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Why Stomach Acid Matters

The primary job of hydrochloric acid (HCl) is to begin the process of digesting protein in the stomach. If this isn’t done appropriately, poorly digested food arrives in the small intestine, which can trigger the immune system to react to something it doesn’t recognize. This can lead to food sensitivities and eventually, leaky gut.

Not only that, but HCl as part of the chyme dumped from the stomach into the small intestine serves as a trigger for peristalsis, the smooth muscle contractions in the intestines that move our food on down the digestive tract. Because of this, bowel motility is linked to adequate levels of HCl. Slower peristalsis can mean constipation. But on the flip side, one of the hormones that triggers HCl release is gastrin, which stimulates gut motility. If there isn’t enough HCl released, gastrin increases to try compensate, which can mean diarrhea, too.

Due to its low pH, HCl also helps to kill any potential offending organisms, protecting us from food-borne illnesses. Lack of it renders us more susceptible. By the same token, HCl together with bile help to prevent SIBO. While gallbladder dysfunction can set us up for SIBO, so can low stomach acid. (And then we have two potential causes for reflux: the stomach acid is too basic to trigger the esophageal sphincter to close, and the SIBO ferments our food, creating gas. The pressure from the gas then forces the esophageal sphincter open.)

Additionally, HCl is also necessary for adequate absorption of iron, B12, folate, ascorbic acid (Vitamin C), beta carotene (a precursor for Vitamin A), calcium, magnesium, and zinc. Since the first two are critical for energy, this is another reason why low HCl can lead to fatigue.

What’s Required for Stomach Acid Production

Like any biochemical process, there’s a chain of events involved in production of stomach acid, kind of like a Rube Goldberg machine. If inadequate HCl production occurs, the problem could be anywhere along the chain of events.

Overall Metabolism

Low thyroid function means low metabolism, and that means slow digestive functioning. This most commonly means constipation, but low stomach acid can be a part of that.

While I don’t subscribe to the Blood Type Diet for the most part, it is certainly well documented that people who are blood type A tend to produce less HCl as a general rule, too.

Blocks in Stomach Production

Gastritis, or inflammation of the stomach lining, means that the tissue won’t be able to do its job. There are a number of possible causes of gastritis, both acute and chronic.

Pernicious anemia is an autoimmune condition in which the body specifically attacks the parietal cells, which secrete both HCl and Intrinsic Factor (necessary for absorption of B12). Those with pernicious anemia will therefore have low stomach acid as well as low B12.

Histamine and Methylation

Histamine triggers release of stomach acid by binding to histamine receptors in the parietal cells of the stomach lining—so even if the stomach lining is fine, low histamine levels can lead to low stomach acid. This may be due to a deficiency in the amino acid histidine, the precursor for histamine. (Histidine is found in protein, such as meat, fish, poultry, soy, dairy, eggs, nuts, and seeds).

Another possible cause of low histamine levels may be overmethylation, which can be genetic, or due to taking excessive amounts of methyl donors as supplements. This is because methylation is one of the main pathways for histamine elimination.

Common over-the-counter H2 blockers such as Zantac/ranitidine, Pepcid/famotidine, Tagamet/cimetidine, etc work at this level as well.

Acetylcholine and Gastrin

The parietal cells in the stomach that produce HCl receive three signals to do so: histamine, the hormone gastrin and the neurotransmitter acetylcholine.

Gastrin is a peptide hormone, requiring adequate amino acid building blocks from protein.

Acetylcholine is made from the nutrient choline, found in milk, eggs, liver, and peanuts. Since liver isn’t a common part of the Western diet, and the other three are common allergens, it’s possible that deficiency could result.

Biochemical Precursors and Cofactors

Once the parietal cells receive the signal to produce HCl, the biochemical reaction requires salt, water, and carbon dioxide, which will proceed to produce HCl in multiple separate steps.

This means there must be adequate levels of salt as a chloride source (which may be one reason why hyponatremia, or low salt, can manifest with slight anorexia, as in adequate HCl production may result from hyponatremia). Many people avoid salt out of concern for its blood pressure effects; this could be one of many unintended consequences of this practice.

There must also be enough CO2, as well—the body’s primary vasodilator. Acidity in the extracellular space is often correlated with low CO2 levels.

Cofactors for HCl production (vitamins and minerals required for the enzymes that make it go) include iodine, zinc, and Vitamin B1, or thiamine. Deficiencies in any of these can result in inadequate HCl production. Thiamine can be found in brown rice, soy, beef, sunflower seeds, whole grains; iodine in seaweeds, iodized salt, fish, and seafood primarily; zinc in oysters, turkey (dark meat), mustard greens, pumpkin seeds, soy beans, tuna, ginger root, peas, cashews, sunflower seeds, pecans, tahini, crab, peanuts, red meat, beans, whole grains, and dairy.

This is also the level at which Proton Pump Inhibitors (PPIs) work, and of course they’ll block HCl production.

Roadblocks Downstream

Even if all of this goes according to plan, the presence of H pylori might produce an enzyme called urease. Urease counteracts stomach acid and damages the stomach lining. (H pylori isn’t always a problem, though; in some people, it’s normal flora.)

Natural Stomach Acid Stimulation

One way to compensate for inadequate HCl is either with the supplement betaine-HCl, or with Apple Cider Vinegar with meals, as it’s about the same pH as the stomach acid, and will have a similar effect.

But an old time approach is a combination of digestive herbs known as Swedish bitters. These appear to work essentially by increasing blood flow to the gut, which triggers increased release of all digestive juices, including HCl. They also stimulate taste receptors (even if you take them in capsule form!), and in so doing, help to boost appetite.

The Upshot

Low stomach acid can occur anywhere along the line. If there isn’t an obvious cause, though, Swedish bitters are a good approach to try to stimulate the body to make adequate acid.