Stomach Acid: Function, Deficiency & Health Impacts
Heartburn, bloating, reflux: Most people immediately think of too much stomach acid. But what if the exact opposite is true? In fact, a lack of stomach acid can also trigger the same symptoms – a connection that is often overlooked in practice. This article highlights the functions of stomach acid, explains what happens when there is a deficiency, and objectively classifies the risks of long-term acid blockade.
Note: This article was created based on practical knowledge from naturopathy and current specialist literature. It does not replace medical advice or diagnosis.
What is stomach acid – and why do we need it?
Stomach acid mainly consists of hydrochloric acid (HCl) and is one of the strongest acids in the human body. When fasting, the pH value in the stomach is between 0.8 and 1.5. The acid is produced by the parietal cells in the stomach lining. The body produces about 2 to 3 liters of gastric juice daily.
The pH value in the stomach is not constant. After eating, it temporarily rises to values up to pH 7 because the food ingested buffers the acid. A single pH measurement is therefore not very informative. Acid production is primarily controlled by the hormone gastrin, which stimulates the parietal cells to release HCl.
The Key Functions of Stomach Acid
Stomach acid is much more than an aggressive digestive secretion. It fulfills several vital tasks simultaneously.
Protein Digestion by Pepsin
Stomach acid activates the enzyme pepsin from its inactive precursor pepsinogen. Pepsin breaks down food proteins into smaller building blocks. Without a sufficiently acidic environment, this first digestive step remains incomplete, and proteins enter the small intestine only partially digested.
Gatekeeper of the Immune System
Stomach acid is one of the body's first lines of defense against pathogens. Bacteria, viruses, and parasites that enter the stomach with food are killed by the extremely low pH value. This protective barrier prevents potentially harmful germs from entering the small intestine and further into the body.
Nutrient Absorption
Several essential micronutrients depend on an acidic environment in the stomach to be dissolved and absorbed from food. These include vitamin B12, iron, calcium, and magnesium. A persistently elevated pH value in the stomach can significantly limit the bioavailability of these nutrients.
Control of Digestion
Stomach acid regulates the rate of gastric emptying and sends chemical signals to the small intestine. These signals trigger the release of digestive enzymes from the pancreas and bile from the gallbladder. Without this coordinated sequence, the entire digestive process grinds to a halt.
Too Little Stomach Acid (Hypochlorhydria): The Underestimated Problem
Hypochlorhydria refers to a persistently low production of stomach acid. This problem is more common than generally assumed but is rarely considered first.
The paradox is that too little stomach acid can cause exactly the same symptoms as too much. Heartburn, bloating, gas, and reflux occur in both conditions. The mechanism behind this is understandable: If the stomach acid is insufficient to fully digest the food, undigested food begins to ferment in the stomach. This produces gases that build up pressure and push the stomach contents upwards. The result is a burning sensation in the esophagus, even though the actual cause is an acid deficiency.
The possible consequences of a chronic lack of stomach acid extend beyond digestive problems. Impaired nutrient absorption can lead to vitamin B12 deficiency and iron deficiency. The gut flora can change unfavorably because germs pass through the weakened stomach barrier. An increased susceptibility to infections is also associated with hypochlorhydria.
Another relevant factor: Stomach acid production tends to decrease with age. Especially in older people, a creeping acid deficiency can unnoticeably contribute to nutrient deficiencies.
Hypochlorhydria and SIBO: An Underestimated Connection
The connection between too little stomach acid and small intestinal bacterial overgrowth (SIBO) is hardly known to the general public but is regularly observed in practice.
Normally, stomach acid ensures that bacteria are killed before they reach the small intestine. In hypochlorhydria, this protective barrier is absent. Bacteria that should actually be located in the large intestine can multiply in the small intestine and cause symptoms such as bloating, abdominal pain, and diarrhea.
Reduced stomach acid production is considered one of the main risk factors for the development of SIBO. This connection is particularly relevant with the long-term use of proton pump inhibitors (PPIs), which specifically suppress stomach acid production. In 2021, around 3.7 billion daily doses of PPIs were prescribed in Germany, not including over-the-counter self-medication. The actual number of PPI users is therefore likely to be significantly higher.
Proton Pump Inhibitors: What to Consider with Long-Term Use
Proton pump inhibitors are among the most frequently prescribed medications in Germany. In 2018, 14.7% of all women and 12.2% of all men received at least one PPI prescription. For many patients, they are useful and necessary in the short term. However, with long-term use, some aspects deserve special attention.
Since PPIs permanently reduce stomach acid production, the absorption of acid-dependent nutrients can be impaired. This particularly affects vitamin B12, vitamin C, calcium, magnesium, and iron. This is a relevant point for people who pay attention to good nutrient supply or take dietary supplements.
Another aspect is the so-called acid rebound effect. During PPI intake, the body produces more of the hormone gastrin as a counter-reaction. If the medication is stopped abruptly, a temporary increase in acid can occur, which exacerbates the original symptoms. Many affected individuals then take PPIs again, a self-perpetuating cycle.
In addition, studies show that the risk of Clostridium difficile infections is 1.7 to 2 times higher in PPI users. Individual studies suggest a possible link between long-term PPI use and an increased risk of dementia. Other studies contradict these results, so the data situation is considered contradictory, and further research is needed.
Important: This section is not an invitation to stop medication on your own. PPIs have clear medical indications. It is about informing yourself about the topic and seeking discussion with the treating physician if you have questions.
What Influences Stomach Acid Production?
Stomach acid production is influenced by numerous factors that can lead to both overproduction and underproduction.
Factors that promote too much stomach acid:
- Chronic stress
- Alcohol and nicotine
- Excessive coffee consumption
- Fatty diet
- Helicobacter pylori infection
- Certain medications such as non-steroidal anti-inflammatory drugs (NSAIDs)
Factors that promote too little stomach acid:
- Increasing age
- Chronic stress (due to a dysregulation of the autonomic nervous system)
- Long-term PPI use
It is striking that chronic stress appears in both categories. Depending on individual constitution and duration of stress, stress can promote both overproduction and underproduction of stomach acid. Around 5 to 10 percent of the population develop a stomach ulcer during their lifetime, which is closely related to stomach acid balance.
Simple everyday measures can support digestion: conscious, thorough chewing, regular mealtimes, and targeted stress reduction. These factors do not replace therapy but create favorable conditions for functioning digestion.
Conclusion: Stomach Acid in Balance – Why Understanding Matters
Stomach acid is not an enemy but an indispensable component of digestion, nutrient absorption, and immune defense. The widespread notion that stomach acid must always be reduced is too simplistic. Both an excess and a deficiency can impair health. Those who understand the connections can communicate more informed with their own body and the treating physician and make more targeted decisions for their digestive health.