Can Cyanocobalamin Be Obtained from Plants? The Surprising Truth

October 31, 2025 •

2 min read

Approximately 52% of vegans have been reported to have vitamin B12 deficiency. A common misconception is that cyanocobalamin can be obtained directly from plants, but the reality is much more complex and depends on microbial life.

Quick Summary

Cyanocobalamin is synthesized by certain bacteria and archaea, not by plants. Natural food sources are almost exclusively animal-derived, requiring vegans and some vegetarians to rely on supplements or fortified products.

Key Points

Microbial Origin: Cyanocobalamin (Vitamin B12) is produced by specific bacteria and archaea, not by plants.
Animal Sources: Animals get B12 from bacteria in their environment or gut, concentrating it in their meat, dairy, and eggs.
Plant Unreliability: Trace amounts of B12 found in some plant foods are inconsistent and often mixed with inactive analogs.
Inadequate Absorption: Inactive B12 analogs, like those found in spirulina, can block the absorption of true B12 in humans.
Supplements and Fortified Foods: For vegans and vegetarians, supplements and fortified foods are the only dependable way to get cyanocobalamin.
Deficiency Risk: Failing to supplement can lead to serious health issues, including anemia and permanent neurological damage.

The Origin of Cyanocobalamin

Cyanocobalamin, a form of vitamin B12, is essential for human health, supporting nerve function, DNA synthesis, and red blood cell formation. However, plants cannot produce vitamin B12. Only certain bacteria and archaea synthesize this vitamin. Animals obtain B12 from these microbes, either through their diet or symbiotic gut bacteria, which is then passed to humans who consume animal products.

Unreliable Plant Sources and Analogs

While some plant-based foods have been claimed to contain B12, such as spirulina, nori, and tempeh, research indicates these are not reliable sources. Any trace amounts found may be due to soil contamination or inconsistent bacterial activity in fermentation. More often, these foods contain B12 "analogs" or "pseudovitamin B12". These compounds are similar to B12 but are inactive in humans and can even hinder the absorption of true B12. Some algae might contain true B12, but levels are highly variable.

Why are some plant foods linked to B12?

Potential reasons include:

Absorption from soil bacteria.
Bacterial activity during fermentation.
Contamination during processing.

Reliable Vegan Sources for Cyanocobalamin

Vegans must rely on fortified foods and supplements for sufficient cyanocobalamin. These contain bioavailable B12, often cyanocobalamin, produced through bacterial fermentation.

Reliable sources include:

Fortified Plant Milks.
Fortified Nutritional Yeast.
Fortified Breakfast Cereals.
B12 Supplements. The Vegan Society advises regular supplementation or consumption of fortified foods for all vegans.

Comparison of B12 Sources


Source Type	Natural Origin	Typical B12 Form	Reliability	Examples
Animal Products	Microbial synthesis (absorbed by animal)	Methylcobalamin, Adenosylcobalamin	High	Meat, Dairy, Eggs
Fortified Foods	Bacterial fermentation (synthetic)	Cyanocobalamin	High	Fortified cereals, Plant milks, Nutritional yeast
Supplements	Bacterial fermentation (synthetic)	Cyanocobalamin, Methylcobalamin	Very High	Oral tablets, Sublingual drops
Algae (e.g., Nori)	Microbial association	B12 and inactive analogs	Low (variable)	Dried purple laver
Fermented Foods	Bacterial activity (inconsistent)	Variable, often inactive analogs	Low (unreliable)	Tempeh, Kimchi
Mushrooms	Absorption from soil bacteria	Variable, some inactive forms	Low (unreliable)	Shiitake, Chanterelle

Conclusion

Cyanocobalamin is exclusively produced by bacteria and archaea, not by plants. Relying on trace amounts in some plant foods is unreliable due to inconsistency and inactive analogs. Therefore, vegans and many vegetarians need fortified foods or supplements to ensure adequate B12 intake for preventing deficiencies that can impact nervous system health and red blood cell production. The Vegan Society offers resources on intake strategies.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult with a healthcare professional regarding specific nutritional needs.

Frequently Asked Questions

Plants do not have the metabolic pathways necessary to synthesize cyanocobalamin, a process performed exclusively by certain bacteria and archaea.

Some seaweeds and algae, like certain nori, contain B12 due to a symbiotic relationship with bacteria. However, the amount is highly variable and inconsistent, and they can also contain inactive B12 analogs.

While some fermented foods like tempeh contain B12 from bacterial activity, the amount is often unreliable and can be overshadowed by inactive analogs, making it a poor primary source.

A B12 analog is a compound structurally similar to true vitamin B12 but is biologically inactive in humans. It can compete with and interfere with the absorption of active B12.

The only reliable vegan sources are B12 supplements and foods that have been fortified with the vitamin, such as plant-based milks, nutritional yeast, and some cereals.

Animals acquire B12 from the bacteria that produce it. Ruminants have symbiotic gut bacteria, while other animals consume soil particles or animal products containing the vitamin.

If not addressed, B12 deficiency can lead to megaloblastic anemia and irreversible neurological damage, which can affect memory, mood, and nerve function.