You’re drinking more water.
You added a fiber supplement.
You’re even making it to the gym most days.
And you’re still constipated.
If this sounds familiar, you’re far from alone. Constipation affects roughly 30% of people every year. For a lot of them, the standard advice simply doesn’t fix it.
That’s because “eat more fiber and drink more water” only addresses lifestyle factors. It doesn’t cover the full list of what can actually drive the problem. Constipation has real, identifiable root causes. Finding yours often makes the difference between managing symptoms indefinitely and actually resolving them.
Why “Eat More Fiber” Isn’t the Full Answer
Fiber and hydration matter, and for some people, thats all it takes. But research shows constipation is often multifactorial. Causes can include gut bacteria imbalance, altered colonic motility, enteric nervous system dysfunction, hormone levels, and psychological factors. Often several overlap at once. If you’ve already tried the basics and nothing’s changed, the answer is likely to look deeper.
The Gut Flora Connection
Your gut bacteria play a direct role in how well your colon moves waste through. Research on slow transit constipation has identified a specific mechanism. Beneficial gut bacteria produce short-chain fatty acids that support serotonin production and nerve signaling in the colon. When beneficial bacteria drop, that signaling weakens and transit slows down.
This is why some people with constipation see lasting improvement once they address gut bacterial balance directly. Adding more fiber on top of an imbalanced system often isn’t enough.
The Thyroid Connection
This is one of the most commonly missed root causes, particularly in women. Thyroid hormone deficiency reduces colonic motility and slows down bowel transit. Hypothyroidism is a well-documented, common trigger for chronic constipation. Hypothyroidism itself is roughly ten times more common in women than in men. That’s part of why this cause disproportionately affects women, though it’s worth checking regardless of sex.
The tricky part is that standard TSH testing alone doesn’t always catch subclinical thyroid dysfunction. That’s the kind mild enough to miss red flags, but still significant enough to slow your gut down.
The Nervous System Connection
Your gut and brain are in constant two-way communication, and chronic stress changes how your digestive system functions. Chronic stress activates the body’s fight-or-flight response, which shifts blood flow and energy away from digestion and toward perceived threats. Over time, this can slow gut motility enough to cause real, persistent constipation.
This connection runs both directions too. Chronic constipation itself can increase stress and anxiety, which feeds back into slower gut motility. That creates a cycle that’s hard to break without addressing the nervous system directly.
Medications That Quietly Cause It
A lot of people don’t connect their constipation to something they’re already taking. Common culprits include opioid pain relievers, iron supplements, certain antidepressants (particularly tricyclics), antihistamines, and some blood pressure medications. Research documents each of these as a cause of medication-induced constipation. If your constipation started around a new prescription or supplement, that timing is worth noting.
This doesn’t mean stopping a needed medication on your own. It means bringing the full picture, medications included, into the conversation about what’s actually driving your symptoms.
Why Standard Workups Often Miss the Cause
A typical GI workup for constipation rules out red flags: blockages, structural issues, more serious conditions. That’s important, and it’s a step you shouldn’t skip. But once doctors rule those out, many people simply hear “increase fiber and fluids.” No one digs into gut bacterial balance, thyroid function, nervous system regulation, or a medication list.
That’s the gap. Ruling out the dangerous causes isn’t the same as identifying your actual cause.
What Functional Testing Adds
At Austin Transformational Health, Dr. Bryn Kanuck uses a broader testing approach to find what’s actually driving constipation, including:
- GI-MAP stool testing to assess gut bacterial balance and identify dysbiosis affecting motility
- A full thyroid panel, not just TSH, to catch subclinical thyroid dysfunction that standard screening can miss
- Broader functional medicine testing to evaluate inflammation, nutrient status, and other contributing factors
From there, Dr. Bryn builds a protocol around what your results actually show. That might mean rebalancing gut bacteria, addressing thyroid function, or supporting your nervous system’s ability to regulate digestion again.
You Don’t Have to Just Manage This Forever
If you’ve been doing “everything right” and still dealing with constipation, that’s a sign. It’s time to look for the actual cause, not try yet another fiber supplement. Once you know the right root cause, the whole picture tends to make a lot more sense.
