I describe the mechanisms by which different wavelengths of light impact the cells, tissues and organs of the human body, and how specifically timed light exposure of specific wavelengths can be used to improve sleep, enhance alertness, modulate hormone levels, and improve mood. I also explain the use of ultraviolet and infrared phototherapies to... See more

effects in your brain? Time of day matters, as T levels are nearly twice as high during the daily circadian peak as during the trough. Whether you’re sick, are injured, just had a fight, or just had sex all influence T secretion. It also depends on how high your average T levels are; they can vary fivefold among healthy individuals of the same sex,

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