A blue muffin could help scientists discover whether the speed of your gut is linked to how sharp your mind is. Researchers want thousands of people, aged five to nearly 100, to eat one and wait for their poo to turn blue.

The citizen science project, led by the Gut Immune Brain Axis (GIBA) Network+, explores whether gut speed is linked to how quickly and accurately people complete simple thinking tasks. Scientists still do not know what gut speed means for the brain.

How the Blue Poo Test Works

Participants bake the muffins at home using a vegan-friendly recipe and blue food dye bought online. After eating one, they record how long it takes for the dye to appear in their stool, a measure of gut health known as gut transit time.

Food typically takes 24 to 72 hours to travel through and leave the body. Participants then play short online games measuring problem-solving and decision-making under pressure.

Parents should supervise children taking part. Anyone with allergies or health concerns should check the recipe or ask their GP first.

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Why the Sweet Spot Matters

Professor Jon Swann, director of the network and professor of biomolecular medicine at the University of Southampton, said the team can 'work out if a faster gut transit means a sharper mind'. It will also test if slower digestion alters thinking.

Gut speed reflects gut function and reveals something about gut health, but its meaning for the brain is unclear. The team wants to map how digestion times vary by age, sex and region, and how they relate to brain performance.

Neither faster nor slower gut transit is automatically better. Transit time varies between individuals, and unusually slow or rapid movement can be associated with digestive problems. Rapid transit may reduce the time available for water absorption, while the health implications of slower transit depend on its cause and other factors.

What Earlier Research Found

A study by ZOE, a health science company, and King's College London researchers used the blue-dye method with 863 healthy people. Average transit time was about 28 hours, though individual times varied widely.

The researchers concluded that transit time was a more informative marker of gut function than stool consistency or frequency. The method is also inexpensive and can be used in large studies. Links to wider health, however, are complex.

How Gut and Brain Communicate

More than 100 million nerve cells line the digestive tract and communicate with the brain, according to Johns Hopkins Medicine. Research suggests digestive activity may affect thinking skills and memory, and gut irritation may trigger mood changes.

Researchers at Stanford Medicine say the brain and gut communicate constantly through the vagus nerve, molecules released by gut microbes and immune cells travelling from the gut. When that communication goes wrong, diseases and disorders can result.

What Happens Next

The GIBA Network+ is funded by the Biotechnology and Biological Sciences Research Council (BBSRC), part of UK Research and Innovation. Researchers expect to publish the results in 2027.

Dr Amanda Collis, the funder's executive director of research strategy and programmes, said research reveals that gut microbes and processes 'may influence far more than digestion alone'. The test shows how citizen science can tackle such questions at scale.

Taking part could improve understanding of the links between gut function and brain performance. Participants also learn how quickly their own gut moves food through the body.

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