If you ever wanted an excuse to bake a bunch of muffins, you’re in luck… just make sure they’re blue.
Experts believe eating the specially-coloured treats may provide a warning sign of poor gut health.
If the coloured muffin passes through your system too quickly, it could potentially indicate inflammatory bowel disease.
Or it could be a warning sign that you’re at risk of type 2 diabetes, if it takes your body takes longer than 60 hours to digest it.
Studies show that 20 hours between eating and expelling a meal is the ‘sweet-spot’ for gut health.
But the time it takes for your body to digest food can vary from between as little as a couple of hours to three entire days.
Dr Sarah Berry, a nutritionist at King’s College London who helped design the muffin test, says the ‘blue poo challenge’ can give medics an ‘early warning’ sign something is not right.
Pictured above are the blue muffins that can help to measure someone’s gut transit times. They can easily be made by co-opting a muffin recipe and adding blue food dye
In tests, scientists asked participants living in the US and Britain to consume muffins coloured with blue dye for breakfast.
They used about a quarter of a teaspoon of Sugarflair Colours Royal blue food dye — available for about £2.15 online — to give the muffins their vibrant colour.
Other colours such as red were not used because they could be mistaken for other substances such as beetroot or blood in faeces.
Participants were asked to note every time they visited the bathroom, and when the blue dye re-appeared.
Most participants (424 people, or 50 per cent) saw the blue dye return in about 24 hours.
But for a fifth of people (186) — also classified as normal — it reappeared in 48 hours.
At the extreme ends of the scale, were a fifth (174) who did not see the dye return for more than 59 hours.
And on the other end almost a tenth (79) who said the dye came back in 14 hours or less.
On average, food took about 28 hours to travel the 8m of intestines and then be expelled.
Dr Berry said the gut transit time was a good indicator of health and the state of the gut microbiome, the community of bacteria inside that help to break down food.
Asked what the best time would be, she told MailOnline you ‘should be pretty happy’ with the 20-hour mark.
She added: ‘But I think for a definitive answer we need to delve more into the data.’
She said digesting the muffin too slowly signalled someone had more visceral fat — the ‘hidden’ fat wrapped around organs including the liver and intestines.
Dr Berry claimed this is a risk factor for type 2 diabetes, when the body stops absorbing food from the blood in response to insulin. It could also indicate someone is at increased risk of heart disease.
Danish scientists also found that the longer food takes to pass through the colon, the more harmful bacterial ‘degradation’ products are produced.
Researchers have previously observed a link between the build-up of such products and bowel cancer.
On the other hand, Canadian scientists say short transit times could indicate inflammatory bowel disease.
In these cases inflammation in the small intestine leads to food passing through faster, and low absorption of nutrients and water causing diarrhoea.
Asked if determining the gut transit time could help diagnose a medical condition, Dr Berry said: ‘I think it can’t be used on its own.
‘But in combination with other measures it could be an early indicator.
‘For example, if someone has a gut transit time below 14 hours there may be adverse clinical and unfavourable things going on.’
NHS medics can recommend people measure their transit time for frequent stomach problems, including constipation, diarrhoea and bloating.
Current tests include swallowing an electric pill which measures how long it takes to move through the gut.
Swallowing a capsule with a camera — in a method called scintigraphy — also allows doctors to measure the time taken.
To improve the gut transit time, Dr Berry advised diet changes.
She told MailOnline: ‘The general advice I gave to everyone [wanting to improve their gut transit time] was to consume more plant-based foods.
‘But not just plant, more plant and less processed, and where possible consume fermented foods too.
‘So, certain cheeses, yoghurts and so on. Peppers are also fantastic for the microbiome.’