December is a natural time of year to reflect on the big health stories of the past 12 months; the advances, breakthroughs and even scandals with the potential to transform society. But what about the stories that made us do a double-take? 2012 didn’t disappoint, and one of my favourites was the study that analysed the bugs that like to hang out in the human navel.

The jungle in your belly button

The Belly Button Diversity Project is doing pretty much what the name suggests: asking volunteers to collect samples on Q-tips from their bellybuttons and then analysing what’s lurking in there.

“The belly button is one of the habitats closest to us, and yet it remains relatively unexplored,” wrote the researchers in November in the open-access journal PLOS One, where they detailed the findings from an initial batch of 60 or so navels in the United States.

The trawl showed that the human navel was home to many types of bacteria. But intriguingly, the nature of the inhabitants could vary wildly between individuals: the study turned up more than 2,000 “phylotypes” of bacteria, but only a few species were common inhabitants. Meanwhile, some belly buttons sported more than three times the diversity of bugs than others.

Why on earth would you want to know what's living in your belly button, or anywhere else on your body? Because the bacteria that live on our skin could be doing more than just sitting there: "Several recent studies suggested that skin bacteria have a beneficial effect on skin immune function," note the authors. The studies of what likes to live on us are continuing, see yourwildlife.org

Food for thought

If all that gazing at navel microbes hasn’t put you off your food, how about the conversation-starting study that looked at whether chocolate consumption and Nobel prizes are linked?

The paper, which has prompted questions about whether it is actually a prank, is certainly written in a light-hearted fashion.

It appeared online in the New England Journal of Medicine in October, complete with a graph plotting countries’ annual per capita chocolate consumption versus the number of Nobel laureates per 10 million of population.

So what was the skinny on that? According to the paper, there was a “surprisingly powerful correlation between chocolate intake per capita and the number of Nobel laureates in various countries” and Switzerland topped the charts both in eating chocolate and in accepting prizes from the Nobel committee.

It goes to show that if you go looking, you can find correlations between the most unusual of bedfellows. But does it actually mean anything?

Study author Franz Messerli (who hails from Switzerland) at Columbia University in New York notes that “. . . of course, a correlation between X and Y does not prove causation”.

And as another caveat before you dive headlong into the sugar, fat and calories, the paper also points out that “the data are based on country averages, and the specific chocolate intake of individual Nobel laureates of the past and present remains unknown”.

Nevertheless, the researcher indulges: “Dr Messerli reports regular daily chocolate consumption, mostly but not exclusively in the form of Lindt’s dark varieties,” states the paper.

Perhaps unsurprisingly, the bizarre study gave readers plenty to chew on, with some arguing that the juxtaposition of chocolate consumption and Nobel success made little sense, and that other factors were more likely to contribute.

“It’s not that we have a special craving for chocolate here in Switzerland,” noted one witty commenter on the Scientific American website. “We only eat this much in order to maximise our output of Nobel laureates.”

Assault on the ears

Another eye-catching – or maybe ear-bending – study that warrants a mention looked at how the human brain reacts to various unpleasant noises.

Thirteen volunteers got to spend time in a scanner while listening to a range of sounds, including some of the “set-your-teeth-on-edge” variety – such as a knife on a bottle, nails scraping on a blackboard, a baby crying, an angle grinder and an electric drill.

It doesn’t sound much like fun, but bear with it – there was a purpose. The researchers used fMRI scans to assess changes in activity in parts of the brain associated with hearing and with emotional response.

The findings, published in The Journal of Neuroscience, suggest that when we encounter an unpleasant noise, a part of the brain called the amygdala, which is associated with emotion and fear, modulates the response of the brain region associated with hearing.

And, much like the belly button’s microbial jungle, you might reasonably ask why it helps to know this.

“Scientifically, a better understanding of the brain’s reaction to noise could help our understanding of medical conditions where people have a decreased sound tolerance such as hyperacusis, misophonia [literally a “hatred of sound”] and autism when there is sensitivity to noise,” states a release from Newcastle University.

It’s a point echoed by researcher Prof Tom Griffiths. “This work sheds new light on the interaction of the amygdala and the auditory cortex,” he says.

“This might be a new inroad into emotional disorders and disorders like tinnitus and migraine in which there seems to be heightened perception of the unpleasant aspects of sounds.”