Table of Contents
- What is Vitamin B12
- Deficiency symptoms
- Causes of deficiency
- Health benefits
- What are the best absorbable forms?
- The mechanism of absorption
- Best B12 supplement – vegan brands
- Possible side effects
- Vitamin B12 from Mushrooms?
- Fortified Foods or Supplements for Vitamin B12
- Top Foods for Vitamin B12 that are Vegan
What is Vitamin B12
Vitamin B12, also known as cobalamin, is a complex molecule necessary for human health.
This important water soluble B vitamin has the largest and most complex structure of all the vitamins.
Vitamin B12 is required for proper metabolic function, blood cell formation, DNA synthesis, and other processes within your body.
Vitamin B12 deficiency is therefore implicated in certain forms of anemia, neuropathy, heart disease, stroke, cancer, depression, neural tube defects, and other diseases.
Pernicious anemia is an autoimmune disease that affects the gastric mucosa and results in gastric atrophy. This leads to the destruction of parietal cells, achlorhydria, and failure to produce intrinsic factor, resulting in vitamin B12 malabsorption. If pernicious anemia is left untreated, it causes vitamin B12 deficiency, leading to megaloblastic anemia and neurological disorders, even in the presence of adequate dietary intake of vitamin B12.¹
Vitamin B12 is unique in that the molecule involves the metallic element cobalt.
Along with folate (B9), vitamin B12 is necessary for complex metabolic reactions which control blood cell formation in your bone marrow.
Deficiencies can cause immature red blood cells, low in hemoglobin, to be circulated.
This is seen as a megaloblastic anemia.
Vitamin B12 is produced by bacteria.
People ingest B12 by consuming other animals who have B12 stored in their tissues, or through bacteria.
The mollusks (shellfish) as a group all contain high levels of vitamin B12, as does beef liver, but this is vegan diet society, so we’re going to discuss some good quality sources of vitamin b12 suitable for vegan and vegetarians.
Sometimes vitamin B12 has been reported in seaweed, mushrooms, miso, tempeh, and other fermented foods.
While these foods may indeed have active forms of the vitamin in or on them, they should not be regarded as an adequate and reliable supply of the vitamin.
- lack of energy;
- an inflamed, swollen, tongue;
- lack of motivation;
- irregular heartbeats;
- lack of appetite;
- hormone imbalance;
- hallucinations or paranoia;
- yellowed skin.
Note – intaking large amounts of vitamin B9 can mask the damaging effects of B12 deficiency by ameliorating the megaloblastic anemia (when your body produces red blood cells that are larger than normal) caused by B12 deficiency without actually remedying the neurological damage that also appears.
Causes of deficiency
- gastrointestinal disorders, such as Crohn’s disease and celiac disease;
- fish tapeworm infestation;
- surgical procedures in the gastrointestinal tract;
- pernicious anemia, which is an autoimmune disease characterized by a lack of intrinsic factor. Pernicious anemia is relatively easy to treat with B-12 injections;
- a vegan diet;
- alcohol consumption;
- potassium supplements;
- metformin, the common diabetes drug.
The most precise test for B12 status is MMA (methylmalonic acid) testing along with a homocysteine test.
Also, it helps to prevent and treat the occurrence of Alzheimer’s disease.
It is needed in the lining of the gastrointestinal and respiratory tracts and regeneration of bone marrow.
During pregnancy, B12 is a key component of developing a healthy child and also reduces the risk of birth defects such as Down’s syndrome (a genetic condition which occurs when an individual has a partial or full extra copy of chromosome 21).
In addition, it helps the body convert carbohydrates into glucose (the most important simple sugar), therefore leading to energy production and a decrease in lethargy and fatigue in the body.
What are the best absorbable forms?
There are four types of B12 when it comes to their chemical composition:
- methylcobalamin is an activated form of B12;
- hydroxocobalamin is produced by bacteria but can be converted in the body in order to be useable;
- adenosylcobalamin is an active form, making it immediately available for use by the body;
- cyanocobalamin is the most used form in supplements but has an extra conversion before being converted to adenosylcobalamin or methylcobalamin.
Note – Dr. Greger states that cyanocobalamin is the only form of B12 that has been used in the majority of the medical studies on this vitamin.
He also explains that methylcobalamin had no effect on some patients.
More importantly, he recently updated his review of all of the medical literature about this vitamin and sticks to his original recommendation, to supplement with cyanocobalamin.
The mechanism of absorption
In order to fully absorb this vitamin, it has to bind with the gastric intrinsic factor, a protein found in your stomach.
The maximum amount of this protein production will only help you absorb around 10 mcg of vitamin, even if the ingested dose is 500 mcg.
According to some studies, healthy raw food vegans may require less B12 due to an improved gastric function and a high capacity to recycle B12.
In addition, the less frequently you intake this vitamin, the more you need to take.
B12 injections go right into your bloodstream without the need of digestion, thus, it is one of the best methods to get this important vitamin into your body.
Studies suggest no difference in efficacy between sublingual and oral forms.
So, if you do have a deficiency, the important thing is to make sure you get the dosage high enough and not rely on sublingual having any higher absorption rate.
The US recommended dietary allowance for B12 is 2.8 mcg/day for nursing or pregnant women and 2.4 mcg/day for adults. 
Factors such as rate of stress and metabolism can also determine our differing and often changing needs.
More recent studies put the ideal intake at 4-7 mcg/day.
Note – because this vitamin is a water-soluble vitamin, the body has the capacity to flush out any excess that it doesn’t need.
As a result, it is considered non-toxic and safe.
Best B12 supplement – vegan brands
Ideally, you want to look for a supplement that is vegan certified and non-GMO.
The majority of supplements range from 500 mcg all the way up to 5,000 mcg.
Possible side effects
It has the potential to interact with some prescription medications.
Moreover, these supplements contain artificial sweeteners like mannitol and xylitol, so be wary if you are sensitive to these substances.
Vitamin B12 from Mushrooms?
This is an interesting finding which deserves some consideration given the information one usually hears regarding vitamin B12 and vegetarianism.
You’ve most likely heard a version of this, “Vegetarians can’t get enough B12 eating just plants.”
I’m not going to argue that taking a supplement is a bad idea, in fact it remains the gold standard for vegetarians to safely and inexpensively get the required vitamin B12.
However, you’re definitely getting more B12 through your diet than you think, and if you enjoy mushrooms, rejoice!
Studies have demonstrated that the fruiting bodies of shiitake mushrooms contain this important nutrient.
Research has also shown that the B12 in mushrooms is bacteria derived and most prominent on the outer peel of the mushrooms.
The vitamin content seems to vary from farm to farm as well.
Fortified Foods or Supplements for Vitamin B12
Many foods are fortified with vitamin B12 and are suitable for vegans and other plant based diets.
Certain other at risk populations for vitamin B12 deficiency are also encouraged to supplement their diets with this essential nutrient, such as the elderly, who may not have adequate stomach acid to cleave the vitamin from protein.
Adult vegans and vegetarians can easily get the 2.4 recommended micrograms of vitamin B12 by consuming fortified cereals, soymilk, nutritional yeast, tofu, energy bars, and many other products.
Please check your food labels and you will learn which of your favorite foods are already being fortified with vitamin B12.
You will also no doubt be getting some amount of vitamin B12 from bacterial presence on or in the food you are already eating, again, please do not rely on these small amounts as they will not add up to the necessary daily amount.
Supplements are also a very inexpensive and effective way to make sure you are getting vitamin B12.
A daily or weekly vitamin B12 supplement should be adequate in most cases to insure yourself against deficiency.
Top Foods for Vitamin B12 that are Vegan
Here’s my list for vegan foods containing vitamin B12:
- Nutritional Yeast – sprinkle this on popcorn or broccoli
- Soymilk – or another B12 fortified non-dairy milk
- Tofu – check the labels to make sure it is fortified
- Cereal – many vegan breakfast cereals are fortified with B12
- Tempeh – many contain vitamin B12, read those labels
There are many vegan foods that contain trace amounts of vitamin B12 due to bacteria being present on or within the food.
Bacterial action alone should not be relied upon for adequate dietary intake of vitamin B12 in a vegan, vegetarian, or other plant based diet.
It is both economical and advised to eat a diet fortified with vitamin B12 or to take a vitamin B12 supplement to make sure you are getting the recommended amount and to avoid the symptoms and health risks of vitamin B12 deficiency.
- Combs G. Vitamin B12 in The Vitamins. New York: Academic Press, Inc., 1992.