Stomach acid blocking drug packet

The Importance of Stomach Acid

The thought of stomach acid, for many, no doubt evokes memories of spicy meals or having eaten too much. Maybe the occasional episode of heart burn and for many the terms acid reflux and GERD (gastroesophageal reflux disease) will come to mind. Another word that tends to crop up time and time again is ‘excess’. It’s easy to see why.  Walk into any pharmacy or supermarket and you can easily find scores of over-the-counter medicines and remedies to help soothe away or block excess stomach acid. TV commercials promoting such products are rife, so it’s little wonder that the assumption that digestive issues are all to do with excess acid is a commonly held belief. But what about low stomach acid? Never heard of it? You’re not alone.  Surprisingly, low stomach acid (hypochlorhydria) is a common occurrence, much more common in fact than excess stomach acid. Indeed, it may be that the vast majority of people who believe they are suffering from ‘excess’ stomach acid are really actually suffering from the opposite. This, at first, might seem hard to swallow but let’s take a look at the evidence.

Excess stomach acid

First, let’s take a look at conditions related to excess stomach acid just to put things into perspective. Below is a table listing hypersecretory (excess stomach acid) conditions, taken from a 2009 paper (1) I then searched the internet looking for how common these conditions are.

Condition How common is it? Notes
Zollinger-Ellison syndrome  0.1-3 cases per million patients per year (2)
Antral G cell hyperplasia/hyperfunction  Listed as very rare (3)
Helicobacter Pylori infection  Extremely common  H.Pylori infection can just as easily cause a lack of acid, too
Gastric Outlet obstruction  Around 5% of people with peptic ulcer disease. 2000 operations in the US per year (4)
Short-bowel syndrome  Around 2 in every million have this condition (5)
Retained gastric antrum syndrome  Difficult to find numbers, stated as very rare (3)  Seems to be a rare condition following gastric surgery in the first half of the 20th century (6)
Chronic renal failure  ~350 per million (7)  Also known as end-stage renal disease
Cysteamine treatment in children with cystinosis  Extremely rare, 15 cases of cystinosis in the US per year  Genetic disorder
Systemic mastocytosis  Extremely rare (8)
Basophilic granulocytic leukemia  ~6000 cases in the US in 2014 (9)  Equated with chronic myeloid leukemia
Idiopathic hypersecretion  Seems to be a defunct term as our understanding has progressed
Associated with non-gastrin secreting tumor (non-ZES tumour)  Difficult to find accurate numbers for  Stomach cancers are quite common in certain populations though
Rebound hypersecretion  Common  Caused when acid blocking medication is stopped
Possible association with gastric hypersecretory states a. Hypertrophic, hypersecretory gastropathy b. Associated with stress c. Associated with head lesions d. Cystic fibrosis  a. related to H.Pylori d. from 1 in 377 to 1 in 90,000 depending on the population  b. It’s unclear what type of stress is meant though possible stress induced gastritis (10) c. Little data available

As you can see from the table most conditions related to excess stomach acid are, fortunately, rare and probably the last thing you would want to be doing if you were suffering from any of these conditions is self-medicating with acid blocking medication or antacids. So if excess stomach acid is indeed an uncommon thing, often caused by very unpleasant conditions, why does the idea of excess acid persist? Well, that is the subject of another post. For now, just make a note of H.Pylori and rebound hypersecretion in the above table and let’s have a look at stomach acid and what a lack of it can mean.

What does stomach acid do?

Stomach acid performs two important functions; the sterilisation of the stomach and anything that enters and the breaking down of foods and helping with absorption of nutrients. Both of these things are vital to our wellbeing and a reduction in stomach acid can and will severely compromise both. There are essentially four outcomes from having low stomach acid

  1. Reduced ability to absorb nutrients
  2. An increased chance of bacterial overgrowth
  3. A decreased resistance to infection brought about by the above two factors
  4. An increased risk of cancer and other diseases

I would hope you would agree that any one of these things are pretty serious conditions so let’s dig a little deeper.

Malabsorption of Nutrients

Stomach acid is essential for breaking down proteins and liberating  nutrients from food. Hydrochloric acid converts pepsinogen into pepsin; one of the enzymes responsible for the breakdown of protein into peptides and amino acids. Pepsin works best in a strongly acid environment. Gelatinase, an often overlooked enzyme, requires an acidic environment to break down collagen, too. With low levels of acid, or in cases with no stomach acid (achlorhydria), protein will not be digested as quickly or as properly as it should be. This can explain the ‘heavy’ feeling that some people have after eating meat. A lack of stomach acid will allow the meat to ‘sit’ in your stomach, and the stomach will take much longer to empty as a result. It’s worth noting at this point that though protein digestion begins in the stomach it’s actually completed in small intestine and I’ll take a closer look at that in the future.

Studies have shown that people with low or no stomach acid fail to absorb other nutrients properly, too. One study showed that both Helicobacter Pylori infection (which suppresses stomach acid) and acid suppression using the drug omeprazole reduced the bioavailability of vitamin C (11). Studies have also linked low stomach acid to the malabsorption of beta-carotene (a vitamin A precursor); (12), zinc (13), (14), (15), iron (16), vitamin B12, (17), (18), (19), folate (20), (21). Research also suggests that low stomach acid adversely affects the absorption of magnesium (22) and possibly calcium, though studies on calcium tend to be inconclusive with some stating a link and others claiming no link. Though, those claiming no link tend to be short term studies using acid blocking drugs.

Increased Chance of Enteric Infections

As one of the main functions of stomach acid is to destroy incoming pathogens it’s perhaps unsurprising that a loss or reduction of acid greatly increases the chance of enteric (intestinal) infections. In laboratory experiments it was demonstrated that the common pathogenic micro-organisms Escherichia coli (strains c690 and K-12), Helicobacter pylori, Klebsiella, Salmonella, Shigella flexneri, Proteus, Enterobacter, Enterococcus faecalis, Enterococcus faecium, Staphylococcus epidermidis, Staphylococcus aureus and Candida albicans, did not survive at pH 1.0 or 2.0 (a healthy human gastric pH), but at pH 4.0 -hypochlorhydria is defined as having a gastric pH between 4 and 7- all micro-organisms survived (23), however, this was in an in vitro acid only environment.

In a 2011 systematic review looking at the use of proton pump inhibitors (drugs used to block the production of acid) and increased susceptibility to enteric infections the report authors wrote

“The use of PPIs increases gastric pH, encourages growth of the gut microflora, increases bacterial translocation and alters various immunomodulatory and anti-inflammatory effects. Enteric pathogens show variable gastric acid pH susceptibility and acid tolerance levels. By multiple mechanisms, PPIs appear to increase susceptibility to the following bacterial enteropathogens: Salmonella, Campylobacter jejuni, invasive strains of Escherichia coli, vegetative cells of Clostridium difficile, Vibrio cholerae and Listeria. We describe the available evidence for enhanced susceptibility to enteric infection caused by Salmonella, Campylobacter and C. difficile by PPI use, with adjusted relative risk ranges of 4.2–8.3 (two studies); 3.5–11.7 (four studies); and 1.2–5.0 (17 of 27 studies) for the three respective organisms.” (24)

What this means is that medications that blocked stomach acid production made it easier for pathogenic bacteria to gain a foothold in the stomach as there wasn’t enough acid to effectively kill them.

There are also studies that show that suppression of acid can lead to not just gastroenteritis but also pneumonia (25), (26)

Small Intestine Bacterial Overgrowth

Small intestine bacterial overgrowth, usually shortened to SIBO, is a complex disorder that can arise from many different conditions (27). As the name suggests it results from having too many bacteria in the small intestine. Low stomach acid (pH above 4) allows bacteria to pass through the stomach and into the small intestine.

Acid also plays another very important role when it comes to the small intestine. When chyme enters the small intestine from the stomach it should be highly acidic. This acidity is required to turn the prohormone prosecretin into its active form secretin.

Secretin performs a number of important functions which include increasing the pH of the small intestine and increasing the potency of cholecystokinin, a hormone which amongst other things stimulates the release of digestive enzymes in the small intestine. If the chyme isn’t sufficiently acidic then the secretin/cholecystokinin response will be diminished.


Atrophic gastritis is a condition in which the stomach loses the parietal cells; the cells that it needs to produce acid. There are two primary types of atrophic gastritis; H.Pylori infection and autoimmune gastritis (though H.Pylori has also been suggested as a cause of this variant, too (28).) Loss of the ability to secrete acid leads to a condition known as hypergastrinemia which can, over time, lead to cancer. Note: hypergastrinemia can also be caused by PPI use (29) and certain types of cancer, too.

Low stomach acid can also spell problems for vitamin C, which is actively released into the stomach. Vitamin C, otherwise known as ascorbic acid, prefers an acidic environment. Above a pH of 4 it can undergo an irreversible reaction to form 2,3-diketogulonic acid, which can’t be used by the body and so is excreted (30). Why is this important? Vitamin C inhibits the formation of carcinogenic N-nitroso compounds within gastric juice.

Another study found that acid suppressing medication which led to microbial overgrowth in turn led to alcohol being converted to the carcinogen acetaldehyde within the gut (microbial overgrowth can also produce ethanol in the gut through fermentation.) (31)


As mentioned above, teasing out the evidence of whether low stomach acid leads to poor calcium absorption and in turn diseases like osteoporosis is difficult. In an comprehensive review entitled
Gastric Acid, Calcium Absorption, and Their Impact on Bone Health the authors write

“…it is experimentally difficult to unmask the potential correlation between a reduction in gastric acidity and calcium absorption, given our body’s high capacity for compensation. In addition, slight alterations in mineral homeostasis may take years to manifest themselves clinically, for example, in osteopenia or fractures. Without following up on test subjects on a long-term basis, snapshot measurements which may still lie within clinically normal range can be misleading.”

They go on to conclude

“In summary, it should be noted that the stomach secretes not only acid, but also hormones that have been shown to directly alter calcium and/or bone homeostasis. The secretion of these hormones depends on the neuroendocrine machinery that also regulates acid secretion. It is therefore plausible that the correlation between states of impaired acid secretion and impaired bone mineralization is multifactorial by depending on intragastric pH and serum levels of gastric hormones.”


A 2010 review paper looking at antacid medications and their role in food allergies concluded that in addition to current warnings about antacid medications

“….to this list, we suggest that ‘Increased risk for sensitization against dietary proteins’ and ‘Lowering the food allergens levels needed to elicit hypersensitivity reactions in food-allergic patients’ should be added. Therefore, we question over-the-counter sale of anti-ulcer drugs and suggest prescribing them according to strict indications during a therapeutically useful period of time, especially during pregnancy.” (32)

They found that proteins that were incompletely digested due to lack of acid and lack of stimulation of secretin (see above) provoked an immune response which led to allergy. The use of aluminium compounds in some medications also appeared to act as an immunostimulant.

Perhaps most shocking of all they found evidence that pregnant mothers who take acid blocking medication developed allergic responses that were passed on to the unborn baby! The cited study also appeared to show a link between in utero exposure to antacid medication and the development of childhood asthma (33).

Gastroesophageal Reflux Disorder

Gastroesophageal reflux disorder or GERD for short is so often attributed to excess acid, and whilst it may certainly be present in such cases the vast majority of cases are caused by a lack of stomach acid not an excess. At a later date I will take a closer look at GERD and low stomach acid.

Helicobacter Pylori and PPIs

Time and time again these two keep popping as key factors in low stomach acid, one by design and one via evolution. With PPI’s the very notion that eliminating stomach acid- an integral part of our biology for hundreds of millions of years (that is, a mechanism from our earliest forms)- almost completely and for years on end seems like utter lunacy. Many of the studies referenced in this article directly involve the use of PPIs either as an experimental tool or causative agent in disorders and illnesses. There may be a few cases in which it is a good idea to take these substances but the evidences suggests that they are over prescribed by doctors or misused as an over the counter medicine. In future posts I’ll be looking at this truly bizarre practice and what the alternatives are.

For H.Pylori, the issue is perhaps more complicated, even now as study after study implicates this bacteria in disease states there seems to be much we still don’t know, though I’ll be taking a look at this in future posts, specifically how and why it alters stomach acid production and what to do about it.

All in all we may need to rethink the idea of excess stomach acid and come to a better understanding of just what goes on in the stomach and how essential stomach acid is. You might want to think twice before you reach for those stomach acid medications.

7 thoughts on “The Importance of Stomach Acid”

    1. Change your diet. Eliminate coffee alcohol, tomato based sauces, vinegar, chocolate, mint and any carbonated beverages. Stop eating at least 2 hours before bed. Sleep with your head elevated. Take HCL supplements with meat meals because if you’ve been on PPIs you most likely have low stomach acid.

      1. One cup of coffee per day, easy on the sauce, a little vinegar is very good for you and so is a little chocolate. No soda pop is good for you. It is only good for cleaning drains and battery terminals. Moderation is the best solution. People need far less food than is consumed by the average American.

    2. Hi Orit,

      Sorry for my very late reply. Gastroesophageal reflux is a complex issue with many contributing factors. I really hope to have a look at this in more detail in the future and I have a pile of studies waiting to be read. One interesting aspect I came across though was that it appears that the vast majority of people have some form of hiatal hernia For now, bearing in mind that I’m not a doctor nor in any position to give medical advice, I found that my own GERD completely resolved itself when I switched to a more paleo like diet, minimising grains, and introducing more organ meats and fermented foods whilst cutting right back on sugary things.

  1. My son took prescription drugs for acid reflux for 14 years. He is only 27 now. We eat paleo and have for a long time. His acid reflux started when he was away from home for an extended time. He never felt that he could give up the meds. He would try and the pain was excruciating. A few weeks ago he was studying about the work of stomach acid and decided that he needed a healthy gut. So he stopped the meds, Already no refined sugar in his diet. He did suffer for a while but nothing that he could not bear. I kept on sharing Dr. Wahl’s articles to encourage and educate him. He changed up his diet cutting out foods that could cause trouble. The last thing to go was tomatoes. Tomatoes are not his friend. He is careful not to ever eat as that causes trouble. He gut has healed nicely. Daily he drinks Ginger tea with cammomile added.
    He feels great! Very thankful!!

    1. Raw goat milk may help restore the good bacteria in his gut. I used it for two of my children and their stomach health improved quite nicely.

Got a question or maybe something to add? Leave a comment and let me know!