Blue Poop Challenge Muffins #ScienceSundays

by Erin

Have you heard about the Blue Poop Challenge Muffins? It’s a fun experiment designed to help you learn about your gut health while enjoying blue muffins.

Bite out of a Blue Poop Challenge Muffin.

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Nothing like a title with poop in it to draw in readers for a recipe, amiright? It’s only partly as gross as you think.

A couple weeks ago a friend asked if I had heard of the Blue Poop Challenge where you eat not just one blue muffin, but two and track when the dye comes out the other end in the form of, you guessed it, blue poop. It’s based on research examining gut health conducted by healthcare science company ZOE and researchers at King’s College London.

To be honest, I was immediately skeptical because ZOE asks you to sign up for their services upon completion of the muffin challenge. Anytime a healthcare company tries to sell you something is a huge red flag, especially when gut health research is still so very new.

Close up of Blue Poop Challenge Muffins in Pan.

What are the Blue Poop Challenge Muffins based on?

As mentioned above, the Blue Poop Challenge was derived from research done by a group of scientists who work with ZOE, published September 2021 in Gut. In this study, they used several different methods to track gut transit time of 863 healthy people. They concluded that not only is transit time a better measure of your gut microbiome that frequency and appearance, but that blue dye is a cheaper and easier option for measuring gut transit time that previously used methods.

By tracking their participants blue poo transit time and sequencing stool samples, they observed a correlation of the gut microbiome composition to transit time groups. Meaning, if you have a longer transit time, you tend to have a different gut microbiome composition than a shorter transit time.

Blue Poop Challenge Muffins.

Can Blue Poop Challenge Muffins really predict gut health?

It is important to point our that they are not making specific claims about health in this study, just correlations. After all, gut transit time it only one factor contributing to your over all “gut health”. However, a previous study by the same team published January 2021 in Nature Medicine did show a strong link between overall health, the foods you eat, transit time, and the presence of certain gut microbes. In other words, the faster the blue dye moves through your body, the more likely you are to have a healthy gut microbiome. But there isn’t enough scientific data yet to determine exactly what transit time is optimal for health.

Another short-fall of the Blue Poop Challenge? Eating two muffins one day only gives you a transit time for that particular day. Tomorrow may be different based on your diet, sleep, exercise, etc. So if you try the Blue Poop Challenge muffins, don’t stress about your results because there’s not enough data to say what it truly means – it’s more of a fun experiment.

The one intriguing thing about their program is that it effectively is crowdsourcing science which in beneficial in many ways, including getting a bigger picture of what is going on, which is what we need for their field to develop a bigger picture.

Blue Poop Challenge Results.

How long should the blue poop challenge take?

For the participants in their Nature Medicine study, gut transit time ranged from less than 12 hours to several days, but averaged around 29 hours.

Since I am completely enthralled by gut health and enjoy a fun little experiment, I set out to bake blue muffins for my coworkers, first ensuring that I had enough of the right blue food coloring.

Without divulging too much information, all 6 participants in my mini Blue Poop Muffin Challenge were around the average found in the published study.

Blue Poop Challenge - ZOE Red Flag.

What information does the Blue Poop Challenge provide?

After calculating our transit time on the ZOE website and answering some questions about our eating habits it paired us with one of the participants in their study whom had similar transit time and eating habits. By no way it is diagnostic but it goes on to tell you the good microbes that were common in your “gut twin”.

This is where the red flags come in because if you want to actually learn what microbes are in your microbiome you have to enroll in their program which will tell you what to eat based off the results. Since, as I mentioned above, there isn’t enough data I am not advocating for anyone to sign up. Maybe if you have bowel issues already and have not had success remedying it other ways, talk to your doctor about it.

Blue Poop Challenge Muffins in Pan.

Bite out of a Blue Poop Challenge Muffin.


Yield: 6 servings Prep Time: Cooking Time:
Nutrition facts: 200 calories 20 grams fat


  • 2 cups (250g) all-purpose flour*
  • 1 Tbsp (15g) baking powder
  • 1/2 tsp salt
  • 1/2 cup (120g) buttermilk
  • 1 Tbsp lime zest
  • 1 tsp vanilla extract
  • 1 tsp Wilton Royal blue food coloring
  • 1/2 cup (100g) vegetable oil
  • 1/2 cup (100g) sugar
  • 1/2 cup (100g) dark brown sugar
  • 2 eggs, room temperature
  • 1 pint fresh blueberries
  • Coarse sugar


  1. Preheat oven to 350 degrees and grease a 12-count muffin pan with non-stick spray, set aside.
  2. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
  3. In a small bowl mix the buttermilk, lime zest, vanilla extract, and blue food coloring. Set aside.
  4. In a large bowl with an electric mixer, beat together the oil and sugars until light and fluffy. Add the eggs and beat until just incorporated. Alternate adding in the flour mixture and buttermilk mixture, mixing just until combined. Gently fold in the fresh blueberries trying not to break them as you stir.
  5. Fill your muffin pans about 3/4 of the way full and smooth the top as best as possible.
  6. Top each muffin with coarse sugar.
  7. Bake for about 25 minutes or until the muffin a toothpick inserted into the center comes out clean. Let cool 10 minutes before removing from pan.


*Can be made gluten-free by substituting with a 1-to-1 gluten-free all purpose flour.

Did You Make This Recipe?
I want to see! Tag me on Instagram at @TheSpiffyCookie and hashtag it #TheSpiffyCookie.

Source: Adapted from my Blueberry-Lime Streusel Muffins and Zoe.

Did you make this recipe? I want to see! Tag @THESPIFFYCOOKIE on Instagram and hashtag it #THESPIFFYCOOKIE
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Jenni March 23, 2024 - 10:12 am

I have sort of a gross question, I am SO so sorry lol. But is the “result” after eating these very noticeably blue? Or could it be like a barely perceptible greenish tinge? I had confusing results after eating these, so I was wondering…

Erin March 24, 2024 - 5:25 pm

Mine was pretty darn obvious, but I used the exact food coloring they indicated (Wilton Royal Blue Icing Color). if you used a different food coloring then that may be the issue.

Inger February 13, 2023 - 11:49 am

So interesting! I have been reading about gut health too and have started making my own yogurt again. Looking forward to the possibility of targeting specific conditions with different gut bacteria someday.

Erin February 13, 2023 - 7:07 pm

Same, but still so much to learn! I am currently working to shift my research at my day job to examining the gut microbiome in relation to chronic Salmonella infections.


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