With the summer solstice just behind us, we’re in one of the most light-filled seasons of the year. This abundance of daylight presents a perfect opportunity to explore how light influences our health and well-being.
At BioLounge, we focus on helping our patients establish foundational health habits that harness the body's innate ability to heal. Light hygiene routines that optimize circadian biology have emerged as one of the best ways to support health and healing.
The importance of contrast in health
Human biology thrives on contrast. For example, in exercise science, a bout of exercise is a stressor on the body, but, with adequate rest and recovery, the body rebuilds stronger, which provides health benefits. Similarly, we need robust signals of both light and darkness to thrive.
Light and our biological clock
We evolved in close proximity to the natural world, experiencing predictable and alternating periods of light and dark every 24 hours. As diurnal mammals, we are active during the day and rest at night. Our bodies tell time through environmental signals known as zeitgebers, with light being the most significant one. Other powerful zeitgebers include meal timing and physical activity.
Our brain’s “master clock,” the suprachiasmatic nucleus (SCN), receives light signals through photosensitive nerve cells in our eyes. These cells read light energy and send information to the SCN, which then signals the rest of our body to help it “tell time.” Additionally, we have peripheral clocks in nearly every cell, creating their circadian rhythm based on the SCN’s light-induced signals and meal timing.
Syncing our circadian rhythm
For optimal health, our master clock should align with our peripheral clocks, syncing with the light-dark signals in our environment. This alignment translates environmental input into hormonal and neurochemical signals, helping our body function at its best.
The impact of modern living
However, modern living disrupts this natural alignment. Indoor living and light-emitting devices cause us to be “out of sync” with the sun’s cycles. This misalignment, or circadian disruption, can lead to various health issues. Shift work and jet lag, for example, have been linked to negative health outcomes, including psychiatric disorders, sleep and cognitive impairments, and even cancer. The World Health Organization has classified shift work as a potential carcinogen. Even if you’re not a shift worker, many of us experience social jet lag and digital jet lag, chronically disrupting our circadian rhythms.
Bright light in the morning optimizes cortisol rhythms
Bright light exposure in the morning is essential for optimizing circadian rhythms primarily through its influence on cortisol rhythms. Cortisol, generally maligned as a stress hormone, is also a key signal for the circadian system. Cortisol is an "awakening and alerting" hormone that helps us feel energized during the day. Ideally, it follows a daily 24-hour curve with the lowest concentrations at night and a peak right before we wake up. Additionally, there should be a sharp peak in concentration within the first hour after waking, which is known as the cortisol awakening response (CAR). One signature of depression (and circadian misalignment) appears to be a blunted cortisol awakening response.
One way to induce an optimal cortisol awakening response is to view sunlight in the morning. This sets up a cascade that optimizes both cortisol and melatonin rhythms.
Another significant benefit of getting ample daylight exposure is that it helps your body be less sensitive to the harmful impacts of bright light at night. Specifically, studies have shown that experiencing sufficient daylight during the day reduces the negative impact of blue light on melatonin production in the evening. As a result, you have a bit more grace around your nighttime light exposure, making it easier to maintain healthy sleep patterns.
Optimizing light hygiene
One of the simplest and most potent wellness tools is to optimize your circadian system by improving your light hygiene. Aligning your internal clock with natural light-dark cycles activates ancient biologic systems that promote health.
Our top tips for better light hygiene:
- Maximize daylight exposure: Spend at least 5-10 minutes outside in the morning and take outdoor breaks throughout the day. Avoid wearing sunglasses during these times to let natural light reach your eyes. For bonus points: Schedule at least 3 outdoor breaks during your day. This can be as simple as taking a 5-10 minute walk in the morning, at lunch and right after work.
- Minimize light at night: Use dim, warm-toned lights and blue-light-blocking technology in the evening. Establish a digital curfew and engage in relaxing, screen-free activities before bed.
- Ensure total darkness during sleep: Use blackout curtains and an eye mask to eliminate light exposure during sleep. Remove electronics from the bedroom or use a non-phone alarm clock.
By embracing the natural light-dark cycles, especially during this light-filled season, you can support your circadian rhythm and improve your overall health. Light is a free, powerful tool for well-being, so step outside and let nature’s light work its magic!