Vitamin D and sun bed UV

ResearchBlogging.orgLight is good for your health. Most notably, there are significant health benefits from vitamin D, which is produced in our bodies by the absorption into the skin of ultraviolet (UV) radiation. There are also dietary sources of vitamin D, but one of the best and most enjoyable involves simply sitting back and soaking up the sun's rays.


Sun bed

According to recent medical research we generally don't get enough vitamin D. This can be attributed to our modern lifestyles, which involve far longer periods spent inside, shaded from the sun, than did the lives of our ancestors. For those living in latitudes far from the equator, such as in northern Europe, there is also the problem that the sun does not rise high enough in the sky during the winter months for it to produce vitamin D in our skin.

Vitamin D is linked to a legion of health benefits, including reduced rates of internal cancers, diabetes and arthritis. But if we can't get our vitamin D from the sun, such as in high latitudes during the winter, is there a way of adequately producing it with artificial light? To answer this question, scientists in Norway studied the effects of UV exposure from a commercially available sun bed, on human vitamin D levels.

Their 12 week study was conducted with 23 healthy, adult participants living in Oslo, Norway. These were both male and female, mostly Caucasians, whose average age was 34. The study was conducted during the winter months when sunlight produced no vitamin D at this latitude (59° N) and participants were asked to stick with their usual diet during this time to avoid variations due to dietary intake of the vitamin. Blood samples were taken from the participants to obtain a measure of their vitamin D levels. These were taken before the trial began and then every two weeks thereafter. Exposure to UV radiation on the sun bed occurred twice each week for the first 5 weeks of the trial.

The participants were split into two groups, one of which received double the radiation exposure of the other (both considered safe). The scientists wanted to compare the resulting change in vitamin D levels of each group and study the rates of increase of these levels as a result of the sun bed sessions, as well as the ensuing decay rates after they were stopped.

The increase in vitamin D levels from repeated sun bed sessions during the first 5 weeks, was similar for both groups, resulting in an overall increase of between 25 and 30%. Those with lower initial levels saw the greatest rate of increase, whilst also showing a tendency toward a more rapid decay in levels when the sessions were stopped. This warrants a separate study to investigate why some people may naturally have lower levels, perhaps related to their body's metabolic rate.

These results suggest that even modest UV exposure from a commercial sun bed might be good for the health. However the benefits must be weighed against the dangers: too much UV exposure carries the risk of developing skin cancer.

This cancer is associated with the narrow band of UV radiation known as UVB, which lies between the wavelengths of 280 and 320 nm. Because of this, sun beds are usually designed to emit only the UVA radiation (320 to 400 nm). Unfortunately UVA does not contribute to the production of vitamin D; for that we need the UVB. Despite that, sun beds rated as UVA do still emit UVB radiation, just as the sun bed in these experiments did.

The researchers stop short of advocating the whole population of Norway buy sun beds or otherwise move south, but they do point out the potential health benefits of sustaining the summer levels of vitamin D throughout the winter months. They say this could decrease mortality rates from cancer in their country by as much as one third.

Modest exposure to UV from sun beds may be the solution to our vitamin D deficit and have a positive impact on our health, but how we do that safely is still a matter of debate. Until it is decided and we better understand the difference between health-giving UV exposure levels and those which are potentially dangerous, it would be wise to continue to guard against the harsh rays of the sun with hats and sunscreen and perhaps consider vitamin D supplements to top up our bodies stores.

 

 

Moan, J., Lagunova, Z., Cicarma, E., Aksnes, L., Dahlback, A., Grant, W., & Porojnicu, A. (2009). Sunbeds as Vitamin D Sources Photochemistry and Photobiology DOI: 10.1111/j.1751-1097.2009.00607.x

‡ Image by robigouk. (Creative Commons Attribution).


 
 

Comments

How has the link between cancer and UVB (rather than UVA) exposure been established? Has this been done experimentally or is it a conclusion derived from first principles (you need the energy found in the high energy photons in UVB to create thymine dimers, etc)?

As you pointed out, the UVB photons possess higher energy than their UVA counterparts. This provides them the capability to cause direct DNA damage, thereby increasing the risk of some skin cancers. It's a more complicated matter than just energy, however, because absorption and scattering within the skin at different wavelengths will vary for its constituent parts. UVA may be responsible for some skin cancers, but the DNA damage mechanism would have to be an indirect one.

This paper points to a study published in Cancer Research, which investigated the effectiveness of UV light in causing skin cancer in albino hairless mice (Wavelength Dependence of Skin Cancer Induction by Ultraviolet Irradiation of Albino Hairless Mice). A plot of effectiveness as a function of wavelength showed a peak at around 300nm in the UVB range, with the curve dropping off rapidly in the UVA range.

Thanks!

this is great !!! There's certianly not enough,research about vitamin D...


 
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