Why Is My Toddler Still Constipated? When More Fiber Isn’t Enough

Toddler constipation is rarely as simple as “eat more fiber.” Here’s why the developing gut microbiome deserves a place in the conversation and why I started Persephone.

Pears. Prunes. More water. More fiber.

If you have a constipated toddler, chances are you have tried it all. And sometimes, they still can’t poop comfortably.

I understand the frustration not only as a scientist studying the early life gut microbiome, but as a mom to a young child. I have lived through the food negotiations, counting fiber and water, and worrying when another day passes without a poop.

Why is my toddler still constipated?

Fiber and hydration matter. But so can picky eating, potty training, stool withholding, and your child’s developing digestive system.

There is another piece we think deserves more attention:

The gut microbiome. Exactly what Persephone supports. 

What does Bifidobacterium have to do with poop?

Gut microbes are part of what happens between the food your toddler eats and the poop that comes out.

One important group of early life bacteria is Bifidobacterium. These bacteria interact with components of the diet and produce metabolites that help shape the intestinal environment.

Research examining specific Bifidobacterium strains has explored their potential to support bowel movement frequency, stool consistency, digestive comfort, and a healthy intestinal environment.²⁻⁶

That does not mean any probiotic will make a constipated toddler poop. Not all probiotics are the same. Different species and strains can have different functions.

But healthy digestion is not only about what children eat. The microbial ecosystem interacting with their diet matters too.

Your toddler’s microbiome is still under construction

The first few years are an important period of gut microbiome development, and Bifidobacterium are hallmark bacteria of the early life gut.

In our published My Baby Biome study, we found that more than 9 out of 10 U.S. infants were missing one or more key species of Bifidobacterium during early life.¹

As a scientist, that fascinated me. As a mom, it made the issue feel much more personal.

The microbiome continues developing as babies become toddlers and transition to a broader diet. That makes the toddler years an important period for microbiome development.

Healthy poops can be a long game

When your child cannot poop, you want to help them now. I do too.

Persistent or painful constipation should be discussed with your pediatrician. But there is also a longer term question:

How can we support healthy digestion as our children grow?

Supporting the microbiome is not an overnight fix. It is about supporting a developing ecosystem over time. Our daily synbiotic can help with this. 

Why do toddlers hold their poop?

Sometimes constipation starts with one painful poop. Your toddler remembers that it hurt, so the next time they feel the urge, they hold it.

The longer stool remains in the colon, the more water can be absorbed, potentially making it harder to pass.

This can create a cycle:

Hard poop → pain → withholding → harder poop → more pain

Breaking that cycle can take time, particularly during potty training.

Why isn’t more fiber fixing it?

Fiber and fluids are important, but they are not the entire digestive story.

Certain carbohydrates and fibers reach the colon, where gut microbes use them and produce compounds that help shape the intestinal environment.

And once a child begins withholding because pooping hurts, another serving of fruit may not address that cycle.

Instead of asking only, “Is my toddler eating enough fiber?” we should also ask, “What is happening inside their developing gut?”

Why we created our infant and toddler synbiotic

At Persephone, we wanted to understand the early life microbiome and use that science to build a product specifically for babies and toddlers.

Our synbiotic combines proprietary infant derived Bifidobacterium infantis, Bifidobacterium breve, and Bifidobacterium longum with four human milk oligosaccharides, or HMOs, selected to nourish beneficial bacteria, plus vitamin D to support healthy immune function.

The goal is not an overnight constipation remedy.

Our goal is to help replenish key Bifidobacterium and support digestive health during an important period of gut development.

If you feel like you have tried everything

If you have served the pears, offered the water, counted the fiber, and wondered why your toddler is still constipated, you may not be missing some magical food.

Fiber matters. Hydration matters. Stool withholding matters. And the developing gut microbiome deserves to be part of the conversation too.

As a scientist, that is what I study. As a mom, I understand why it matters so much.

When should I talk to my pediatrician?

Persistent or painful constipation should be discussed with your child’s healthcare provider.

Seek medical attention for blood in the stool or rectal bleeding, persistent abdominal pain or swelling, vomiting, or weight loss.

A synbiotic is not a substitute for medical evaluation or treatment of constipation.

References

1. Jarman JB, et al. Bifidobacterium deficit in United States infants drives prevalent gut dysbiosis. Commun Biol. 2025;8:867.

2. Lv S, Qiao W, Wang Y, et al. Probiotics for constipation relief in infants and young children: efficacy and mechanisms. Journal of Future Foods. 2025.

3. Okada K, Takami D, Makizaki Y, et al. Effects of Bifidobacterium longum CLA8013 on bowel movement improvement. Bioscience of Microbiota, Food and Health. 2023.

4. Makizaki Y, Kishimoto M, Tanaka Y, et al. Activation of chloride channels and promotion of bowel movements by heat-killed Bifidobacterium longum CLA8013. Bioscience of Microbiota, Food and Health. 2024.

5. Takeda T, Asaoka D, Nojiri S, et al. Usefulness of Bifidobacterium longum BB536 in chronic constipation. American Journal of Gastroenterology. 2023.

6. Wang L, Wang L, Tian P, et al. A randomized, double-blind, placebo-controlled trial of Bifidobacterium bifidum CCFM16 for chronic constipation. Food & Function. 2022.