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What’s your poop personality?

Ready to go? Let’s get you started.

The ZOE team, in collaboration with world-leading scientists, recently published a paper all about blue poop. Yep, you read that right! We gave blue muffins to thousands of people and discovered that gut transit time — the time it takes for food to travel through the gut — can say a lot about a person’s gut microbiome. Now for the most exciting part: you can test your own gut with blue muffins too!

Ready to go? Let’s get you started.


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What is the #bluepoopchallenge?

Scientists working with ZOE recently published a new paper in the peer-reviewed journal, Gut, all about blue poop. Yep, you read that right!

As part of our PREDICT studies, we measured the gut transit time — the time it takes for food to travel through the gut — of thousands of people using muffins colored with blue dye. We discovered that understanding a person's gut transit time can tell us really interesting things about their gut health.

What's exciting is that these blue muffins aren't just limited to clinical research. Our newest scientific research makes understanding your gut health easy and affordable. That's why we've launched the #bluepoopchallenge — to help as many people as possible!

How can I do the #bluepoopchallenge?

Anyone can test their gut using blue muffins! To take part in the blue poop challenge, you will need to:

  • Eat two blue muffins for breakfast (note the date and time)
  • Look out for blue-green poop when you go to the toilet (note the date and time when you spot it)
  • Enter your time and answer a few questions here, and discover interesting things about your gut!

To get your hands on blue muffins, you can either:

  • Bake your own: Head to this page to find an easy recipe that you can use to bake your own blue muffins at home. We've also listed a few different types of blue coloring that are suitable for the blue muffin test.
  • Buy blue muffins for you and a friend: If you are based in the US, we have a limited number of blue muffin test kits available to purchase here. We'll even send you an extra set of muffins so you can share them with a friend and compare results. It's our goal to make gut health accessible to as many people as possible, so we're providing them to you at cost and not taking a profit.
Will my poop really go blue? What if it doesn't?

Your poop should turn blue if you eat two blue muffins (2.3oz/65g each) made using the correct amount of one of the recommended blue dyes. If you don't see any blue (or greenish-blue) poop, this could be because:

  • The blue dye hasn't passed through your digestive system yet
  • You pooped blue and didn't notice it — we recommend paying attention to the color on your toilet paper after you wipe!
  • There wasn't enough blue dye added to your blue muffins

You can either re-do the blue muffin test or select "Can't remember" when asked "When did you see the blue poop?" when entering your results. We will use the typical gut transit time (28.7 hours) from our research, but please note that this will impact the accuracy of your results.

What kind of blue food coloring can I use?

There are many different blue food coloring options that you can use to bake your own blue muffins at home. The blue dye will need to be a professional gel/paste (rather than a water-based version).

Here are a few different examples that you can choose from if you live in the US or UK:

If you're based in the US

If you're based in the UK

Is the blue food coloring safe to eat?

The dye used to bake blue muffins is a highly concentrated icing coloring that is safe to consume in small quantities. The pigment in the dye used to bake these blue muffins passes through your digestive tract unchanged, which is why they turn your poop blue.

Can my kids participate in the #bluepoopchallenge?

While the #bluepoopchallenge is designed for adults aged 18 and up (those younger than 18 won't be able to complete the blue poop quiz to get results), we view this campaign as a great way for families to talk with their kids about how food impacts the health of their gut, how food fosters good health, and poop. Baking and eating blue muffins with your kids can be an engaging and memorable activity that can also serve as a quick science lesson about the gut microbiome.

I've already done the challenge. How can I get my results?

After you've eaten two blue muffins, you'll need to look out for blue poop when you go to the toilet. When your blue poop appears, you can click on 'get results' in the top right of your screen to get your personalized insights. You will need to input your gut transit time and answer a few more questions to discover your poop personality and learn some really interesting things about your gut!.

Why should I care about my gut?

Through our research (published in the leading journal, Gut) we have discovered that gut transit time, measured using blue muffins, says a lot more about your gut microbes than how often you poop or what your poop looks like.

This builds on previous research that our team published in Nature Medicine in January 2021, which revealed the strong links between your health, the foods you eat and specific “good” and “bad” gut microbes.

Your gut microbiome is made up of trillions of bacteria, fungi and other microbes, and each time you poop, you flush away billions of them. What you eat has a huge impact on the kinds of microbes that live in your gut. The gut microbiome plays a very important role in your health by supporting digestion, immune health, and many other aspects of your overall health.

The wrong balance of "good" and "bad" gut microbes can contribute to weight gain, high blood sugar, high cholesterol, obesity and other health problems. While gut transit time is just one piece of the puzzle, understanding yours can give you some insight into what's going on inside your gut.

Where can I join the #bluepoopchallenge conversation?

Community is at the heart of what we're doing with this campaign. We would love to see pictures of your blue muffins on social media. Follow along and tag us:

Who is behind the #bluepoopchallenge?

ZOE is a healthcare science company that uses the most cutting-edge science and research to help people meet their health goals. We’re combining the latest technologies, artificial intelligence, and collaboration with world-leading scientists, to move beyond a ‘one-size-fits-all’ approach to nutrition.

We believe the first step to reaching your best health is to discover exactly how your body works and then retrain your biology from the inside out. We offer comprehensive insights about how your body works and teach you how to eat for lifelong health.

Through our first-of-its-kind at-home-kit, we use the most cutting-edge science available to help you understand your unique gut health, blood fat and blood sugar responses. Paired with our personal nutrition app, we teach you sustainable ways to eat for your own biology, without restriction.

Got any other questions?

If you have any other questions, please reach out to our team at and we'll get back to you as soon as we can.

*This is a fun challenge, not a substitute for professional medical advice and does not diagnose, prevent, or treat any disease. If you have any concerns or unusual gut-related symptoms, please consult your physician.