The idea has spread widely in wellness circles: your heartburn isn’t from too much stomach acid, it’s from too little. Antacids and acid-reducing drugs make things worse. The fix is to add acid back in, usually as betaine HCl capsules, increasing the dose with each meal until you feel a warm sensation, then backing off by one.
It sounds plausible and a little rebellious, which helps it spread. But when you look at how reflux actually works and what has been studied, most of the claim doesn’t hold up. A small part of it does, and that part is worth understanding.
The Claim, Broken Down
The low-acid theory usually makes four claims:
- Most people with heartburn have low stomach acid.
- Low acid causes food to sit and ferment, building pressure that pushes contents up into the esophagus.
- You can check your acid level at home with a baking soda “burp test.”
- Betaine HCl supplements restore normal acid and resolve the reflux.
Let’s take them one at a time.
Claim 1: Most Heartburn Comes From Low Acid
This is the central claim, and it doesn’t match what is known about reflux.
Acid reflux happens when stomach contents move up into the esophagus. The main reason is mechanical. The lower esophageal sphincter, a ring of muscle between the esophagus and stomach, relaxes when it shouldn’t. Hiatal hernia, extra abdominal pressure from weight or a large meal, lying down after eating, and certain foods, alcohol, and smoking all make this more likely.
People with reflux disease generally don’t produce unusually large amounts of acid. The problem is acid in the wrong place. But there’s also no good evidence that they typically produce too little. Acid-suppressing medications relieve symptoms and help an inflamed esophagus heal because they make whatever does come up less irritating. If reflux were caused by low acid, lowering acid further should make most patients worse, and that’s not what clinical experience shows.
Verdict: The valve and pressure explanation is well established. The idea that low acid causes most reflux is a hypothesis with no good supporting evidence.
Claim 2: Low Stomach Acid Is a Real Problem
This part is true, just not in the way the theory uses it.
Hypochlorhydria, meaning reduced stomach acid production, does occur. It becomes more common with age and shows up in:
- Atrophic gastritis, a chronic inflammation that damages acid-producing cells, sometimes autoimmune
- Long-term H. pylori infection
- Long-term use of proton pump inhibitors (PPIs) and other acid reducers
- Some types of stomach surgery
Low acid has real consequences. Stomach acid helps release vitamin B12 from food and supports iron and calcium absorption. That is why long-term acid suppression and atrophic gastritis are linked to low B12 and iron. Our guide to acid-reflux medication and nutrient depletion and our vitamin B12 explainer cover this in detail.
But these are medical conditions, diagnosed with blood tests, H. pylori testing, endoscopy with biopsy, or specialized gastric pH testing. They aren’t something you can identify by how your stomach feels after lunch.
Claim 3: The Baking Soda Burp Test
The test goes like this: dissolve a quarter teaspoon of baking soda in water, drink it on an empty stomach, and time how long it takes to burp. A quick burp supposedly means plenty of acid, and a slow or absent burp means too little.
The chemistry is real. Baking soda reacts with acid to make carbon dioxide gas. But burping depends on far more than acid: how much air you swallowed, how quickly your stomach empties, your posture, how fast you drank, and what’s left from your last meal. The test has never been validated against actual gastric pH measurement, and there are no accepted cutoffs. It’s a guess with a stopwatch.
Verdict: Unvalidated. Don’t make decisions based on it.
Claim 4: Betaine HCl Restores Acid and Fixes Reflux
Betaine hydrochloride is a source of hydrochloric acid in capsule form, often sold with pepsin, a digestive enzyme. (It’s a different product from TMG, or trimethylglycine, which is sold for methylation; our TMG research brief covers that confusion.)
What research exists is narrow. A small study in healthy volunteers whose stomach acid had been suppressed with medication found that about 1,500 mg of betaine HCl temporarily lowered stomach pH, and the effect faded within roughly an hour. That’s a useful proof of concept: the supplement can briefly acidify the stomach.
What hasn’t been shown:
- That betaine HCl relieves heartburn or reflux in controlled trials
- That it improves digestion, bloating, or nutrient absorption in people without diagnosed low acid
- That the “increase until you feel warmth” approach is safe or accurate
The warmth sensation many protocols rely on may simply be acid irritating stomach or esophageal tissue. That’s a poor endpoint to aim for.
Verdict: Betaine HCl can briefly add acid. Using it to treat heartburn is speculative and may be risky for the people most likely to try it.
Who Should Not Take Betaine HCl
This is the most important section. Betaine HCl is acid, and it can damage tissue that’s already irritated.
- People taking NSAIDs (ibuprofen, naproxen), aspirin, or corticosteroids (such as prednisone). These drugs already raise the risk of stomach ulcers and bleeding, and adding acid increases it.
- Anyone with a peptic ulcer, gastritis, or esophagitis, current or past, unless directed by a gastroenterologist.
- People on PPIs or H2 blockers. Taking acid and acid suppressants together makes no sense, and you shouldn’t swap one for the other on your own. Stopping a PPI abruptly often causes rebound acid that’s worse than the original symptoms. Any change should be a planned taper with your prescriber.
- Pregnancy and nursing. There’s no safety data, so avoid it.
- People with dietary restrictions. Pepsin is often derived from pork.
Other practical notes: swallow capsules whole with a meal, never on an empty stomach, and never open them, since the acid can damage tooth enamel and the throat. Stop right away if you feel burning or pain.
If you’re considering it anyway, talk to a clinician first, ideally after testing that shows you actually have low acid. Products typically contain 325-750 mg per capsule. There’s no established dose, and stacking several capsules per meal is not a validated approach.
When Heartburn Needs a Doctor
Occasional heartburn after a big meal is common. Some situations call for a medical evaluation instead of self-treatment:
- Heartburn more than twice a week, or lasting more than a few weeks
- Difficulty or pain swallowing
- Unintentional weight loss
- Vomiting blood, or black or tarry stools
- Chest pain, especially with exertion, shortness of breath, or sweating. Get emergency care, because heart problems can feel like heartburn.
What Actually Helps Common Reflux
The evidence-backed first steps aren’t supplements: smaller meals, not lying down for two to three hours after eating, raising the head of the bed, cutting back on alcohol and smoking, and noticing your personal trigger foods. Weight loss helps many people with frequent reflux. Our digestive enzymes guide explains why enzyme products are a separate question from acid.
Bottom Line
Low stomach acid is a real condition in specific groups, especially older adults and people on long-term acid suppression, and it matters for B12 and iron. But the idea that most heartburn comes from too little acid isn’t supported, the baking soda test has never been validated, and betaine HCl hasn’t been shown to relieve reflux. For people taking NSAIDs or steroids, or with an ulcer or gastritis, it can do real harm. If heartburn is frequent, get it evaluated rather than adding acid.
This article is for educational purposes only and is not medical advice. Consult a healthcare provider before starting any supplement — especially if you’re pregnant, nursing, taking medication, or managing a health condition.