Scientists digging into ‘floaters’ and ‘swimmers’ finally have some answers (Picture: Getty Images/iStockphoto)

How was Stonehenge built? What are the Easter Island head statues? Why do some poos float, while others sink to the bottom of the bowl?

These are just some of the big questions we face in life.

It is one of the many mysteries of toilet time, and admittedly it has kept us awake at night.

Well, now scientists have taken a fresh look at an old study, which seems to offer some insight.

According to research from University of Minnesota Hospitals, whether your poo is a ‘floater’ or a ‘swimmer’ depends on the types of bacteria in your gut and how much gas they produce.

Published in 1972, the study examined waste from 13 people and found they all sank when the gas inside was removed by increased pressurisation, even if they had high fat content.

Back then, gastroenterologist Michael Levitt and his student William Duane were inspired to look into the subject as Mr Duane’s poos always floated.

It is all about the gut bacteria, it seems (Picture: Getty Images/iStockphoto)

‘About two hours after our discussion, he passed a stool, we put it in a flask, and pressurised the flask and watched the stool sink, demonstrating the stool floated because of its gas content,’ Mr Levitt said.

They believed this gas came from gut bacteria that became incorporated in the faeces but were never able to confirm their suspicions.

Now, Dr Nagarajan Kannan at the Mayo Clinic in Minnesota, and his colleagues have confirmed this hunch, the New Scientist reported.

They noticed that mice bred so they do not have any gut bacteria – known as germ-free mice – always produce sinkers, whereas nearly half of standard mice produce floaters.

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‘Now, there is no confusion as to what makes stool float, it is gas from gut microbes, not from swallowed air or other sources, Dr Kannan said.

‘Closer analysis of the mouse floaters revealed they contained multiple gas-producing bacteria, including Bacteroides ovatus and Bacteroides uniformis, which are known to increase methane production and the frequency of flatulence in people.’

But his team are still far away from establishing floaters or sinkers indicate better gut health.

‘It probably depends on exactly which gut bacteria are producing the gas,’ he said.

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