Dr Dingle's Blog / stomach acid

Gut Health and our Stomach pH.

Gut Health and our Stomach pH.

One of the most important factors in regulating our gut health, digestion and controlling our microbiome is the pH or acid level.

While often mentioned in terms of the stomach, the pH has a controlling role to play in the health of the entire GI tract from the mouth to the anus; changes in the “normal” pH anywhere in the gut can have major implications on the rest of the GI tract. The pH scale goes from 1, being very acidic, to 14, being very alkaline. The level in our blood and tissues should be constantly around 7.36, neutral, and the level in our GI tract varies from 1 to 8. We cover this a lot more in our book Overcoming Illness, which focuses on the role of inflammation, oxidation and acidosis in illness.

After initial breakdown by chewing, food is churned by the smooth muscles of the stomach and is broken down by hydrochloric acid and stomach juices (enzymes). The pH of the stomach is highly acidic, around 1.5 (1.0 to 2.5) due to the hydrochloric acid that helps to kill harmful micro-organisms, denature protein for digestion, and help create favourable conditions for the enzymes in the stomach juices, such as pepsinogen.[1] Not to mention sending messages along the GI tract that everything is working well in the stomach. If the pH is too high, say 3 or 4 (low acidity and more alkaline), then the system does not work and you end up with poor gut health, digestive and health complications. For example, premature infants have less acidic stomachs (pH more than 4) and as a result are susceptible to increased gut infections.[2] Similarly, the elderly show relatively low stomach acidity and a large number of people, more than 30%, over the age of 60 have very little or no hydrochloric acid in their stomachs.[3]

Similarly, in gastric bypass weight loss surgery, roughly 60% of the stomach is removed. A consequence of this procedure is an increase in gastric pH levels that range from 5.7 to 6.8 (not 1.5) making it more alkaline and, as a result, more likely to experience microbial overgrowth.[4] We see similar patterns in other clinical cases such as acid reflux in which treatment involves the use of proton-pump inhibitors[5] and celiac disease[6] where delayed gastric emptying is associated with reduced acidity and increased disease.

Unfortunately, acid reflux is often wrongly treated as a condition that involves the production of too much acid. It is, in fact, the stomach finding it difficult to digest the foods, most commonly as a result of not having enough acid to complete digestion. Medications (see my other posts) which further reduce stomach acid have serious and sometimes deadly side effects on health, the digestive process and the gut microbiota. Acid reflux affects about 20% of the adult population and is much higher in older people, which is consistent with studies showing lower stomach acid as we age.


[1] Adbi 1976; Martinsen et al., 2005.

[2] Carrion and Egan, 1990.

[3] Husebye et al., 1992.

[4] Machado et al., 2008.

[5] Amir et al., 2013.

[6] Usai et al., 1995.

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Proton pump inhibitors (PPIs) and increased illness

Proton pump inhibitors (PPIs) and increased illness

The human stomach, when healthy, is not a suitable host for micro-organisms, but in pathological conditions such as gastritis, when gastric acid secretion is impaired, microbial overgrowth can be observed. The use of gastric acid suppression drugs has been shown to have profound effects on the microbiome.[1] Acid-blocking drugs, or proton pump inhibitors (PPIs) used for gastroesophageal reflux disease (GERD) to reduce gastric acid secretion, are among the most commonly prescribed medications in the world with approximately 6%–15% of the general population receiving acid suppression therapy.[2] Once initiated, they are often used for long periods of time without question,[3] despite the guidelines saying “for short term use only.”

PPIs increase the stomach pH to make it less acidic,[4] which is what they are designed to do, and as a result, change the composition of the intestinal microbiota[5] and impact the pH of the rest of the gut. They are associated with a decrease in small bowel beneficial Bifidobacteria and increase in the toxic gram-negative bacteria, as well as being associated with a significant decline in microbial diversity within seven days of beginning therapy.[6]

PPIs dramatically increase the risk of stomach bacterial overgrowth (SBO) and small intestinal bacterial overgrowth (SIBO), with increased risk of these bacteria getting into the blood[7] and the potentially fatal infection, Clostridium difficile.[8] Bifidobacteriaceae, important and beneficial bacteria of human gastrointestinal microbiota, can over-colonise the stomach of people with low stomach acid. Bifidobacteriaceae species, typically found in the oral cavity, readily colonise the low acid stomach[9] and become good bacteria but in the wrong place as a result of altered pH.

Proton pump inhibitors also promote progression of both alcoholic and non-alcoholic fatty liver disease in mice and contribute to the increasing incidence of chronic liver disease as a result of dysbiosis.[10] The list of side effects for PPIs is extensive, serious and even life-threatening and they are all mediated through the gut.

A growing number of studies are showing connections between autoimmune conditions linked with dysbiosis, including antibiotics and the use of protein pump inhibitors (PPIs) in controlling gastric reflux.[11] The use of PPIs can potentially create far greater problems in the long run.


[1] Krezalek et al., 2016; Mackenzie et al., 2017.

[2] Johansen et al., 2014.

[3] Reimer and Bytzer, 2009.

[4] O’May et al., 2005.

[5] Bajaj et al., 2014; Imhann et al., 2016; Jackson et al., 2016.

[6] Seto et al., 2014; Wallace et al., 2011.

[7] Choung et al., 2011.

[8] Lo and Chan, 2013; Janarthanan et al., 2012.

[9] Mattarelli, 2014.

[10] Llorente et al., 2017; Reveles et al., 2017.

[11] Andresson et al., 2016.

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Stomach acid

Stomach acid

Many people get confused about stomach acid and acidosis. These are two totally different things. In fact, the higher your stomach acid, the lower the acidosis or acid levels in the body. Let me explain. Your stomach and gastrointestinal tract form a beautiful, amazing tube that runs through your body, but not inside—they run through your body, not through your cells or in your blood. To get into the body, things have to pass over a barrier such as the gut wall, respiratory tract or skin. The stomach is meant to be acidic, very acidic so it can digest foods, particularly proteins, and destroy pathogens like deadly bacteria, viruses and parasites.

When the stomach is very acidic, in conjunction with digestive juices it breaks down proteins into amino acids. Some of these, like lysine and arginine, once absorbed into the body are alkalising. The high acidity level also allows for foods to be broken down, mostly the proteins, releasing the minerals which they are bound to and thereby allowing more ash minerals to be available for absorption through the gut wall and alkalising the blood. Because the foods are digested better, it also creates better conditions for the rest of digestion and the gut microbiota to function at optimal levels and increase digestion and absorption of even more minerals. Two totally different situations around the acid or pH levels but both influence each other.

Ironically, sufficient stomach acid is needed to absorb many of the same minerals and a lack of stomach acid inhibits the absorption of the B vitamins B6, B12 and folate. Lack of stomach acid also blocks the proper breakdown of proteins, since the protein digestive enzyme pepsin cannot work without sufficient stomach acid.
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