review of Public Health, 41:309–28.

This review of 109 papers concludes that circadian disruption may be the pathway that causes the well-known adverse cardiovascular conditions associated with nighttime noise. TLDR: Living in a quiet place is better for health and circadian rhythmicity.

Cited in Circadian Coaching.

Okamoto-Mizuno, K., Mizuno, K. (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology, 31:14.

This study, which in turn references 104 additional studies, concludes that maintaining a comfortable ambient temperature, particularly during the sleep period, is important for quality of sleep and circadian rhythmicity. In particular, overnight temperatures should not be too warm. TLDR: Turn down the thermostat at night.

Cited in Circadian Coaching.

Naval Postgraduate School. (2017). Crew Endurance Handbook: A Guide to Applying Circadian-Based Watchbills. Center for Educational Design, Development, and Distribution (CED3).

This handbook from the Navy describes a method for designing Circadian watch schedules that optimize crew performance around the clock (24 hours). TLDR: If you work night-shift or rely on those who do, you need to read this handbook to understand how to prevent “worse-than-drunk” performance from yourself or others.

Cited in Worse-than-drunk and Circadian Coaching.

Reiter, R., Tan, D., Korkmaz, A., et al. (2013). Melatonin and stable circadian rhythms optimize maternal, placental, and fetal physiology. Human Reproduction Update, 20:2, 293-307.

This review of around 200 papers gives dire warnings and a srong recommendation for avoiding bright light at night, particularly for parents-to-be. TLDR: The light/dark cycle is an overlooked aspect of fertility.

Cited in Rhythmicity from the Start.

Walker, W., Walton, J., DeVries, C, Nelson, R. (2020). Circadian rhythm disruption and mental health. Translational Psychiatry, 10:28.

This review of 177 papers concludes that resynchronization of circadian rhythms improves symptoms of mood disorders including major depressive disorder, bipolar disorder, and schizophrenia. TLDR: If you or a loved one suffers from mental illness, a lifestyle of rhythmicity may improve your quality of life.

Cited in Save a Life, Circadian Coaching, and Rhythmicity from the Start.

Wehr, T. (1991). In short photoperiods, human sleep is biphasic. Journal of Sleep Research, 1, 103-107.

This research paper, referencing 19 earlier studies, describes the eight hour sleep schedule as the Circadian result of 16-hour monotonous bright lighting schedules. The paper describes several alternative Circadian sleep patterns that arise spontaneously under different lighting schedules (such as 24-hour monotonous dim lighting and 14/10 bright/dark schedule). TLDR: There are a variety of natural sleep patterns besides the 8-hour nightly regime.

Cited in Consolidated vs unconsolidated sleep.