Lux levels and circadian clock?

Lux levels have a direct impact on the human circadian clock. Natural sunlight can vary significantly in brightness, reaching up to 300,000 lux on a sunny day, while typical indoor environments rarely exceed 6,000 lux, which is significantly lower than the amount of light required to optimally impact our circadian rhythms. The circadian clock, specifically the region known as the suprachiasmatic nucleus, operates as a photon-summing system. This means that it integrates light over time to impact circadian rhythms and various other functions like mood and alertness 1.

Moreover, exposure to at least 100,000 lux of sunlight, particularly in the morning, is recommended to properly set the circadian clock and promote better mental and physical health. This exposure should ideally happen before 9:00 AM to capture enough photons necessary to signal to the brain that it is morning. In cases where natural light is insufficient, such as during winter months or in certain geographical regions, artificial light sources can be used as a substitute, but natural sunlight is preferred due to its unique qualities 2.

Additionally, photoreceptors in the eyes not only help in image forming but are crucial for detecting light necessary for setting the circadian rhythm. This interaction emphasizes the importance of direct light exposure to the eyes without intermediaries like glasses or windows which can significantly diminish the light's effectiveness by filtering out essential wavelengths 3.

Maintaining a healthy exposure to natural light during appropriate times of the day supports the synchronization of the body's internal clock, which can enhance overall well-being, improve sleep quality, and regulate energy levels.