Your Poop Might Be Aging Your Brain: What a 112,000-Person Study Reveals About Gut Health & Cognition

For years, many of us were told that anything from a few bowel movements a week to once a day was “normal.” But new research is changing how scientists think about what optimal digestion really looks like, and the implications go far beyond just gut comfort.

A landmark 2023 study analyzing over 112,000 adults found that infrequent bowel movements were linked to significantly worse cognitive performance and faster cognitive aging. In short: how often you go may be deeply connected to how your brain ages.

Let’s break down what the research actually found, and why your daily digestion might matter more than you ever realized.

🔬 The Study at a Glance 

Researchers from Harvard and collaborators analyzed data from three major long-running health studies:

• Nurses’ Health Study (NHS)

• Nurses’ Health Study II (NHSII)

• Health Professionals Follow-Up Study (HPFS)

Together, this included 112,753 participants who reported their bowel movement frequency and later completed cognitive assessments.

Participants were grouped by how often they had bowel movements:

• Multiple times per day

• Once daily

• Every 2 days

• Every 3+ days

The researchers then evaluated:

• Subjective cognitive decline (how people felt their memory was changing)

• Objective cognitive testing (memory, attention, processing speed)

• Gut microbiome composition in a subgroup

🧠 The Key Findings 

People who reported fewer than 4 bowel movements per week showed:

• Cognitive performance equivalent to ~3 additional years of aging

• ~73% higher odds of subjective cognitive decline compared to those with daily bowel movements

• Less favorable gut microbiome profiles, including reduced levels of beneficial, short-chain fatty-acid–producing bacteria

Importantly, these associations remained even after adjusting for:

• Diet

• Physical activity

• Age

• BMI

• Chronic disease

• Medication use

This suggests that bowel movement regularity itself may be an independent marker of brain health.

🧬 Why Would Digestion Affect the Brain?

This is where the gut–brain axis comes in.

Your gut and your brain are in constant two-way communication through:

• The nervous system

• The immune system

• Gut-derived metabolites

• Inflammatory signaling

• The microbiome

When stool sits in the colon for longer periods:

• Waste products and inflammatory compounds remain in contact with the gut lining longer

• The gut microbiome can shift toward less favorable species

• Beneficial compounds like butyrate (a key anti-inflammatory metabolite) may decrease

All of this may influence:

• Systemic inflammation

• Neuroinflammation

• Cognitive performance over time

The gut, quite literally, helps shape the environment your brain ages in.

🚽 What’s “Normal” vs. What’s Optimal?

Historically, doctors defined “normal” bowel frequency as anything from three times per week to three times per day. This study suggests that while that range may be common, it may not be ideal for long-term cognitive health.

In this study, the best cognitive outcomes consistently appeared in people with daily bowel movements.

That doesn’t mean everyone must be perfectly once-a-day; but it does reframe daily regularity as a meaningful wellness benchmark, not just a comfort issue.

💡 What This Means for Everyday Gut Health

This research doesn’t prove that constipation causes cognitive decline; but it strongly suggests that digestive regularity is an important biomarker of overall health, including brain health.

Factors that influence regularity include:

• Fiber intake

• Hydration

• Physical activity

• Gut microbiome composition

• Stress and sleep

• Daily routines

In other words, your bathroom habits can reflect how well your gut ecosystem is functioning as a whole.

🌿 Why Gut Health Is About More Than Just “Not Feeling Bloated”

For many people, digestive health is something only addressed when it becomes uncomfortable. But this research adds to growing evidence that the gut plays a foundational role in:

• Immune regulation

• Hormone signaling

• Mood and stress response

• Metabolism

• And now cognitive aging

Regular digestion isn’t just about relief. It’s about creating internal conditions your entire body relies on.

✨ The Takeaway

This massive study sends a clear message:

Your gut and your brain are deeply connected, and daily digestion may be one of the simplest outward signs of that relationship.

If you’re not going regularly, it’s not just an inconvenience. It may be your body’s way of signaling that your gut ecosystem needs more support.

A Gentle Note from Let Loose

At Let Loose, we believe gut health should feel natural, empowering, and supportive -not stressful or shame-based. Research like this reinforces why daily digestive wellness matters, not for perfection, but for long-term whole-body health.

Your gut works for you every day. Supporting it consistently may be one of the most underrated investments you can make in your future well-being.

Ma C, Li Y, Mei Z, Yuan C, Kang JH, Grodstein F, Ascherio A, Willett WC, Chan AT, Huttenhower C, Stampfer MJ, Wang DD. Association Between Bowel Movement Pattern and Cognitive Function: Prospective Cohort Study and a Metagenomic Analysis of the Gut Microbiome. Neurology. 2023 Nov 14;101(20):e2014-e2025. doi: 10.1212/WNL.0000000000207849. Epub 2023 Sep 29. PMID: 37775319; PMCID: PMC10662989.