Light as a Nutrient

Depending on where you live, you may have recently entered Daylight Savings Time, a time to “fall back” one hour. In the weeks leading up to this change, you might have noticed yourself staying up later or lingering in bed longer on dark mornings. Without conscious effort, your circadian rhythm gradually adjusted to the seasonal shift.

Recent research highlights that light profoundly influences human health, affecting metabolism, sleep, mood, and cellular function. Exposure to natural sunlight helps regulate circadian rhythms, initiates vitamin D synthesis, impacts mental health, enhances energy levels and cognitive performance, and influences appetite and metabolism.

Light and Circadian Rhythms
In 2017, the Nobel Prize was awarded to Jeffrey C. Hall, Michael Rosbash, and Michael W. Young for their discoveries of molecular mechanisms that control circadian rhythms. Circadian rhythms are driven by an internal biological clock that anticipates day/night cycles to optimize physiology and behavior (Nobelforsamlingen, 2017). Each mitochondrion, present in every cell, contains molecular timekeeping machinery that strongly influences body rhythms.

Research now shows that light stimulates these tiny clocks, programming circadian rhythm and activating mitochondria (Jiang et al., 2025; Trajano et al., 2025; Mezhnina et al., 2022). Because light directly nourishes mitochondria, the body’s powerhouses and timekeepers, it can be considered an essential nutrient.

By analogy, plants require light to thrive. While human physiology differs, light similarly drives cellular and molecular pathways. Insufficient natural light can impair mitochondrial function, affecting sleep, energy production, reproduction, and brain function (Trajano et al., 2025; Singh et al., 2025; Song et al., 2022).

Recent Research Linking Light to Health
Recent research highlights that light profoundly influences human health, affecting metabolism, sleep, mood, and cellular function. Exposure to natural sunlight initiates vitamin D synthesis, which is essential for bone health, immune regulation, and calcium absorption. Inadequate vitamin D production due to insufficient sunlight exposure can lead to conditions such as rickets and osteoporosis (Uçar & Holick, 2025).

In addition, light exposure has a significant impact on mental health. Sunlight increases serotonin levels, which improve mood and emotional well-being. A lack of light exposure, particularly in winter months, is associated with Seasonal Affective Disorder (SAD) and other depressive symptoms (Sanes et al, 2022).

Research also connects light to energy levels and cognitive performance. Exposure to bright, natural light during the morning and midday enhances concentration and productivity throughout the day (Islay et al., 2024).

Finally, studies show that light influences appetite regulation and metabolism. The timing and intensity of light exposure can affect glucose metabolism, insulin sensitivity, and energy expenditure, linking disrupted light patterns to obesity and metabolic disorders (Ishihara et al., 2024).

Taken together, these findings support the concept that light functions as a vital nutrient, nourishing both body and mind through its wide-ranging physiological effects.

Light exposure is as essential as nutrition – and perhaps looking at it from this perspective, we can learn ways to optimize our light diets.

Light in Modern Life
Our modern lifestyles can create imbalances in both nutrition and light exposure. While we carefully monitor food intake, we rarely consider how artificial lighting (LEDs, screens, and indoor lighting) affects our health. Excessive artificial blue light can disrupt circadian rhythms, mitochondrial function, and cellular health, in a manner comparable to processed foods that damage DNA (McNish et al., 2025; Trajano et al., 2025; Singh et al., 2025).

Morning sunlight acts as a “timestamp” for the circadian rhythm, regulating sleep and other physiological processes. Conversely, blue light exposure in the evening can suppress melatonin, affecting sleep quality (Ishizawa et al., 2021). Intentional daytime light exposure helps maintain natural rhythms, recharge mitochondria, and support overall health.

Practical Tips
Ask yourself: have you had your daily dose of natural light today? Morning exposure is ideal. Even a few minutes outside or near a bright window can help meet daily light requirements. If screen time is unavoidable in the evening, using blue-blocking glasses may reduce disruption to your sleep cycle (Ishizawa et al., 2021).

The Course
In Nutrition Perspectives in Pelvic Rehab, we go beyond nutrition basics. We delve into a systems approach to nourishment and introduce factors beyond foods that nourish our body, mind, and soul. We learn about our interconnected nature. And we are reminded that we are not nourished by food alone. Life requires light and is as essential as other nutrients for our health and well-being.

Please join us as we explore the many intriguing connections between nourishment, our cells, our systems, and our health and how we can better serve our pelvic health clients from this standpoint.

Nutrition Perspectives will be offered December 6-7, 2025, and quarterly in 2026.

References:

1. Cohen T, Medini H, Mordechai C, Eran A, Mishmar D. Human mitochondrial RNA modifications associate with tissue-specific changes in gene expression, and are affected by sunlight and UV exposure. Eur J Hum Genet. 2022 Dec;30(12):1363-1372. doi: 10.1038/s41431-022-01072-3. Epub 2022 Mar 4. PMID: 35246665; PMCID: PMC9712611.
2. Ishizawa M, Uchiumi T, Takahata M, Yamaki M, Sato T. Effects of pre-bedtime blue-light exposure on ratio of deep sleep in healthy young men. Sleep Med. 2021 Aug; 84:303-307. doi: 10.1016/j.sleep.2021.05.046. Epub 2021 Jun 8. PMID: 34217920.
3. Jiang Z, Wu S, Zhou S, Zheng H, Bai Y, Zhang Y, Yao M. Photobiomodulation mediates endoplasmic reticulum-mitochondria contact and ameliorates lipotoxicity in MASLD via Mfn2 upregulation. J Photochem Photobiol B. 2025 Sep; 270:113209. doi: 10.1016/j.jphotobiol.2025.113209. Epub 2025 Jul 2. PMID: 40633245.
4. McNish H, Mathapathi MS, Figlak K, Damodaran A, Birch-Machin MA. The Effect of Blue Light on Mitochondria in Human Dermal Fibroblasts and the Potential Aging Implications. FASEB J. 2025 Jun 15;39(11):e70675. doi: 10.1096/fj.202500746R. PMID: 40421626; PMCID: PMC12107506.
5. Mezhnina V, Ebeigbe OP, Poe A, Kondratov RV. Circadian Control of Mitochondria in Reactive Oxygen Species Homeostasis. Antioxid Redox Signal. 2022 Oct;37(10-12):647-663. doi: 10.1089/ars.2021.0274. Epub 2022 Feb 18. PMID: 35072523; PMCID: PMC9587791.
6. Nobelforsamlingen. Scientific Background Discoveries of Molecular Mechanisms Controlling the Circadian Rhythm. https://www.nobelprize.org/prizes/medicine/2017/advanced-information/  Accessed November 2, 2025.
7. Singh J, Kumar D, Kaur J, Singh A. The rhythm of decline: Circadian disruption in neurodegeneration. J Food Drug Anal. 2025 Sep 18;33(3):224-240. doi: 10.38212/2224-6614.3553. PMID: 41066745; PMCID: PMC12510711.
8. Song Y, Yang J, Law AD, Hendrix DA, Kretzschmar D, Robinson M, Giebultowicz JM. Age-dependent effects of blue light exposure on lifespan, neurodegeneration, and mitochondria physiology in Drosophila melanogaster. NPJ Aging. 2022 Jul 27;8(1):11. doi: 10.1038/s41514-022-00092-z. PMID: 35927421; PMCID: PMC9329351.
9. Trajano LADSN, Siqueira PB, Rodrigues MMS, Pires BRB, da Fonseca AS, Mencalha AL. Does photobiomodulation alter mitochondrial dynamics? Photochem Photobiol. 2025 Jan-Feb;101(1):21-37. doi: 10.1111/php.13963. Epub 2024 May 22. PMID: 38774941.
10. Uçar, N., & Holick, M. F. (2025). Illuminating the Connection: Cutaneous Vitamin D3 Synthesis and Its Role in Skin Cancer Prevention. Nutrients, 17(3). https://doi.org/10.3390/nu17030386
11. Sanes, J. R., et al. (2022). Researchers discover brain pathway that helps to explain light’s effect on mood. Proceedings of the National Academy of Sciences. (via Brown University). https://www.brown.edu/news/2022-07-06/light-mood
12. Campbell Islay, Sharifpour Roya, Aizpurua Jose Fermin Balda, Beckers Elise, Paparella Ilenia, Berger Alexandre, Koshmanova Ekaterina, Mortazavi Nasrin, Read John, Zubkov Mikhail, Talwar Puneet, Collette Fabienne, Sherif Siya, Phillips Christophe, Lamalle Laurent, Vandewalle Gilles (2024) Regional response to light illuminance across the human hypothalamus eLife 13:RP96576. https://doi.org/10.7554/eLife.96576.1
13. Ishihara, A., Courville, A. B., & Chen, K. Y. (2023). The Complex Effects of Light on Metabolism in Humans. Nutrients, 15(6), 1391. https://doi.org/10.3390/nu15061391

AUTHOR BIO
Megan Pribyl, PT, CMPT, CMPT/DN, PCES

Megan Pribyl (she/her) is a mastery-level physical therapist at the University of Kansas Health System in Olathe, KS, specializing in orthopedic care for a diverse outpatient population, including pelvic health, pregnancy, and postpartum rehabilitation. Her approach emphasizes the integration of health, wellness, and evidence-based practice.

Megan began her career in physical therapy in 2000 after earning her Master of Science in Physical Therapy from the University of Colorado Health Sciences Center. She also holds dual bachelor’s degrees in Nutrition and Exercise Sciences (B.S. Foods & Nutrition; B.S. Kinesiology) from Kansas State University. She later earned her Certified Manual Physical Therapist (CMPT) credential through the North American Institute of Orthopedic Manual Therapy and became certified in dry needling in 2019. Since 2015, Megan has served as a faculty member at the Herman & Wallace Pelvic Rehab Institute, where she enjoys both teaching and developing course content.

Her passion for nutrition and manual therapy inspired her to create Nutrition Perspectives for the Pelvic Rehab Therapist, a course designed to deepen understanding of human physiology as it relates to pelvic conditions, pain, healing, and therapeutic response. Megan combines traditional and contemporary approaches to provide clinicians with practical, immediately applicable tools to enhance patient care. Her teaching encourages a deeper appreciation for the complexity of clinical presentations in orthopedic manual therapy and pelvic rehabilitation.