Supporting Your Brain When There’s Less Sunlight

Notice yourself getting sleepy earlier and earlier in the day this time of year? These feelings of fatigue aren’t just you, but a sensation that’s grounded in science.

Evolutionary speaking, in periods of less daylight, like the fall and winter, our bodies are programmed to seek more rest. Once, these seasons were marked by food scarcity and extreme cold, so energy conservation was necessary for human survival (i.e., hunkering down in a cave). While we no longer face the same threats in the modern age, our bodies still respond to seasonal changes (i.e., hunkering down in bed at 7 p.m.).

There are ways to support our brains through these seasonally afflicted changes, from supplementation to sunlight-mimicking lamps. It also requires a bit of a mindset shift: these periods of stillness and lower productivity can be good for our health, providing us with the time we need to recharge and restore natural balance. (Consider the Danish concept of hygge, all about savoring warmth, comfort, and simple pleasures come cold, dark winter—like candles, steaming mugs of tea, and cozy, carb-laden dishes.)

The circadian rhythm is the body’s natural internal clock, responsible for regulating sleep and wakefulness. It responds to light and dark cues to help your body align with day and night cycles. If you've ever woken up moments before your alarm, you can thank your circadian rhythm. Between the light cues and an increase in hormone production, your circadian rhythm anticipates regular sleep patterns and nudges you awake.

Melatonin and cortisol are directly involved in regulating the circadian rhythm, with additional influence from neurochemicals like adenosine, serotonin, and dopamine.¹ (Fluid intake, stress levels, physical activity, social environment, and temperature also impact the circadian rhythm.)

Melatonin is a hormone produced by the pineal gland (a tiny endocrine gland in the middle of your brain) in response to darkness. It gives your body the green flag to wind down, ultimately pulling you into a deep slumber. Its counterpart is cortisol, a stress hormone that, although harmful when constantly elevated, is necessary for waking up. Cortisol peaks in the morning, energizing you for the day. It gradually decreases throughout the day while melatonin levels simultaneously rise. Shorter days can tip this delicate see-saw of sleep and wake, leading to higher melatonin levels for longer periods.² In turn, it can cause feelings of fatigue. 

The winter also impacts serotonin, a neurotransmitter that regulates mood, well-being, and happiness and is also involved in regulating sleep and appetite. Its production is directly influenced by exposure to sunlight, so it makes sense that, during months when the sun sets before you even leave the office, serotonin levels can be low in comparison to summer months. The science aligns: One study confirmed that the brain’s serotonin turnover was lowest in the winter, which could contribute to lower mood and Seasonal Affective Disorder (SAD).³

Reduced sunlight has also been studied for its effect on dopamine production, a neurotransmitter linked to pleasure, motivation, and reward.⁴ Less sunlight can mean less dopamine production, which can contribute to a decrease in motivation and lower productivity in the colder months (AKA why you want to have a movie marathon, not a real one).

With all of these biological changes happening in your brain and body as a response to the seasonal change in daylight, it’s no wonder you may be feeling particularly tired, unmotivated, or down. 

With the constant demands and requirements of our professional and personal environments (and without hibernation as a viable option), it’s important to actively support our energy levels and productivity throughout the fall and winter when the days are shorter.

This is especially important for anyone living above 37° latitude (New York, Chicago, Seattle, Stockholm, Tokyo, Toronto, etc.). In these places, from November to February, the angle of the sun is too low in the sky for UVB rays—the UV ray responsible for Vitamin D synthesis, an essential vitamin for mood regulation and sleep.⁵⁻⁶ 

Getting enough sleep isn’t just about feeling rested—it’s also when our brains do some of their most important work. During sleep, the brain clears out toxins and consolidates memories.⁹ This vital cleaning process primarily happens during deep sleep, so aiming for seven to nine hours each night is key.¹⁰

Creating a bedtime routine that promotes good sleep hygiene can help. A cool, dark room is ideal, and avoiding blue light from screens an hour before bed can prevent disruptions to melatonin production.¹¹ During your wind-down, try making a sleep mocktail with tart cherry juice and sparkling water; the tart cherry juice helps to naturally boost melatonin production.¹² Also, by sticking to a consistent bedtime (and not varying greatly between weekdays and weeknights), we give our brain the opportunity to get the rest it needs to function at its best.¹³

A few ways to support your brain this season:

• Get natural light. While there’s still morning light, aim to get sunlight first thing in the morning. This will help regulate your sleep-wake cycle and boost serotonin levels to help fight the seasonal blues.⁷

• Supplement with Vitamin D. In the summer months, we get Vitamin D from the sun, synthesized by the skin. With less sunlight, Vitamin D supplementation can help make up for those discrepancies. (Before adding any supplements in your routine, consult with your healthcare provider. They can check your Vitamin D levels via a blood test to ensure they’re within a healthy range.)

• Or, eat foods high in Vitamin D. Fatty fish, like salmon, mackerel, and cod liver oil, are all good sources of vitamin D. Egg yolks, fortified milks, and mushrooms, too.⁸  

• Incorporate UV Lamps into your morning routine. UVB lamps or light therapy boxes are designed to mimic sunlight, which can help boost vitamin D levels and hormone production. Use a 10,000-lux bright light early in the morning for 30 minutes. (Try habit stacking with journaling or eating breakfast.⁹)

• Supplement with dopamine-boosting nootropics. TeaCrine® and N-Acetyl-L-Tyrosine (NALT) have both been studied for their ability to help enhance dopamine production in healthy individuals.¹⁰⁻¹¹ TeaCrine® is a standardized alkaloid, naturally derived from a tea plant, and L-tyrosine is found in animal proteins, dairy products, and whole grains.

Feel equipped to thrive this winter, armed with the right outdoor gear, actionable ways to support your brain, and the permission to let yourself savor a slower pace. A cup of hot cocoa also helps. 

1. Brum, M. C. B., Senger, M. B., Schnorr, C. C., Ehlert, L. R., & Rodrigues, T. D. C. (2022). Effect of night-shift work on cortisol circadian rhythm and melatonin levels. Sleep science (Sao Paulo, Brazil), 15(2), 143–148. https://doi.org/10.5935/1984-0063.20220034

2. 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). https://doi.org/10.1186/1476-069X-8-34

3. Lambert, G. W., Reid, C., Kaye, D. M., Jennings, G. L., & Esler, M. D. (2003). Effect of sunlight and season on serotonin turnover in the brain. The Lancet, 362(9385), 682-684. https://doi.org/10.1016/S0140-6736(02)11737-5

4. Suva Roy, G. D., & Field, D. (2019). Dopaminergic modulation of retinal processing from starlight to sunlight. Journal of Pharmacological Sciences, 140(1), 86-93. https://doi.org/10.1016/j.jphs.2019.03.006

5. Huiberts, L. M., & Smolders, K. C. H. J. (2021). Effects of vitamin D on mood and sleep in the healthy population: Interpretations from the serotonergic pathway. Sleep Medicine Reviews, 55, 101379. https://doi.org/10.1016/j.smrv.2020.101379

6. Abboud M. (2022). Vitamin D Supplementation and Sleep: A Systematic Review and Meta-Analysis of Intervention Studies. Nutrients, 14(5), 1076. https://doi.org/10.3390/nu14051076

7. Daut, R. A., & Fonken, L. K. (2019). Circadian regulation of depression: A role for serotonin. Frontiers in neuroendocrinology, 54, 100746. https://doi.org/10.1016/j.yfrne.2019.04.003

8. Institute of Medicine (U.S.) Committee on Use of Dietary Reference Intakes in Nutrition Labeling. (2003). Dietary reference intakes: Guiding principles for nutrition labeling and fortification. National Academies Press. Available from: https://www.ncbi.nlm.nih.gov/books/NBK208880/

9. Daut, R. A., & Fonken, L. K. (2019). Circadian regulation of depression: A role for serotonin. Frontiers in neuroendocrinology, 54, 100746. https://doi.org/10.1016/j.yfrne.2019.04.003

10. Kuhman, D. J., Joyner, K. J., & Bloomer, R. J. (2015). Cognitive performance and mood following ingestion of a theacrine-containing dietary supplement, caffeine, or placebo by young men and women. Nutrients, 7(11), 9618-9632. https://doi.org/10.3390/nu711548

11. Hensel, C., Becker, M., Düzel, S., Demuth, I., Norman, K., Steinhagen-Thiessen, E., Gallinat, J., Lindenberger, U., & Kühn, S. (2019). Influence of nutritional tyrosine on cognition and functional connectivity in healthy old humans. NeuroImage, 193, 139-145. https://doi.org/10.1016/j.neuroimage.2019.03.005

Figure 1: PCLM, Inc. (n.d.). Sleep health infographic [Anatomy & Physiology of the Circadian System]. PCLM, Inc. https://www.pclm-inc.org/sleep-health.html

Figure 2: Wickham, R. (2015). Americans living north of 37° latitude are at greater risk for vitamin D [Image]. ResearchGate. https://www.researchgate.net/profile/Rita-Wickham/publication/264009699/figure/fig1/AS:601579715563524@1520439189212/Americans-living-north-of-37-latitude-shaded-area-are-at-greater-risk-for-vitamin-D.png