March 31, 2023

Understanding Melanopic Light: The Science Behind Light's Impact on Circadian Rhythm

Light plays a crucial role in regulating our circadian rhythm, the body's internal clock that regulates our sleep-wake cycle. Specifically, melanopic light, a type of light that stimulates the melanopsin cells in our eyes, can have a significant impact on our circadian rhythm. In this post, we will explore the science behind melanopic light and its effects on our health.

What is Melanopic Light?

Melanopic light is a type of light that is detected by a specific group of cells in our eyes called melanopsin cells. These cells are located in the retina and are responsible for regulating our circadian rhythm. When melanopsin cells are stimulated by melanopic light, they send a signal to the suprachiasmatic nucleus (SCN), which is the body's master clock. The SCN then sends signals to other parts of the body, regulating everything from hormone levels to body temperature.

Melanopic light is measured in units of melanopic lux, which takes into account the sensitivity of the melanopsin cells to different wavelengths of light. The amount of melanopic light that we are exposed to can have a significant impact on our circadian rhythm and overall health. Melanopic sensitivity peaks at ~480nm sky blue at over 6x compared to the lux of that same wavelength, this means that while sky blue may appear less bright to the eye, the biological action is far greater. Below in grey is the melanopic action curve. The red portion shows the light that is able to pass though Carbonshade melanopic light blocking glasses, that block 99.8% of all melanopic light.

The grey area is the melanopic light response curve.  The red section is the light that is able to pass through Chroma Carbonshade glasses.

The Impact of Melanopic Light on Circadian Rhythm

Melanopic light is most effective at regulating our circadian rhythm when it is present in the morning and daytime. Exposure to melanopic light during these times can help to reset the body's internal clock, leading to better sleep quality and overall health. However, exposure to melanopic light at night can have the opposite effect, disrupting our circadian rhythm and leading to sleep disorders and other health problems.

Sources of Melanopic Light

Melanopic light can be found in a variety of sources, including sunlight, indoor lighting, and electronic devices. Sunlight is the most potent source of melanopic light, with natural daylight containing up to 100,000 melanopic lux. Indoor lighting can also provide melanopic light, but the amount of melanopic light present will depend on the type of light source and the time of day. Electronic devices such as computers, smartphones, and televisions emit blue light, which can also stimulate melanopsin cells and disrupt our circadian rhythm. This is why red glasses in the evening are often recommended as the first step in circadian correction. It's roughly 100x brighter outside than inside during the day, and nearly 100x brighter inside than outside at night.

The Importance of Managing Melanopic Light Exposure

Given the impact of melanopic light on our circadian rhythm and overall health, it is important to manage our exposure to this type of light. Some strategies for managing melanopic light exposure include:

  • Getting natural daylight exposure & supplementing melanopic light when inside during the day.
  • Using blue light-blocking glasses or filters on electronic devices at night.
  • Using warm, dim lighting in the evening, ideally incandescent lights or candles.
  • Minimizing exposure to electronic devices before bedtime.

Conclusion

Melanopic light plays a significant role in regulating our circadian rhythm and overall health. By understanding the impact of melanopic light and implementing strategies to manage our exposure to this type of light, we can optimize our sleep quality and improve our overall health.

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