Circadian rhythms are 24-hour cycles in our biology that regulate sleep, wakefulness and other bodily functions. When viewing light, melanopsin molecules inside the retina become activated, sending signals to the suprachiasmatic nucleus (SCN), located in the hypothalamus. The SCN, acting as the body's master clock, receives light information from photoreceptors and orchestrates the circadian rhythm. Through complex neuroendocrine pathways, it indirectly influences processes like cortisol release via the hypothalamic-pituitary-adrenal (HPA) axis and melatonin production through the pineal gland.

Signals from the SCN communicate with virtually every cell in your body to coordinate the timing of various physiologic processes, which is why keeping your circadian rhythm consistent has such wide-ranging health effects. In fact, knowing the time is so important that each cell in your body has its own circadian clock regulated by genes such as the PER, BMAL and CLOCK genes. 

Different types of light exposure significantly impact mental and physical health in unique ways. Natural sunlight is especially powerful: in addition to being magnitudes brighter than indoor light, retinal nerves can detect the time of day based on the ratio of blue to yellow light. Morning light exposure increases (healthy) cortisol levels, and exposure to outdoor sunlight throughout the day is linked to improvements in sleep quality, hormones and overall mood. Exposure to the afternoon sun helps adjust your eyes’ sensitivity and can buffer against the disruptive effects of artificial lights from screens and TVs in the evening.

On the other hand, increased exposure to artificial light — particularly at night — not only has negative effects on your sleep schedule but is also associated with increased symptoms of depression, anxiety and poor overall mental health.

How your mind and body feel during the first few hours after waking has a strong influence on the rest of your day. Following evidence-based waking and morning protocols can support energy, hormone and neurotransmitter levels that contribute to a focused, productive and subjectively more enjoyable (or at least pleasant) day.

To support your circadian rhythm, expose yourself to bright light soon after you wake up — preferably natural sunlight, or artificial light if it's still dark outside. Morning physical activity may also help align your body's natural rhythms. These practices can complement your body's innate cortisol-awakening response (CAR), potentially enhancing overall circadian synchronization. Consider delaying caffeine intake for 90-120 minutes after waking as a strategy to support your body's natural cortisol rhythm. While this approach may help optimize alertness for some individuals, keep in mind that responses to caffeine and its effects on cortisol can vary from person to person.

Everyone’s mornings look different, especially if you have children, work atypical hours or have other extenuating circumstances. These protocols are simply a guide towards better health; if you cannot implement these protocols perfectly, using them when you can is better than not at all.

The top contours of your body’s daily rhythm follows a general sleep-wake pattern, but there are several smaller fluctuations within your waking hours that contribute to either increased or decreased feelings of energy and alertness. Fluctuations in body temperature, hormone levels and neurotransmitter activity contribute to variations in alertness and focus throughout the day. 

While some studies have observed patterns of increased alertness at certain intervals after waking, these patterns can vary significantly among individuals and may be influenced by factors such as sleep quality, diet and personal circadian rhythms. Most people will feel a decrease in energy after lunch (called a postprandial dip), and while it is a natural ebb, there are protocols you can implement to lessen the intensity and stay alert and focused throughout the rest of your day.

Shift work, jet lag and intermittent sleep deprivation cause disruptions to your body’s natural circadian rhythms due to a mismatch between your internal clock and the external time cues in both environment and behaviors, like light exposure, body temperature and meal timing. This misalignment affects your mood, sleep timing and quality, metabolic health and overall physiological functions. 

Experiencing chronic circadian misalignment is linked to poorer mental and physical health outcomes — but there are protocols you can implement that can lower the negative effects. When working a night shift, keep the same schedule for at least two weeks (if possible) and use red light to maintain alertness without disrupting cortisol levels. If you’ve experienced a night of poor sleep or are adjusting to a new time zone, utilize exercise, meal timing and light exposure to get your circadian rhythm back on track.