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Stress, a temporary reaction or eating something your stomach can't handle may be some of the first things that come to mind that can cause stomach upset. Concomitant symptoms such as feeling unusually tired, getting out of breath more easily than before or getting tingling in your hands and feet may indicate that something else is behind it.
Stomach and intestinal diseases which can cause poorer absorption of vitamin B12 are a common but often overlooked explanation for low B12 levels.
Gastrointestinal diseases that can cause poorer absorption of vitamin B12
Vitamin B12 is not absorbed in the same way as many other vitamins. First, the stomach must release the vitamin from the food with the help of stomach acid. Then the body needs a carrier protein, called intrinsic factor, which is formed by special cells in the stomach. Finally, the actual absorption takes place at the bottom of the small intestine, in the part called the terminal ileum. If any of these steps are disrupted, you can develop a B12 deficiency, even if you eat enough.
B12 deficiency can in turn cause anemia, but also symptoms from the nervous system. Common signs of this are fatigue, paleness, palpitations, decreased energy, memory problems, numbness, tingling and balance problems. In some cases, nervous symptoms appear before the blood value has time to drop significantly.
Autoimmune gastritis – when the stomach no longer helps absorption
One of the most important stomach causes of B12 deficiency is autoimmune gastritis. This is an inflammation in which the immune system attacks the lining of the stomach, especially the cells that produce stomach acid and intrinsic factor. When these cells are damaged, it becomes more difficult to release vitamin B12 from food and even more difficult to transport it to the small intestine for absorption.
This condition can develop slowly over several years. Therefore, many people first notice diffuse symptoms such as fatigue, impaired concentration or tingling in the feet. In the past, the diagnosis of pernicious anemia was often used, but modern guidelines emphasize the underlying disease itself – autoimmune gastritis – because the B12 deficiency is a consequence of the stomach no longer functioning normally.
Celiac disease can interfere with nutrient absorption more than you think
Celiac disease is a disease in which the immune system reacts to gluten and damages the lining of the small intestine. When the intestinal villi become inflamed and regrow, the absorption of nutrients can be impaired. Iron and folate deficiencies are common, while vitamin B12 deficiency can also occur.
The typical symptoms are not always obvious stomach problems. Some have diarrhea, gas, weight loss or a distended stomach, while others seek treatment primarily because they experience fatigue, have a proven anemia or recurrent low vitamin levels. If you have B12 deficiency together with iron deficiency, loose stomach or unexplained weight loss, celiac disease is a reasonable question to investigate.
When celiac disease is treated with a strict gluten-free diet, the intestinal mucosa usually recovers gradually. This often improves absorption, but it can take time. In the meantime, you may need to monitor both B12, folate and iron to see that the body is actually replenishing its stores.
Crohn's disease and disease in the last part of the small intestine
Crohn's disease is an inflammatory bowel disease that can affect the entire gastrointestinal tract, but the inflammation is often located at the end of the small intestine. And it is there, at the end of the small intestine, that the normal absorption of vitamin B12 occurs. Therefore, Crohn's disease is a clear risk factor for B12 deficiency, especially if the inflammation is long-lasting or if part of the intestine has been removed by surgery.
This means that two different mechanisms can interact. Inflammation in the mucosa impairs absorption here and now, and surgery reduces the intestinal surface area that is left for future absorption. For those living with Crohn's, B12 deficiency can therefore occur even during periods when the diet is completely reasonable.
Typical situations that could indicate an investigation of this condition are that you have had recurrent diarrhea, abdominal pain, weight loss or previous intestinal surgery and then notice new fatigue, weakness or tingling. In this case, it is not enough to just think "iron deficiency". B12 is often an equally relevant part of the picture.
Surgeries in the stomach and intestines can lead to long-term poorer B12 absorption
But other factors than diseases can also affect, surgery in the gastrointestinal tract is another common explanation for B12 deficiency. After gastrectomy, gastric bypass, sleeve gastrectomy or surgery where the last part of the small intestine has been removed, absorption can be impaired in a more permanent way. This is because the body either loses parts of the stomach that are needed for intrinsic factor and acid production, or the part of the intestine where B12 is normally absorbed.
This is something that can come on insidiously. The body stores vitamin B12 for a long time, so the deficiency does not always show up immediately after surgery. That is why you can feel fine for the first year and still later experience symptoms such as fatigue, decreased energy or neurological problems.
If you have had stomach or intestinal surgery, it is wise to see B12 as something that should be monitored over time, not just immediately after the procedure. The same applies if you are also taking medications that can further reduce levels, such as metformin or acid-suppressing treatment for a long time.
Other gastrointestinal conditions: pancreatic insufficiency and widespread malabsorption
Not all absorption problems are due to inflammatory bowel disease or celiac disease. Exocrine pancreatic insufficiency, often called pancreatic failure, can also contribute to malabsorption. In this case, the pancreas produces too few digestive enzymes, which means that the breakdown of food works worse and that several nutrients can be affected. Clinical guidelines mention pancreatic failure as a possible underlying cause of B12 deficiency.
In everyday life, it can manifest itself as loose, fatty or difficult-to-flush stools, weight loss, gas problems and fatigue. When several nutritional deficiencies occur at the same time, it usually speaks more of a broader absorption problem than a pure dietary deficiency. In this case, you need to look at the entire gastrointestinal function, not just a single test result.
There are also situations where absorption is impaired without a single clear main diagnosis. European consensus documents describe how autoimmune gastritis, intestinal diseases, bacterial overgrowth and surgical changes can cause malabsorption. For the patient, this means that the combination of symptoms, previous illnesses and test results is often more important than a single sign.
When should one suspect that a gastrointestinal disease is behind the B12 deficiency?
It is easy to think that low vitamin B12 is just a matter of diet, especially if one eats little animal foods. However, certain patterns suggest that a gastrointestinal disease may be behind it. One such pattern is when B12 remains low despite eating a varied diet or having already taken supplements.
Other warning signs are:
- prolonged diarrhea or recurrent loose stools
- bloating, abdominal pain or unintentional weight loss
- previous surgery in the stomach or small intestine
- concurrent iron or folate deficiency
- numbness, tingling or balance problems
- known Crohn's disease, celiac disease or autoimmune gastritis
In healthcare, the whole picture is usually assessed: symptoms, blood status, B12 value and sometimes additional tests. If the cause does not seem to be dietary, you need to consider whether the problem lies in the stomach, pancreas or small intestine. The treatment then involves not only replenishing the vitamin, but also understanding why the body is not absorbing it normally.
Low B12 is sometimes the body's way of signaling that something in the gastrointestinal tract is not working properly. A test result can therefore be the starting point for discovering an underlying disease in time, before nerve damage or more pronounced anemia has time to develop.
Do you want to know what your values look like? Order a B12 test or a broader health check and get concrete information to take further if you need to investigate whether your stomach is affecting your nutrient absorption.
