Thank you for taking part!

Thank you for taking part in our Blue-Poo Gut–Brain Study.

By baking a muffin, tracking when you ate it and when the blue colour appeared in your poo, and completing our short brain games, you have contributed valuable data to help scientists understand the fascinating connection between the gut and the brain.

We still have much to learn about how the gut influences our brain, how this relationship changes as we get older, and why people differ so much in their gut and brain function.

Your contribution will help us investigate these questions across a wide range of ages, from children through to older adults.

 

Every muffin counts!

 

What is gut transit time?

Your gut transit time is the time it takes for something you eat to travel through your digestive system and appear in your poo.

In this study, we used a simple food-safe blue dye as a marker. The time between eating your blue muffin and seeing the blue colour in your poo gives us an estimate of your whole-gut transit time.

Transit time varies considerably between people. There is not one “perfect” transit time, and having a faster or slower transit time does not automatically mean that something is wrong.

However, transit time is an important part of how your digestive system works. It can influence the environment in your gut, including how long food and microbes interact with each other and the types and amounts of substances produced by your gut microbes.

This is one reason why scientists are interested in whether differences in gut transit might be linked to other aspects of health – including brain function.

 

Is there a “healthy” transit time?

There is not a single transit time that is considered ideal for everyone.

Transit time varies between individuals and can be influenced by many things, including age, diet, physical activity, hydration, medications and the way your digestive system works.

Research studies using different methods have found a wide range of transit times in healthy people. This means that your result should not be interpreted on its own as a test of whether your gut is “healthy” or “unhealthy”.

Instead, we are interested in understanding why transit time differs between people and whether these differences are associated with other aspects of health, including cognition.

As we collect more data, we hope to understand how gut transit varies across different ages and populations.

 

Your transit time can be influenced by many factors

• Diet and fibre

Fibre can influence stool bulk, water content and the movement of material through the gut. The daily recommended amount of fibre for adults is 30 g per day.

• Hydration

The amount of fluid you drink can affect stool consistency and bowel function. Most adults should aim for around 6-8 glasses of fluid each day.

• Your gut microbes

The trillions of microorganisms living in your gut can influence how your digestive system works. Probiotics contain live microorganisms, while prebiotics are types of dietary fibre that can be used by gut microbes as food. Both can influence bowel function, and some probiotics have been shown to alter gut transit time. However, their effects vary depending on the type of probiotic or prebiotic and the individual.

• Stress and your nervous system

Your gut and brain communicate constantly through the nervous system, hormones and immune system. Stress can affect bowel function in some people.

• Physical activity

Regular physical activity is associated with bowel function and can influence intestinal motility.

• Age

Gut function changes throughout life, although the relationship between age and transit is not simply linear.

• Sex

Some studies have found differences in transit between men and women.

• Medications

Some medicines can speed up or slow down gut transit. For example, laxatives can accelerate transit, while some medications can slow it.

Your gut is constantly responding to what you eat, how you live and what is happening in your body.

 

Your poo can tell us a surprising amount about your gut. 

The Bristol Stool Form Scale classifies stools from Type 1 (hard separate lumps) through to Type 7 (entirely liquid).

Importantly, stool form is related to intestinal transit: harder stools generally occur with slower transit, while looser stools tend to be associated with faster transit. In experimental studies, Bristol stool form has correlated with measured whole-gut transit time.

• Shape and consistency

Can give clues about how quickly material has travelled through the gut.

• Water content

Stool contains a large amount of water. How much water remains in the stool is strongly influenced by transit and water absorption.

• Microbes

A large proportion of stool is made up of microorganisms and microbial material. By studying the microbes in the stool we can gain an understanding about the microbes in your gut.

• Fibre

Undigested plant material contributes to stool bulk.

• Colour

Stool colour can be influenced by food, bile pigments and transit. Some unusual colours can occasionally be a sign of illness.

• Smell

The smell of poo comes partly from chemicals produced by gut microbes as they break down food.

 

“Did you know?”

Your poo isn’t just waste. It is a window into what has been happening inside your gut.

 

Your gut and brain are connected

Your gut and brain are in constant communication through a network sometimes called the gut-brain axis.

Messages travel between them through:

• the nervous system, including the vagus nerve
• hormones
• the immune system
• chemicals produced by gut microbes

Scientists are increasingly interested in whether differences in gut function and the gut microbiome can influence brain function.

One particularly interesting question is whether gut transit time is linked to cognition.

Your participation helps us investigate this.

 

Cognition changes as we get older

Does getting older affect your brain?

Yes, but ageing affects different aspects of cognition in different ways, and people age very differently.

In healthy adults, some cognitive abilities tend to decline with age, particularly:

• processing speed
• working memory
• episodic memory
• reasoning
• some aspects of attention

Large longitudinal studies show that cognitive ageing is highly variable: some people experience substantial decline, while others maintain a high level of cognitive performance well into older age.

Getting older does not mean that your brain inevitably stops working well.

There are substantial differences between individuals, and scientists are trying to understand what explains those differences.

The games you have played give us a simple way of measuring aspects of cognitive performance across a very wide age range.

These games are for research purposes and are not a medical or diagnostic assessment of cognitive health. Your results will help us understand how cognition varies across the population and whether differences in gut transit are associated with differences in brain performance.

 

So, what does your gut have to do with your brain?

That’s the question we are trying to answer.

By collecting data from thousands of people across the UK and beyond, we can investigate whether gut transit time, bowel habits and cognitive performance are related.

We are particularly interested in how these relationships change with age, sex and other factors that influence gut and brain health.

Your blue muffin has given us one small but important piece of the puzzle.

 

Thank you for helping us explore the gut-brain connection.