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Vitamin B12 and the Gut Microbiome

Vitamin B12 is an essential nutrient that our bodies need to survive and feel well. Vitamin B12 deficiencies are commonly known to cause low energy levels and an inability to focus. However, Vitamin B12 has more effects than just these. Vitamin B12 levels affect and are affected by gut health, too. Today we will explore Vitamin B12: what it’s good for, what happens when you’re deficient, how it affects the gut, and how to get more if you need it.Vitamin B12 and the Gut Microbiome

What does Vitamin B12 do?

Vitamin B12 is an essential nutrient that helps to make DNA. From there it’s easy to understand that it affects your cells and bodily functions pretty drastically. All of the B vitamins go by other names:

  • B1 — Thiamin
  • B2 — Riboflavin
  • B3 — Niacin
  • B5 — Pantothenic Acid
  • B6 — Pyridoxine
  • B7 — Biotin
  • B9 — Folate
  • B12 — Cobalamin

B12 (sometimes referred to as cobalamin) is extremely important to your central nervous system, protein and lipid metabolism, and the synthesis of red blood cells. 

B12 keeps your nerve cells healthy and directly affects your mental health and mood in addition to nerve sensations and muscular function.

Vitamin B12 keeps your blood healthy which is why deficiencies can lead to anemia and related conditions. B12 also helps to keep homocysteine levels normal which helps combat problems related to histamine level abnormalities like SIBO, histamine intolerance (contributing to headaches, sinus issues, autoimmune conditions, fatigue, etc.), and histapenia (contributing to anxiety, depression, food sensitivities, cognitive issues, etc.).

B12 and other B vitamins are used in multiple cellular processes throughout the body, especially those related to metabolic health. This is where the gut microbiome and digestive systems come into play.

Vitamin B12 and the Gut

Our body gets vitamin B12 two main ways: 

  1. The food we eat 
  2. Given off by the microbes that live in our gut

When we eat foods that contain vitamin B12, the B12 is absorbed in the small intestines where it is used by the body. This means that not much B12 is passed along to the large intestine where the gut microbes reside.

Studies show that approximately 20% of gut microbes can produce their own B12. However, 80% of gut microbes require B12 to complete their metabolic reactions. These bacteria need to get B12 in other ways.

Lactobacillus species were originally thought to not have a B12 biosyntheic pathway, however, by converting glycerol into propanediol they were able to produce their own B12. So even microbes that don’t necessarily create their own B12 initially, may have ways of sustaining their own requirements outside of dietary intake. 

A lot of the research with B12 and the gut is fairly novel. Studies have conflicting findings on whether supplementation can help improve gut function and how B12 works with the gut. Since certain bacteria can provide their own sources of B12, it seems like it can maintain its own health. However, this has only been studied in healthy specimens and it appears to differ from person to person. 

Many studies don’t find a significant difference of bacterial diversity or richness between those with or without B12 deficiency when otherwise healthy. However, those with gastrointestinal or other health complications were slightly different. Whether this is related to the condition and B12 deficiency has not been concluded.

B12 is a rising concern in multiple communities. People with autoimmune disorders, those with restricted diets, and others are finding themselves deficient in B12 which can lead to many different health complications.

Vitamin B12 Deficiency

B12 deficiency (along with other nutrient deficiencies) is a rising concern across the globe. B12 deficiency is most commonly associated with:

There are 3 main causes of B12 deficiencies. 

  • Dietary insufficiency and Restrictive diets — especially vegetarian or vegan diets/
  • Autoimmune disorders
  • Malabsorption

Dietary Insufficiency and Vegetarian/Veganism

People who are not consuming enough animal products are often at risk for a deficiency in B12. Animals who adhere to these diets often eat their stool and get their B12 from that. However, this would be dangerous for humans to do, so they are often deficient and run the risk of other conditions. 

Interestingly people who are born in India who also are vegan do not experience this problem. However, when they move to Western countries and continue their normal vegan diet they do become deficient in vitamin B12. 

If you think about it, when people from Western countries visit India they often get sick from the water that the indigenous people drink all the time. When this was looked into further, it was found that they have bacterial species that reside in the small intestine that give off more B12. 

In the Western world, this is the condition SIBO which causes bloating, abdominal pain, and abnormal bowel movements. But in other countries, this is actually normal and they don’t experience these bad side effects because their bodies have adapted to accommodate bacteria in the small intestines. Plus it gives them additional B12 so eating vegan is no problem. 

Autoimmune disorders

Pernicious anemia is an autoimmune disorder that causes antibodies to attack intrinsic factor (a protein necessary for B12 to be absorbed). Pernicious anemia is a form of megaloblastic anemia that causes red blood cells to become too large and do not function as they should. 

Since this affects both the absorption ability of the body and the blood cells this can be a very dangerous condition. Doctors will typically treat this with B12 supplements or, in extreme cases, by blood transfusions.

Poor B12 Absorption

As with pernicious anemia, other conditions can cause the body to be unable to absorb B12. Any conditions or surgeries that have affected the stomach or ileum, can affect your B12 absorption because they affect your intrinsic factor levels. Intrinsic factor is the protein necessary for B12 to be absorbed into the body. Otherwise, it can be consumed but isn’t used and is passed on as waste. 

Surgeries for Crohn’s disease and gastric bypass are known to cause this problem. Damage to the intestines from Celiac disease and tapeworms can also affect intrinsic factors and B12 absorption ability. 

For conditions like this, oral B12 supplementation is not going to be helpful as it isn’t a lack of dietary B12, it’s the inability of the body to actually absorb the B12 because of a depleted intrinsic factor. 

How to get more vitamin B12

The best way to get more vitamin B12 is by making sure it is in your diet. The best dietary sources of B12 include:

  • Red meat
  • Dairy
  • Eggs
  • Fish

Those who cannot or prefer to not eat these foods will need to consult their doctor for the best methods of supplementation. Your doctor will give you the option of supplementing orally or with shots. 

Those who have a deficiency of intrinsic factor will need to get the shots as their body will not be able to use any other form of B12. 

Always do this under a doctor’s supervision. Studies in animals have shown that over supplementation is possible and can cause complications.

Be careful if you are on other medications like metformin or gastric acid inhibitors as they can be affected by B12 supplements. 

As always if you suspect you have a problem, consult your primary care physician and they will guide you on what is best for your individual situation. 

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