The Importance of Sunlight

July 8, 2019 Latest News

It’s that time of year again when the sun is bigger, brighter, hotter and higher, and the days are longer!

That means it’s time to go out in the sun and allow our bodies to photosynthesize!

The sun emits a continuous spectrum of electromagnetic radiation, and 99% of it is in the form of light, both visible and invisible, from infra-red to ultra-violet.

Over time, ultraviolet light can damage elastin fibers in the skin. When they break down, the skin can sag, stretch, and lose its’ elasticity. Sun exposure contributes to the formation of wrinkles and “age spots,” but these are all cosmetic changes that occur naturally with aging anyway; excessive sun exposure merely speeds them up.

But by far, the most dreaded results of sun exposure can be skin cancers. Excessive sun exposure, particularly sunburns, have been associated with higher risks of developing pre-cancerous lesions (actinic keratoses) and some forms of skin cancers (basal cell carcinoma, and squamous cell carcinomas). While these precancers and cancers are easily treated and cured, malignant melanoma is a much different story.

To start, the relationship between malignant melanoma and sunlight is a bit more complicated. Melanoma frequently occurs on parts of the body that are rarely, if ever exposed to sunlight, raising serious questions about the role that sunlight plays in causing this type of cancer. Some studies suggest that intermittent sunlight exposure increases risk of melanoma, while continuous lifelong exposure reduces the risk.1

Interestingly, the use of sunscreen to prevent sunburns has been associated with an increased risk of developing melanoma, not a reduction. In a meta-analysis of 313,717 participants published in the European Journal of Dermatology in 2018:

“The cumulative evidence before the 1980s showed a relatively strong positive association between melanoma and sunscreen use”

In other words using sunscreen was associated with an increased risk of developing melanoma (by 235%). For some unknown reason, perhaps due to the development of less toxic sunscreens, the risk of developing melanoma with sunscreen use has gradually lessened over time:

“While the current evidence suggests no increased risk of skin cancer related to sunscreen use, this systematic review does not confirm the expected protective benefits of sunscreen against [any type of] skin cancer in the general population.”2

In plain English: these researchers found that, even though sunscreen use no longer seemed to cause melanoma, using sunscreen failed to protect against any form of skin cancer. These are remarkable findings, particularly since the use of sunscreen is a key component of U.S. public health campaigns to reduce skin cancer.

Sunscreens may not prevent cancer, but they certainly pose significant environmental risks and have been associated with significant damage to phytoplankton populations and coral reefs.3

Additionally, a report published in the Journal of the American Medical Association (JAMA) was recently reviewed by The New York Times.4 The study found that the chemicals used in sunscreens are directly absorbed by the skin and circulate throughout the body in the blood. Additionally, the levels of chemicals that were detected in the blood exceeded the safety limits set by FDA regulations:

“In this preliminary study involving healthy volunteers, application of 4 commercially available sunscreens under maximal use conditions resulted in plasma concentrations that exceeded the threshold established by the FDA for potentially waiving some nonclinical toxicology studies for sunscreens. The systemic absorption of sunscreen ingredients supports the need for further studies to determine the clinical significance of these findings.”5

The active ingredient in most sunscreens, in use today, is a derivative of two benzene rings linked together into a single molecule known as “avobenzone.” According to the National Cancer Institute (NCI), benzene itself is a strong carcinogen.6 The chemical avobenzone, which absorbs ultraviolet (UV) light, releases “free radicals” (also known to cause cancer ) and degrades in sunlight to form a new molecule known as a “benzil,” which is cytotoxic (it kills cells).8 These circulating chemicals disseminate throughout the body.

The skin, which is the largest organ in the body, has some very important functions:
• It absorbs most substances that are applied to it, to varying degrees
• It photosynthesizes

One should never apply any substance to the skin that isn’t safe to eat. This is because the skin literally “eats” what is applied to it: It absorbs most substances. Trans-dermal medication delivery systems take advantage of this function by utilizing adhesive patches saturated with drugs to provide a continuous stream of delivery over time.9

The skin is also designed to absorb sunlight and to transfer solar energy into molecular bonds in the form of vitamin D, in a similar manner to the way plants photosynthesize glucose from carbon dioxide and water. In the skin, vitamin D is formed when sunlight reacts with the cholesterol molecule. This single photosynthetic process provides two immediate benefits: It synthesizes vitamin D and it lowers cholesterol.10 Perhaps lack of sunlight plays a role in elevated blood cholesterol levels?

Vitamin D plays many important roles throughout the body. It helps the body absorb calcium to maintain healthy bones and teeth and it also protects against a range of conditions such as cancer, type 1 diabetes, and multiple sclerosis.11

This information raises an important and curious question: If sunlight produces vitamin D (and lowers cholesterol); vitamin D protects against cancer (among other things); and sunscreen use increases (or at least doesn’t lower) the risk of cancer, then wouldn’t studies evaluating sun exposure without sunscreen use demonstrate significant health benefits?

They do.

A study performed in southern Sweden, published in 2016, showed this to be true. This study evaluated the effects of varying amounts of sunlight on nearly 30,000 women over more than 20 years. It found that those women who received the most sun exposure, lived the longest. The researchers determined that “avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking.”12 They also found that women who received the most sun exposure lived the longest and had the lowest “all-cause mortality,” including lower risk of death from cardiovascular diseases.

Additionally, by comparing only those women with cancer (including skin cancer), those who received the most sun exposure lived longer than those who received less.

These findings are consistent with other studies that have found that the incidence of many types of cancer (except skin) increases in direct proportion to the distance that one lives from the equator.13 In other words, sun exposure (which tends to be higher closer to the equator) helps prevent many forms of cancer (except skin cancer)14 and it increases longevity from all known causes of death, including all forms of cancer.15

Public health authorities in the United States have long recommended reduced exposure to sunlight, based on their concerns that it promotes skin cancer. But, these findings suggest that those recommendations are short-sighted and misguided. As a result of Americans avoiding sun exposure, increasing numbers are suffering adverse effects of vitamin D deficiency and other serious health problems that are directly caused by insufficient sun exposure. A recent review published in the journal Dermato-Endocrinology concluded:

“This review considers the studies that have shown a wide range health benefits from sun/UV exposure. These benefits include among others various types of cancer, cardiovascular disease, Alzheimer disease/dementia, myopia and macular degeneration, diabetes and multiple sclerosis. The message of sun avoidance must be changed to acceptance of non-burning sun exposure sufficient to achieve serum 25(OH)D concentration of 30 ng/mL or higher in the sunny season and the general benefits of UV exposure beyond those of vitamin D.”

All these studies add up to a few simple conclusions:

  1. Sunlight, in moderate (non-burning) amounts is not only important, but it is essential for health and longevity.
  2. While excessive sunlight might cause cosmetic changes to the skin, some forms of skin cancer are caused by sunlight.
  3. Most forms of cancer are prevented by sunlight exposure, and all forms of cancer demonstrate improved prognosis with continued sun exposure.
  4. Sunlight promotes the photosynthesis of vitamin D and other benefits.
  5. Sunlight lowers cholesterol and lowers “all-cause mortality”.
  6. Those who avoid, or have the lowest levels of sun exposure have the same life expectancy as “1 pack per-day” cigarette smokers.
  7. Recommendations that warn against regular (non-burning) sun exposure should be questioned.
  8. Sunscreens may expose individuals to toxic, and carcinogenic substances that circulate throughout the body.
  9. Sunscreens do not protect against the risk of developing any type of cancer, but they have been found to increase it.
  10. The season of the sun is upon us. Moderation is the key. Go out and get sun, but, for heaven’s sake, don’t burn.

 

References

  1. Oliveria SA, Saraiya M, Geller A, et al.  Sun exposure and risk of melanoma.  Arch Dis Child. 2006 Feb; 91(2): 131–138.
  2. Silva ESD, Tavares R, Paulitsch FDS, et al. Use of sunscreen and risk of melanoma and non-melanoma skin cancer: a systematic review and meta-analysis.  Eur J Dermatol. 2018 Apr 1;28(2):186-201. doi: 10.1684/ejd.2018.3251.
  3. https://www.icriforum.org/sites/default/files/ICRI_Sunscreen_0.pdf
  4. Carroll AE. How Safe Is Sunscreen?A recent study on absorption into the bloodstream has caused concern, but you should be more worried about skin cancer.  New York Times 2019;June 10. https://www.nytimes.com/2019/06/10/upshot/how-safe-is-sunscreen.html
  5. Matta MK, Zusterzeel R, Nageswara RP, et al.  Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients. A Randomized Clinical Trial.  JAMA. 2019;321(21):2082-2091. doi:10.1001/jama.2019.5586
  6. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/benzene
  7. Dreher D, Junod AF.  Role of oxygen free radicals in cancer development.  Eur J Cancer. 1996 Jan;32A(1):30-8.
  8. Karlsson I, Hillerstrom L, Stenfeldt AL, et al.  Photodegradation of dibenzoylmethanes: potential cause of photocontact allergy to sunscreens.  Chem Res Toxicol. 2009 Nov;22(11):1881-92. doi: 10.1021/tx900284e.
  9. https://www.poison.org/articles/2012-aug/using-skin-patch-medicines-safely
  10. Wacker M, Holick MF.  Sunlight and Vitamin D.  A global perspective for health.  Dermatoendocrinol. 2013 Jan 1; 5(1): 51–108.
  11. Ware M.  What are the health benefits of vitamin D?  Medical News Today. Mon 13 November 2017.  https://www.medicalnewstoday.com/articles/161618.php
  12. Lindqvist PG, Epstein E, Nielsen K, et al. Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort.  J Intern Med. 2016 Oct;280(4):375-87. doi: 10.1111/joim.12496. Epub 2016 Mar 16.
  13. Bilinski K, Bythe K, Boyages J.  Association between Latitude and Breast Cancer Incidence in Mainland Australian Women.  J Cancer Research 2014. Article ID 149865, 9 pages.  http://dx.doi.org/10.1155/2014/149865
  14. Freedman DM, Dosemeci M, McGlynn K. Sunlight and mortality from breast, ovarian, colon, prostate, and non-melanoma skin cancer: a composite death certificate based case-control study,” Occupational and Environmental Medicine 2002; 59(4): 257–262.
  15. van der Rhee H, de Vries E, Coomans C, et al. Sunlight: For better or for worse? A review of positive and negative effects of sun exposure. Cancer Res Front 2016: 2:156-83; http://dx.doi.org/10.17980/2016.156
  16. Hoel DG, Berwick M, de Gruijl FR, et al. The risks and benefits of sun exposure 2016.  Dermatoendocrinol. 2016 Jan-Dec; 8(1): e1248325.
The Importance of Sunlight