Here Comes the Sun!

Here Comes the Sun!

May 5, 2023

Joy Stepinski, MSN, RN-BC

In the month of May, flowers are blooming and leaves somehow magically appear on the trees. The hint of summer’s arrival brings thoughts of the salty ocean air, long walks, and outdoor gatherings. With the increased daylight hours arriving to the northern hemisphere, the warmth of the sun is welcomed.

Soaking up the warm rays of sunlight is a reminder of how integrally connected the human body is to the natural world. The skin, the largest organ of the body, interacts with the sun, leading to profound health effects. Not only does sunlight activate the vitamin D pathway, but research also shows that the sun’s ultraviolet radiation has important considerations for the cardiovascular system independently of vitamin D.

The skin synthesizes vitamin D3 (cholecalciferol) after it is exposed to sunlight [1], which is how the body acquires 80% of vitamin D [2]. Through a series of steps in a metabolic pathway that involves both the liver and kidneys, cholecalciferol transforms into a biologically active form called calcitriol. Once in this usable form, it will then bind to vitamin D receptors found in cells and tissues.

Vitamin D has historically been labeled a vitamin. However, the literature discusses that hormone is actually a proper description. A vitamin is obtained through food and acts as a coenzyme or a precursor to coenzymes that regulate metabolic processes, yet does not provide energy [1]. Although 20% of vitamin D comes from food, sunlight is its main source [2]. Some have suggested that vitamin D is a hormone precursor, which must be synthesized by sunlight in order to be activated. A hormone circulates in body fluids and affects target cells or organs to help control and regulate different activities in the body [1].

Why is vitamin D so important? One well-known function is to help prevent bone turnover. Among its many roles in bone health, vitamin D promotes calcium absorption from the gastrointestinal tract for bone mineralization. Its importance does not end with bones, however. Vitamin D is used widely by the body and thought to be involved with brain function, the cardiovascular system, pain regulation, insulin production, and immune function.

Research suggests that low vitamin D levels (25[OH]D) are actually markers for poor health [3]. Although the public is constantly advised to take vitamin D supplementation to promote good health, most trials have shown that supplementation does not prevent such diseases as cardiovascular disease or cancer, accelerate healing of infectious illnesses, or improve mood and cognition. The dropping of vitamin D levels is likely related to illnesses characterized by inflammation. C-reactive protein (a marker for inflammation) is inversely correlated with vitamin D levels. The authors relay that although more studies are warranted, a strong hypothesis is that once the inflammatory process is healed, vitamin D levels may be restored.

Independent from vitamin D, more research [4] shows that the cardiovascular system greatly benefits from the sun. The dermal and epidermal skin layers contain nitrogen oxide stores, mostly in the form of nitrate (NO3). Thanks to nitrate-reducing bacteria that generate nitrite (NO2–) from sweat, nitric oxide (NO) can be produced. Why is NO so important? Among its roles are vasodilation of the arteries. Studies have shown that sunlight can lead to lower blood pressure.

You may be asking, “so what about cancer?” Adequate sunlight appears to be essential despite cancer concerns related to the sun. There is a strong inverse correlation between ovarian cancer and sunlight. In looking at ovarian cancer mortality, women in northern USA are five times more likely to die from the disease than women in the southern part of the country [5]. Another study showed an inverse relationship between sunlight and colon cancer [6]. Of primary concern are sun-related skin cancers. Melanoma is the most fatal in 20% of patients diagnosed. The risk appears to be greatest among fair-skinned people who burn due to intense repeated sun exposure or engage in frequent use of tanning beds [7].

Swedish research [7] enrolling 29,518 women found “women who avoid sun exposure are at an increased risk of all-cause death with a two- fold mortality rate as compared to those with the highest sun exposures” (p.85).  As stated by one author, “all-cause mortality and its reduction should be the primary aim of physicians, not the narrow avoidance of skin cancer” (p. 133) [4].

Although touted as safe, sunscreen and sunblock lotions are known to contain harmful chemicals and heavy metals. A 2023 Pakistani pilot study discussed that using sunblock on a daily basis can lead to an accumulation of chemicals in the body [8].

How much sun is needed? Sun time will vary according to skin tone [1]. Fair-skinned people may need 15 to 45 minutes per week, while darker toned individuals may require 3 to 5 times more due to the higher amounts of melanin in the epidermis. Instead of sunblock, consider obtaining sufficient sunlight that avoids sunburn and then covering up and limiting time in the direct sun.

When considering whole health, connection with the sun is extremely important. With spring comes the warmth of its rays, vital to the health of human bodies.

References:

1.    Ellison, D. L., & Moran, H. R. (2021). Vitamin D: Vitamin or hormone?. The Nursing Clinics of North America, 56(1), 47–57. https://doi.org/10.1016/j.cnur.2020.10.004

2.    Sassi, F., Tamone, C., & D'Amelio, P. (2018). Vitamin D: Nutrient, hormone, and immunomodulator. Nutrients, 10(11), 1656. https://doi.org/10.3390/nu10111656

3.    Autier, P., Boniol, M., Pizot, C., & Mullie, P. (2014). Vitamin D status and ill health: a systematic review. The Lancet Diabetes & Endocrinology, 2(1), 76-89. http://dx.doi.org/10.1016/S2213-8587(13)70165-7

4.    Weller, R. B. (2016). Sunlight has cardiovascular benefits independently of vitamin D. Blood Purification, 41, 130 – 134. https://doi.org/10.1159/000441266

5.    Lefkowitz, E. S., & Garland, C. F. (1994). Sunlight, vitamin D, and ovarian cancer mortality rates in US women. International Journal of Epidemiology, 23(6), 1133-1136.

6.    Garland, C. F., & Garland, F. C. (1980). Do sunlight and vitamin D reduce the likelihood of colon cancer?. International Journal of Epidemiology, 9(3), 227-231.

7.    Lindqvist, P. G., Epstein, E., Landin‐Olsson, M., Ingvar, C., Nielsen, K., Stenbeck, M., & Olsson, H. (2014). Avoidance of sun exposure is a risk factor for all‐cause mortality: results from the Melanoma in Southern Sweden cohort. Journal of Internal Medicine, 276(1), 77-86. https://doi.org/10.1111/joim.12251

8.    Ali, M., Shahzad, L., Hayyat, M. U., Sharif, F., Ghafoor, G. Z., & Nasir, R. (2023). Determination of heavy metals and their associated health risk assessment in the commonly available sunblocks. International Journal of Environmental Analytical Chemistry, 1-18.