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Vitamin D, UV exposure, and skin cancer in a nutshell

Posted on: May 22, 2012   by  Brant Cebulla

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May 25th is National Don’t Fry Day, a campaign by the National Council for Skin Cancer Prevention to make sure people protect themselves from the sun. They contend that skin cancer is a growing epidemic so be sure to protect yourself from the sun, which doesn’t make perfect sense considering skin cancer is increasing despite the growing trend to stay out of the sun.

Nevertheless, it’s a good week to take a look at what is known about vitamin D, UV and sun exposure, and skin cancer, especially heading into Memorial Day Weekend and the beginning of summer. We’re here to break it down for you!

To date, research is not complete and there are many unknowns. Generally speaking, UV exposure is a risk factor for skin cancer. On the other hand, vitamin D sufficiency is protective against skin cancer. You can see the contradiction here, but let’s take a closer look.

There are three types of skin cancer:

1.  Basal cell carcinoma: The role of UV exposure in basal cell carcinoma (BCC) is not clear, but observational studies have found a 50% increased risk in those who  tan. The number of BCC cases outnumbers the number of squamous cell carcinoma cases (SCC) by a ratio of 4 to 1, and approximately 3 in 10 people will develop it in their lifetime. In a randomized controlled trial, the use of sunscreen did not reduce the risk of developing BCC, which makes the relationship between UV exposure and BCC a bit puzzling.

2. Squamous cell carcinoma: The risk of SCC is more strongly related to cumulative UV exposure. Observational studies have found a two-fold increased risk in those who tan. In the same randomized controlled trial with BCC, researchers found a 40% reduction in the risk of SCC with use of sunscreen.

3. Malignant melanoma: The incidence of stage one melanoma has increased since the 1950s, though some studies suggest this rise can be attributed to increased diagnosis and not incidence. It is generally accepted that melanoma risk is determined by a combination of genetic factors and UV exposure. The greatest risk factor is the number of moles one is born with, and it is thought, though yet to be proven, that UV exposure induces these types of moles to become malignant.

Paradoxically, sun exposure and UVB increase vitamin D levels, a known anti-cancer agent. Although there have been no controlled trials that look at vitamin D for prevention or treatment of skin cancers, researchers have identified mechanisms where vitamin D inhibits all three types of skin cancer, and they have demonstrated this in animal models.

Furthermore, an observational study found that vitamin D levels greater than 30 ng/ml decreased the incidence of non-melanoma skin cancers by half compared to those with levels under 16 ng/ml. Levels between 16 to 30 ng/ml were not quite as protective as levels above 30 ng/ml.

To add to the confusion, one study found no correlation between vitamin D levels and skin cancer risk, while another found a correlation between higher levels of vitamin D and higher incidence of non-melanoma skin cancers, probably due to overly excessive sun exposure.

What does this all mean? That there is probably a sweet spot for sun exposure. You need sun exposure to produce vitamin D, but you don’t want to overexpose yourself. Get some sun exposure for vitamin D production, but don’t burn yourself.

Given all this, the Vitamin D Council recommends these 6 essential points regarding your sun exposure habits:

1. Regular and sensible sun exposure is a healthy practice. Vitamin D production is very high when your shadow is shorter than you are.

2. When sunbathing, the Vitamin D Council recommends exposing your skin for half the time it takes to turn pink. After this, cover up with clothing or shade.

3. Overexposure is unnecessary and dangerous.

4. If the intention in sunbathing is to produce vitamin D, the Vitamin D Council does not recommend sunscreen as it will not allow you to optimally produce vitamin D. Furthermore, sunscreen is not proven to be consistently protective and safe.

5. Tanning beds with low pressure lamps are a suitable substitute to sun exposure as long as the same sensibility is applied to their use. Don’t burn! Just get a little vitamin D.

6. Consistent sun exposure in the 21st century is not easily achieved. Additional measures should be taken, including supplementation and/or the use of low pressure tanning beds.

Let’s also not forget that vitamin D does lots of things, and that skin cancer is a small part of the equation.  One million people die per year due to breast and colon cancers; cancers where vitamin D deficiency is a known risk factor. Without reducing the seriousness of melanoma (which accounts for fifty thousand deaths worldwide per year), common sense suggests that the benefits of sensible sun exposure are well worth the risk.

Sources

Tang, JY and Epstein Jr, EH. Vitamin D and Skin Cancer. In Vitamin D, Third Edition by Feldman D, Pike JW, and Adams JS. Elsevier Academic Press, 2011.

2 Responses to Vitamin D, UV exposure, and skin cancer in a nutshell

  1. theguru

    Great article! Maybe it could be worth to add that in order for UVB (the UV-rays that makes vitamin D) to reach the earth, the sun must be higher than 45 degrees above the horizon. That is when your shadow is as long, or shorter, than your height. That is why the so often repeated mantra about having a tan before 11 am and after 3pm is not very good. At least not for those living in northern USA and Canada even at this time of the year. It will not give you any vitamin D but the UVA-rays will give you a surface tan without any extra production of new melanin.
    For more about how to tan, see here …
    Do You Know How To Tan?

    • Brant Cebulla

      Thanks Guru! You might enjoy my “How do we measure sun exposure” blog as well. In a few examples, I indirectly address the issues you are bringing up.

      Cheers,
      Brant

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