The Sun provides photosynthesis, vitamin D, warmth, and even prevents Seasonal Affectve Disorder. Why is it that the sun can make all the difference in the world on our attitude toward life? But beyond that, it's the major source of Vitamin D which has an enormous beneficial role in our bodies. Let's dive in:
Sun, Melatonin, and Serotonin:
The sunlight hits the back of our eyes and triggers a cascade of chemical responses straight to the part of our brain that tells us to WAKE UP. This is the hypothalamus. When we get that waking response, hormones and neurotransmitters respond in kind. You get an increase in cortisol, which is intended to happen, and you'll also get dopamine and serotonin secretions. When you have shorter or darker days, the sunlight exposure dramatically decreases. The hypothalamus produces more melatonin, because it's darker, making us sleepy, lethargic, and melancholic. The melatonin will also cause a decrease in serotonin, again making us a bit melancholic.
Sun, Serotonin, and Skin
It is proposed that the skin actually MAKES some serotonin! Your gut also makes serotonin but let's not go down that tract right now. There is a proposed theory that there might be a connection where the sun hitting the skin actually up-regulates serotonin production and increases seratonin binding to receptors...therefore making is more active. When I think about it, just the "feeling" of the warmth on my skin puts a smile on face.
It was a small study but 42 subjects were tested for the "cutaneous serotonin pathway"
and all wore opaque goggles to block out UV-A radiation, which eliminated the retinal or eye-sunlight response. 11 subjects were the control. Those who were exposed to light all had measurably more blood levels of serotonin than the controls. This would certainly open the door for more exploration into the science behind the "sun to skin to serotonin" pathway.
Sun and Vitamin D
Well, I could easily do an entire blog post on vitamin D which is in fact a hormone after all. But let's talk about it as it relates to the sun. The sun hits the skin and cholesterol is then converted into Vitamin D1. Then it's carried to the liver to be converted into D2, and then carried off to the Kidneys to be converted into the active form and the form most commonly found in supplements, D3.
Vitamin D helps with calcium absorption through the gut and prevents calcium from being excreted by the kidneys, thus contributing to bone health. It up regulates gene expressions to boost our immune system and promotes serotonin and dopamine production. It's shown to decrease complications in pregnancy such as per-ecalmpsia, gestational diabetes, and post postpartum depression. It has shown to decrease risk factors for heart disease, metabolic syndrome, and even neurological diseases like Multiple sclerosis.
Not so obvious benefits:
The sun is a major player of photosynthesis. This is how our plants get their food from Carbon dioxide and water. The process is pretty incredible but without the sun, our plants don't grow. Without our plants, we don't have fresh fruits, vegetables, nuts, or seeds. We can then go into the world of plant eating animals that we in turn might eat ourselves. Aka- grass fed beef. The sunlight provides food to our coral reefs thereby feeding the circle of life under the sea.
Get out and enjoy the sun, everyday, knowing that beyond the biochemical processes happening in our own bodies, there's a whole world of benefits that blazing ball of light provides.
Dr. Lexi
Resources:
Sunshine, Serotonin, and Skin: A Partial Explanation for Seasonal Patterns in Psychopathology? Randy A. Sansone, Lori A. Sansone Innov Clin Neurosci. 2013 Jul-Aug; 10(7-8): 20–24. Published online Jul-Aug 2013. PMCID: PMC3779905 Article PubReader PDF–115KCitation
Light, melatonin and the sleep-wake cycle. G M Brown J Psychiatry Neurosci. 1994 Nov; 19(5): 345–353. PMCID: PMC1188623 Summary Page Browse PDF–1.4MCitation
Shining a Light on Winter Depression. Light Therapy can help with seasonal affective disorder. Harvard Health Publishing. Harvard Men's Health Watch. Published Nov 2019.
Suzanne E. Judd, Vin Tangpricha Am J Med Sci. Author manuscript; available in PMC 2010 Apr 8.Published in final edited form as: Am J Med Sci. 2009 Jul; 338(1): 40–44. doi: 10.1097/MAJ.0b013e3181aaee91
PMCID: PMC2851242
Abedi, Parvin et al. “The Relationship Between Vitamin D and Postpartum Depression in Reproductive-Aged Iranian Women.” Journal of medicine and life vol. 11,4 (2018): 286-292. doi:10.25122/jml-2018-0038