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Vitamin B12 for Vegan Deficiency Symptom & Solution

Vegan, Vitamin

Veganism is a lifestyle that becomes challenging sometimes since vegans eat the choosiest food. At each step, they must ask themselves questions like, what are vegan foods? What is Vitamin B12 for Vegan, what is vitamin B12 good for, what are the symptoms of deficiency of vitamin B12, etc.? to balance the diet and stay away from the complication related to deficiency since very few plant sources have dietary Vit B12.

However, this doesn’t stop vegans from following a cruelty-free diet and lifestyle. To overcome the limitation, there is research to identify vitamin B12-rich foods and widen the vegan food grocery list choices.

Vitamin B12 for Vegan

What is vitamin B12 for Vegan

Vit B12 is a water-soluble vitamin also known as cobalamin. In a healthy human being, dietary Vit B12 binds to the salivary gland-secreted protein called R-factor. In the small intestine, the R-factor & B12 gets separated with the action of pancreatic enzymes. Upon cleavage, the B12 binds with glycoprotein called intrinsic factors, which can then bind to the ileum, which allows absorption of B12 [1].

Upon absorption, Vit B12 gets involved in many metabolic pathways of neurological and hematologic functions [1]. The metabolically active forms of B12 are Methyl cobalamin and 5-deoxyadenosylcobalamin [2].

Vitamin B12 benefits

Vitamin B12 is the cofactor for L-methyl malonyl-CoA mutase and methionine synthase. Methionine synthase catalyzes the conversion of methionine from homocysteine, and methionine is essential for the formation of S-adenosylmethionine, which is a methyl donor for DNA, RNA, proteins, and lipids [3].

Moreover, Vit B12 plays roles in myelination, development, central nervous system functioning, DNA synthesis, and red blood cell formation [4].

According to one of the studies, vitamin B12 can help strengthen the fight against the virus by balancing the immune response and treatment of persisting symptoms of COVID-19, primarily related to the muscle-gut-brain axis [5].

What are the symptoms of a deficiency of vitamin B12?

The recommended Dietary allowance (RDAs) for an adult is 2.4 mcg. B12 can be assessed by measuring its concentration in serum or plasma. The assessment is based on serum methylmalonic acid (MMA) levels, a vitamin B12-associated metabolite. Levels higher than 0.271 micromole/L of methylmalonic acid indicate B12 deficiency [2].

As we have seen, vitamin B12 plays an essential role in key functions like DNA synthesis, central nervous system functioning, RBC formation, and so on. Hence the lack of Vit B12 can cause severe chronic problems for a human being. Therefore, it’s important to understand “what are the symptoms of a deficiency of vitamin B12,” but before that, let’s dig into what causes the deficiency of vitamin B12.

Reasons for deficiency of vitamin B12


The exact cause of Pernicious anemia is not known, but what is known is that it is an autoimmune disorder that affects the stomach. It also attacks the cells that produce intrinsic factors; therefore, B12 can hardly get the intrinsic factor that B12 binds to reach the ileum for absorption. Hence B12 absorption is prohibited [7].

Medicines and other health conditions

Medicines can be a reason for the impaired absorption of B12; for instance, the medication taken to treat indigestion, in turn, inhibits the proton pumps, which indirectly blocks the acids required for the absorption of B12 [7].

Certain health conditions like bypass surgery, celiac disease, inflammation with tapeworms, or in case of illnesses like Crohn’s disease can also prevent the absorption of B12 [1].


Since very few vitamin B12 plant sources are present, low serum B12 is common in people following vegan and keto-vegan diets. In fact, some vegetarians following a lacto-ovo-vegetarian diet are also at risk of b12 deficiency because of low milk and egg consumption.


Often, older people with growing age lose the ability to the physiological secretion of intrinsic factors may deplete; hence, the Vit B12 absorption is hampered as an intrinsic factor is necessary for the absorption ileum [8].

Lack of vitamin B12 symptoms

With mild B12 deficiency, you might not feel any symptoms, but if you remain untreated, you may feel extreme tiredness initially, and you may become anemic.

Following are the other symptoms you can get as signs of Vit B12 deficiency.

  • Weakness
  • Heart palpitations and shortness of breath
  • A pale-yellow tinge to your skin
  • Mouth ulcers
  • Para esthesia
  • Issues in walking and talking
  • Eyesight weakening
  • Irritability and depression
  • Mental retardation, loss of memory, and dementia

Effect of Vitamin B12 Deficiency

  • Megaloblastic anemia is caused because of compromised red blood cell synthesis caused due to abnormal DNA synthesis.
  • Neurological functions impairment

Vegan sources of vitamin B12

Purple laver (Nori)

Among naturally occurring high Vitamin B12-containing plant-based foods, Nori is on top of the list since consumption of 4 g of dried purple laver covers the RDA of 2.4 mcg/day [12]. Also, the same was proven in the clinical trials on rats, where a nine-week-old B12 deficient was fed with dried purple laver (10 mcg/kg for 20 days); a substantial amount of decrease in the methylmalonic acids in the urine suggested an increase in the level of B12 [15].

It is also ideal for consumption as Lori has a lower amount of iodine concentration as compared to other seaweeds; hence excess intake will not have a harmful intake of dietary iodine [13].

A subsequent amount of Nori can be consumed through sushi, like vinegared rice rolled in nori. In fact, it can also be consumed by toasting since toasting to the point of changing color from purple to green couldn’t change the B12 levels. Not only in Japanese sushi but dried purple lavers can be integrated into Italian, French, and other western dishes [14].


The B12 deficient male weanling Wistar rats fed with Spirulina could positively alter the several atrophic changes and architecture in the lung and spleen of the B12 deficient group. Therefore, it was validated that Spirulina can improve B12 levels [11]. Moreover, methylcobalamin is the bioavailable form of vitamin B12 present in Spirulina on an average of 35-38 mcg/100g [16].

In order to test the Vit B12 content of algae, smoothies were prepared with different algae, out of which Chlorella and Spirulina smoothies showed higher Vit B12 (33.3 and 15.3 mcg/kg resp.) content [17].

Another study explored the ability of Vit B12 from both Spirulina biomass and Spirulina extract to treat gut gastric ulcerations and found that Spirulina-based food can be used as a gastroprotective agent [18].

According to Food and Agriculture Organization (FAO), Spirulina is a superfood as it contains protein 60-70% of dry mass, a high concentration of beta-carotene, vitamin B12 (3.6 mcg/g), iron, dietary fiber, etc., which is highly digestible [16].

However, a concern is raised on the labeled concentration of B12 isolated from Spirulina and actual levels of biologically active methylcobalamin levels. Although both cobalamin and pseudo-cobalamin are present in the Spirulina supplements, the presence of Pseudo-cobalamin (“the ability to bind intrinsic factor is 500 folds lower than methylcobalamin and hence not absorbed by ileum and physiologically unavailable for mammals”) is higher as compared to cobalamin. Spirulina product producers, instead of mentioning separate values, mention higher levels of Pseudo-B12 level rather than actual levels of cobalamin, which is against consumer protection as they rely on nutritional labels [19]. Hence a reform is explicitly required in the interest of vegans and vegetarian consumers as they have limited sources of B12.

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Chlorella pyrenoidosa:

According to the research, B12 from Chlorella can be isolated, purified, and formulated in Chlorella tablets and general levels of physiologically active cobalamin are present in Chlorella [10, 19]. In another study published in the Journal of Medicinal Food, 9g/day Chlorella pyrenoidosa, a commercial whole-food supplement believed to be physiologically active form, was given to 17 vegan or vegetarian healthy but with Vit B12 deficiency adults between 26- 57 years of age (serum MMA high than 270 nmol/L) for 60 days. Upon 60 days, the decrease in serum MMA by ~34% was noticed, along with the B12 level going up [9].

The Chlorella tablets available in the market has biologically active Vit B12 but with varying concentration of B12 from 0 to 100 mcg/100g; thus, check the label [12]. Nevertheless, the only issue with relying on Chlorella is that they don’t produce B12; instead, they absorb from the environment generally from microbiota. Hence, a potential process, if understood, can be replicated at the industrial level to produce B12 [10].

Fortified and fermented foods

The lower availability of Vit B12 from plant sources for vegans has opened the market for fortified food items like cereals, meat analogs, soy milk, rice milk, almond milk, etc. [21] These food items fortified meaning added vitamins (here Vit B12) is added these highly consumed foods to increase the nutritional value [22].

Nutrition yeast is another source of Vit B12, which generally does not produce B12 but is fortified with vegan-friendly synthetic B12. With the consumption of two tablespoons, one can get up to 733% of the daily value of vitamin b12 [23].

Fermented foods like sauerkraut (7.2 mcg/100g), natto, and tempeh (approx. 0.7 to 8 mcg/100g) have a significant amount of cobalamin; however, the level of cobalamin depends upon environmental bacteria randomly present in the fermentative microorganism pool [24, 25].


The vitamin B12 benefits are immense; however, the lack of vitamin B12 is quite common in vegan and vegetarian diet followers. Along with diet, Pernicious anemia, medications, and other health conditions can cause Vit B12 deficiency. Therefore, to know the answer What are the symptoms of a deficiency of vitamin B12? is highly in their interest. Nevertheless, for B12 deficiency treatment, they should consume vegan sources of B12 like Spirulina, Chlorella, Nori, and fortified & fermented foods.

FAQ- Frequently asked questions

What are B12 deficiency neurological symptoms?

– Eyesight diminishing
– Par aesthesia (Tingling or prickling sensation in arms, hands, legs, or feet)
– Memory-related problems (short-term or long-term memory loss)
– Difficulty in speaking, walking, or physical coordination
– Damage to parts of the nervous system

What is the B12 deficiency treatment?

The best way to recover from B12 deficiency is to adjust your diet; if the food is unable to fulfill the requirement, then include fortified foods or Vit B12 supplements. Intracellular injection of B12 can also be used for B12 deficiency treatment.

How prevalent is vitamin B12 deficiency among vegetarians?

Fever vegetarian plant-based b12 sources mainly stands out for the lack of Vit b12 among vegetarians and vegans. According to the studies, 11- 90% of elder vegetarian people are at risk of deficiency, whereas 62% of pregnant women and 25 – 86% of children following a vegetarian diet can be deficient [6].

How long does it take to recover from vitamin b12 deficiency?

1000 mcg of B12 intramuscular ingestion once a week can replenish stores in newly deficiency-diagnosed patients, and then switching to 1000 mcg once a month is recommended [1].

What is the vegan b12 myth?

Some speculations that are naturally occurring bacteria in vegan mouths can help them get vitamin B12, but this is a big fat vegan b12 related myth.

What are the stages of b12 deficiency?

A pale-yellow tinge to your skin
A sore and red tongue
Mouth ulcers
Para esthesia
Problems in walking
Memory loss

How long does vitamin b12 last in your system?

For most vitamins, our body maintains a reservoir mainly in the liver, where it stores them for emergencies. Similarly, Vit B12 is also stored, and if you stop taking it, the vitamin b12 reserve can last for 2 to 4 years in your system [7].

Which fruit is rich in vitamin B12?

Most fruits and vegetables either lack or contain trace amounts of less than 0.1 mcg/100g. For instance, broccoli, asparagus, Japanese butterbur, mung bean sprouts, and Korean fermented vegetable kimchi contain traces of vitamin B12, which is not at all reliable for meeting the dietary requirement of B12 [20].

Written by

Sobin S. Gupta (MSc)

Sobin S. Gupta is a multifaceted professional—nutritionist, researcher, writer, and diabetes educator. She founded "Nutrition Meet," dedicated to educating the community on preventing and curing chronic diseases. With a passion for health and wellness, Sobin empowers individuals to take control of their well-being through informed dietary choices.

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