Hormones and light through the eyes

Hormone production and light through the eyes (why I never wear sunglasses). Light into the eyes, or lack thereof, primes certain hormonal pathways. Everything in nature is in balance. The same is true with our hormones.

There is a connection between the light the eye receives and the hormones made by the pituitary gland. Conversely, there is a connection between lack of light entering the eye and hormones made by the pineal gland. They work in balanced opposition, yoked to the cycling of darkness and light.

What happens when we shift away from this balance and use artificial light at night? Similarly, what if we block the sun’s light during the day by wearing sunglasses? Nothing good.

The pituitary gland and the pineal gland work in opposing ways. The pituitary gland is stimulated by bright light, especially blue wavelengths. When morning light contains nature’s perfect balance of blue and red frequencies, the hypothalamus instructs the pituitary gland to elevate cortisol. This is a “stress” hormone which is beneficial to have elevated in the morning because it transiently increases blood glucose and other chemicals that help us fight or flee; essentially, it energizes us to take action at the start of the day.

The communication pathway between the light entering the eye and the brain gets disrupted by artificial blue light at night. The pathway to making cortisol gets elevated again, and because they are opposing, the production of melatonin by the pineal gland gets suppressed. If we consistently do this at night, we begin to think of nighttime as our “productivity time” because we get an artificial “second wind.” This delays sleep and creates a vicious cycle of delaying sleep to get stuff done.

When we get our eyes in touch with the natural light and dark cycles, cortisol and melatonin regain balance. Studies on “night owls” have shown they can completely regain circadian rhythm in 2-10 days of camping. This pathway is built into us. We just need to sync back up with nature’s cycles. This means:

  • outdoor light first thing in the morning
  • no sunglasses
  • dim house at night
  • block the artificial light with blue blockers

This is just one example of hormone balance tied to light.

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