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CORTISOL: Another important hormone for the body, made in the adrenal glands and also entrained by light, though indirectly.



Functionally, if melatonin is your body’s natural sleeping pill, with its onset preceding and preparing one for sleep, then cortisol is your body’s natural cup of coffee with its onset preceding and preparing one for wakefulness in the morning (see above graph). As seen in the graph, these two hormones work antagonistically.  A simplified understanding of melatonin would be to refer to it as the repair/sleep hormone. Using the same simplified logic, we could then think of cortisol as the productivity/awake hormone.

Using proper light hygiene usually maintains the proper timing, durations and amounts of both of these important hormones. A person’s complete 24-hour cycle of sleep/repair and awake/productivity encompasses every cell’s well-being in the body, ultimately affecting the total body/mind state of health. Levels and timing of cortisol in the bloodstream can be negatively affected by disease, stress and too much activity before sleep. For this reason, the recommended practice is to work-out during the day rather than late after dinner, as that time should be reserved for less light stimulation, general slowing down and, ultimately, a resting state before sleep. Working-out in a brightly lit gym at night can raise the overall cortisol level, prohibiting it from falling to healthy low levels during the 24-hour cycle. Chronic high cortisol causes disease.

Although proper light hygiene may subtract from late evening productivity, productivity in the morning is very enhanced, and overall productivity is also enhanced due to deeper REM sleep, thus promoting both a healthier and better-functioning mind and body.  To lose some evening productivity in exchange for an overall increase in productivity and repair is well worth it. Cortisol relies on melatonin timing to base its timing.

Click for CORTISOL pronunciation.

Click Circadian Light Phase Response to follow logical sequence of explanation.

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