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Feeling the winter blues?


The days are getting shorter and your mood may be darkening too. Did you know that light plays an important role in human health and productivity and can be used to improve your health, mood, sleep, and energy levels this winter?

As many people are aware, daylight directly affects the human body’s systems.   Adequate daylight exposure can increase a person’s health, mood and overall wellbeing. But at the onset of wintertime, as we have less and less opportunity to enjoy natural light, artificial light can be used to mimic daylight, and comes with the same health benefits.  The key is paying close attention to spectrum, intensity, and timing.

Most human body processes are programmed by light exposure, and without adequate daylight exposure can experience a ‘daylight deficiency’ of sorts.  A region of the brain known as the hypothalamus controls these numerous functions, which include the sleep cycle and the immune system, among others.  The hypothalamus receives signals from the retinal ganglion cells (neurons located in our eyes) which sense darkness, light and intensity of light.  These retinal ganglion cells are particularly sensitive to blue light, therefore artificial blue light can be used to overcome daylight deficiency during the winter months. 

Exposure to blue light wavelengths (peaking at a 460 nm) stimulates the body’s production of serotonin and dopamine.   Serotonin is a neurotransmitter that affects mood, appetite, sleep, temperature regulation, and some social behavior.   Dopamine is another neurotransmitter that plays an important role in behavior and cognition, motor activity, motivation, sleep, mood, attention, and learning.  

However, while this wavelength of light is important to maintain typical processes, the body also requires darkness.  Melatonin is a hormone produced in the pineal gland that causes drowsiness and reduced body temperature, preparing the body for sleep when cued by the hypothalamus.   As mentioned previously, the hypothalamus receives signals from retinal ganglion cells related to the intensity and wavelength of any incoming light.   So when the ganglion cells perceive no light, the hypothalamus signals for melatonin to be produced.   While complete darkness is optimal for the production melatonin, if artificial lighting is present at nighttime, it should not include these blue wavelengths, because the production of melatonin is inhibited by light.   The body’s anticancer cells (T-cells and Natural Killer cells) are also activated in the evening, but only when there is no light or only red light.   If the retinal ganglion cells are exposed to light, particularly blue light, on a continuous basis it is possible that fewer of the anticancer cells will be active. 

To summarize, blue wavelengths at high intensities are important, but should only be received in the morning and afternoon. In the evening, light, particularly blue light should be avoided.   These recommendations directly follow the natural timing and intensity of daylight and can be used year-round.   

Blue light therapy devices are becoming more mainstream and are currently available at and Target.  But a therapy device may not be necessary.   Many stores sell light bulbs that incorporate more blue wavelengths into their spectrum output.  Try using the GE Sunshine or Daylight bulbs or any bulbs with a color temperature 4000K or higher.  When you are replacing bulbs, keep in mind that the bulbs with this color temperature may not have the best color rendering, so keep standard bulbs in bathrooms and kitchens.