Over the last couple of years, the significance of sun exposure and how it relates to our Vitamin D levels has begun to become better understood. As well, recent studies have described how our immune function is affected by different wavelengths of UV radiation. The picture of just how much sun to get is getting to be much more complete. Moreover, what we’ve taken to be common sense fact is beginning to look entirely wrong.

For most of my life, I’ve known that we should avoid sunlight during times when it’s close to its zenith. “Stay indoors between the hours of 10 and 2” was nearly a family mantra, and when you did venture out during those hours in the summer, we were warned to be sure to have on plenty of sunscreen. The sun, apparently, was our enemy. Our skin would age prematurely at best. At worst, we’d get skin cancer.

Current research is disagreeing with this age-old common sense approach to the sun. We’ve long known that UVA radiation is the so-called “bad” UV and that UVB is the good stuff that encourages our bodies to utilize cholesterol in the production of Vitamin D. What is less well known is that while UVA is almost equally prevalent throughout the daylight hours, UVB is filtered the closer the sun is to the horizon. This means that our optimal UVB exposure comes during those zenith hours between 10 and 2. In other words, the common sense we’ve been taught all these years is just plain wrong.

Similar to how we require exposure to zenith-oriented sunlight to optimize our Vitamin D production, our immune system likewise responds positively to UVB. UVB wavelengths encourage reduced inflammatory response in the body. UVA, on the other hand, encourages inflammatory response. Ideal exposure, therefore, maximizes UVB content as a means of balancing our inflammatory response.

The latest research seems to indicate that we really need to be optimizing our sun exposure to be aligned with solar noon. From an evolutionary standpoint, this makes sense. Whereas our cityscape is mostly devoid of trees, our ancestors spent most of the day under the canopy. Under the canopy, UVA exposure was limited because direct sunlight was blocked most of the day. It wasn’t till the sun was mostly overhead that sunlight made its way to the forest floor. As such, we evolved to best respond to that direct, overhead light.

What strikes me as so important is the realization that many of our common sense facts seem to be patently incorrect. It’s important to not just take things at face value just because somebody said it was true. People make mistakes, and that includes writers of blogs, such as the one you’re reading here. As such, I strongly recommend that you keep current with what goes on in the medical and scientific communities so that you can come up with your own conclusions.

Let that sunshine in.

  1. The research I have done certsinly corroborates the above advice. One point not mentioned is the use of sunscreen. The widespread use of sunscreen prevents our bodies from absorbing the beneficial vit D that we vitally need to stay healthy. Lots of new research out there, so it’s importsnt to keep yourself informed and not just accept what we have been told for years as being the absolute truth. Ten minutes of middle of the day sunshine without sunscreen seems to be the very minimum you should be getting for optimum health

    • Hi, Wendy.

      I completely agree about the use of sunscreen. As for the minimum amount of exposure to sun, it’s not a simple matter. Complicating the equation are the latitude, season and skin colour of the person in question. For example, for a given latitude and season, persons of darker skin colour require longer exposure to sunlight to stimulate Vitamin D production. The farther away from the sun we are, the less intense even the sun at zenith is, so we need more time.

      Humans have proven to be remarkably migratory and this situation requires us to compensate. Each of us needs to monitor our exposure and adjust duration accordingly. Mercola advocates slightly pinkening of the skin as a barometer for exposure, but I personally think that’s going a bit far. Pinkening of the skin is already a sign of distress and should, I think, be avoided. Best for one to learn how it feels to achieve a “near pink” threshold such that one maximizes the benefits and minimizes any physical damage caused from excessive exposure.

      Done right, it’s a win-win scenario!

  2. Surprisingly, glass allows the UVA rays through, while limiting or blocking, the beneficial UVB rays! This is why we need to be outdoors. Sitting in a nice window or in a sunny room or in the car is not that good for us. Direct exposure to sunlight is the best . I believe that instead of worrying about our skin colors , latitudes, times of day, and seasons we can just expose ourself to what feels comfortable.

    Sunglasses cause sunburn. The skin’s response to sunlight is regulated by the sensors on our eyes. if you are wearing sunglasses less light enters your eyeball . when light enters your eyeball it triggers a healthy defensive response of the skin . I can’t make this stuff up. Look it up.

    • Hi! Yes, I completely agree about the filtering through window glass. There has been some indication that office workers who sit near windows that are exposed to direct sunshine have an increased incidence of cancer. Because of this, I think it’s really important for us to rethink the way we expect people to work. For sure, we need offices and the like, but there needs to be a better way than expecting somebody to sit indoors for most or all of the daylight hours.

      There’s another element of sunglasses that should be known: Because less direct light hits the eye, the pupils are more dilated than they would be without the sunglasses. This permits that UVA to enter the eye in greater amount, as you rightly pointed out, and this is turning out to be a major contributor to cataracts.

      Personally, I don’t wear sunglasses unless I’m up on a glacier. Then the glasses block out all incidental light.

      Peace. And thanks for the contribution!

  3. oh and thank you for your blog entry

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