Vegan Vitamin B12
Vitamin B12, also known as cobalamin, is one of the thirteen essential vitamins that the body requires to survive. It is involved in many crucial processes, including (1) creating DNA, cell division and, maintaining and repairing Myelin Sheath (a protective coating around nerve cells). Unfortunately, there are limited vegan vitamin B12 sources as plant based foods do not naturally contain this vitamin.
Animal products including meat, chicken, fish, eggs and dairy products are rich in this vitamin.
Consuming enough B12 is crucial for proper blood and brain function and it can be stored in the liver for many years. Deficiency can lead to a range of health consequences including nerve damage and pernicious anaemia.
It is important for those following a vegan or vegetarian diet ensure they are getting enough each day through foods or supplements.
This article explores vitamin b12 on a vegan diet, where you can find it, supplement recommendations and how to avoid deficiency.
What does Vitamin B12 Do In The Body?
Vitamin B12 is an essential nutrient that almost every cell in the body requires for proper functioning. It is involved in two main biochemical processes in the body and acts in two main forms – methylcobalamin and adenosylcobalamin. Each of these forms have a different role.
Methylcobalamin acts as a cofactor to the enzyme methionine synthase, which catalyses the transfer of a methyl group from N-methyltetrahydrofolate to homocysteine, yielding methionine and tetrahydrofolate. This reaction occurs in the cell cytoplasm (2).
From methionine, S-adenosyl-methionine is formed, which is a universal methyl donor for many important substrates, including DNA, RNA, hormones, proteins, and lipids. This reaction is also important as it converts methyltetrahydrofolate to tetrahydrofolate, the active form of folate, which is another essential B-vitamin.
Adenosyl cobalamin acts as a cofactor in the methyl-malonyl CoA mutase transformation of methyl-malonyl CoA into succinyl CoA in the mitochondria (2).
How is it absorbed?
The absorption of vitamin B12 contains a number of steps.
In animal based foods, it is found in the form of methyl-, deooxyadenosyl-, or hydroxy-cobalamin.
When this form of B12 nutrition reaches the stomach, two digestive enzymes – pepsin and hydrochloric acid break down the binding protein, releasing the cobalamin portion of the nutrient known as “free vitamin b12”.
When synthetic (man made) B12 is added to fortified food or supplements, it is already in its free form and therefore does not require this separation step.
Free vitamin b12 then combines with Intrinsic Factor (IF). IF is a type of protein secreted by parietal cells in stomach. This complex is then able to be absorbed in final section of the small intestine known as the illeum.
Absorption can also be influenced by age, reduced gastric acidity and other gut disorders.
This vitamin also has many inactive analogues. These are molecules that look like its active form, but actually are not, and can interfere with it’s function and absorption.
How much vitamin B12 can be absorbed at once?
Vitamin B12 absorption depends on how much is consumed at one time. When added to foods such as soy milk or veggie delight sausages in low amounts (less than 5 mcg per dose) it has a similar absorption rate to animal products. It is absorbed at approximately 56% of a 1mg dose.
Meaning, if you drank a glass of Sanitarium So Good Soy milk which contains 1mcg per cup, you would only be able to absorb approximately 0.5mcg.
However, absorption decreases significantly with high doses of B12. Doses above 500mcg have absorption of 1% or less.
This means, that if you take a supplement of 500mcg, you’re only able to absorb 5mcg at one time.
How Much Vitamin B12 Do I Need?
How much you require each day is based on the Recommended Daily Intake (RDI). The RDI is the average daily dietary intake that meets the nutrient needs of 97-98% of the population.
For children under 12 months of age the RDI cannot be determined and therefore Adequate Intake (AI) is used. The AI is based on the average daily nutrient intake deemed to be adequate based on estimates of healthy groups.
Vegan Vitamin B12 Food Sources:
Our bodies can not create B12, meaning that it must be eaten in the diet.
Vitamin B12 is bound to protein. It is found in all animal foods with the exception of honey. This includes meat, poultry, fish, eggs and dairy products (3).
Individuals who follow plant-based diets must rely on fortified foods and supplements to meet their daily requirements.
Vegan vitamin B12 food sources include:
- Certain plant-based milks (i.e. Sanitarium soy milk)
- Nutritional yeast
- Reduced salt Vegemite (note: the original vegemite is not fortified with B12)
- Certain meat substitutes (i.e. Vegie Delights products)
If you are wanting to meet your daily needs through fortified foods it is essential that you read the ingredients list and nutritional panel as not all products listed above will be fortified with this nutrient.
It is also important to note that nutritional yeast, also known as savoury yeast flakes, may not be a reliable source. The vitamin levels contained within nutritional yeast can vary between brands, meaning it is not recommended as a sole source B12.
If you want to try and meet your requirements through food alone you will need to consume 2-3 servings of fortified foods, at least 4 hours apart for optimal absorption.
The number of servings required daily will vary depending on which fortified products you consume. Due to this not being feasible for many individuals, it may be beneficial to consider a vegan vitamin b12 supplement.
Poor Sources of Vitamin B12
Some vegan foods claim that they contain B12. This includes tempeh, seaweed, organic foods and spirulina. Unfortunately these contain inactive analogues. This means, when analysing these compounds in the lab they may look like vitamin B12, but they are not biologically active meaning humans cannot absorb them.
Signs of Vitamin B12 Deficiency
Deficiency can be common amongst vegans and those following a mostly plant-based diet.
Sign of vitamin B12 deficiency include (3):
- Megaloblastic anemia, meaning red blood cells are not produced properly and are larger than normal
- Loss of appetite
- Weight loss
- Tingling of the hands and feet
Signs of deficiency in infants include (7):
- Failure to thrive
- Movement disorders
- Developmental delays
- Megaloblastic anemia
A 2013 systematic review investigating the prevalence of deficiency among vegetarians and found rates of 62% amongst pregnant women; 32% amongst vegetarians; and 30% to 76% amongst vegans (depending on the definition of deficiency) (6)
Normally, anaemia is the first symptom of deficiency to occur. Often deficiency can go undetected in vegans as it is masked by high intakes of folate, found in fruits, vegetables and wholegrains (3). If someone’s diet is high in folate and low in B12, the folate will “mask” the anemia and nerve damage will be the first symptom to occur.
Although textbooks and articles state that deficiency can take 2-5 years, our dietitians have seen deficiency occur in as little as 6 months. It is essential to commence supplementation or ensure you are eating adequate amounts as soon as you adopt a completely plant based diet
It is also important for plant-based eaters to regularly check their blood status. Failure to do so can increase the risk of irreversible brain and nerve damage.
Should vegans supplement Vitamin B12?
Even though there are some plant-based foods fortified with B12, the selection is quite limited and these foods need to be consumed daily to meet the RDI.
For this reason it is often recommended that those that follow a largely plant-based diet, consider taking vegan Vitamin B12 supplements.