Heartburn: 14 Causes, Natural Approaches, and the Probiotic Connection

Heartburn is one of the most common digestive complaints in the world — and one of the most misunderstood. The burning behind your sternum after dinner isn’t actually happening in your heart, and it isn’t always caused by “too much acid.” It’s a mechanical problem with biochemical, microbial, and lifestyle contributors, and the path to real relief usually involves more than one approach. Here’s an evidence-grounded look at what causes it, what you can do about it naturally, and where probiotics and traditional ingredients like mastic gum fit into the conversation.

What heartburn actually is

Heartburn is the burning sensation behind the breastbone that happens when stomach contents — acid, pepsin, sometimes bile — wash backward into the esophagus. The esophagus doesn’t have the thick protective mucus layer the stomach has, so contact with acidic material irritates the tissue, and that irritation registers as burn, pressure, or a sour taste at the back of the throat.

The mechanical culprit is almost always the lower esophageal sphincter (LES), the ring of muscle that’s supposed to close after food passes from the esophagus into the stomach. When the LES relaxes at the wrong time, weakens with age, or gets pushed open by pressure from below, reflux happens. That’s the underlying mechanism — and crucially, it’s not the same as the stomach producing “too much” acid. The acid is doing its job. The problem is that it’s ending up where it shouldn’t be.

Occasional heartburn is normal — most adults will experience it at some point. Chronic, frequent heartburn (more than twice a week) is the clinical condition called GERD, and it deserves real medical evaluation. The American College of Gastroenterology’s GERD guidelines are explicit about this: persistent symptoms warrant a workup, not endless over-the-counter antacids.

The 14 causes of heartburn

Heartburn rarely has a single cause. Most people who get it regularly have several contributing factors stacking together. Here are the 14 most common ones, roughly in the order they show up in clinical research and gastroenterology guidelines:

1. Trigger foods

Some foods relax the LES; others delay gastric emptying; others are simply irritating to inflamed esophageal tissue. Classic culprits include citrus, tomato and tomato sauce, coffee (both caffeinated and decaf), alcohol, spicy foods, chocolate, peppermint, raw onion, garlic, fried and high-fat foods, and carbonated drinks. Triggers are individual — tracking what you eat alongside symptoms for two weeks usually identifies the top two or three for you specifically.

2. Large meals

A distended stomach pushes upward on the LES. Eating to the point of feeling overly full is one of the most consistent triggers for postprandial reflux. Smaller, more frequent meals reduce the mechanical pressure.

3. Lying down after eating

Gravity is one of the few free tools you have. Lying flat removes it, and stomach contents can flow back into the esophagus much more easily. Most clinical guidelines recommend staying upright for 2–3 hours after meals.

4. Hiatal hernia

When part of the stomach pushes up through the diaphragm into the chest cavity, the anatomy of the LES is disrupted. Hiatal hernias are common (especially over age 50) and often go undiagnosed unless someone scopes for them. They don’t always cause symptoms, but when they do, reflux is the most frequent presentation.

5. Pregnancy

The growing uterus increases intra-abdominal pressure, and pregnancy hormones (progesterone in particular) relax smooth muscle, including the LES. Heartburn affects up to half of pregnant women, especially in the third trimester. It usually resolves after delivery.

6. Obesity and excess abdominal weight

Excess weight around the midsection mechanically increases pressure on the stomach and LES. Weight loss is one of the few interventions with strong evidence for reducing reflux frequency in people with elevated BMI, and even modest weight loss can produce noticeable symptom improvement.

7. Smoking

Nicotine relaxes the LES, reduces saliva production (saliva helps neutralize acid that does reflux up), and impairs esophageal motility. Smoking cessation produces meaningful improvement in reflux symptoms over time and is among the most consistent recommendations in clinical guidelines.

8. Certain medications

A surprising number of common medications either relax the LES or directly irritate the esophagus. NSAIDs (ibuprofen, naproxen, aspirin) are the most frequent offenders. Others include calcium channel blockers, certain blood pressure medications, anticholinergics, benzodiazepines, tricyclic antidepressants, bisphosphonates, iron supplements, and some asthma medications. If your reflux started or worsened after a new prescription, that timing is worth bringing to your prescriber — never stop a medication on your own.

9. Stress and the gut-brain axis

Stress doesn’t increase acid production as much as folklore suggests, but it does increase esophageal sensitivity (the same amount of reflux feels worse), alter motility, and influence eating behavior. The gut-brain axis is real, and stress management is more than a wellness platitude when it comes to chronic heartburn.

10. Helicobacter pylori

A bacterium that colonizes the stomach lining. Its relationship with heartburn is complicated — it’s associated with peptic ulcers and gastric cancer risk, but also (paradoxically) with lower rates of GERD in some populations. H. pylori testing belongs with a gastroenterologist; if you have a strong family history of stomach cancer, persistent symptoms, or risk factors, it’s worth asking about.

11. Hypochlorhydria (low stomach acid)

This is the one most people don’t expect. Stomach acid production declines naturally with age, and low acid — not high acid — can drive reflux through delayed gastric emptying, fermentation pressure, and impaired LES signaling. The symptoms can closely mimic high-acid reflux, which is why so many people end up on long-term acid suppression that doesn’t fully resolve their problem. More on this below.

12. Tight clothing

Belts, waistbands, shapewear, and tight pants increase abdominal pressure mechanically — the same way excess weight does. It sounds minor, but for people on the edge of symptomatic reflux, loosening up clothing around the midsection can make a real difference.

13. Eating too fast

Rushed meals mean more swallowed air, larger boluses of food, less chewing, and reduced satiety signaling that leads to overeating. All of those factors increase reflux likelihood. Slowing down at meals is unglamorous but consistently helpful.

14. Caffeine sensitivity and late-night eating

Caffeine relaxes the LES and stimulates acid production. The window matters too — afternoon coffee combined with a late dinner combined with bedtime puts maximum strain on the LES at exactly the time gravity stops helping. Most reflux specialists recommend cutting off eating 3 hours before bed and watching caffeine intake after early afternoon.

The low-stomach-acid angle

The single most counterintuitive piece of heartburn research is that low stomach acid — not high — is a more common driver than most people assume, particularly in adults over 50. Stomach acid (hydrochloric acid) declines with age, and certain medications, chronic stress, and H. pylori infection can suppress it further.

Low acid can drive reflux through several mechanisms:

• Inadequate acid means food sits longer in the stomach, fermenting and producing gas pressure that pushes against the LES.
• Acid is part of the feedback signal that closes the LES. Without enough acid, the sphincter may not get the message to close properly.
• Low acid impairs protein digestion and creates an environment where opportunistic microbes can thrive in the upper GI tract.
• Low acid reduces absorption of B12, magnesium, iron, and calcium — nutrients that themselves play roles in motility and tissue integrity.

The clinical implication is that simply suppressing acid further sometimes provides short-term symptom relief but doesn’t address the underlying issue. If you suspect low acid is part of your picture, that’s a conversation for a gastroenterologist or functional medicine practitioner — there are actual tests (gastric pH studies, Heidelberg test, others) that can assess this. Self-treating with acid-boosting supplements without diagnosis can be risky.

Long-term PPI concerns

Proton pump inhibitors (omeprazole, esomeprazole, pantoprazole, and others) are among the most prescribed medications worldwide. They’re effective at suppressing stomach acid and provide real relief for many people with GERD. They were also designed for short-to-medium term use, but in practice many people end up on them for years or decades.

The peer-reviewed research on long-term PPI use has documented several downstream effects:

• Gut microbiome disruption. Imhann and colleagues (Gut, 2016) showed clear shifts in gut microbiome composition with PPI use — reduced diversity and changes in specific bacterial populations.
• Reduced nutrient absorption. B12, magnesium, calcium, and iron all rely on adequate stomach acid for proper absorption. Long-term suppression has been associated with measurable deficiencies in each.
• Bone density concerns. Multiple studies have linked long-term PPI use to increased fracture risk, likely mediated through calcium absorption.
• Increased risk of certain GI infections, including C. difficile and small intestinal bacterial overgrowth (SIBO).
• Rebound acid hypersecretion when stopped abruptly — sometimes worse than the original symptoms, which is one reason people stay on PPIs longer than intended.

This is not a recommendation to stop your PPI. Abrupt discontinuation can cause severe rebound symptoms, and for some people the benefit-risk calculation absolutely favors continued use. It’s a recommendation to have an informed conversation with your prescriber: is the current dose still necessary? Is there a structured tapering plan? Are there lifestyle changes that could reduce reliance over time? Those are the right questions, and they’re questions for a qualified provider — not the internet.

The probiotic-heartburn research

Probiotic research for heartburn and reflux is still emerging, and the honest summary is: the picture is mixed but interesting. Most positive findings relate to upper-GI comfort markers — bloating, regurgitation, dyspepsia — rather than reversing GERD itself.

The strains with the most relevant research:

• Lactobacillus gasseri. One of the few probiotic species naturally found in the human stomach — it can tolerate the acidic environment. Research has explored L. gasseri for post-meal bloating, dyspepsia, and gastric discomfort.
• Bifidobacterium lactis. Studied for general digestive comfort, transit time, and bloating. Most research focuses on lower-GI outcomes, but it’s a foundational strain in multi-strain blends.
• Saccharomyces boulardii. A beneficial yeast with research across multiple digestive contexts. Unaffected by antibiotics, which makes it relevant for people whose digestive issues developed after antibiotic courses.

Cheng and Ouwehand’s 2020 systematic review in Nutrients examined 13 studies on probiotics and GERD-related symptoms. Most (11 of 13) showed some benefit on at least one symptom domain — regurgitation, heartburn, or dyspepsia — but study designs, strains, and durations varied widely. The reasonable interpretation: probiotics are a supportive tool worth considering for digestive comfort, particularly for mild, occasional heartburn or post-meal regurgitation. They are not a treatment for GERD.

Mastic gum — the upper-GI ingredient

Mastic gum is the resin of the Pistacia lentiscus tree, harvested for thousands of years on the Greek island of Chios. Traditional Mediterranean medicine has used it for digestive complaints for millennia, and modern research has investigated it for upper-GI applications more directly than most probiotic strains.

Dabos and colleagues (Phytomedicine, 2010) ran a randomized pilot study on mastic gum for H. pylori, with results suggesting meaningful activity. Other research has explored mastic gum for functional dyspepsia and gastric mucosal integrity. It’s the ingredient that most directly addresses upper-GI comfort in supplement form — which is part of why we built mastic gum into Complete Gut Defense alongside the probiotic strains.

The framing matters: mastic gum is a supportive nutrient, not a treatment for GERD or any diagnosed condition. If you’re on prescribed acid-suppressing medication, talk to your healthcare provider before adding mastic gum or any new supplement. Combinations with prescription medications — even traditional, well-tolerated ingredients — need a knowledgeable provider in the loop.

Natural and lifestyle approaches

The unglamorous truth about heartburn is that lifestyle factors usually outweigh any single supplement or medication. The interventions with the strongest research support, in roughly the order they appear in major gastroenterology guidelines:

1. Elevate the head of the bed 6–8 inches. Not just extra pillows — lifting the head of the bed itself, using bed risers or a wedge. Gravity matters, and this is one of the highest-evidence interventions for nighttime reflux.
2. Stop eating 3 hours before bedtime. An empty stomach significantly reduces overnight reflux events.
3. Identify and avoid trigger foods. Track meals and symptoms for two weeks. Common culprits are listed above; your personal list will narrow quickly.
4. Eat smaller, slower meals. Large meals distend the stomach; rushed meals lead to overeating and swallowed air. Both increase pressure on the LES.
5. Lose weight if applicable. Even modest weight loss in people with elevated BMI shows meaningful reflux improvement in clinical research.
6. Don’t lie down after eating. Stay upright for at least 2–3 hours.
7. Quit smoking. Nicotine relaxes the LES.
8. Manage stress. Not a platitude — chronic stress measurably affects esophageal sensitivity and motility.
9. Loosen clothing around the midsection. Mechanical pressure adds up.
10. Sleep on your left side. Anatomically, left-side sleeping reduces reflux events compared to right-side or supine sleep.

Combine these with microbiome support — multi-strain probiotics, prebiotic fiber, dietary diversity — and you have a comprehensive approach that doesn’t rely on indefinite acid suppression. The principles that apply after antibiotics apply broadly to any situation where the gut microbiome has been disrupted. For underlying gut-lining integrity, our piece on intestinal permeability walks through what the research actually says. And if any of the terminology in this article is unfamiliar, our gut health glossary covers 100+ terms in plain English.

When to see a doctor

This page is informational. Heartburn symptoms that meet any of the following criteria warrant medical evaluation, sooner rather than later:

• Heartburn more than twice a week for several weeks
• Difficulty swallowing or food getting stuck
• Unintentional weight loss
• Vomiting blood or coffee-ground material
• Black or tarry stools
• Persistent cough, hoarseness, or asthma-like symptoms suspected to be reflux-related
• Chest pain (always rule out cardiac causes first — if there’s any doubt, go to an ER)
• Heartburn that started suddenly after age 50
• Symptoms worsening despite lifestyle changes and over-the-counter measures

Chronic, untreated reflux can lead to esophageal damage, including a condition called Barrett’s esophagus that has implications for long-term cancer risk. That’s a real medical concern that needs real medical care, not a supplement strategy. A gastroenterologist can run actual tests — endoscopy, pH monitoring, manometry, H. pylori testing — that tell you what’s actually going on rather than guessing.

The bottom line

Heartburn is a mechanical problem with biochemical, microbial, and lifestyle contributors. The popular framing — “too much acid, suppress it” — is incomplete, and the long-term cost of relying solely on acid suppression is increasingly well-documented in the peer-reviewed literature. The honest emerging picture: most heartburn has multiple causes stacking together, lifestyle interventions outperform any single supplement, low stomach acid is a more common driver than people expect, specific probiotic strains have research worth taking seriously for upper-GI comfort, and mastic gum has more direct upper-GI research than most ingredients marketed for heartburn.

Probiotics, mastic gum, and lifestyle changes are supportive tools. They are not a treatment for GERD. If you’re struggling with persistent heartburn, work with a qualified healthcare provider to understand what’s actually happening — and use everything else (diet, lifestyle, microbiome support, mastic gum) as part of a broader strategy that includes, not replaces, appropriate medical care. The 14 causes above don’t all apply to you, but two or three almost certainly do. That’s where to start.