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So now sunbathing keeps you young? Well, no, not really…

by Henry Scowcroft | Analysis

9 November 2007

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As if there wasn’t enough confusion already with all the media to-ing and fro-ing over obesity and cancer (more on that soon), yesterday’s headlines suggested that sunbathing might slow the ageing process and reduce cancer rates.

But a closer examination of the actual research reveals that it didn’t actually say that. At all.

The research team, based at King’s College London, were looking for ways to measure the amount of ‘ageing’ a person has experienced (biologically speaking), and for things that might slow this down – such as vitamin D levels.

Their paper looked at the length of telomeres – the ‘tips’ of the DNA ‘shoelaces’ in each of our cells that Kat wrote about last month – in people’s white blood cells, and compared this to the levels of vitamin D in their blood. The researchers looked at 2,300 blood samples from people with an average age of 54.

Now, telomeres get shorter every time a cell multiplies. So cells with longer telomeres are, biologically speaking, ‘younger’ – they have multiplied less often than cells with short telomeres.

The research found that people with the highest levels of vitamin D had long telomeres in their white blood cells.

But why did they look at white blood cells?

These cells are involved in controlling inflammation. And many scientists think that long-term, low-level, ‘chronic’ inflammation is one of the key processes that can encourage cancers to develop (as we discussed a few months back on this blog).

Inflammation causes white blood cells to multiply rapidly, and this shortens their telomeres. The researchers reasoned that people with longer telomeres in their white blood cells might have experienced less inflammation in their lifetimes, as the cells had multiplied less often.

So they suggested that telomere length might be a ‘marker’ for inflammation, and that vitamin D might prevent this inflammation by stopping the white blood cells from dividing.

And this ties in with other evidence about the health benefits of getting sufficient vitamin D, including mounting evidence that this vitamin might reduce cancer risk.

But vitamin D is made by the body when the skin is exposed to the sun. So adding another speculative leap, you might possibly, tentatively, propose that getting extra vitamin D from the sun might lead to a reduction in chronic inflammation – and thus ageing.

Or you might want to just completely simplify all of the above, remove all the caveats, and write a headline that says, boldly, “Sunbathing ‘slows ageing process'”.

But let’s step back from this research paper (which, incidentally, doesn’t look at disease rates at all), and consider what we know about sunbathing.

Here’s another couple of thing we could say, just as boldly, but with no missing caveats:

  • Heavy exposure to UV radiation from the sun seriously damages DNA in your skin cells, including the telomeres. This causes premature ageing and skin cancer.
  • The amount of time in the sun it takes to generate enough vitamin D is always less than the time it takes to redden or burn.