Sunlight — how much is enough for good health?

Sun exposure is one of the more hotly-debated issues among health pros today. Some demonize the sun as a skin cancer culprit while others extol the many health benefits of sunlight. What’s the real score?

The following information is straight from the US National Library of Medicine of the National Institute of Health and not just from any blog so please read on for your guidance. This info is timely in the context of the blistering heat this summer.

The primary message of the past century focuses on overexposure to the sun which is the cause of skin cancer, especially the often-fatal melanoma. Excessive exposure to the sun causes skin cancer by two mechanisms:
  • UVA radiation, which comprises 95 to 97% of the UV rays that reach the earth, penetrate deep into the skin layers, generating molecules that damage the DNA structure.
  • UVB radiation causes sunburn which in turn leads to DNA damage.

It is important to note that both forms of ultraviolet radiation cause destruction of collagen fibers and Vitamin A in the skin thereby accelerating aging and increasing the risks for various skin cancer types.

Disease due to overexposure to the sun is rare
Here’s the catch though: Only a very measly 0.1% of the “total global burden of disease due to ultraviolet radiation” is caused by overexposure to the sun. Take note that this finding comes from a 2006 WHO report. My paternal grandpa, who worked from sunup to sundown in his farm, all his life, did not die of skin cancer and lived up to more than a hundred years!

Diseases due to very low exposure to the sun are many and prevalent
It would surprise you to know that the global burden of disease due to very low exposure to UV rays is high and includes disorders of the musculoskeletal system, debilitating autoimmune diseases and worse, many types of cancers.

While overexposure to the sun can cause skin cancer, very little exposure to the sun can also cause cancers and other diseases. Studies show that those living at higher latitudes where the angle of the sun affords little UV rays had higher risks for developing Hodgkin’s Lymphoma, and cancers of the breast, colon, ovary, prostate, pancreas and others.

Health Benefit of Sunlight
Increases the body’s Vitamin D store
The active form of Vitamin D regulates at least 1,000 genes that govern virtually every tissue of the body. Let that sink in for a minute. This means Vitamin D impacts nearly all metabolic pathways, including calcium metabolism, immune system and neuromuscular functioning.

Vitamin D is different from other vitamins which must be synthesized by the body out of the nutrients we take in. Vitamin D can only be synthesized in the skin via a photosynthetic mechanism set off by exposure to UVB.

Penetration of UVB photons can be hindered by various factors such as:
  • the amount of skin pigment or melanin
  • amount of body fat
  • sunscreen application
  • clothing

To illustrate, 30 minutes of sun exposure in a bathing suit during the summer would trigger different amounts of Vitamin D production in different people. To wit,
  • 50,000 IU of Vitamin D in most white people
  • 20,000 to 30,000 IU of Vitamin D in tanned people
  • 8,000 to 10,000 IU in dark-skinned people

Just how excessive is excessive?
Sadly, there is no fixed quantifiable answer to this question. Excessive sun exposure is defined as exposure that is “inappropriately high for your skin type under a particular level of ambient UVR.”

How much is enough?
Experts draw up this recommendation: 4,000 IU of Vitamin D3 supplementation if without sun exposure or 2,000 IU Vitamin D3 plus 12 to 15 minutes of exposure to midday sun. Note that sunlight enters through the skin even with a high-SPF sunscreen, allowing Vitamin D production while at the same time providing greater protection against skin damage.


Recommendations may still be fuzzy but to be safe, modest exposure to the sun is the goal. Detaching yourself from gadgets, heading out to the sunny sea, playing outdoors or doing yard work for at least a quarter or half of an hour each day while slapping on sunscreen would be a good idea.

Remember, overexposure to the sun is bad, but under exposure to the sun is even badder.

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