Could Low Stomach Acid Be Behind Your Reflux? What the Evidence Really Says
Could Low Stomach Acid Be Behind Your Reflux? What the Evidence Really Says
You've probably come across the claim that reflux isn't caused by too much stomach acid, but too little. It's a popular idea in natural health spaces, and it's appealing because it offers a different path than simply suppressing acid indefinitely with medication. But because this is exactly the kind of claim that can do real damage to your trust in natural medicine if it's overstated, it deserves a properly evidence-based look rather than a confident retelling of the theory. Here's what's actually well-supported, what's plausible but unproven and what the mainstream gastroenterology literature says is really going on.
What gastroenterology actually says causes reflux
A comprehensive 2025 review of GERD pathophysiology, published in the journal Digestion by a team of Italian gastroenterologists, describes reflux disease as arising from an imbalance between your body's defensive mechanisms and a set of disruptive mechanical and motility factors (Bertin et al., 2025). The factors they identify as the key drivers are: dysfunction at the junction between your stomach and oesophagus, transient relaxations of the lower oesophageal sphincter (brief, inappropriate openings of the valve that's meant to stay shut), abnormalities in oesophageal motility, delayed stomach emptying and pressure changes in the abdomen and chest. Mucosal damage is then made worse by prolonged exposure to acid, bile and the digestive enzyme pepsin alongside heightened visceral sensitivity in the oesophagus itself.
Notice what's not centred in that explanation: insufficient stomach acid production. The mainstream, current understanding of GERD is fundamentally a story about a faulty valve and abnormal motility not a story about too little acid being made in the first place.
So is the "low stomach acid" theory just wrong?
Not entirely but it's being asked to do more work than the evidence supports. Hypochlorhydria, genuinely low stomach acid output, is a real and well-documented condition. It becomes more common with age, with long-term use of acid-suppressing medication, with H. pylori infection, with autoimmune gastritis and with chronic stress affecting the cells that produce stomach acid. What's genuinely well-evidenced is that hypochlorhydria impairs protein digestion and the absorption of minerals like iron, calcium, magnesium and zinc and can allow bacterial overgrowth in the small intestine because stomach acid normally acts as a sterilising barrier against bacteria travelling further down the gut.
What's far less settled is the specific causal claim that low acid itself is the primary driver of reflux symptoms for most people. The dominant mechanism that gastroenterology research keeps coming back to is mechanical: a sphincter that relaxes when it shouldn't, motility that doesn't clear refluxate efficiently and a nervous system that registers normal reflux events as painful.
Where the genuine evidence-based concern lies: long-term acid suppression
This is where the conversation becomes more useful and more nuanced than "PPIs bad, hypochlorhydria explains everything." Long-term use of proton pump inhibitors does carry real, measurable risks but the size of those risks can be more modest than is sometimes claimed. A risk-assessment table published in the Journal of Allergy and Clinical Immunology rated the risk of iron deficiency from chronic PPI use as low (odds ratio 2.49), vitamin B12 deficiency as low based on meta-analysis data (hazard ratio 1.83), and severe low magnesium as rare. Each of these was also described as treatable and reversible once identified. There's also a more clearly established link between long-term PPI use and an increased risk of SIBO, plausibly related to the loss of stomach acid's role as a bacterial barrier. A 2025 systematic review and meta-analysis pooling 29 studies and almost 3,700 PPI users found SIBO prevalence of roughly 37% among PPI-treated patients compared with about 20% in controls, with the highest risk seen in people using PPIs for more than six months (Khurmatullina et al., 2025). The honest clinical takeaway here is that chronic, unnecessary, indefinite acid suppression deserves real scrutiny, not because it disproves the gastroenterology model of reflux, but because of its own separate, genuine downstream effects on nutrient status and gut bacteria.
What this means for how reflux should actually be approached
Rather than starting from "your acid is too low" or "your acid is too high," a more honest starting point is asking what's actually driving the mechanical and motility picture for you specifically: is it a hiatus hernia, delayed gastric emptying, particular trigger foods, body weight and pressure changes, stress and visceral hypersensitivity or a combination? And separately, if you've been on long-term acid suppression, it's worth genuinely checking iron, B12 and magnesium status periodically, and looking at whether ongoing suppression is still required, rather than assuming either that PPIs are uniquely dangerous or that they're entirely risk-free long-term.
Frequently Asked Questions
Does low stomach acid cause reflux?
The mainstream gastroenterology evidence points to mechanical and motility factors, particularly a malfunctioning lower oesophageal sphincter, as the primary drivers of reflux, not insufficient acid production. Low stomach acid is a real condition with well-documented effects on nutrient absorption and bacterial overgrowth risk, but it isn't the established primary cause of GERD, there are other factros involved.
Are proton pump inhibitors dangerous to take long-term?
The evidence shows real but generally modest risks from long-term use, including a higher chance of iron, B12 and magnesium deficiency and an increased risk of SIBO, particularly beyond 12 months of use. These risks are treatable and definiately worth monitoring rather than reasons to panic.
What are the genuine signs of low stomach acid?
Poor protein digestion, nutrient deficiencies despite an adequate diet (particularly iron, B12, zinc), and an increased susceptibility to small intestinal bacterial overgrowth are the better-evidenced signs, rather than reflux specifically.
Should I just stop taking my reflux medication?
This isn't something to decide based on a blog post, and stopping suddenly can cause rebound acid symptoms. Any change to long-term medication should be done with your GP or gastroenterologist, alongside addressing the underlying drivers naturopathically where appropriate.
Want to actually understand what's driving your reflux?
If you're tired of generic advice on either side of this debate, let's look at your specific picture properly. Book your free 15-minute Discovery Call (https://earthflow-health.au4.cliniko.com/bookings) and we'll work out what's actually going on for you.
References
1. Bertin, L., Savarino, V., Marabotto, E., Ghisa, M., de Bortoli, N., & Savarino, E. V. (2025). Pathophysiology of gastroesophageal reflux disease. Digestion. https://pmc.ncbi.nlm.nih.gov/articles/PMC12279320/
2. Yadlapati, R., & Kahrilas, P. J. (2018). The "dangers" of chronic proton pump inhibitor use. Journal of Allergy and Clinical Immunology, 141(1), 79–81. https://www.jacionline.org/article/S0091-6749(17)31095-3/pdf
3. Khurmatullina, A. R., Andreev, D. N., Kucheryavyy, Y. A., Sokolov, F. S., Beliy, P. A., Zaborovskiy, A. V., & Maev, I. V. (2025). The duration of proton pump inhibitor therapy and the risk of small intestinal bacterial overgrowth: A systematic review and meta-analysis. Journal of Clinical Medicine, 14(13), 4702. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12250812/