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Vitamin B12 For Vegetarians and Vegans

vitamin b12

Vitamin B12 – Obtaining sufficient amounts of vitamin B12 is essential for every cell in the body as it plays a key role in DNA replication [1]. The recommended daily intake of vitamin B12 is 2.4mg per day [2] to ensure a wide range of health benefits including energy production, regulation of the nervous system, reduction of cardiovascular disease, encouraging optimal digestion, and essential for hair, skin, and nails [1]. Vitamin B12 is synthesized only by certain bacteria [3] in the digestive tract which is found in high concentrations in bodies of predators located higher in the food chain.

The highest sources of B12 are found in foods such as:

  • Red meat
  • Poultry.
  • Milk.
  • Eggs.
  • Fish and shellfish.

Lifestyle and dietary choices such as Lacto-ovo diets, raw-veganism, or fruitarianism are highly restricted in these sources of Vitamin B12 which coincides with the high prevalence of B12 deficiencies in these particular groups. This raises the question of which plant-based foods offer the most therapeutic levels of Vitamin B12 to ensure adequate amounts are met in vegetarian-based diets?

B12 Nutrient Perspective

Vitamin B12 comprises of different types with the most common form being cyanocobalamin as it is the most chemically stable yet most unnatural form. Cyanocobalamin is used in fortified foods and supplements.[4]

From a nutrient perspective, a vegetarian diet is usually rich in carbohydrates, dietary fibers, carotenoids, folic acid, Vitamin C, Vitamin E, Omega-6, and magnesium, however, the diet is commonly low in Vitamin B12 [5], proteins, saturated fatty acids, Omega-3, Vitamin A and vitamin D3.

Vegan diets are well known to have a high intake of dietary fibers, low intake of saturated fats, and health-promoting phytochemicals found in fruits and vegetables, promoting a healthy weight and heart health. Despite this, due to the vital role B12 plays in metabolizing homocysteine, vegetarians are still at risk of cardiovascular diseases along with other neurological degenerative diseases. [6]

Risk Factors

These risk factors are one of the main reasons to introduce fortified foods in the western diet with aims to address Vitamin B12 deficiencies. The most common form of B12 used fortified foods such as bread and cereal is cyanocobalamin due to it being the most commonly stable yet most unnatural form.

Cyanocobalamin needs to convert into methylcobalamin and 5-deoxyadenosylcobalamin in the body to become active. Questions are raised as to whether this form of Vitamin B12 is safe as it requires using ‘methyl groups’ in our body that are used in the breakdown of homocysteine which may further increase the risk of cardiovascular diseases. With many vegetarians becoming more aware and seeking unprocessed foods, fortified foods have not been effective in addressing B12 deficiencies in vegetarian diets.

Vitamin b12 – Going back to Grassroots

Seeking vegetables sourced from organic farms that use permaculture philosophy is a common choice for vegetarians. One study found an increase in vitamin B12 levels in spinach leaves (approximately 0.14mg/100gm) occurred when grown from organic fertilizer derived from cow manure. However, to receive the Recommended Daily Intake (RDI) of 2.4mg/day for an adult, consumption of several hundred grams would need to be ingested, which is hard to obtain.

More interestingly another study found that most organic fertilizers made from animal manures had high amounts of inactive B12 which were excreted in human feces of more than 98% which indicates a poor conversion rate into the active forms methylcobalamin and 5-deoxyadenosylcobalamin. More popular foods that have has recent attention in vegetarian-based diets are fermented foods such as tempeh, kimchi, sauerkraut, and kombucha. Unfortunately, these fermented foods only contain trace amounts and do not hold a sustainable source of Vitamin B12 (ie. Kimchi <.01 for every 100mg)Kimchi

Vitamin B12 – Limited plant source options

With limited plant-based sources of Vitamin B12 in the western diet and ineffective attempts of fortifying foods to address the deficiency showing to have very little ability to meet the standard recommended daily intake, we need to look at other therapeutic and exotic sources that are being used in different parts of the world to improve vitamin B12 sufficiencies. Embracing edible mushrooms and edible algae may be the key to a sustainable vegetarian diet with adequate B12 consumption!

Edible mushroom species are popular among vegetarians in European counties and are yet to have as much appreciation in the western world. Mushrooms such as porcini mushrooms, parasol mushroom, oyster mushroom, and black morel show trace levels of vitamin B12 (.09 mg/100gm dried weight). More excitingly the black trumpet and golden chanterelle contain higher levels of vitamin B12 (1.09-2.65 mg/100g dry weight). Shitake mushrooms may prove to be the most beneficial in vegetarian diets as dried shiitake mushrooms are around 5.6mg per 100 gm dried weight). This means that the daily intake of approximately 50gm of dried shiitake mushroom will meet the 2.4mg/day for the average adult. [7]


The edible algae laver is also known as nori and is most commonly seen in Sushi Trains wrapped around rice and tuna. Nori shows to have one of the highest bio-available sources of B12 that may hold many benefits for correcting vitamin B12 deficiencies in vegetarian diets. Dried green laver and purple laver are the most widely consumed edible algae and contain a substantial amount of Vitamin B12 (approximately 63.6 mg/100g [7] and 32.3 mg/100g dry weight). It is important to note that the processing stages of algae such as toasting or seasoning can affect the vitamin B12 status.

In one study where dried purple laver was treated by toasting until the laver color changed from purple to green, decreased in Vitamin B12 due to the heating process. Despite this, edible purple laver, in particular, contains a coenzyme that increases the bioactive forms of vitamin B12 in the body. Further health benefits of consuming purple laver were emphasized in nutritional analysis of six vegan children who consumed a diet including brown rice and dried purple laver for 4-10 years, which suggested that nori may prevent vitamin B12 deficiency vegans.

Don’t forget the Mushys!

Edible mushrooms and edible algae are undoubtedly the most nutritional and highly active sources of vitamin B12 needed a vegetarian-based diet. Incorporating these functional foods will decrease the amount of vegetarians with vitamin B12 deficiencies and allow for the recommended daily intake of B12 to be met, which most vegetarians struggle with. In doing this, vegetarians will lower the risk of degenerative diseases and increase their vitality and live in the most optimal health possible.


  1. Das KC, Herbert V. Vitamin B12–folate interrelations. Clin Haematol. 1976 Oct;5(3):697-745. PMID: 10122.
  3. Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human small intestinal bacteria. Nature. 1980 Feb 21;283(5749):781-2. doi: 10.1038/283781a0. PMID: 7354869.
  4. Paul, C., & Brady, D. M. (2017). Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements With Potential to Mitigate B12-related Genetic Polymorphisms. Integrative medicine (Encinitas, Calif.)16(1), 42–49.
  5. Pawlak R, Lester SE, Babatunde T. The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. Eur J Clin Nutr. 2014 May;68(5):541-8. doi: 10.1038/ejcn.2014.46. Epub 2014 Mar 26. Erratum in: Eur J Clin Nutr. 2016 Jul;70(7):866. PMID: 24667752.
  6. Son P, Lewis L. Hyperhomocysteinemia. [Updated 2021 May 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  7. Watanabe, F., Yabuta, Y., Bito, T., & Teng, F. (2014). Vitamin B₁₂-containing plant food sources for vegetarians. Nutrients6(5), 1861–1873.