Stomach Acid: What You Need to Know About Hypochlorhydria

Stomach acid, scientifically known as hydrochloric acid (HCl), plays an essential role in our digestive system, helping us to break down foods and providing protection from potentially dangerous bacteria. However, when stomach acid production is too low, a condition known as hypochlorhydria may develop, leading to uncomfortable digestive symptoms and potential health implications, although this is rare. In this article, we will explore the causes of low stomach acid, symptoms of low stomach acid and discuss other more common conditions with similar effects.

What is stomach acid?

Stomach acid is a digestive fluid produced by the stomach that helps break down food into smaller particles. It is composed primarily of hydrochloric acid, pepsin (an enzyme that breaks down proteins), and mucus. The acidic environment created by stomach acid also helps to kill harmful microbes, spores, and parasites that may be present in our food, reducing the risk of gastrointestinal infections (1).

Achlorhydria is the complete loss of stomach acid production while Zollinger-ellison syndrome is when the stomach to produce too much acid.

What is the pH of stomach acid?

The strength of stomach acid is measured using the pH scale, which measures the acidity of liquids. This scale ranges from 1 (most acidic) to 14 (least acidic, or alkaline). Stomach acid should have a pH of between 1.5 and 2 (2). Reduced stomach acid secretions lead to an increased pH (i.e., the stomach becomes less acidic and more alkaline). When the pH of stomach acid exceeds 4 it is considered to be too high and is referred to medically as hypochlorhydria. If the stomach is unable to produce any acid, it is called achlorhydria. This phenomenon is relatively uncommon, with an incidence rate of 2-5% (3).

Symptoms of low stomach acid

The symptoms of hypochlorhydria can include heartburn, bloating, flatulence, gut inflammation, and chronic indigestion. Because these signs overlap significantly with other upper gastrointestinal conditions, experiencing them regularly means it is vital to consult a healthcare provider to determine the precise underlying cause.

Interestingly, the vast majority of heartburn and indigestion cases are not caused by low stomach acid, but rather by Gastro-Esophageal Reflux Disease (GERD)—which occurs when stomach contents flow back up into the esophagus. While it is occasionally claimed in wellness spaces that GERD itself is caused by insufficient stomach acid, there is very limited clinical evidence supporting this.

The conventional treatment plan for severe GERD typically includes Proton Pump Inhibitors (PPIs, such as omeprazole) and antacids. PPIs effectively block gastric acid release to offer rapid symptom relief. However, long-term, chronic use of these medications can inadvertently cause low stomach acid. While PPIs are one of the most frequently prescribed classes of drugs worldwide, clinical studies consistently report that they are widely overprescribed.

Over time, low stomach acid may lead to nutrient deficiencies as many digestive enzymes, such as pepsin, are more active at lower pH and are therefore less efficient in a higher pH environment. Furthermore, a pH increase in the stomach renders the gastric environment less lethal to harmful microbes, increasing the risk of intestinal infections and small intestinal bacterial overgrowth (SIBO) – so low stomach acid may increase the risk of developing SIBO.

When to test for SIBO

If you’ve been struggling with symptoms such as bloating, gas, abdominal discomfort or changes in bowel habits, you may be wondering if you could have SIBO. Many people experience SIBO symptoms after eating, within around 30 – 90 minutes of a meal. Ask your healthcare provider about a SIBO test.

What is a SIBO Breath Test?

The SIBO breath test detects hydrogen and methane gases produced when bacteria growing too high up in your intestine ferment carbohydrates too early in digestion. You can take the test at home and receive a doctor-led diagnosis in the app, which can help your clinician recommend appropriate treatments.

We have  launched our SIBO eBook, which explains more about SIBO, what causes it, how to know if you have it, and how to treat and prevent it from recurring. You can download the free using the link below.

What causes low stomach acid?

Low stomach acid is relatively uncommon, and there has been little research on its underlying cause. Causes of low stomach acid may be age, autoimmune disorders damaging the stomach lining or thyroid, or the use of (PPIs), antacids and acid blockers (5). Helicobacter pylori infection is also a known cause of hypochlorhydria, due to the bacteria’s interference with the stomach’s acid-producing cells.

Low stomach acid tests

If it is thought that you are showing signs of low stomach acid, you may need a low stomach acid test. A gastric acid output test is often used. This is conducted with a capsule or probe and a pH sensor that is placed into the stomach. A standardised meal is given, such as a nutrient drink, that will buffer the acid levels in the stomach. The time it takes for your stomach to reacidify after the meal is then recorded.

How to increase stomach acid levels

If low stomach acid is diagnosed, you may be thinking, how do I increase stomach acid? It can be treated with supplements containing hydrochloric acid to lower the pH environment of the stomach, as well as digestive enzymes to help break down food properly. Apple cider vinegar has a similar pH to stomach acid, around 2.5, and there have been claims it can be a helpful treatment. However, further research is needed.

A diet for hypochlorhydria should include easily digestible foods, and in some cases, foods that help stimulate stomach acid production, such as ginger or apple cider vinegar, may be beneficial. Consulting with a healthcare provider can guide dietary changes for managing low stomach acid effectively.

While low stomach acid is a real condition, it is relatively rare and is not the origin of most digestive symptoms. If you are experiencing persistent heartburn, indigestion, or other digestive symptoms, it is important to speak with a healthcare provider to determine the underlying cause and develop an appropriate treatment plan. If you are unsure what’s causing your gut health issues, we recommend asking your healthcare provider about a SIBO test. Getting a clear doctor-led diagnosis will enable your healthcare provider to recommend suitable treatments.

Ask your healthcare provider about the at-home SIBO Breath Test

References

1. Hunt RH, Camilleri M, Crowe SE, et al. The stomach in health and disease. Gut. 2015;64(10):1650. doi:10.1136/GUTJNL-2014-307595
2. Fujimori S. Gastric acid level of humans must decrease in the future. World J Gastroenterol. 2020;26(43):6706-6709. doi:10.3748/wjg.v26.i43.6706
3. Fatima R, Aziz M. Achlorhydria. South Med J. 2023;21(11):920-924. doi:10.1097/00007611-192811000-00010
4. Wang KK, Genere JR. Gastroesophageal Reflux Disease (GERD). Mo Med. 2018;115(3):214. doi:10.1016/B978-0-12-801238-3.65937-8
5. Freedberg DE, Lebwohl B, Abrams JA. The impact of proton pump inhibitors on the human gastrointestinal microbiome. Clin Lab Med. 2014;34(4):771. doi:10.1016/J.CLL.2014.08.008
6. Forgacs I, Loganayagam A. Overprescribing proton pump inhibitors. BMJ : British Medical Journal. 2008;336(7634):2. doi:10.1136/BMJ.39406.449456.BE