Low stomach acid – fact or fiction

Low stomach acid – fact or fiction

By Jennifer Haynes – Trainee Physiologist – FGC

A quick google search of ‘stomach acid’ returns multiple blog articles about the importance of appropriate acid levels, with many providing tips on how to increase gastric acid production. In the world of online practitioners ‘low stomach acid’ is currently used as the scapegoat on which the root cause of many gastrointestinal disorders is pinned on. From gastro-oesophageal reflux disease (GORD) to Irritable Bowel Syndrome (IBS), there is an internet article out there linking the condition to low stomach acid; and along with that 10 quick ways to increase your stomach acid from your own home. But, what is the real scientific evidence about low stomach acid and what role does it play in gastrointestinal conditions?

‘Low stomach acid affects up to half of the population and you can cure it yourself at home’

Low stomach acid is extremely common among the present population and can cause people to become protein malnourished and mineral deficient. It can be diagnosed at home using baking powder, which will react with the acid in the stomach to create carbon dioxide. If you experience belching within 5 minutes of ingesting the baking powder, your stomach acid levels are normal. No belching equates to low stomach acid. If you do have low levels of gastric acid there are natural supplements you can take which can help; these include apple cider vinegar and manuka honey. There are also digestive enzyme and acid supplements which can help increase gastric acid levels.

The highly acidic nature of the stomach is pivotal to life. The average human stomach contains between 20 and 100ml of gastric acid, the pH of which fluctuates between 1.5 and 2.2. This creates a treacherous but necessary environment; the acidic stomach contents allows efficient digestion of food, effective absorption of nutrients and enables the body to receive essential minerals such as vitamin B12, folic acid and proteins.

Low stomach acid, known as hypochlorhydria, is a condition where an insufficient amount of gastric acid is produced in the stomach and the pH of the acid present is above 3. Although the exact mechanisms of the condition are unclear, it is thought that it can arise from chronic inflammation, an autoimmune response, or as a consequence of a H. Pylori infection. The prevalence in the middle-aged population is around 4%, rising to around 15% in the elderly; much lower than many of the figures quoted online. While there are no studies looking at the effectiveness of baking powder to diagnose this condition; there are other validated diagnostic tests available. One of which is a blood test which detects pepsinogen. Pepsinogen is an inactive enzyme secreted by the glands in the stomach which is converted to its active form in the presence of gastric acid.  Studies have shown that there is a significant correlation between the gastric acid secretion and the level of pepsinogen in the serum, which can be measured through a blood test.  Additionally, another method to measure gastric acid secretion involves using a wireless motility capsule to determine gastric pH. When the patient eats a standard meal of known buffering capacity, the capsule can be used to measure the acidification of the meal and therefore determine the volume of acid secretion in the stomach.

For patients who are diagnosed with hypochlorhydria, commonly advised treatments include hydrochloric acid supplements and pepsin.

‘Low stomach acid is the cause of GORD’

Stomach acid can be the bane of people’s lives; that burning sensation in the throat, continuous heartburn and a pesky cough are all symptoms of GORD, which is characterised by a backflow of stomach acid into the oesophagus. A reduced amount of stomach acid can lead to an increase in intra-abdominal pressure (IAP), which can cause the lower oesophageal sphincter (LOS) to open allowing small amounts of stomach acid to touch the oesophagus causing the familiar burning sensation experienced in reflux patients.

The scientific evidence

Although there are many blog articles that state low stomach acid is the underlying cause of acid reflux there is little to no evidence to back this up. There are many different components which can act as risk factors for GORD, including obesity or a high-fat diet consisting of smoking and an excess of chocolate, caffeine or alcohol. Additionally; stress, pregnancy, the presence of a hiatus hernia or a condition called gastroparesis; where the stomach takes longer to get rid of excess acid, can all contribute to the weakening of the LOS.

Throughout the literature, there is no evidence that low stomach acid can cause increased IAP or has any relation to GORD symptoms, in fact, a study showed that the higher the gastric pH value the less acid reflux events were detected in the oesophagus. Whereas a meta-analysis of various studies looking at the correlation of high body mass index (BMI) with GORD symptoms found that there is a significantly increased risk of symptoms in people that are overweight, and the risk progressively increases as weight increases. This study also highlighted that in fact obesity can cause increased IAP and decreased LOS pressure.

It is more likely that being overweight, eating a fatty diet or one of the other risks previously mentioned are causing the increase in IAP rather than reduced gastric acid.

‘Low stomach acid is the cause of small intestinal bacterial overgrowth (SIBO)/IBS’

Stomach acid is crucial for the effective digestion of food, and when the level of gastric acid is reduced some food particles will not be fully digested allowing the bacteria in the digestive tract to feed on them. The low acidity of the stomach fails to eradicate bacteria successfully and this can lead to the colonisation of the usually sterile small intestine. SIBO is associated with IBS-like symptoms such as abdominal pain, bloating and flatulence.

The scientific evidence

Although the reasoning behind this myth has more backbone than the others, the issue with this statement is the that prevalence of true low stomach acid in the general population is very low. Therefore, it is likely this myth has been exaggerated overtime. There is evidence to support that low gastric acidity can contribute to the development of bacterial overgrowth throughout the digestive system, which if left untreated could persist and develop into SIBO, in reality this occurs in a small percentage of the population. There are many factors which can contribute to the development of SIBO (read about it in our blog on SIBO here), and low stomach acid is just one of the less common factors.

The scientific evidence shows that although low stomach acid is a genuine condition; it’s prevalence in the general population is exaggerated and in reality, it is not the underlying cause of many gastro intestinal disorders as is stated on the internet. It is evident that more research into gastric acid levels is needed to fully understand how to appropriately treat and diagnose patients with low stomach acid. At The Functional Gut Clinic we are passionate about expanding our knowledge on functional gut disorders through research, which allows us to provide the highest quality care for our patients.

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