Health Benefits of Sunlight Exposure


Sensible, limited exposure to sunlight is important to your overall well-being. But with people avoiding sun and increasingly spending more time indoors, health experts are worried about the consequences. Reduced sunlight exposure can give rise to a number of conditions – affecting your bones, hormones, mental and emotional health, eyes, immunity and even your heart.  Reduced sunlight exposure can give rise to a number of conditions – affecting your bones, hormones, mental and emotional health, eyes, immunity and even your heart.   

So, how could you benefit from catching some sunrays? Let’s start with the fact that sunlight exposure helps you make vitamin D, and then dig further into how sunlight also produces a number of other health benefits. The fear of sun is not only making us deficient in vitamin D but also depriving us of mood-enhancement, an immunity boost and other effects that come from healthy exposure to full spectrum sunlight.

Let’s find out more.

Vitamin D Synthesis  


When you expose your skin to natural sunlight, UVB stimulates the production of vitamin D in the skin. Vitamin D helps the body to absorb calcium and contributes to healthy, strong bones. And there is a substantial body of evidence that vitamin D, also called the sunshine vitamin, is an important component for your overall health.

The sunshine vitamin helps regulate immunity, lower inflammation, cut down the risk of heart disease, maintain muscle and bone health, improve mood and cognitive functions, lower depressive symptoms and may even provide protection against many forms of cancer. Vitamin D is also required for a healthy pregnancy and to maintain healthy bone and immune development in the new-born.  

Interestingly, sunlight has many health benefits to offer that are independent of vitamin D.

Basking in the sun: Health benefits beyond Vitamin D


1.    Boosts immunity


One way that sunlight helps boost immunity is through the production of vitamin D. We already know by previous research that vitamin D stimulates the production of anti-microbial proteins in the body; for example, cathelicidin and ß defensin 2. These naturally produced antibiotics are capable of destroying bacteria, virus and fungi; and can fight a wide range of infections including tuberculosis and respiratory infections such as asthma, influenza, colds and wheezing disorders. [1] [2] [3]

Tuberculosis, you ask? Well, the link between sunlight and tuberculosis is hardly new. Long before modern anti-tuberculosis drugs were discovered, this condition was mainly treated by sending patients to sanatoria where sunlight and clean air were in abundance. Experts have long believed that sunlight could kill germs and help control infections. Notably, low vitamin D levels and poor immunity are two main risk factors for tuberculosis.

Now, scientists have found evidence for how sunlight boosts immunity in a mechanism entirely independent of vitamin D.  A new research study shows that exposure to blue and UV light increases the activity of T cells, white blood cells that play a crucial role in natural immunity. T cells specialize in hunting down and destroying pathogens, infectious cells and can even kill cancerous cells.

Blue light, at low levels, triggers the production of hydrogen peroxide (H2O2) in T cells. This action allows them to move faster to the site of infection. [4] The study reported that “T cells possess intrinsic sensitivity to blue and UV light…..Photosensitivity is greater in activated T cells and enhances T-cell motility. Thus, T cells are a new type of photoreceptive cell and their photosensitivity may contribute to the effects of sunlight on immune function.”

What is interesting is that your skin has large concentration of T cells, about double the number circulating in the blood. This shows how your body is naturally designed to effectively and promptly respond to any foreign invaders that may try to enter the body through the skin. The researchers added that while prolonged exposure to UVB rays can cause skin cancer and other skin problems, blue light from the sun causes no such adverse effects.

2.    Improves mood and lowers depression


Sunlight affects your mood and overall mental health through complex mechanisms, that include the synthesis of mood enhancing neurotransmitters and vitamin D.

Sunlight stimulates the production of serotonin, a hormone majorly associated with regulating mood, happiness and anxiety. Less exposure to sunlight causes a dip in the serotonin levels, which is linked with anxiety, depression and generally feeling low. In fact, getting sufficient sunlight is known to produce effects similar to antidepressants, which also work by increasing the levels of serotonin in the brain.

Shortage of vitamin D, a by-product when you don’t expose the body to enough sunlight, is also strongly linked to a higher risk of depression. [5] And there is also evidence that vitamin D supplements may be helpful in lowering symptoms of depression. [6] Going by the research in this area, improving your mental health and symptoms of depression might be as simple (and inexpensive) as getting plenty of sunshine, eating vitamin D rich foods and taking vitamin D supplements.

This 2016 study looked at how various weather factors, such as sunshine, cloudy days, rain and pollution, could influence one’s mood. The researchers found that people are more vulnerable to feeling mentally distressed when the days are shorter and there is less sunshine. Among all the weather variables, the amount of time between sunrise and sunset was found to be the most significant in affecting mental and emotional health. The study concluded that: “Seasonal increases in sun time were associated with decreased mental health distress. This suggests the need for institutions and public health entities to plan for intervention and prevention resources and strategies during periods of reduced sun time.” [7]

In addition, getting some sun is found to be helpful in managing seasonal affective disorder (SAD) – a type of depression that typically hits during the fall and winter months when your exposure to sunlight is minimum. However, it is not always about sunshine as seasonal depression is a culmination of many factors such as genetic, biological and environmental but lack of sunshine is considered one of the most important risk factor at play here.  


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3.    Improves sleep


Natural sunlight regulates your body’s internal rhythm and circadian cycle – a system that regulates your sleep-wake up time and other biological mechanisms such as regulation of hormones and metabolism. Less exposure to sunlight upsets this natural internal beat, disrupting the play of hormones that control sleep, mood and energy levels. Healthy sun exposure re-aligns your internal clock – contributing to restful, sounder sleep.

4.    Lowers blood pressure


Sun exposure plays an important role in controlling high blood pressure. There is compelling evidence that the risk of high blood pressure and cardiovascular disease increases during winter months. The synthesis of vitamin D with the exposure to the UVB part of the sunlight is known to play some part in reducing blood pressure as well as the risk of cardiovascular disease (by lowering inflammation, vascular stiffness and endothelial dysfunction). [8] But there is another interesting aspect to sunlight and its link with hypertension, which is not related to vitamin D.

A 2014 study found that UVA light stimulates the skin to release nitric oxide (NO) into the bloodstream. NO dilates blood vessels and significantly lowers blood pressure. This effect also translates into reduced risk of heart attack and stroke. [9]

5.    Decreased myopia risk later in life


Lack of sunlight exposure could even damage your eye health. A study published in JAMA Ophthalmology revealed that people who get more sunlight or UVB exposure, especially in adolescence and early adulthood, are less vulnerable to developing myopia or near-sightedness than those who don’t. [10] Interestingly, the researchers didn’t find any evidence that could imply the role of vitamin D in reducing this risk. According to the team, it is possible that sunlight stimulates specific cells in the retina and affects a particular type of growth in the eye that is associated with myopia.  

Moderation is the key


There is no denying that overexposure to the sun’s UV rays can have detrimental effects on the skin. UV rays can damage cellular DNA and cause skin cancer. But sensible exposure of 15-20 minutes is enough to catch the benefits that sunlight has to offer.

It is definitely time to add a little sunshine in your life!!

References:
  1. Adrian F Gombart. The vitamin D–antimicrobial peptide pathway and its role in protection against infection. Future Microbiology. 2009 
  2. Youssef et al. Antimicrobial implications of vitamin D. Dermatoendocrinol. 2011
  3. Martineau et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ, 2017
  4. Phan et al. Intrinsic Photosensitivity Enhances Motility of T Lymphocytes. Scientific Reports.
  5. Ju SY, Lee YJ, Jeong SN. Serum 25-hydroxyvitamin D levels and the risk of depression: a systematic review and meta-analysis. The Journal of Nutrition, Health and Aging. 2013
  6. Shaffer et al. Vitamin D supplementation for depressive symptoms: a systematic review and meta-analysis of randomized controlled trials. Psychosomatic Medicine. 2014
  7. Beecher et al. Sunshine on my shoulders: Weather, pollution, and emotional distress. Journal of Affective Disorders. 2016.
  8. Ioana Mozos, Otilia Marginean. Links between Vitamin D Deficiency and Cardiovascular Diseases. BioMed Research International. 2015
  9. https://www.ncbi.nlm.nih.gov/pubmed/24445737
  10. K.M Williams et al. Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study. JAMA Ophthalmol., 2017