Sarah Giardenelli, ND, MSOM, LAc, is a certified naturopathic doctor and licensed acupuncturist.

“Each day, Apollo’s fiery chariot makes its way across the sky, bringing life-giving light to the planet.  For the ancient Greeks and Romans, Apollo was the god of medicine and healing as well as of sun and light—but Apollo could bring sickness as well as cure.”  (1) ~ M. Nathaniel Mead

I think it’s fair to say that by this time of the year, we are all missing the sun!  Have you heard about Seasonal Affective Disorder (SAD)?  SAD is a form of depression that most commonly affects people during the fall and winter months in northern climates.  It is a recognized medical condition and is not something to ignore.  Common symptoms include increased fatigue or lethargy, increased irritability, an overall feeling or sadness or hopelessness, and increased or decreased appetite, lacking desire to socialize, and/or inability to concentrate. (2)

I find it super interesting that both lack of exposure and over-exposure to sun light can affect us in such a strong way.  This points to the fact that human physiology is interdependent on nature for healthy function.  So, I started thinking of all the ways that sunlight benefits out health.  You may be questioning my thought process, as we’ve been conditioned to think that exposure to sunlight is not good for our health.  Public health messages have warned us that overexposure to sunlight leads to direct DNA damage to the skin, reduction of the important antioxidant vitamin A, and damage to the collagen in our skin that keeps our skin young and supple.  And, these health messages are extremely important because they have been helpful in reducing skin cancer.  However, in my opinion, this has overshadowed the important benefits of sun exposure.  The 2006 World Health Organization report on The Global Burden of Disease Due to Ultraviolet Radiation pointed out that excessive ultraviolet radiation (UVR) accounts for only 0.1% of the total global burden of disease in disability-adjusted life years, compared to 3.3 billion disability-adjusted life years from lack of sun exposure.  (1)

So, what are the health benefits from sun exposure?  The first: Vitamin D.  While vitamin D is commonly known for its role in bone health, vitamin D is really an important pro-hormone that has a multitude of health benefits.  Naturopathic Doctor Teerawong Kasiolarn, ND writes about the health benefits of vitamin D in this blog post.  Vitamin D is present in some foods like fish, liver, egg yolks, and mushrooms, but humans get the bulk of their vitamin D from the sun.  Active vitamin D is produced in human skin, mostly through a photosynthetic reaction triggered by UVB radiation.  The amount of vitamin D produced by the skin is dependent upon a number of factors including the amount of clothing a person is wearing, his or her level of body fat, sunscreen, and the amount of skin pigment (melanin).  So, the more clothes, fat, sunscreen, and/or skin pigment, the less vitamin D is able to be produced by the body.

By the late 1800s, “Approximately 90% of all children living in industrialized cities of northern Europe developed rickets.”  Rickets is severe vitamin D and or calcium deficiency that leads to delayed growth, bone pain or malformations, and muscle weakness. (3)  This was a result of a cultural shift, making it common to cover the body from neck to feet year-round.  Today, vitamin D deficiency is very common, with more than 3 million Americans being affected per year (5).  I especially see this among my patients here in Northern Virginia.  This is because our population is typically office-bound, getting very little sun exposure.

Sunlight is also important for helping to set our circadian rhythms – our body’s natural rhythms – and our sleep cycle.  Exposure to sunlight or a sun lamp has been shown to increase the body’s production of melatonin at night.  Melatonin is a hormone produced in the pineal gland and is the key hormone for setting this body’s circadian rhythm.  Serotonin is the neurotransmitter precursor to melatonin.  Serotonin helps to regulate mood and is commonly known for promoting happiness and a positive outlook.  In patients affected with SAD, the serotonin levels appear to be low.  The pineal gland can only convert serotonin to melatonin in complete darkness.

The light of the sun is much brighter than indoor light.  Therefore, exposure to weaker, artificial light can cause disruption to our sleep cycles.  Several recent studies have demonstrated that the amount of one’s electronic screen time is highly correlated to sleep disturbances (6, 7).  I commonly see this in my patients and I am always surprised when they tell me that they’ve tried everything under the sun – (pun intended!) – in terms of medications and supplements to try to aid their sleep, but they haven’t tried reducing their screen time, as they didn’t realize that this could disrupt their sleep.  I often find they do not WANT to believe this either!  But, in every case where I’ve recommended this, the patients have seen some improvement in their sleep.  Even the American Academy of Pediatrics recommends that children and teens limit screen use to 1-2 hours per day, and I recommend that my adult patients avoid any electronic screens at least 2 hours before bed. (7)

Aside from helping us to produce vitamin D, there are a number of other UV light dependent pathways in the human body including:

  • Sun exposure up-regulates cytokines TNF-alpha and IL-10, important in immune regulation
  • Increases the production of pigment and skin cells (melanocytes and keratinocytes) that are important for limiting skin damage from sun exposure, and therefore helps to reduce melanoma risk
  • Increases the release of substance P which is an important neuropeptide involved in pain and immune system regulation
  • Causes the release of endorphins from pigment cells (1).

So, yes, you read correctly: A little sun may bolster your immune system, protect you from skin cancer, help you with your pain management, and help you feel more happy and euphoric… There is a reason why everyone is happier when the sun is shining!

While public health programs have pushed standard recommendations for all, the amount of sun exposure necessary for health is really individual per skin type and genetic risk.  As we learn more about genetics, exposure recommendations for health will likely also become more personalized.  If you think you may be suffering from SAD, be sure to discuss this with your doctor – there are a variety of therapeutic options, including blue light therapy that can be quite effective.

If you are an office worker who doesn’t see the light of day, do your best to get outside to get some sun exposure – even for a few minutes per day!  If it’s too cold, some of my patients get their rays from a few minutes of sitting in front of a 10,000 lux therapeutic blue light.  These lights can be found online from various vendors at reasonable prices.  I think the lights that double function as “light alarm clocks” – waking you with UV light instead of the annoying sounds – are especially useful.

Hang in there – the days are getting longer and brighter – spring will be here before we know it!


  1. Mead, M. N. (2008). Benefits of Sunlight: A Bright Spot for Human Health. Environmental Health Perspectives, 116(4), A160–A167.
  5. Arora, T et al. Exploring the complex pathways among specific types of technology, self-reported sleep duration and body mass index in UK adolescents. International Journal of Obesity 37, 1254-1260 (September 2013) | doi:10.1038/ijo.2012.209
  6. Hale, L and Guan, S. (2015). Screen time and sleep among school-aged children and adolescents: A systematic literature review. Sleep Medicine Reviews. 21, 50-58.

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