July 1, 2011

Sunscreen: Can this by hurting us?

By Tim Lochhead

Let’s put our thinking hats on a quick minute and think outside the box. Remember, thinking outside the box is thinking inside your head.

We are going to think about the religious recommendations to lather on sunscreen every 5 minutes and never let so much as a pinkie finger see the sun “unprotected”. We will look at some practical guidelines for getting Vitamin D from the optimal source, the sun. And to be fair, we will conclude with some “smart” tips for using sunscreen.

A quick recap from the last blog: we talked about how 20-30 minutes of summer sun (with about half body exposure) can provide about 10,000 IUs of Vitamin D.

We also learned how everyone’s required exposure for a certain production of Vitamin D varies. Typically, when your skin (without sunscreen) becomes a light pink, you have reached your max limit for producing Vitamin D that day. Some fair skinned people may only need 15-20 minutes, while those with darker complexions have a built in SPF, so they need more time.

Additionally, obese individuals may have less ability to produce Vitamin D, and may also require more time as well.

So today we get into some facts about sunscreen and SPF.

Our bodies go through a process to make Vitamin D from the suns UVB rays.

Surprising fact 1: Did you know that over 90% of UVB rays can be blocked from even a low (say SPF 15) sunscreen?

About 96% of the sun’s rays are UVA, which penetrate deeply into the skin and have been linked to cancers and immune suppression. The other 4% are UVB rays. (To be fair, UVB rays cause the burns on skin which can also be cancerous). Sunscreen users have been found to have less incidence of squamous cell carcinoma, a slow-growing tumor that is readily treatable by surgery, but studies are mixed about melanoma, the deadliest type of skin cancer.

UVA rays are fairly constant at all times during the day, while UVB rays are low in the morning and evening.

Surprising fact 2: So, UVB rays, which are our primary source of Vitamin D, are highest at midday.

Time for the thinking caps:

  • What does all of this mean?
  • Could using sunscreen every single second we are exposed to sun be limiting our ability to make Vitamin D? (recall the great benefits of Vitamin D from an earlier blog here)  

So, you might be thinking that at least some exposure to the sun without sunscreen would be a fantastic idea to get Vitamin D.

Scared about not using sunscreen even for a minute? Let’s consider some common sense questions:

  • How many living things (animals, including us, or even plants) rely on sunlight for life?
  • If the sun is so bad, how did we survive for millions of years?
  • Has sunscreen use (and marketing) increased or decreased over the past few decades?
  • Have skin cancer rates gone up or down over the past few decades? (hint: up)

Granted the ozone is less than it was a long time ago, although this does not change our Vitamin D requirements.

Surprising fact 3: According to Zoe Diana Draelos, editor of Journal of Cosmetic Dermatology, 2010 “Sunscreens were never developed to prevent skin cancer. In fact, there is no evidence to recommend that sunscreens prevent skin cancer in humans.”

What are some Guidelines for going without sunscreen?

As noted above, we can make up to 10,000 IUs of Vitamin D in 30 minutes of sun exposure. This may be more or less depending on various factors like where you live, time of day, and skin pigment. Intuitively, we have the ability to recognize how much is too much. For example, when the skin just starts to change hue.

Be mindful of total exposure. THE KEY IS NOT TO BURN. (Severe burns greatly increase risk of cancer, especially if you got one as a kid).

Paradoxically, having sufficient stores of Vitamin D can help us avoid burns.

Sunscreen Tips

Are there times when sunscreen is a must?

After we’ve gotten some sun exposure, sunscreen can be a good idea to avoid burns. The following are some examples:

  • Fair skinned individuals who burn easily
  • Going on a vacation where sun exposure will increase significantly over baseline and you haven’t had a gradual build-up of exposure
  • Working outdoors or otherwise outside for long periods of time

Other sunscreen tips:

  • Choose “safe” (i.e. non-toxic) ingredients. You can search your product on the Environmental Working Group’s database at http://www.ewg.org/skindeep/#
  • Consider “broad spectrum” sunscreen which blocks both UVA and UVB, but even this is a gamble as it’s not regulated and there is much controversy surrounding this matter (there is not as much UVA protection as UVB protection in many brands)

Comments from other sources:

  • The International Agency for Research on Cancer (IARC) has stated that “sunscreens should not be the first choice for skin cancer prevention and should not be used as the sole agent for protection against the sun.”(IARC 2001). They have also stated the sunscreen users may have a false sense of security and remain in the sun longer, leading to an increased risk of cutaneous melanoma. Lastly, they also advocate the use of hats, clothing, timing, and shade as primary sources of protection.
  • Supermodel Gisele Bundchen as spoken out against “conventional sunscreens”, calling them poisons for the ingredients contained within. Check out the story at http://www.naturalnews.com/031247_Gisele_Bundchen_sunscreen.html


Some sunscreen use can be a smart idea, but like all things this can be used and abused. It’s finally being recognized that a fanatical approach to avoiding the sun (without sunscreen) like the plague may not be the best idea.

Enjoy the long-weekend!
And be smart in the sun 🙂