Why is morning sunlight important?

Morning sunlight is important because it helps set your circadian rhythms, support alertness, and prepare your body for sleep later that night. 1

1. Cortisol and wakefulness: Bright morning light helps time the healthy early-day cortisol rise and promotes daytime alertness; it also suppresses residual melatonin that can make you sleepy. 2 3
2. Body clocks and sleep: Light signals the brain’s central clock, which coordinates rhythms throughout the body, including in organs and tissues. It helps set the timing of sleep and supports falling and staying asleep at night. 4 5
3. Metabolism and health: Properly timed light supports metabolism and, through well-timed circadian rhythms, broader health; the cited discussion also connects disrupted cortisol and melatonin rhythms with metabolic and cardiovascular effects. 6 7
4. If sunlight is unavailable: Bright artificial light, such as a suitable light simulator, can help when sunlight isn’t accessible, but ordinary indoor lights or a phone generally aren’t enough to set the clock as effectively as outdoor daylight. 8 9
5. Consistency: Aim to get morning light on about 80% of days. If you miss a day, the guidance is to extend the next morning’s exposure—Huberman suggests about twice as long. 10