What Causes Heartburn?

What Causes Heartburn?

Here’s a fun little question for you – which of these statements is false?
A) A Banyan Tree near Kolkata, India is larger than the average Walmart
B) There are more nerve connections in your brain than there are stars in our galaxy
C) Heartburn is usually due to too little stomach acid, not too much
Okay, that was a trick question. They’re all true. The sources for the first two facts are here, and in this post we’ll dive into the clinical research that supports number three.

Now, maybe you’re thinking, “That can’t be right. I’ve taken an antacid when I had heartburn and it helped, so clearly the issue was too much acid.”

That’s certainly what I thought when I was one of the 60 million Americans struggling with heartburn. However, according to Jonathan Wright, M.D., author of Why Stomach Acid Is Good For You, the “Chances are very high – over 90 percent – that the real culprit is actually underproduction of stomach acid.”

So if antacids aren’t reducing excess acid, what are they actually doing? Unfortunately, there’s a downside to these medications – both over-the-counter and prescription – that you won’t find on the label.

Before we dive into the details, I want to remind you that I am not a doctor and this is not medical advice or a diagnosis. I’m just a former heartburn sufferer passing along information I’ve found helpful from respected physicians, clinical studies conducted by places like Johns Hopkins University, and articles from Scientific American and the New York Times. 

What we misunderstand about heartburn

According to Dr. Wright, who has worked with thousands of heartburn patients at the Tahoma Clinic, “stomachs are built for the very purpose of containing and working with very strong acid, acid that is one-hundred-thousand times stronger than the acidity of our blood.”

This acid plays an essential role in helping us to break down food so that nutrients can be absorbed, and also kills a variety of bacteria, parasites, and other pathogens on contact. When levels are normal, you’re very unlikely to experience heartburn. However, if they’re low your chances increase. Here’s why:


Just above the stomach there is a valve called the lower esophageal sphincter (LES) – it protects the esophagus from harsh stomach acid. When the LES is functioning normally, it only opens when you eat, drink, belch, or (yep) vomit.

If the LES is working properly, it doesn’t matter how much acid we have on our stomachs. It’s not going to make it up to the esophagus. On the other hand, if the LES is asleep at the switch, even a small amount of acid could reflux into the esophagus under the right conditions. Scientists have found that when we have heartburn or GERD, the LES opens briefly when it’s not supposed to. If we’ve got acid – or anything else – in our stomachs, sometimes even a little bit, and it happens to be in the vicinity of the LES when it pops open inappropriately, we get reflux.” Jonathan Wright, M.D., Why Stomach Acid Is Good For You

So what causes the LES to malfunction? After testing the gastric pH of thousands of heartburn sufferers at his Tahoma Clinic, Dr. Wright has concluded that in 90%+ of cases it’s low stomach acid.

Remember, in addition to breaking down food so that nutrients can be absorbed, stomach acid also provides an “acid barrier” that kills bacteria, parasites, and other pathogens in our food. If the acid is too weak, maldigested food – especially carbohydrates – can become a source of nourishment for these bacteria/pathogens. As they feed, they produce fermentation byproducts (gases) that create pressure in the stomach and push on the LES valve. When the pressure builds, some acid may be pushed through the LES in to the esophagus, causing heartburn.


If you’re still not convinced, consider this: Studies show that our stomach acid levels tend to drop as we age. (source 1source 2) “If heartburn were caused by too much stomach acid,” writes Chris Kresser, LAc., “we’d have a bunch of teenagers popping Rolaids instead of elderly folks. But of course that’s the opposite of what we see.”

That’s not to say teens can’t have low stomach acid – I actually got my first prescription for heartburn when I was nineteen. But on the whole, we tend to have more problems with heartburn as we get older despite dropping levels of stomach acid.

Dr. Wright’s “argument is with the mistaken concept that it takes ‘too much’ stomach acid to do the damage. Even a small amount of acid in the wrong place (such as the esophagus) can cause symptoms and ultimately tissue damage. (After all, we know that stomach acid is strong stuff, if it can help reduce a tough beefsteak into the equivalent of beef soup in an hour or so.)” (Why Stomach Acid Is Good For You)

What causes low stomach acid?

There are several possibilities:

  • Stress, particularly the chronic type, can inhibit the body’s secretion of hydrochloric acid (stomach acid). (source 1source 2)
  • Certain gut infections, such as H. pylori and candida, reduce the body’s production of hydrochloric acid (source) It can be argued, however, that these infections only take hold if gastric acid secretion is already compromised. From that perspective, the presence of these microbes simply further inhibits the production of hydrochloric acid.
  • A mutation in one of the genes that influences gastric acid production (source)
  • Use of antacid medications

Acid reflux medications “not the benign drugs the public thinks they are” – Dr. Shoshana Herzig, Harvard Medical School

Most of us tend to think of heartburn medications as pills that just “take the edge off” and leave us with normal acid levels. Unfortunately, that’s not really the case. Not only do they reduce levels that may already be too low, sometimes they almost completely eliminate it.

The drug most commonly prescribed for heartburn today, Prilosec, virtually eliminates acid in the stomach around the clock, a fact that is proudly promoted in the drug’s widespread consumer-oriented advertising. Prevacid, Aciphex, Protonix and Nexium do about the same thing.” (Why Stomach Acid Is Good For You, emphasis mine)

Although eliminating stomach acid will relieve symptoms of indigestion, it also prevents the stomach from doing its job – digesting food and killing pathogens as they enter our system. “The most popular acid reflux medications — proton pump inhibitors like Nexium, Prilosec and Prevacid, which are taken daily — can have serious side effects and ‘are not the benign drugs the public thinks they are,’” Dr. Shoshana J. Herzig of Harvard Medical School told The New York Times.

Some of the problems mentioned are decreased resistance to infection, nutritional deficiencies and increased risk of certain diseases.



As we covered earlier, the stomach is supposed to be an “acid barrier” that protects against intestinal tract infection. Unfortunately, according to John Clarke, a gastroenterologist at Johns Hopkins Hospital in Baltimore, lowering stomach acid using proton-pump inhibitors like Nexium, Prilosec and Prevacid “leaves people vulnerable to nutritional deficiencies and infections, including food poisoning like salmonella, a serious, sometimes life-threatening digestive system infection called Clostridium difficile, and perhaps pneumonia.” (source)

Other studies have found individuals who take acid suppressing drugs have an increased risk of getting pneumonia. (source 1)

And because I couldn’t leave it out . . .

Here’s an extreme, but very revealing, incident: Decades ago, public health officials in India investigated why some people in a village in the midst of a cholera epidemic didn’t contract the disease, while others did. They found that more of those who stayed healthy had normal levels of stomach acid, while those that developed the disease usually did not. Apparently, the strong stomach acid killed the bacteria before it could ‘colonize’ (and damage) the entire gastrointestinal tract.” Why Stomach Acid Is Good For You


Stomach acid triggers a whole cascade of digestive processes, including the release of enzymes and bile to break down fats, proteins, etc.. Without this “acid trigger,” an individual may become malnourished due to a lack of absorption – even when they’re eating a very healthy diet.

If acid reducing drugs are taken on a long-term basis, it may lead to severe nutritional deficiencies. For example, the long-term use of proton pump inhibitors like Prilosec, Nexium and Prevacid may “lead to low levels of magnesium in the blood, which can precipitate seizures, arrhythmias and muscle spasms, according to the F.D.A.” (Source: The New York Times)


In this article, Chris Kresser, LAc discusses the association of low stomach acid with:

  • Stomach cancer
  • Allergies
  • Bronchial asthma
  • Depression, anxiety, mood disorders
  • Pernicious anemia
  • Skin diseases, including forms of acne, dermatitis, eczema, and urticaria
  • Gall bladder disease (gallstones)
  • Autoimmune diseases, such as Rheumatoid arthritis and Graves disease
  • Irritable bowel syndrome (IBS), Crohn’s disease (CD), Ulcerative colitis (UC)
  • Chronic hepatitis
  • Osteoporosis
  • Type 1 diabetes

Recent news articles have also reported on links between acid reducing drugs and other problems:

Scientific American: Heartburn Meds Alter The Gut

The New York Times: Heartburn Drugs Tied to Dementia Risk

The New York Times: Taking Heartburn Medications Long-Term (Discusses bone fractures, seizures, arrhythmias & potentially life-threatening intestinal infections)

Washington Post: Popular heartburn medication linked to chronic kidney disease

Stanford Medicine: Some heartburn drugs may boost risk of heart attack, study finds

Science News: Heartburn drugs can damage cells that line blood vessels

This article was medically reviewed by Madiha Saeed, MD, a board certified family physician. As always, this is not personal medical advice and we recommend that you talk with your doctor.

We've all heard that heartburn is caused by excess stomach acid. But what if that's not true in over 90% of cases? After testing thousands of heartburn patients at his Tahoma Clinic, that's what Jonathan Wright, M.D. concluded. Here's what he says is the most common cause of heartburn, plus how antacids often work against us . . .

A Natural Approach To Heartburn

Since low hydrochloric acid levels are the main cause of heartburn, most people find that raising acid levels helps significantly. Using that approach I’ve been heartburn-free for well over ten years now, and I’m able to enjoy all my favorite foods. In fact, I’m eating homemade pizza doused in red chili flakes and pepperoncini’s right now, and yesterday I ate eggs slathered in my favorite store-bought habanero sauce.
In this post on getting rid of heartburn naturally, we’ll discuss several strategies for lowering stomach pH (making it more acidic), improving digestion, and supporting nutrient absorption.