Why Experts Want You To Get A Double Dose of Daylight

We spend nearly 90% of our time indoors,¹ getting far too little bright light during the day and far too much artificial light at night.

Research suggests this light mismatch matters: less time in outdoor daylight is linked with poorer sleep and circadian-related outcomes, while room light before bed can delay and shorten the body’s natural melatonin signal.^{2 3}

The resulting "circadian confusion" may manifest as morning tiredness, afternoon energy crashes, and fragmented nighttime sleep.

According to neuroscientist and health educator Dr. Andrew Huberman, the advice is remarkably simple: step outside twice a day.⁴

Getting natural sunlight soon after waking and again in the late afternoon or around dusk provides two environmental signals that help anchor your internal clock. One ignites early daytime alertness, while the other helps prepare your body for sleep.⁴

Here is what the research says about taking a daily "double dose" of daylight, and how it can improve your energy, mood, and sleep quality.

Read More: Dr Rangan Chatterjee Explains How Light Can Help You Sleep Better

Benefits of morning light

"I consider viewing morning sunlight in the top five of all actions that support mental health, physical health and performance,” says neuroscientist Dr. Andrew Huberman.⁴

Most morning routines happen in near-darkness; lux is the measurement given to the amount of light reaching your eyes.⁵

• Waking up in a dimly lit bedroom might register 30 to 40 lux.
• A typical home living area, indoor office or kitchen might reach ~300 to 500 lux.⁵,⁶
• Outside and daylight can range from around ~1,000 to 10,000 lux on a heavily overcast day to more than 100,000 lux in bright, direct sunlight.⁵,⁶

This is why outdoor daylight is so powerful for the circadian system: even when it looks grey or cloudy, it can provide a much stronger daytime light cue than typical indoor lighting.

(Photo from iStock of a woman outside in the morning) 

1. Natural awakening response

Morning light influences the body’s natural cortisol awakening response - the normal rise in cortisol that occurs after waking and helps the body shift into daytime mode.⁷,⁸ This is not the same as chronic stress-related cortisol; it is a healthy daily rhythm that supports wakefulness, energy and alertness.

In a small controlled study of sleep-deprived men, bright white light between 5am and 8am was found to increase cortisol levels by more than 50% compared with dim light. Exposure to the same bright light between 1pm and 4pm had no significant effect on cortisol levels.⁹

2. Influences circadian timing

Morning light's one of the strongest environmental signals for the circadian rhythm - the internal clock that helps regulate sleep–wake timing and alertness.¹⁰

Light exposure during the morning tends to shift circadian timing earlier, while light in the evening or night tends to shift it later.¹⁰

In a small study of eight men, bright light exposure between 6am and 9am for three consecutive days advanced the evening rise in melatonin and the time of waking by around one hour compared with dim light, showing that morning bright light can move the body clock earlier.¹¹

3. Improves sleep quality

A sunlight-and-sleep study found that greater morning sunlight exposure, especially before 10 am, was associated with an earlier sleep midpoint and better self-reported overall sleep quality.¹²

Your sleep midpoint is the halfway point between falling asleep and waking up. An earlier midpoint may reflect an earlier sleep–wake pattern and circadian timing. In practical terms, this may help you feel more awake in the morning, feel sleepy at a more appropriate time in the evening and experience better sleep quality.

Read More: Which Side Should I Sleep On? The Science Behind Sleep Position And Your Biology

4. Improves alertness

Morning light can help you feel more awake. In a small study of 15 university students, one hour of morning exposure to blue-enriched white light was associated with reduced subjective sleepiness and improved self-reported alertness and mood when compared with warmer white light.¹³

5. Supports mood

Natural daylight has also been linked with mood-related wellbeing in observational research. A large study of more than 400,000 UK adults found that spending more time outdoors during daylight hours was associated with greater happiness and less frequent low mood.² While the study cannot establish cause and effect, its findings suggest a positive relationship between daytime outdoor light and mood-related wellbeing.²

Artificial morning light has been studied as a tool for mood-related outcomes in small clinical and laboratory studies. In a crossover study of eight people with winter depression, morning bright light was found to be more effective than evening light at reducing depressive symptoms.¹⁴

Researchers suggested this benefit may come from morning light’s ability to correct delayed circadian timing by shifting the internal clock earlier.¹⁴ Separately, a small study noted above found higher self-reported mood ratings after morning exposure to blue-enriched white LED light than after warmer white light.¹³

6. Counter modern indoor living

Modern life often gives us too little bright light during the day and too much artificial light at night. A large UK study of more than 400,000 people found that low daytime outdoor light exposure was associated with poorer mood, sleep and circadian-related outcomes.²

Greater daytime outdoor light exposure was associated with easier waking, earlier sleep–wake timing, fewer sleep difficulties and less frequent tiredness.²

Benefits of evening light

“Viewing light circa sunset [also] adjusts the sensitivity of the cells in the eye such that it buffers you against some of the negative effects of light late at night." - Dr. Andrew Huberman.¹⁵

(Photo by iStock of a woman enjoying a sunset) 

1. A second circadian anchor

Late afternoon or evening sunlight helps tell the brain that the day is ending.

Huberman describes afternoon sunlight as a second “anchor point” that helps the brain and body register the time of day and maintain consistency in the circadian clock, especially on days when morning outdoor light exposure is missed.⁴

2. Signals the transition to sleep

Sunlight viewed in the late afternoon or evening communicates to the brain’s circadian clock that evening is approaching and that it is time to begin preparing for sleep later that night.⁴

3. Influence responses to later artificial light

Exposure to brighter light earlier in the day or early evening may make the body less sensitive to later evening light. In a small crossover study of 12 healthy young women, early-evening bright light reduced some of the melatonin-suppressing and alerting effects of later evening light.¹⁶

This does not mean bright screens or overhead lights at night are harmless, but it suggests that getting enough natural light before sunset may help buffer some of the effects of modern indoor lighting.¹⁶

4. Supports melatonin production

Your body relies on contrast: bright light during the day and dim light at night. Evening sunlight can help mark the end of the daytime window, but after dark, bright artificial light can interfere with melatonin.³

One study found that room light before bedtime suppressed melatonin onset in 99% of participants and shortened melatonin duration by about 90 minutes.³

Why the double dose matters

Combining morning and evening sunlight creates the ultimate high-contrast signal for your brain’s circadian clock.⁴

While early daylight can enhance a healthy cortisol awakening response to ignite focus and help align circadian timing, sunset light may lower your eye's sensitivity to late-night screens and prevent your internal clock from drifting.⁸,¹²,¹⁶

Together, these two daily anchors help to keep your 24-hour circadian rhythm stabilized - maximizing daytime energy when you need to be active and supporting deep, restorative sleep when it's time to rest.^{2 4}

Read More: The Science of Feeling Good: What Your Mind, Body, Skin and Rhythm Need to Thrive

The Non-Negotiable Rules

Understanding the science is step one; getting the protocol right is step two.

To get the full biological benefit, Dr. Andrew Huberman emphasizes that how you view sunlight matters just as much as when:⁴

• On a clear, sunny morning, 5 to 10 minutes outdoors is all it takes. On overcast or cloudy days, you’ll need to extend that to 15 to 20 minutes to receive enough outdoor light.⁴
• Looking through a glass window or car windshield will not work - glass filters out the specific wavelengths of light required to signal your master clock. You have to be outside.⁴
• Leave your sunglasses and blue-light blockers inside where safe and appropriate, regular corrective glasses and contact lenses (even those with UV protection) are completely fine to wear.⁴
• Face in the general direction of the sun, but never look directly at it. Do not stare into any light source that causes pain or discomfort - blink naturally and look away as needed.⁴
• You don't need to stand around, you can use this time to walk the dog, sip your morning coffee, exercise, or journal.⁴
• If you wake up before sunrise, turn on as many bright overhead indoor lights as possible to start waking your system - then step outside for real sunlight as soon as the sun comes up.⁴
• For afternoon daylight, step outside late in the day or around sunset when the sun is low in the sky. The unique spectrum of yellow, orange, and red wavelengths at dusk signals to your brain’s circadian clock that night is approaching.⁴

How BON CHARGE can support your light routine

Indoor lighting is not a replacement for outdoor daylight, especially in the morning. Even on cloudy days, natural light outside is usually far brighter than the light inside your home or office.⁵,⁶

Buy Blue Light Blocking Glasses Here

But if you wake before sunrise, work in a windowless space, or spend long hours indoors, you can still make your environment more circadian-friendly.

The BON CHARGE Full Spectrum Lamp is designed to support different parts of the day with a daytime full spectrum setting, a morning/afternoon low blue light setting, and an evening/night zero blue light setting. Use it to create a more natural-feeling indoor light environment until you can get outside.

Then, after sunset, switch to BON CHARGE Blue Light Blocking Glasses or a BON CHARGE Blue Light Blocking Light Bulb to create a softer, blue-free evening and support your body’s natural wind-down routine.

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References

1. US Environmental Protection Agency. Indoor Air Quality. EPA 

2. Burns, A. C. et al. Time spent in outdoor light is associated with mood, sleep, and circadian rhythm-related outcomes: a cross-sectional and longitudinal study in over 400,000 UK Biobank participants. J. Affect. Disord. 295, 347-352 (2021). 

3. Gooley, J. J. et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J. Clin. Endocrinol. Metab. 96, E463-E472 (2011). 

4. Huberman Lab. Using Light for Health. Huberman Lab 

5. TIME. The Morning Light Habit Sleep Experts Swear By. TIME 

6. Dautovich, N. D. et al. A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults. Sleep Health 5, 31–48 (2019). 

7. Stalder, T. et al. The cortisol awakening response: regulation and functional significance. Endocr. Rev. 46, 43–59 (2025).

8. Petrowski, K., Schmalbach, B., Niedling, M. & Stalder, T. The effects of post-awakening light exposure on the cortisol awakening response in healthy male individuals. Psychoneuroendocrinology 108, 28–34 (2019).

9. Leproult, R., Colecchia, E. F., L’Hermite-Balériaux, M. & Van Cauter, E. Transition from dim to bright light in the morning induces an immediate elevation of cortisol levels. J. Clin. Endocrinol. Metab. 86, 151–157 (2001).

10. St Hilaire, M. A. et al. Human phase response curve to a 1 h pulse of bright white light. J. Physiol. 590, 3035-3045 (2012). 

11. Dijk, D. J., Beersma, D. G., Daan, S. & Lewy, A. J. Bright morning light advances the human circadian system without affecting NREM sleep homeostasis. Am. J. Physiol. 256, R106-R111 (1989). 

12. Menezes-Júnior, L. A. A. et al. The role of sunlight in sleep regulation: analysis of morning, evening and late exposure. BMC Public Health 25, 3362 (2025). 

13. Lee, S. I. et al. Awakening effects of blue-enriched morning light exposure on university students’ physiological and subjective responses. Sci. Rep. 8, 345 (2018). 

14. Sack, R. L. et al. Morning vs evening light treatment for winter depression. Evidence that the therapeutic effects of light are mediated by circadian phase shifts. Arch. Gen. Psychiatry 47, 343-351 (1990).

15. Huberman, A. Viewing light circa sunset minimizes adverse effects of evening artificial light exposure. PodClips 

16. te Kulve, M., Schlangen, L. J. M. & van Marken Lichtenbelt, W. D. Early evening light mitigates sleep compromising physiological and alerting responses to subsequent late evening light. Sci. Rep. 9, 16064 (2019). 

BON CHARGE: This content is for general education and is not medical advice. Our products are not intended to diagnose, treat, cure, or prevent any disease. Always follow product instructions and consult a qualified healthcare professional for guidance tailored to you. Individual results may vary.