SIBO Causes Vitamin B12 Deficiency - Learn How To Deal With It

SIBO Causes Vitamin B12 Deficiency

With the growing number of people being affected by Vitamin B12 deficiency, it is imperative for you to address an important underlying cause that most sufferers are not aware of – SIBO.

Many of those who are deficient in Vitamin B12, are usually given supplements, to raise their levels. They generally do not address the reason the deficiency occurred in the first place.

SIBO and Vitamin B12 Deficiency

SIBO is an intestinal condition in which bacteria accumulate in your gut, causing various digestive issues like bloating, diarrhea, gas, reflux, weight loss, and constipation. As compared to these gut problems, the deficiency of B12 is a lesser-known complication of Small Intestinal Bacterial Overgrowth (SIBO).

People with normal intestinal flora depend on intrinsic factors of the stomach to permit binding and absorption of B12 in the ileum. Although the rate of Vitamin B12 is higher in vegans than that in omnivores, it does not mean that it is uncommon in omnivores. Research has shown that 1 out of 20 omnivores suffers from Vitamin B12 deficiency 1.

Why Vitamin B12 is Necessary for Your Body

Also called cobalamin, the water-soluble Vitamin B12 is an essential nutrient needed for keeping your red blood cells, nerves, and DNA healthy. B12 is also useful for preventing a form of anemia, known as megaloblastic anemia, which makes you tired and weak. It works as a donor of the methyl group in many of the detoxification pathways of your body.

One of the natural forms of Vitamin B12, methylcobalamin, is used for relieving the symptoms of degenerative neurological conditions like Parkinson’s disease, multiple sclerosis, motor neuron disease, and Huntington’s disease 2.

What are the Common Symptoms of B12 Deficiency

The common symptoms of B12 Deficiency include:

  • Chronic fatigue, low energy, constantly feeling tired
  • Weakness, muscle aches, joint pain
  • Shortness of breath, difficulty breathing
  • Inability to concentrate, poor memory
  • Dizziness
  • Mood changes, anxiety, and increased depression
  • Having palpitations and other heart problems
  • Dental problems such as diarrhea, cramping, or nausea
  • Loss of appetite
  • Numbness/tingling sensation in your hands or feet

Aside from the symptoms mentioned above, a severe deficiency of Vitamin B12 can lead to a critical condition called pernicious anemia, which may cause confusion, memory loss, and long-term dementia.

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Why does Vitamin B12 Deficiency Occur?

The causes of deficiency of Vitamin B12 are typically classified as follows:

1. Low Intake of B12

Since your body does not naturally make Vitamin B12, you must depend on dietary sources and supplementation. The average daily requirement of an adult is about 2.4 micrograms, with the best sources being animal products 3.

Although there are plant-based sources of Vitamin B12, studies have proved that they are not well absorbed and does not have any effects on the B12 levels in the blood. For this reason, people following a vegetarian or vegan diet are at a greater risk of suffering from Vitamin B12 deficiency.

2. Reduced Absorption of B12 in Small Intestine

Despite having adequate amounts of Vitamin B12 in your diet, if your body cannot absorb the nutrient well enough, then you may develop a deficiency. There are many complex steps associated with the absorption and assimilation of Vitamin B12 in your intestine. Poor absorption of B12 usually takes place due to the following reasons:

Low levels of stomach acid – Without adequate amounts of pepsin and HCl, the animal-based proteins bound to B12 are not digested. It means that B12 cannot attach freely with other glycoproteins and travel through the gut for absorption. Those with atrophic gastritis or low stomach acids occurring due to H. pylori infection are specifically at risk.

Bacterial overgrowth and intestinal infections – Bacterial overgrowth in the small intestine (like SIBO) and infections caused by protozoan parasites (e.g., Giardia) do not allow your body to absorb the Vitamin B12 obtained from dietary sources.

Insufficient production of digestive enzymes – Without sufficient production of pancreatic enzymes, your body cannot break down the Vitamin B12 complexes in the duodenum. Therefore, the nutrient is unable to bind with the Intrinsic Factor (a substance secreted by your stomach) and complete its journey through your small intestine.

Surgical removal or disease of the lower end of the small intestine – Since B12 is absorbed by the lower part of the small intestine, an impairment like an inflammatory condition (such as Celiac or Crohn’s disease) or surgical removal (for example, weight-loss surgery) of the distal ileum will hinder the absorption of B12.

3. Mutation of MTHFR Gene

People affected by the mutation of MTRR or MTHFR (genes that provide instructions for the production of enzymes) cannot methylate B12 into the usable form.

Therefore, while your body may absorb adequate amounts of B12 in the blood, it cannot be absorbed by the tissues where it is actually needed. Despite the B12 levels being normal or high, your body struggles in using it properly.

What are the Functional Lab Tests Needed for Identifying the Cause of B12 Deficiency?

Primarily, you need to do a standard blood test for identifying the levels of B12. Then, the underlying cause can be detected by the Organic Acid Test, a comprehensive Stool Test, or SIBO breath test. If none of the tests can identify the underlying gut dysfunction, then it is time for you to do an MTHFR gene testing.

How to Deal With a Vitamin B12 Deficiency

Even though we have discussed that Vitamin B12 can be obtained from the intake of animal products, simply eating meat will not help in alleviating B12 deficiency. Recovering from Vitamin B12 deficiency usually involves one or all the following things:

1. Eating Foods Rich in Vitamin B12

Although the rate of Vitamin B12 absorbability depends on your digestive health, the following are the top dietary sources of B12 that you need to have:

  • Salmon
  • Herring
  • Sardine
  • Tuna
  • Trout
  • Mackerel
  • Beef
  • Lamb
  • Turkey
  • Chicken and beef liver
  • Eggs
  • Organic Greek yogurt
  • Octopus, crab, and lobster

Nutritional yeasts, breakfast cereals, and some food products are also fortified with B12.

2. Healing your Gut for Improving Vitamin B12 Absorption

gut function

Since a healthy, well-functioning gastrointestinal tract is essential for the absorption of B12, healing it could be the most critical way of improving a Vitamin B12 deficiency. In addition to SIBO, parasitic and H. pylori bacteria infections are the most common stomach-related conditions that typically impair B12 absorption.

After identifying the cause of B12 malabsorption, you can try and heal your gut. To help improve your gut health and absorb B12 from food sources, you may consult a medical practitioner and supplement with digestive enzymes and HCl 4.

3. Taking Vitamin B12 Injections

Those with pernicious anemia and inflammatory gut disorders such as Crohn’s disease can have impaired absorption of B12 throughout their lives and will probably need Vitamin B12 injections indefinitely. It may also hold true for people with severe deficiency of B12 that cause neurological symptoms.

4. Taking B12 Dietary Supplements

While it is found in most multivitamins, supplements containing only B12 or B12 with other nutrients like B vitamins and folic acid are also available. Aside from pills, it is available in nasal gel and sublingual forms 5.


If B12 deficiency is suspected, the initial step is to get yourself tested. If the test shows that you are deficient in Vitamin B12, the next step is to find out the underlying cause. By assessing the visible symptoms of a patient and using the lactulose breath test, it is possible for your doctor to readily identify small intestinal bacterial overgrowth (SIBO) as a causative factor for the occurrence of malnutrition and Vitamin B12 deficiency.

Once the causative factor is identified, you need to have the appropriate form of supplements (for example, injection, sublingual, or oral), along with the required dosages as well as follow the length of treatment. Eradicating SIBO not just helps in dramatically improve the symptoms but also reduces the adverse effects of bacteria on nutrition.

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