All over the world right now people are turning their poo blue – and then talking about it on social media. Just a bizarre new trend involving way too much sharing? Possibly. But it can reveal important insights into your internal health. Here’s why some scientists are suggesting we all take the blue muffin challenge.

It’s not news that food you put in one end comes out the other – but have you ever wondered how long it takes to do that? “This is your gut transit time and when we recent- ly measured it in a trial of 1000 people, the average time taken was around 28 hours – although anything from 14-58 hours is considered normal,” says Dr Sarah Berry, a nutritional scientist from Kings College London, who worked on the trial alongside research team ZOE.

That same trial also triggered what is now known as the Blue Poop Challenge. This sees people eating a muffin containing an amount of blue food colouring shown to survive the digestive process intact. They note what time the muffin went in, and when a blue poo then comes out.

The resulting time is then entered into an app allowing the team to collect data from thousands more people than they could ever hope to attract to a clinical trial.

They’re not just doing this for fun. Their original trial threw up some important new information. It revealed for the first time that the more ‘normal’ your gut transit time, the more plentiful the amount of bacteria in your gut – and that’s something we know is linked to better health.

“The bacteria in the gut are fuelled by fibre in the food we eat,” says Dr Berry. “The duration that the food is in our gut will determine how long the microbes can feast on it which in turn impacts their growth and diversity.”

Short transit times move food out of the bowel effectively ‘starving’ the bacteria while overly long transit times are likely a sign of a low fibre diet that simply does not provide enough material in the gut for the microbes to feast on. And changing their diversity is not the only way transit time affects the gut bacteria.

In 2016, Danish researchers found that longer transit times may actually make these good bacteria turn bad. After consuming carbohydrates within fibre, gut bacteria usually produce helpful by-products that fight inflammation and help restore the mucus layer that protects the intestine.

“But if the gut transit time is slow the bacteria run out of carbohydrates to consume and start to feed on leftover protein which changes those by-products,” explains the study’s author, Professor Henrik Munch Roager from University of Copenhagen.

Instead of producing healthy bowel-restoring compounds, they now produce ones high in ammonia and sulphur that, not only might damage the cells of the bowel directly, they also dissolve its protective mucus layer – and a bowel with a thinner mucosal layer is believed to be more prone to DNA mutations that lead to bowel cancer.

Even before we started exploring things at a cellular level though, transit time was known to matter. “A malfunctioning digestive system is the start of ill-health in many ways,” says Dr Anneline Padayachee, registered nutritionist and adjunct senior lecturer at the University of Queensland.

“Every nutrient you eat has to pass through the digestive system before it gets to the bloodstream, and a fast transit time can mean there’s not enough time for vital nutrients to be absorbed,” she says.

It could also be a sign of something irritating the gut wall (eg. an intolerance) or an infection (bacterial or viral) that the immune system is trying hard to get rid of. “A slow transit time means constipation which can lead to discomfort from bloating and a risk of hernias and polyps from the straining involved in passing a stool,” says Dr Padayachee.

The exact length of your transit time relies on many factors. Diet, particularly how much fibre you consume, is a big one, but generally: women’s bowels are slower than men’s; stress speeds everything up; and health issues like diabetes or thyroid imbalances can make a bowel sluggish.

Taking the Blue Poop Challenge can reveal where in the 14-58 hour range your transit time falls, giving you the choice to optimise things further if you fall on the outer range – you should definitely make some changes if you’re well outside it.

Although, Dr Padayachee points out, most of this latter group probably don’t need to wait for the arrival of a blue poo to tell them that. “The appearance of a normal poo can reveal a lot about your gut transit time.”

If your poo is very liquid, that’s a sign that your gut transit time is probably too fast, she says. “Conversely, a stool should take no longer than eight seconds to pass so, if you’re straining and passing things more slowly, or if it comes out as pellets, that’s probably a sign that you need to speed things up a little.”

If you do want to nudge things closer to the norm, how to do it varies on whether you need to speed things up, or slow them down.

A bowel that regularly moves too quickly (defined as a transit time of less than 14 hours, or where poo is regularly liquid) needs to be checked by a doctor as there might be a medical cause – for example, allergy, intolerance, IBS, inflammatory bowel disease or long-term infection.

A sluggish bowel though can usually be tackled at home. “Write down everything you’ve eaten in the last 24 hours and the amount of water you’ve drunk – and you’ll probably notice it’s mostly white carbohydrates like bread, pasta and pies and few wholegrains, fruit or vegetables and not enough water,” Dr Padayachee suggests.

Changing these three things will probably help – and if it doesn’t, see your GP to check why things are sluggish.

And that’s where the Blue Poop Challenge can help us all; “it’s opening up the conversation about gut health in a fun, informative way,” says Dr Berry.

And the more willing we are to talk about our bowels, the more likely we are to seek help for uncomfortable symptoms affecting our quality of life, or unusual ones that might be an early warning of bowel cancer. Who knew a dab of blue food colouring could be so good for you?


All images: Getty Images


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