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Why Your Symptoms may be caused by Low Stomach Acid (not High)

Low stomach acid (or low hydrochloric acid) is a very under-rated problem.

When people are faced with symptoms, they usually think they have too much stomach acid and in fact, GPs would usually prescribe antacids or PPIs in these cases.

However, the symptoms for low and high stomach acid are very similar, so it is hard to know which one is present. Finding out is key to effective treatment – taking antacids or PPIs in the case of low acid could make matters a lot worse.

Why do we even need stomach acid?

Stomach acid, or hydrochloric acid (HCl) is one of the most vital secretions to help us digest and absorb food and also to help protect our bodies from disease.

HCl is one of the key components for efficient digestion and the body’s first line of defense against pathogenic viruses, bacteria and yeasts.

Low levels of HCl can cause an array of problems and symptoms and may be the root cause of various seemingly unrelated disorders.

One of the key functions of HCl is to acidify the environment in the stomach. This sterilizes the food, which is important to prevent the food from putrefying and thus becoming a source of toxicity for the body.

Furthermore, HCl can kill off any pathogenic bacteria, viruses or yeasts that might be entering the body through food.

Pathogenic microbes generally prefer a more alkaline environment and as such have a hard time surviving in the acidity of the stomach.

Therefore, sufficient stomach acid may prevent viruses from causing food poisoning or other microbes from taking hold in the stomach and interfering with normal digestion.

The next key function of HCl is to ‘unravel’ the chains of amino acids present in proteins in order to prepare them for digestion. Moreover, it activates the protein-digesting enzyme pepsin.

This starts the digestion of proteins that we need as building blocks to keep our bodies healthy and to produce enzymes and hormones.

We also need HCl to absorb vitamin B12, which is important for producing new blood cells and therefore preventing anemia. Moreover,

HCl helps to ionize certain minerals like calcium, which is important for mineral absorption.

What happens if we don’t have enough stomach acid?

Because HCl has so many important functions, low levels (hydrochloridia) may therefore lead to unwanted symptoms.

First of all, proteins are hard to break down without sufficient HCl and can start to rot and putrefy in the stomach. This can produce a lot of gas, potentially leading to bloating, indigestion and belching.

Protein could also sit undigested in the stomach, causing a feeling of fullness and sometimes nausea. Without adequate digestion there may also be a malabsorption of proteins, minerals and vitamins potentially leading to symptoms of deficiencies.

Mineral absorption can be inhibited if HCl levels are compromised, even if minerals are supplemented.

If calcium, for example, is not ionized by HCl it may deposit in the wrong places, like arteries, and cause problems. The vitamins B12, B6 and folate all need HCl for absorption and are potentially deficient in people suffering from low HCl (1).

Chronic nutrient deficiencies in turn may have a negative impact on all aspects of health, leading to, for example: imbalance of hormones, immune deficiencies, weak muscles and bones and difficulties with stress. A deficiency of Vitamin B12 can also lead to anemia.

Without enough HCl, the contents of the stomach may not have their optimal pH so when they enter the duodenum in the small intestine, it may try to reject the food and force it back up into the oesophagus. Here, it is too acidic and may cause painful heartburn and reflux.

With age, the production of HCl can drop and at the same time the prevalence of gastric atrophy can rise.

This may be due to an infection by the H. pylori bacterium, which can take hold in the stomach when acid levels are low and then survive HCl even if it levels are raised subsequently (1, 2).

Other bacteria may also overgrow in the stomach, potentially fermenting undigested food particles and producing excess gas.

Pressure from gas could cause the lower oesophageal sphincter to malfunction leading to acid reflux (3).

Bacterial overgrowth may also lead to malabsorption of nutrients, has the potential to raise inflammation and the risk of cancer (3) and can lead to poor immune status when the lymphatic system becomes overworked.

Studies have shown that the use of PPIs to suppress HCl production raises the risk of catching the antibiotic resistant C. Difficile bug, which can lead to severe diarrhea that can be fatal (4).

Moreover, some studies suggest that 50% of people using PPIs develop SIBO (small intestinal bacterial overgrowth) (3). Changes of pH in the stomach due to low levels of HCl can also change the pH in the remainder of the digestive tract which can allow bacteria to live in places they would not normally be present.

So we can see that low levels of stomach acid has the potential of creating an array of problems and symptoms.

How to know if you have low stomach acid?

The most obvious symptoms can include:

  • digestive discomfort shortly after eating a meal
  • bloating
  • wind
  • burping
  • burning
  • inability to eat large portions
  • acid reflux
  • feeling of fullness
  • nausea
  • diarrhea
  • constipation
  • GERD or GORD

Many other chronic ailments may also be indirectly linked to low levels of stomach acid. These can include (but are not limited to):

  • Anemia
  • Hair loss
  • Brittle nails
  • Acne
  • Nutrient deficiencies
  • Calcium deposits
  • SIBO
  • C. Diff
  • Dysbiosis
  • H. Pylori
  • Hormonal imbalances
  • Neurotransmitter imbalances


How to test for stomach acid levels?

The gold-standard functional test for HCl levels is the Heidelberg Capsule Test. A small radio transmitter capsule is swallowed and measures resting HCl levels, alternating with an alkaline bicarbonate challenge. The physician then checks how well the stomach returns to an acid condition, which determines whether or not adequate levels of HCl are produced. As far as I know there is no private lab in the UK offering this test and I don’t know if it is available in NHS hospitals.

The VEGF Test is a lab test that measures ‘vascular endothelial growth factor’ (VEGF) in the saliva, which is proportionate to the amount of HCl produced in the stomach. This non-invasive test is available privately in the UK and costs around £80.

The Bicarbonate Challenge Test is an easy and cheap test that can be done at home. It is based on the idea that an alkaline bicarbonate solution would react with the acidic HCl in the stomach, causing burping. As all DIY tests, it is probably not 100% accurate. In the morning a solution of ¼ tsp bicarbonate plus 250 ml of water is consumed on an empty stomach. Belching should occur if HCl is present. The time it takes until belching occurs is then measured:

  • 1-2 minutes: normal HCL
  • 2-3 minutes: normal to slightly low HCl
  • 3-5 minutes: low HCl
  • 5+ minutes: potentially no HCl

How to treat low stomach acid?

Eat enough protein: Without sufficient protein in the diet the production of HCl and pepsin would be very low. Long-term vegetarians and vegans (including me) often develop low levels as production of HCl diminishes with the lack of protein in the diet.

Chew well: The first stage of digestion is chewing. Chewing and tasting food triggers HCl to be produced in the stomach.

Don’t eat when stressed: When the body is stressed, the sympathetic side of the nervous system favors the functioning of vital organs that would be needed in a ‘fight or flight’ situation and lowers function of the digestive system, including HCl secretion.

Don’t drink with your meals: Consuming too many liquids with food can dilute stomach acid. Leave at least 30 mins on either side.

Apple cider vinegar: A tsp of ACV mixed into an equal amount of water taken right before a meal can help to acidify stomach contents (it does not stimulate HCl production however)

Betaine HCL: Talk to your doctor/therapist about taking betaine HCL supplements

Bitters: Herbal bitters have long been used to stimulate digestive secretions

Eat real food: Eating a balanced, real food diet will help the body to optimize its functions. Depending on your issues, consider a healing diet. Eventually the stomach should return to producing adequate HCl levels


Do you have problems with low stomach acid? How have you been able to overcome them?

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Why your symptoms may be caused by low stomach acid, not high | Real Food Real Health UK


Disclaimer: I am not a licensed healthcare practitioner and as such do not seek to diagnose or treat any medical condition. When in doubt always consult with your doctor



  1. Lovat, L. B. Age related changes in gut physiology and nutritional status. Gut 1998 [cited 38: 306-309] Available from:
  2. Marshal BJ et al. Pyloric Campylobacter infection and gastroduodenal disease Med J Aust. 1985 Apr 15;142(8):439-44.,f1000m,isrctn
  3. How your antacid drug is making you sick (Part A), Chris Kresser;
  4. People taking stomach acid drugs more likely to catch diarrhea bug, What Doctors Don’t Tell You;

Photo credit: “Human Experience” via photopin (license)

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