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  • Writer's pictureDr. Charlotte Morgan, D.Ac.

Morning Sunlight + Sleep Cycles

I often believe that by returning to the most basic aspects of our evolutionary traits, we are able to heal in a more profound way. As a society, we continuously search for new ways to “bio hack” our health (hyperbaric chambers, supplements, IV bars), so we can continue to burn the candle at both ends without sacrificing productivity or taking time to rest. Humans evolved to rise with the sun and sleep when it sets, not work 12 hour days 😵‍💫.

Many people are aware that sunlight is essential for vitamin D production, and that low vitamin D can lead to depression, fatigue, a weakened immune system, pain, and a multitude of other symptoms. However, sunlight is also essential for healthy circadian rhythm and sleep cycles, maintaining healthy blood pressure, a strong immune system, and reducing inflammation. Supplementing with vitamin D instead of prioritizing moderate sun exposure does not replace the sun’s rays for the following benefits:

Circadian Rhythm: Our eyes are the ocular pathway to the brain- when light waves are sensed in the morning, our brain begins processing information (including the time of day) and alerts the rest of our body on how to function and remain on schedule. Studies show that blood flow in the brain improves after light therapy. Decreased blood flow in the brain is related to cognitive issues, insomnia, and mood disorders. Without enough light wave exposure to our brain throughout the day, we don’t produce enough melatonin (a hormone that the brain produces in response to darkness) which signals our bodies to sleep. If we aren’t producing adequate melatonin, chances are, we are getting poor quality sleep and therefore sleeping in later. This decreases our opportunity for morning sunlight exposure, which starts the cycle all over again. If you are supplementing with melatonin, research indicates you may be doing more harm than good (see my earlier blog on melatonin).

Blood Pressure: When exposed to sunlight, the skin releases nitric oxide into the bloodstream. This triggers our arteries to dilate, which lowers blood pressure. Chronic stress can result in higher blood pressure.

Immune System: When our immune system isn’t functioning optimally, it can become either suppressed or stimulated which can result in autoimmune disease or inflammatory conditions. People with autoimmune disorders are often lacking in regulatory T cells, which suppress other cells in the immune system and control immune response. Sunlight can increase the activity of regulatory T cells, which supports the immune systems ability to regulate itself and protect the body from inflammation and neurodegenerative disorders like multiple sclerosis. MS is 3x more common in the Pacific Northwest, where sunlight is less prevalent.

The best time to reset our internal clocks through sun exposure is in the morning. I like to drink my morning coffee on the porch or outdoors, and whenever I am able, I take a walk first thing after waking. Sunglasses filter sunlight to the eyes, so it is best to leave them at home or use them sparingly in the morning. 5-10 minutes of morning sun per day is enough to reset your circadian rhythm, and small amounts of exposure throughout the day will allow your body to maintain a healthy sleep cycle.

Laying in the sun for prolonged periods of time or staring at the sun can be harmful- please do your own research and engage in what is appropriate for your skin and body type.

With Love,

Dr. Charlotte Morgan, D.Ac.


Blume, C., Garbazza, C. & Spitschan, M. Effects of light on human circadian rhythms, sleep and mood. Somnologie 23, 147–156 (2019).

Institute of Medicine (US) Committee on Sleep Medicine and Research; Colten HR, Altevogt BM, editors. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington (DC): National Academies Press (US); 2006. 3, Extent and Health Consequences of Chronic Sleep Loss and Sleep Disorders. Available from:

Fleury N, Geldenhuys S, Gorman S. Sun Exposure and Its Effects on Human Health: Mechanisms through Which Sun Exposure Could Reduce the Risk of Developing Obesity and Cardiometabolic Dysfunction. International Journal of Environmental Research and Public Health. 2016; 13(10):999.

Kent, S.T., McClure, L.A., Crosson, W.L. et al. Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study. Environ Health 8, 34 (2009).

Menon V, Kar SK, Suthar N, Nebhinani N. Vitamin D and Depression: A Critical Appraisal of the Evidence and Future Directions. Indian Journal of Psychological Medicine. 2020;42(1):11-21. doi:10.4103/IJPSYM.IJPSYM_160_19

Rajendeeran, A., & Tenbrock, K. (2021). Regulatory T cell function in autoimmune disease. Journal of Translational Autoimmunity. 4.

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