Low stomach acid. The diagnosis hardly anyone makes.
Why your heartburn may not be an excess of acid, why iron, B12 and magnesium stay chronically low, and why your stomach is the most important switch between nervous system, immune system and metabolism.
Imagine that someone has been suppressing the wrong thing for years, because no one asks what is actually burning.
Someone sits across from me, tired, without being able to explain it. An acid blocker has been running along for years, started once after a stressful phase. Iron and vitamin B12 stay in the lower range, although on paper nothing is missing. The belly bloats in the evening, sleep is fragmented, the mood heavy. The report says: all within normal limits. The feeling says something else. I ask how the eating happens and how the breathing goes with it. Fast, on the side, hardly any protein, always a large glass of water with it. I ask about sleep and get a laugh in return. Then I say that there is a hypothesis that appears nowhere in the file, one that could explain a lot coherently. It is called low stomach acid. This picture is a composite pattern from many conversations. It describes no particular person and no particular course.
This pattern keeps coming back to me. Iron deficiency that refuses to leave. Fatigue no one has an answer for. Bloating after every meal. Brittle nails, thin hair, poor sleep. Sudden food intolerances. Borderline bone density. A thyroid that does not run quite smoothly. And in the middle one symptom that everyone files in the same drawer: heartburn. Burning in the oesophagus usually leads to the same first hypothesis: too much acid. That is often correct, and the therapy then makes sense. What rarely has room in a short appointment is the second question.
But what if in some cases it is exactly the other way round? And what if the stomach is not just a digestive organ but a switchboard where your nervous system, immune system, metabolism and hormones meet? In functional medicine we look here first. Not out of fashion. Out of logic.
When the way always leads to a doctor first
Before you try anything from this text: there are signs where a prompt workup comes first. They include difficulty or pain on swallowing, unintended weight loss, repeated vomiting, a documented anaemia, and complaints that newly appear after the age of 45. These signs can point to something that needs an endoscopy and not a self-experiment.
Vomiting blood, vomit that looks like coffee grounds, or black, tarry stool are an emergency. Call the emergency number, in Germany 112, or go to the nearest emergency department. Please do not wait for a practice appointment in that situation.
And a stubborn iron deficiency always carries two questions, not one. First: is too little arriving? Second: is something being lost somewhere? Before we talk about the stomach, the second question belongs answered, meaning a possible bleeding source in the gastrointestinal tract including the colon, and in women the heaviness of menstrual bleeding. That is not a formality, that is the order that protects you.
Section 1Stomach acid is not a detail. It is the gateway to your whole system
Stomach acid sounds aggressive. In fact it is one of the most intelligent tools your body has. A healthy stomach produces a pH between 1 and 3. That is more acidic than pure lemon juice. This acid is not there to torment you. It has five jobs that almost every pill in the world forgets.
It breaks down protein. Acid activates pepsinogen into pepsin. Only through this step are proteins cut into smaller building blocks. Without it, every meal stays a lump that causes problems further down.
It converts minerals into a form you can absorb. Iron, zinc, magnesium, calcium and copper need acid to be released from their food matrix and brought into a chemical form your small intestine can pick up.
It activates the next stage of digestion. When acidic chyme flows into the duodenum, the low pH signals to S-cells in the intestinal wall: now. They release secretin. Secretin travels in the blood to the pancreas and says: send bicarbonate or the wall will burn. Bicarbonate neutralises the acid. At the same time fats and amino acids arrive in the duodenum. I-cells recognise this and release cholecystokinin. CCK tells the gallbladder to release bile and the pancreas to send digestive enzymes. Lipase for fats, trypsin and chymotrypsin for proteins, amylase for carbohydrates. Without the acidic threshold this whole cascade falters. You eat, but your digestive system below the stomach does not know that things are serious.
It sterilises. Stomach acid is the first line of your innate immune system. Whatever survives your acid has truly earned the right to travel further. Lower this threshold for the long term, and more live microbes come through, some of which do not belong there.
It is a sense organ for the nervous system. The vagus nerve and the enteric nervous system constantly measure the pH course. These signals steer gastric emptying, satiety, even mood. Your gut feeling here is not metaphor. It is neurophysiology.
Control runs along two major lines. Through the vagus nerve, which releases acetylcholine and prompts parietal cells to pump acid. And through the hormone gastrin, which comes from G-cells in the gastric outlet. Both respond sensitively to what you do before you eat, and to what is happening in your life.
Digestion begins in the head, not in the stomach
Before you chew the first bite, a phase begins that modern medicine has almost forgotten. It is called the cephalic phase. The sight, smell and thought of your food send signals through the vagus nerve to the gastric cells. A substantial share of your total acid response, often given in textbooks as roughly a third, can form in this preparatory phase, purely through perception and expectation. Anyone who eats standing up, at a screen, with their mind on the next email, largely shuts this phase off. The stomach only sees the food once it has arrived, and reacts late and weakly.
In polyvagal terms, digestion belongs to the ventral vagus, the social, calm part of your nervous system. In fight or flight your stomach works like a colleague no one briefed. This is one of the most important levers in functional medicine.
Stomach acid is not an enemy. It is the bouncer of your metabolism, the entrance where your body decides what gets in and what stays out.
Section 2When too little acid burns like too much
Here comes the part that makes most people listen up. Heartburn often does not arise because your acid is too strong. One essential mechanism can be that the muscle between stomach and oesophagus opens briefly when it should not. This muscle is called the lower oesophageal sphincter. It opens briefly and involuntarily. The research calls these episodes TLESRs, transient relaxations, and they are the main mechanical trigger of reflux.
What triggers these tiny openings? Above all one thing: gastric distension. The fuller and the longer the stomach stays loaded, the more often a reflex signals upwards that the muscle gives way for a moment. Anyone with too little acid digests protein significantly more slowly. The stomach empties with delay. The meal sits heavily in the upper abdomen for longer. The pressure upwards rises. The sphincter opens more often. And suddenly your oesophagus burns, even though the acid in your stomach is below average.
There is something else, which plays a central role in PNI thinking. Digestive stagnation invites fermentation. When carbohydrates sit too long in the upper abdomen they ferment. The resulting gases raise inner pressure. The pressure pushes upward. Burping becomes more frequent, sometimes with the typical sweet, slightly rancid taste that does not taste of acid but of yeast. The constant burping burdens many people more than the burning itself. Too little acid can sit behind it, rather than too much.
What happens then? You receive an acid blocker. The symptom goes away, because even a little acid hurts when it reaches the wrong place. Yet a weak digestion behind it tends to become quieter still under the medication. This is exactly what current research on autoimmune gastritis describes. People with nearly extinguished acid production are treated with acid blockers, although their stomach barely produces acid at all.
A Dutch research group studied in eight healthy volunteers how gastric distension triggers, via a reflex, the short involuntary openings of the lower oesophageal sphincter. These openings are regarded as the main mechanism for reflux. The study did not measure acid strength itself. In the experiment the episodes were dampened by a drug that blocks a particular receptor, not by a smaller meal. That relieving the stomach works in a similar way is therefore not proven, but mechanistically plausible.
Boeckxstaens GE et al., American Journal of Gastroenterology 1998. DOI
A narrative review from 2024, meaning an appraisal by its authors without systematic methodology, argues bluntly. In autoimmune gastritis acid production is irreversibly reduced, and yet many of these patients are still treated with acid blockers. The authors argue that it is worth rethinking the model and not suppressing acid further but supporting it.
Taylor L., Nutrients 2024. DOI
When is it really acid excess, and when is it not?
There are pictures in which too much acid really is at work. Fresh gastritis, acute ulcer, Zollinger-Ellison syndrome, a true hiatal hernia with reflux disease grade B or higher, eosinophilic oesophagitis. These diagnoses belong in gastroenterological hands, not in self-management. Acid blockers can be life-saving there, and nothing in this article speaks against using them where they are really needed.
The question is a different one. It is: does this diagnosis still fit me? Or have I been on a path for years that began correctly once and has been running on autopilot ever since?
Not every heartburn calls for less acid. Some stories begin with too little acid making the stomach speechless, and the body finds another way to tell you.
Section 3The quiet plundering of your metabolism
When acid in the stomach drops, the foundation of your nutrition tips. You can cook however cleanly, eat however much iron pan and leafy greens. Whatever is not broken down does not arrive. And whatever is not brought into the right chemical form is not absorbed. This is where a major part of your fatigue lives.
Iron from plant foods is mostly present as ferric iron, the three-valent form. For your small intestine to absorb it, it has to be converted to the two-valent form first. This conversion needs an acidic environment. If gastric pH rises, the iron can dissolve less well and therefore be absorbed less well. You eat it, but part of it may never arrive. Long-term vegetarians and vegans rely on this acid especially heavily, because the share of plant iron in their absorption is high. That can be part of why an iron deficiency persists despite tablets.
The same picture applies to vitamin B12. For B12 to be absorbed it needs a helper called intrinsic factor, produced by gastric cells. These cells sit right next to the acid-producing cells. Whoever produces little acid often produces too little intrinsic factor as well. Magnesium, zinc, calcium, folic acid and vitamin C react similarly. A 2017 review summarises this whole list for chronic atrophic autoimmune gastritis, meaning for a clearly defined condition. Whether the same pattern holds for every form of reduced acid production is not established by it. Physiologically it is plausible.
The review in the World Journal of Gastroenterology describes the typical deficiencies seen in chronic atrophic autoimmune gastritis: vitamin B12, iron, vitamin C, vitamin D, folic acid and calcium. The authors emphasise that these deficits can carry haematological, neurological and skeletal consequences far beyond the stomach itself. What was studied is therefore a defined condition, not every form of reduced acid production.
Cavalcoli F et al., World J Gastroenterol 2017. DOI
An uncontrolled case series from 2020 described 43 people with iron deficiency on long-term acid blocker therapy. 95 per cent of them responded once they received iron intravenously. Oral tablets had no effect in most of them. The author suspects the missing acid as the reason, but did not measure it. A case series without a control group cannot prove a cause, it can only lay a trail.
Boxer M., eJHaem 2020. DOI
From the stomach to the mitochondria
Your mitochondria are small power plants in almost every cell. To produce ATP, your life energy, they need iron for the cytochromes, B12 and B6 for the citric acid cycle, magnesium for every ATP step, coenzyme Q10 and carnitine, which is built from amino acids like lysine and methionine. All these building blocks pass through the stomach. If acid is missing there, the deficit shows up further down as missing amino acid, missing iron, missing methyl group.
Then there is the methylation cycle. Betaine, also called trimethylglycine, is one of your body's most important methyl donors. It comes from beetroot, spinach, whole grains. It is released in the stomach. It feeds the conversion of homocysteine back to methionine. People with low acid and poor protein breakdown often show elevated homocysteine. And elevated homocysteine is a quiet burden on vessels, brain chemistry and DNA repair.
So someone who has been tired for a long time, who has cold hands, no longer finds the spark for sport and does not regenerate, often does not have a surface lifestyle problem. They have a mitochondrial issue underneath, with a root that can sit in the stomach.
Quiet signals we collect in the clinic
- Fatigue that sleep does not really fix
- Restless legs and night-time calf cramps (iron, magnesium)
- Hair loss on the crown and brittle nails with longitudinal ridges
- A burning tongue or a smooth red tongue (classic B12 hint)
- Early satiety and fullness after small portions
- Burping that tastes like food, an hour after the meal
- Undigested food remnants in the stool
- Sudden new food intolerances
- Trouble concentrating, word-finding difficulties, depressive phases
- Tingling in hands and feet, cold extremities
- Bone pain, osteopenia, early dental decay
- Frequent infections and recurring need for antibiotics
- Iron, ferritin, B12 or holo-transcobalamin chronically in the lower normal range
One sentence on this that is not negotiable. An iron deficiency is not explained through the stomach before a bleeding source has been ruled out. That includes looking at stomach and bowel including the colon, and in women the heaviness of menstrual bleeding. Only after that is it worth asking whether absorption could be the problem.
Perhaps you do not have a primary iron deficiency. An acid deficiency is also possible, with the iron as the first visible trace.
Section 4The stomach as the bouncer of your immune system
Stomach acid does something probiotics alone cannot do. It sorts. It decides which bacteria from your meal arrive alive in the small intestine. When acid drops, microbes pass through that have no business being there. They settle, multiply, ferment carbohydrates, bloat the belly. This picture is often called SIBO, small intestinal bacterial overgrowth.
A very recent meta-analysis from 2025 pooled 29 studies. The direction is the same across many studies, even though the individual studies scatter widely. People on long-term acid blocker therapy show SIBO more often than controls in these data. And the longer the therapy, the higher the rate. Whether the acid blocker is the cause cannot be derived from this. People who receive one are on average sicker than the comparison groups. Beyond that, stomach acid does not only shape the microbes that arrive but also the broader gut microbiome. Studies suggest that helpful, anti-inflammatory species can decrease under acid blockers, while others increase.
A 2025 systematic meta-analysis pooled 29 studies with over 6500 individuals. Among acid blocker users, the SIBO rate was around 37 per cent, in control groups around 20 per cent. With each additional month of therapy, the rate rose further. The individual studies scattered widely, and the data are largely observational. A cause is therefore not proven.
Khurmatullina AR et al., Journal of Clinical Medicine 2025. DOI
A 2018 review summarises how acid blockers shift gut balance. Certain families like Streptococcaceae and Enterococcaceae increase, while a key anti-inflammatory species called Faecalibacterium becomes rarer. Such changes may carry further health consequences.
Naito Y et al., Digestion 2018. DOI
Histamine, mast cells and the leaky-gut stomach
Stomach acid is part of your innate defence. It keeps pathogens at bay, slows the growth of yeasts, regulates how many unfinished protein fragments even reach your small intestine. If large undigested protein pieces remain there, they meet a mucosa that is only one cell thick. PNI calls this the intestinal barrier. It is tightly woven with the gut's lymphatic tissue, the GALT.
If a protein fragment passes that barrier and enters the body, the immune system can build antibodies. Slowly and quietly, food sensitivities can arise that may show up as IgG or IgE reactions. This can appear as a sudden intolerance to nuts, eggs, wheat or soy, foods that used to be tolerated without trouble. It is not their body acting up. It is digestion that fell out of rhythm at the very beginning, at the gateway.
Then there are mast cells. They sit along the entire gastrointestinal mucosa and react to bacterial products, to stress, to histamine from food. With low acid, food histamine can rise because more bacteria survive and produce it. At the same time enzymatic histamine breakdown in the gut can fall. Symptoms like flushing, red cheeks, itching after meals, runny nose or migraine may be connected to this. In functional medicine we then speak of mast cell activation or MCAS. That is a working hypothesis, not an established causal chain.
Helicobacter pylori, the often overlooked player
Behind many stomach stories a bacterium can sit that a short appointment often does not look for. Helicobacter pylori settles in the stomach, can weaken the acid-producing cells over time and can favour both high and low acid phases. In a Zambian analysis of almost 600 people, Helicobacter was the strongest single factor for reduced stomach acid. That population is not comparable to ours, the prevalence there is very high. The pointer is still worth having, because Helicobacter can be underdiagnosed here too. Anyone with chronic heartburn, iron deficiency, fatigue or unclear abdominal symptoms can raise the topic. A stool antigen test or breath test is often enough as a first step.
If Helicobacter is found and treated, that happens with a combination of several antibiotics and an acid blocker over about two weeks. It is a medical decision with its own side effects and consequences for the microbiome, not a small thing on the side.
Many gut problems are at heart stomach questions. When the bouncer weakens, the club gets crowded, and eventually the immune system and the skin start complaining, because no one is asking at the front.
Section 5What happens behind the stomach when the pH at the front is missing
A point that rarely has room in a short appointment: the stomach is only the first stage of digestion. The second stage is the duodenum. There it is decided whether fats, carbohydrates and proteins really get broken down into their building blocks. This second stage is steered from the stomach, and the key is pH.
When acidic chyme enters the duodenum, the low pH alerts the S-cells in the intestinal wall: now. They release secretin. Secretin travels to the pancreas and says: send bicarbonate, or the wall will burn. Bicarbonate neutralises the acid. At the same time fats and amino acids reach the duodenum. I-cells recognise them and release cholecystokinin. CCK tells the gallbladder to release bile and the pancreas to deploy digestive enzymes. Lipase for fat. Trypsin and chymotrypsin for protein. Amylase for carbohydrates.
What happens if the stomach delivers no acidic signal? The whole cascade starts half-heartedly. Pancreatic enzymes stay below their potential. Bile stagnates. Fats are not emulsified. Fat-soluble vitamins A, D, E and K are absorbed less well. The gallbladder becomes sluggish. Some people develop gallbladder sludge or stones in the long run. Others mainly notice that they can no longer tolerate fatty food. Yet others have greasy, foul-smelling stool that does not flush well.
The migrating motor complex also hangs on this cascade. It is a wave that travels through the small intestine every 90 to 120 minutes between meals and cleans it. It is your gut's waste removal. It only works during digestive pauses and depends on the hormone motilin, which in turn is tied to the pH course. Anyone who snacks constantly, who never finishes a meal, who has low acid, switches this cleaning off. Another door for SIBO opens.
Gastrin, CCK, secretin and the thyroid
Stomach acid is embedded in a delicate dance of hormones. Gastrin stimulates acid release. Secretin and CCK carry the signal further downstream. Then there is an often-missed axis: the thyroid. Thyroid hormones regulate metabolic rate and gastric motility. Hypothyroidism, especially the common Hashimoto type, can come with delayed gastric emptying and reduced acid production. In Hashimoto this combination is found frequently. Food sits heavily, iron is low, B12 is low, mood dips. Thyroid, stomach and hormones hang in a loop here.
Oestrogen, progesterone and cortisol also join in. Menopause can shift acid production and mucosal quality. Chronic stress keeps the sympathetic nervous system on overdrive and can dampen both vagus and digestive hormones. Digestion is never only digestion. It is always also a hormonal answer to your life.
Your stomach is not a lone fighter. It is the conductor of an orchestra of bile, pancreas, hormones and microbiome. When it goes quiet, the whole ensemble falls out of time.
Section 6The trap called acid blocker
Acid blockers, in technical language proton pump inhibitors or PPI, are among the most prescribed medications in the Western world. For acute ulcers, severe reflux disease, protection under certain pain medications, they are valuable. Yet many people take them for years, some for decades, often without clear indication. Here it is worth asking critically whether the medication still fits.
The scientific literature of recent years lists a series of possible companion effects. These are not certainties. They are hints from observational studies and selected randomised trials. But the hints repeat themselves, and the responsible professional societies today recommend prescribing acid blockers with sense and measure, and reviewing them regularly.
A 2023 narrative review summarised the main findings on long-term safety of acid blockers. The authors list fractures, kidney disease, cardiovascular events, infections, micronutrient deficiencies, hypergastrinaemia, dementia and cancer as possible companion effects, while emphasising that many of these associations need further testing. The tone of the professional societies is: rational use, the lowest possible dose, the shortest possible duration.
Maideen NMP, Chonnam Medical Journal 2023. DOI
Then there is the most invisible trap of all. It is called rebound acid hypersecretion. Anyone on an acid blocker for a longer period responds with a rise in the hormone gastrin. Gastric cells expand under this stimulation. When the medication is then stopped, acid production can temporarily shoot above its baseline. A new heartburn can emerge that was not there before. Studies in healthy volunteers show that many experience this phenomenon, even though they never had a real acid problem.
A 2024 review summarised what is known about acid blocker discontinuation. After stopping the drug, some users develop reflux complaints even though the original diagnosis may not have been one. The effect comes from the hormonal adaptation in the stomach during therapy. Anyone who does not know this thinks: I really need the medication. Anyone who knows it can plan the withdrawal differently, supported by a doctor.
Namikawa K, Björnsson ES., International Journal of Molecular Sciences 2024. DOI
When an acid blocker has to stay
There are situations in which an acid blocker remains right for the long term and a withdrawal attempt can do harm. They include the state after a bleeding ulcer, a Barrett's oesophagus, severe erosive reflux oesophagitis, an eosinophilic oesophagitis that responds to the acid blocker, and any long-term therapy with painkillers of the ibuprofen type, with ASA or with a blood thinner. In these cases the acid blocker is not a symptom drug, it is protection. Please never stop it on your own there.
Beyond that: the decision to stop belongs to the doctor who prescribed the medication. Not to a text on the internet.
If you have been on an acid blocker for a long time, withdrawal belongs in wise medical hands. Not out of fear, but because your stomach needs time to find its rhythm again.
Section 7What quietly turns your stomach down
Stomach acid is not a constant. It hangs on your nervous system, on your rhythm, on what you ask of yourself. The major levers you already know. They are called stress, sleep, food, movement and a thoughtful relationship to stimulants. In PNI we do not treat them as nice add-on advice. We treat them as therapy.
Stress and the vagus
If you live in constant alarm, your parasympathetic system steps back. That is exactly the part of your nervous system the stomach needs to release acid. The research describes this as parasympathetic withdrawal under chronic stress. In animal studies, a substantial share of food-stimulated acid output runs through the vagus. So anyone who has been eating at a desk, scrolling and rushing for years may be slowing down not only their sense of life, but their digestion too. Breathing exercises before meals, long exhalations, humming, gargling, a few minutes of stillness with closed eyes. It sounds small. It is vagal work. And the vagus is one of the main wires to stomach acid.
Sleep
Lack of sleep can affect digestion directly. Even two nights with only four hours of sleep led to measurably more acid in the oesophagus in a small study of eleven healthy volunteers. A 2024 genetic analysis further suggests that insomnia could be causally involved in the development of reflux. The method allows inferences about cause and effect, but does not replace a clinical trial, and the effect found is small. Melatonin, which you build during sleep, is not only a sleep hormone. It is also discussed as mucosal protection, as an antioxidant and as a co-regulator of gastric motility. Sleep is not the bonus of your day. Sleep is the floor your stomach needs to even start working in the morning.
A small crossover study in eleven healthy volunteers and eleven reflux patients showed that even two nights with four hours of sleep can measurably increase oesophageal acid exposure. About half of the healthy participants then crossed into a pathological range, although they had not been there before. Eleven people per group is few, the result is a pointer, not an established magnitude.
Yamasaki T, Quan SF, Fass R, Neurogastroenterology & Motility 2019. DOI
Sugar, highly processed carbohydrates, alcohol, caffeine
Large amounts of sugar and heavily processed carbohydrates can feed microbes that do not let your stomach and gut rest. They can encourage low-grade inflammation, which in turn can irritate the mucosa. Alcohol can irritate the lining, and regular consumption can change acid production over time. Large amounts of caffeine can further relax the lower oesophageal sphincter and encourage reflux. This is not about never drinking coffee again. It is about recognising a pattern. A simple observation you can make yourself: if your belly feels calmer on the weekend without alcohol and with simple, slowly cooked food, that is a finding. Not a verdict.
Drinking with meals
A much-debated point in functional medicine. Larger amounts of fluid during meals can dilute gastric pH and mechanically impair protein digestion. Anyone with a weak stomach often benefits from small sips during meals and larger drinks outside meals. The study base is small, the clinical impression is often clear.
Movement and breathing patterns
Gentle, regular movement can improve vagal tone. Your nervous system learns to switch into digestive rest more quickly. A walk after a meal is old-fashioned, and old-fashioned here is a compliment. Strength training can support gastric motility indirectly via insulin and blood sugar regulation. Yoga, Qigong and slow breathing can address the ventral vagus and the diaphragm. The diaphragm, by the way, is a direct neighbour of the stomach, and a weak, shallow-breathing diaphragm can mechanically encourage reflux.
Pauses between meals
The migrating motor complex from section five needs digestive pauses to start its wave. Anyone who snacks constantly never grants their gut this cleaning. Three clear main meals with proper four to five hour pauses are often the first quiet lever in functional medicine. Not a dictate. An invitation to the inner waste removal to do its job.
Your vagus nerve is the conductor of your digestion. If he does not show up for rehearsal, the orchestra plays without a plan.
Section 8What you can observe and try yourself
You have read this far. You probably recognise yourself in several places. What now? In practice I approach this topic in two movements. First observation and gentle nudges. Then, when the picture becomes coherent, a carefully guided workup and, if needed, therapy. What I share here is not a prescription and does not replace medical advice. They are building blocks you can use to prepare the conversation with your doctor or with me.
Hints, not diagnosis
There is a simple home hint that can be useful. In the morning, on an empty stomach, drink a little baking soda in water. If your stomach burps quickly and strongly, this can suggest enough acid. If the burp stays away, it is a hint, not proof. This test is not diagnostically reliable. It does not replace a proper investigation. One more note: baking soda is sodium bicarbonate and delivers a noticeable amount of sodium. If you have high blood pressure, heart failure or kidney disease, please leave this experiment out or discuss it first. Reliable answers come from targeted blood tests like a Gastropanel, which measures pepsinogen I and II, gastrin and Helicobacter antibodies. A gastric pH measurement or a gastroscopy with biopsy are the gold standard. These steps belong in medical hands.
A red, smooth tongue surface or a burning sensation on the tongue can indicate vitamin B12 deficiency. That too is a hint, not a diagnosis, and belongs to be clarified by blood work.
Building blocks that may support the stomach, each with its own limits
In my practice I usually reach for several pillars once the diagnostic picture suggests low acid. They do not replace therapy, they can accompany or prepare it.
Bitter herbs before meals. Plants like gentian, wormwood, yarrow, dandelion or centaury can address the gastric cells via the sense of taste and via reflexes. They can activate the cephalic phase. The bitter chemistry of these plants is well characterised. Robust human studies on acid production are lacking. The traditional use is long and the mechanism is plausible, more cannot be said today.
Important alongside this: with an existing gastric or duodenal ulcer and in acute gastritis, bitter herbs are not suitable. For gentian and centaury the common monographs name this explicitly as a contraindication. Wormwood contains thujone and does not belong in pregnancy or breastfeeding, nor with people who have a seizure disorder. Please discuss this before you start. In the anthroposophic apothecary there are stomach tonics we can choose together, if nothing speaks against it.
Apple cider vinegar or lemon in water. A sour starter before a carbohydrate-rich meal is an old kitchen custom that small studies in few volunteers have examined. The results point in one direction, but they are neither large nor conclusive, and no health claim can be derived from them. Try it if it agrees with you. Two limits belong with it: acid attacks tooth enamel, so drink it diluted and through a straw, and rinse with water afterwards. And with an existing inflammation of the oesophagus or the stomach, please leave it out entirely.
Betaine hydrochloride. An acidic food supplement that can temporarily lower gastric pH. In Germany it is not an approved medicine and it replaces no therapy. The application is not suitable for everyone and belongs in a medical conversation. With active ulcers, certain inflammations or ongoing acid blocker therapy it is to be avoided. That is why no dosage at this point. Who it comes into question for at all is something we clarify in conversation.
Fermented foods. Sauerkraut, fermented vegetables, kefir, miso paste, a small portion at the start of a meal. Old folk wisdom that microbiome research is paying increasing attention to. The studies are young and small, more cannot be said today. With histamine issues, dose carefully. If you take an MAO inhibitor, please leave aged and fermented foods out entirely and discuss it with your doctor.
Bone broth and cooked vegetables. For a very sensitive stomach, a warm lightly salted broth is often easier to tolerate than a salad. It delivers minerals and protein building blocks like glycine and glutamine. Whether that helps the gastric mucosa regenerate is not established in humans. For many people a warm broth is simply easier to tolerate, and that is reason enough.
Stress and breathing work. Three deep breaths before every meal, five seconds in, seven seconds out. Sounds small. It can measurably shift your heart rate variability and with it address your vagus. Whether that carries through to stomach acid is not established in humans. The mechanism is plausible, and I will not say more than that.
Vitamin C, zinc and L-glutamine. In justified cases we discuss whether one of these substances could make sense. An established effect on the gastric mucosa cannot be derived from this. What fits you depends on the picture and belongs in a conversation, not in a list.
An open-label cross-over study in nine healthy volunteers examined whether betaine hydrochloride can lower meal-elevated gastric pH again. A high amount was needed for this, smaller amounts were not enough. With it the pH returned to baseline after about 17 minutes on average, without any supplement after about 50 minutes. The participants had normal acid production, they were not people with low acid and not people with reflux disease. The actual aim of the study was drug absorption. A transfer to the group this text is about is therefore not established.
Surofchy DD et al., Pharmaceutical Research 2019. DOI
Pregnancy, breastfeeding, children
This text addresses adults. Different rules apply to children and adolescents, where every stomach question belongs in paediatric hands.
In pregnancy and breastfeeding reflux is very common, and several of the building blocks named here are not indicated there. Wormwood does not belong in that time because of its thujone. Betaine hydrochloride and long gaps between meals are also nothing to try on your own initiative in pregnancy. Please discuss every change with your doctor first during that time.
Five things you can do starting tomorrow
None of these replaces a diagnosis. Together they can give you and me a much better starting point.
- Eat more slowly, chew thoroughly, sit when you eat. Three deep breaths before the first bite. That is physiology, not a nice tip. The vagus needs time for it.
- Try, for two or three days, to structure your meals into three clear main meals and no small snacks in between. You return the cleaning wave to your small intestine.
- Reduce fluid intake during meals to small sips. Drink larger amounts before or a good half hour after. Notice how burping and heaviness change.
- For one week, observe how you eat, sleep and breathe. Write down briefly when symptoms appear. You gather real data, not just impressions.
- Get ferritin, transferrin saturation, vitamin B12, holo-transcobalamin, methylmalonic acid, folic acid, magnesium, zinc, vitamin D and a Gastropanel including Helicobacter status. If thyroid issues are suspected add TSH, free T3, free T4 and antibodies. These values draw a picture a single routine blood test will not provide.
Section 9Differentiate, do not oversimplify
A good article must also say clearly where it stops. Not every heartburn is low acid. Not every reflux is a lifestyle question. There are pictures where a PPI is the right tool. Severe erosive reflux oesophagitis. A bleeding ulcer. A Helicobacter eradication. Certain pain medications that would otherwise destroy the mucosa. A hiatal hernia can fix reflux mechanically. Eosinophilic oesophagitis feels like reflux but is a different illness. Gastric paresis from diabetes or after surgery can look like low acid. Functional dyspepsia overlaps with everything.
That is exactly why this diagnosis is not a self-diagnosis. It is a conversation, a chain of findings, a hypothesis we test together. What I describe is a pattern that I meet in practice and that research is paying increasing attention to. How common it really is I cannot say from my own consulting room. It is not a healing promise. It is an invitation to look differently. When a medication has been running for many years and has never been questioned, this kind of looking is worth doing.
A diagnosis is not a label. It is a story that has to fit your body, not the other way around.
Section 10And now you know why
What such a path looks like depends entirely on the individual person. In principle we go in this order: first the workup, then the conversation about the medication together with the doctor who prescribed it, then step by step the foundations. I do not describe a concrete course here, because it would say nothing about yours. A single course is no guarantee for the next in any case. It would only be an invitation to look differently. I can give you that invitation without a story too.
You are not weak. You are not a hypochondriac. You are right with your feeling that something in the background is not adding up. Sometimes the key is not where the burning is. Sometimes it is where nothing burns, because there is not enough to burn. And it is worth asking that question, before the next prescription is written.
True freedom is not in calming a symptom. True freedom is in trusting your body again, that it knew what it was doing before someone interrupted it.
Sources
- Boeckxstaens GE et al. Involvement of cholecystokininA receptors in transient lower esophageal sphincter relaxations triggered by gastric distension. Am J Gastroenterol 1998. doi.org/10.1111/j.1572-0241.1998.00527.x
- Taylor L. Creating a Framework for Treating Autoimmune Gastritis. The Case for Replacing Lost Acid. Nutrients 2024. doi.org/10.3390/nu16050662
- Vavallo M et al. Autoimmune Gastritis and Hypochlorhydria. Known Concepts from a New Perspective. Int J Mol Sci 2024. doi.org/10.3390/ijms25136818
- Cavalcoli F et al. Micronutrient deficiencies in chronic atrophic autoimmune gastritis. A review. World J Gastroenterol 2017. doi.org/10.3748/wjg.v23.i4.563
- Boxer M. Iron deficiency anemia from iron malabsorption caused by proton pump inhibitors. eJHaem 2020. doi.org/10.1002/jha2.96
- Khurmatullina AR et al. The Duration of Proton Pump Inhibitor Therapy and the Risk of Small Intestinal Bacterial Overgrowth. J Clin Med 2025. doi.org/10.3390/jcm14134702
- Su T et al. Meta-analysis: proton pump inhibitors moderately increase the risk of small intestinal bacterial overgrowth. J Gastroenterol 2017. doi.org/10.1007/s00535-017-1371-9
- Naito Y et al. Intestinal Dysbiosis Secondary to Proton-Pump Inhibitor Use. Digestion 2018. doi.org/10.1159/000481813
- Maideen NMP. Adverse Effects Associated with Long-Term Use of Proton Pump Inhibitors. Chonnam Med J 2023. doi.org/10.4068/cmj.2023.59.2.115
- Namikawa K, Björnsson ES. Rebound Acid Hypersecretion after Withdrawal of Long-Term PPI Treatment. Int J Mol Sci 2024. doi.org/10.3390/ijms25105459
- Yamasaki T, Quan SF, Fass R. The effect of sleep deficiency on esophageal acid exposure of healthy controls and patients with GERD. Neurogastroenterol Motil 2019. doi.org/10.1111/nmo.13705
- Wang J et al. Genetic evidence for the causal impact of insomnia on gastrointestinal diseases. J Gastroenterol Hepatol 2024. doi.org/10.1111/jgh.16678
- Hodges P et al. Helicobacter pylori infection and hypochlorhydria in Zambian adults and children. PLoS One 2021. doi.org/10.1371/journal.pone.0256487
- Surofchy DD et al. Food, Acid Supplementation and Drug Absorption. A Randomized Controlled Trial. Pharm Res 2019. doi.org/10.1007/s11095-019-2693-5
- Johnston CS et al. Examination of the antiglycemic properties of vinegar in healthy adults. Ann Nutr Metab 2010. doi.org/10.1159/000272133
- Olennikov DN et al. Iridoids and Flavonoids of Four Siberian Gentians. Molecules 2015. doi.org/10.3390/molecules201019172
- Bonaz B, Sinniger V, Pellissier S. Vagal tone. Effects on sensitivity, motility and inflammation. Neurogastroenterol Motil 2016. doi.org/10.1111/nmo.12817
This article serves educational purposes and does not replace personal medical advice, diagnosis or therapy. Changes to medications or supplements should only be made in consultation with a physician. Written by Shukri Jarmoukli, ViveCura private practice, Berlin.