The Normal B12 That Wasn't | The Angry Gut, Chapter 6

Atrophic gastritis · B12 absorption

Atrophic Gastritis: When Your Stomach Stops Absorbing B12

In atrophic gastritis the stomach lining loses its parietal cells, the only source of intrinsic factor, the protein that escorts vitamin B12 into the body. With fewer of those cells, B12 travels through without getting in, and a normal blood B12 does not clear the stomach.

A stomach lining can lose the cells that capture vitamin B12 long before any blood count changes. Here is what that means for your numbers, and which measurements can see the damage.

Atrophic gastritis is a thinned, worn-down stomach lining, and it may be present in up to 15% of American adults. Most of them never hear the words, because the condition rarely starts with stomach pain. It shows up years later and far from the stomach: numb feet, a slipping memory, an iron level nobody could explain. The video The Normal B12 That Wasn’t, from The Angry Gut by Dr. Gurpreet Singh Padda, MD, MBA, MHP, and Ami Michelle Grimes, follows one man through four lost years. The lens here is measurement: what a failing lining does to your lab results, what a routine visit checks, and what it leaves unmeasured.

What atrophic gastritis takes away

The gut is the first brain. It decides what enters the body, and the brain in the skull, the second brain, lives on whatever it lets through. Vitamin B12 has the most demanding entry process of any nutrient. Acid pries it loose from food. A protein called intrinsic factor, made only by the parietal cells of the stomach lining, escorts it down the small bowel to a receptor at the far end. In a failing lining those parietal cells are being lost. Fewer cells means less escort, and the vitamin travels through without getting in.

Two biological forces do most of the damage. One is infection: people carrying H. pylori develop new atrophy at 5.0 times the rate of people who are not infected. The other is autoimmunity, the immune system attacking the parietal cells directly. The infection is receding worldwide; the autoimmune form is not. A third force is economic. We subsidize the calories that feed type 2 diabetes and reflux, then treat both with long-term drugs that also pull B12 down, so the lining and the prescriptions push in the same direction. The background of low-grade metabolic inflammation, metaflammation, is the terrain that stomach lives in.

Why a normal B12 does not clear your stomach

The measurement gap fits in one sentence: nobody measures absorption anymore. The Schilling test once did, and nothing has replaced it. What is left is a blood level, which answers a smaller question. The man in the video had a B12 of 348, was told it was fine, and had almost no parietal cells left. Why a lone serum B12 misleads, and how a functional marker fills the hole, is covered in the methylmalonic acid test explained. For the stomach the lesson is different. Even a correctly low B12 is a late signal. By the time the vitamin runs short, the lining has usually been failing for a long while.

What are the early signs of atrophic gastritis?

A failing lining rarely runs short of one thing. Iron tends to go first. When atrophy sits in the acid-making body of the stomach, iron deficiency appears in as many as half of patients, often well before B12 falls, because iron stores drain faster. An old low ferritin that was written off years ago can be the first footprint.

Symptoms are a weak guide. Pooled across many studies, these stomach changes were not statistically more common in people with complaints than in people without them, so waiting for heartburn means waiting too long. The better clues are the company the disease keeps. Autoimmune thyroid disease is found in 36% to 44% of people with autoimmune gastritis, and type 1 diabetes carries roughly three to five times the general population’s risk.

The textbook picture of who gets it is also off. In a Miami biopsy series drawn heavily from Hispanic patients, autoimmune gastritis was found in 4.6%, compared with 1.1% in a Baltimore series of mostly White patients. Being younger, male, Hispanic or Black does not take it off the table.

Which blood tests point to atrophic gastritis?

Two antibodies look for the autoimmune attack, and each one fails in its own direction. Anti-intrinsic factor antibody was 100% specific in one assay comparison but caught only 38% of cases, and it tends to turn positive late. Anti-parietal cell antibody catches more but proves less, and it grows less reliable from age 50 on. Ordered together, the pair reached a sensitivity of 90% and a specificity of 95.7%. If only one was drawn and it was negative, the question is still open.

Two more traps are worth knowing about. Pepsinogen testing, used to estimate atrophy in some countries, is not available for routine clinical use in the United States. And gastrin, another marker used to locate atrophy, is pushed up three to five times by acid-blocking drugs, so it can end up reporting on the pill rather than the stomach. Planning around that is your physician’s call; do not stop a medication on your own.

No blood test is the last word. The lining itself is examined by a gastroenterologist with a scope and biopsies, a different test done elsewhere. In one recent study, only 9% of people diagnosed with pernicious anemia were offered a gastroscopy at the time of diagnosis.

What Measura shows in the same person

Measura [Cardiometabolic and Autonomic Health Analysis] does not scope stomachs and does not diagnose gastritis. It measures what a starved nerve and a strained metabolism leave behind, which is exactly the part a stomach workup never looks at. Results go to your physician, who reads them against the rest of your chart.

Small nerves. Sudomotor testing looks at sweat-gland function in the small nerve fibers of the hands and feet, the fibers that often complain first as burning or numbness.
Balance. Vestibular and balance testing puts a number on unsteadiness, which matters once numb feet start changing how someone walks.
Memory. A cognitive assessment sets a baseline, so a later change is measured instead of guessed.
Metabolism. Laboratory panels map the insulin resistance and inflammation that so often put metformin and an acid blocker in the medicine cabinet to begin with.

Together those numbers answer what the stomach tests cannot: how much the shortfall has already cost the nerves and the brain, and whether that picture improves once the cause is dealt with.

What to ask at your next visit

For years I told patients that stomach acid simply fades as we get older. The measurements say I was wrong. Most older stomachs still make acid, and the ones that stop are usually diseased, not merely old. That correction changes the question to bring. Not whether you are just aging, but whether your stomach lining still works.

Has anyone drawn a methylmalonic acid or holotranscobalamin, or only a total B12?
Was my iron ever low, even years ago?
Were both stomach antibodies checked, or only one?
Do I have thyroid autoimmunity or type 1 diabetes that raises the odds?
How long have I taken metformin or an acid blocker?
Has the stomach lining itself ever been examined?

If the person losing ground is an aging parent, B12 deficiency in older adults covers the family side. Every study behind these numbers sits in the companion deep dive for The Angry Gut. Physicians weighing the screening side can read the clinical version for practices.

Frequently asked questions

What does atrophic gastritis mean on a biopsy report?

It means the glands of the stomach lining have thinned and some have been lost, usually from long-term H. pylori infection or an autoimmune attack. Those glands include the cells that make acid and intrinsic factor, so B12 and iron absorption can suffer. It is a precancerous condition, but progression to stomach cancer is uncommon, about 0.1% to 0.3% per year. Read what a test result can and cannot tell you.

Can atrophic gastritis cause numbness in the feet?

It can, by an indirect route. When the lining stops making enough intrinsic factor, B12 stops getting in, and the long nerves of the legs are among the tissues that suffer over years. Numbness and burning have many other causes, diabetes among them, so the pattern needs a physician’s workup rather than a guess. See what numbness, burning and tingling can mean.

Are B12 shots better than pills if my stomach is damaged?

It depends on the cause, and the choice belongs to your physician. About 1% of an oral dose crosses the gut wall without any intrinsic factor, which is why very high-dose tablets can work for some people. British guidance still advises lifelong injections when autoimmune gastritis is the cause. Bring these questions worth asking your doctor.

Can Measura test for atrophic gastritis?

No. It is confirmed by a gastroenterologist with a scope and biopsies, which is a different test done elsewhere. Measura measures what a long shortfall may already be doing downstream: small-fiber nerve function, balance, cognition and the metabolic picture. Those results go to your physician to sit beside the stomach workup. Learn what Measura actually measures.

Does taking an acid blocker for years affect B12?

Long use is linked to lower B12. In a large study, two or more years of proton pump inhibitor supply carried an odds ratio of 1.65 for B12 deficiency, and higher daily doses carried more. Most deficient people in that study were not on the drug, and the drug has real uses, so any change is a conversation with your physician. See how to approach understanding your results.

Is atrophic gastritis serious?

It can be, mostly because of what it quietly takes away. A failing lining can starve the nerves and brain of B12 for years, showing up as numb feet, a slipping memory or unexplained low iron long before any stomach pain. It is also a precancerous condition, although progression to stomach cancer is uncommon, about 0.1% to 0.3% per year. Waiting for symptoms means waiting too long.

What causes atrophic gastritis?

Two forces do most of the damage. One is H. pylori infection: people carrying it develop new atrophy at 5.0 times the rate of people who are not infected. The other is autoimmunity, the immune system attacking the parietal cells of the stomach lining directly. The infection is receding worldwide; the autoimmune form is not. Either way, the cells that make intrinsic factor are lost.

How is atrophic gastritis diagnosed?

A gastroenterologist confirms it with a scope and biopsies of the stomach lining. Blood tests point toward it: anti-intrinsic factor antibody and anti-parietal cell antibody ordered together reached 90% sensitivity and 95.7% specificity, while either one alone misses cases. A normal total B12 does not rule it out. In one recent study, only 9% of people diagnosed with pernicious anemia were offered a scope at diagnosis.

See what the shortfall has already touched

Ask about nerve, balance, cognitive and metabolic testing so your physician can see the downstream picture beside the stomach workup.

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References

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