The Blue Poop Challenge: The Viral Trend for Checking Gut Health

A muffin tin full of bright blue muffins.


Key Takeaways

  • The "Blue Poop Challenge" is meant to help people check their gut transit time.
  • Bowel transit time—how long it takes for food to move through the digestive tract from start to finish—can provide clues to your gut health.
  • The viral challenge—which involves eating muffins that are dyed blue and seeing how long it takes for you to notice blue in your stool—expands a formal study that used citizen science methods.

What happens in the bathroom is typically not a subject that you'd expect to be trending on social media. But recently, you might have seen the #BluePoopChallenge on Twitter or Instagram.

The viral challenge was started by a health science company called ZOE as a fun way for people to measure their bowel transit time, which can give them insights into their gut health.

Bowel transit time is how long it takes food to move through the digestive system from start to finish.

ZOE sells diagnostic tests that give customers a specific breakdown of how their bodies process food. However, right now there is a six- to an eight-week-long waiting list for the membership service.

That said, the Blue Poop Challenge is free and something that you can do at home with a little food coloring and willingness to monitor your bathroom activity for a few days. Here's what you need to know before you get started.

Why Take the Blue Poop Challenge?

Simply put, the Blue Poop Challenge is a tracking exercise. To take part, you eat two muffins that contain royal blue dye. Then, you track how long it takes to go from food to feces.

The time that it takes for food to move through your entire digestive system and be excreted is called gut transit time.

The timeline can tell you about the health of your gut microbiome, as the time food spends in the digestive tract can be indicative of how well nutrients are being absorbed.

How to Do the Blue Poop Challenge

The first step of the challenge is to get the muffins that you'll need to eat for breakfast. You can buy a kit with four of the muffins from ZOE's website for $2.99 plus $3.99 for shipping, or you can follow the recipe and make them at home.

#BluePoopChallenge Tips

For the results of the challenge to be accurate, you need to eat two muffins to ensure you consume enough blue dye for it to be visible.

If you don't like muffins, you can modify the challenge to make blue pancakes or eggs. You just need to eat solid food for the challenge, as liquids are detected and processed differently by your stomach.

Once you've bought or baked your muffins, you'll eat two of them for breakfast. Then, you'll need to check your stool and make a note of when you notice the blue dye—that's your gut transit time.

Next, you can plug the time into ZOE's website and answer some questions like your age, height, weight, and gender, as well as the food that you eat.

Taken together, this info can give you an idea of whether your gut transit time is fast, slow, or average.

ZOE's site will also match you with a "gut twin" (someone who has also taken the challenge) as an example for comparison. Based on your results, you'll get an idea of the "good" bugs that might be present in your gut microbiome, as well as a gut health tip.

Why Care About Gut Health?

Thanks to attention from celebrities like Eli Manning, Emma Thompson, and Greg Wise, more people are taking the Blue Poop Challenge and talking about gut health on social media. One question that remains, though, is why learning about your gut health is important.

Sarah Berry, MD

By allowing people to take part in these kinds of quite groundbreaking research, we scientists can massively progress our understanding of what determines how we respond to food.

— Sarah Berry, MD

Sarah Berry, MD, a researcher at King's College in London, has been working on finding the answer to that question. She and her colleagues published a study in the journal Gut back in March that highlighted what they've learned so far.

The research found that using a novel marker—such as a colorfully dyed solid food—is an efficient and cost-effective way to measure gut health without analyzing stool consistency and frequency.

In fact, the study indicated that using a novel biomarker provides more information than traditional stool analysis.

Harnessing Citizen Science

Introducing the testing method to the public is creating an even larger data pool for researchers through citizen science. Berry tells Verywell that the Blue Poop Challenge is collecting data while also giving something back to the participants.

"By allowing people to take part in these kinds of quite groundbreaking research, we scientists can massively progress our understanding of what determines how we respond to food," says Berry. "But we also want to give something back to individuals. It's not the same level as anyone participating in the formal studies, but it does give a better understanding about their dietary habits."

To fuel their understanding of their gut health, participants will have access to gut health tips, videos from gut microbiome expert Professor Tim Spector, and a deep dive into the science of the gut microbiome.

If participants are curious about the specifics of their gut health, they can sign up for ZOE's individualized services which complete more traditional stool analysis to get a person's unique microbiome profile.

Gut Health and Overall Health

Beyond increasing the sample size of the formal study exponentially, the Blue Poop Challenge also gets people thinking about how their diet affects their health.

Specifically, Berry wants people to realize that seldom are single foods as big of a problem as conventional nutritional advice would lead you to believe. "We don't consume ingredients. We consume foods," says Berry. "And foods don't act in isolation. They act synergistically."

Although many people look to their gut health as a form of weight management, Berry says that gut health is really an end unto itself through the ZOE service.

"Where I see it from the science, any weight loss is a byproduct of the benefits that we're giving in terms of overall health and internal metabolic health," says Berry. "We're giving you the best diet for your biology and metabolism. An outcome of that is weight loss, increased energy, lower blood lipids, better glucose control, and reduced inflammation."

Talking to Kids About Gut Health

Fiana Tulip, head of communications for ZOE, says that while the website and challenge are based on participants who are 18 or older, kids can take the challenge too.

"We encourage you to do this with your kids because it teaches them about the importance of food and their diet," Tulip tells Verywell. "We spend a lot of time thinking about what we're putting in our children's mouths, but not a lot of time thinking about the end result."

What This Means For You

Much of how our body responds to food is determined by our gut health. That said, the mysterious gut microbiome can be hard to measure. With a simple test like the Blue Poop Challenge, anyone can get a snapshot of their gut health and then take steps to improve their health.

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Asnicar F, Leeming ER, Dimidi E, et al. Blue poo: impact of gut transit time on the gut microbiome using a novel marker [published online ahead of print, 2021 Mar 15]. Gut. 2021;gutjnl-2020-323877. doi:10.1136/gutjnl-2020-323877

By Rachel Murphy
Rachel Murphy is a Kansas City, MO, journalist with more than 10 years of experience.