Which Vitamin B12 is Non Synthetic? Understanding the Natural Forms

October 13, 2025 •

4 min read

Methylcobalamin, adenosylcobalamin, and hydroxocobalamin are the natural, non-synthetic forms of vitamin B12 found in food and used in supplements, while cyanocobalamin is the synthetic version. Understanding the differences is crucial for choosing a supplement, especially for individuals on vegan or vegetarian diets.

Quick Summary

Naturally occurring forms of vitamin B12 include methylcobalamin, adenosylcobalamin, and hydroxocobalamin. Cyanocobalamin is a synthetic form requiring conversion in the body. The natural versions are readily bioavailable, while the synthetic option offers greater stability and lower cost.

Key Points

Natural vs. Synthetic: Methylcobalamin, adenosylcobalamin, and hydroxocobalamin are non-synthetic, while cyanocobalamin is synthetic.
Active Coenzyme Forms: Methylcobalamin and adenosylcobalamin are the two forms of B12 that the body uses directly, meaning they don't require conversion.
Found in Food: Natural B12 is primarily found in animal products like meat, fish, eggs, and dairy, as well as some fortified plant foods.
Conversion Process: The synthetic cyanocobalamin must be converted by the body into the active forms, a process that can be less efficient in some individuals.
Cost and Stability: Synthetic cyanocobalamin is generally cheaper and more stable, leading to its widespread use in fortified foods and many supplements.
Individual Needs: The best form of B12 depends on a person's diet, genetics, and overall health, with natural forms often preferred by those with methylation sensitivities or certain health issues.
Consult a Professional: Always talk to a healthcare provider before starting a new vitamin B12 supplement to determine the right choice for your specific needs.

What is Vitamin B12?

Vitamin B12, also known as cobalamin, is an essential water-soluble vitamin vital for numerous bodily functions, including red blood cell formation, DNA synthesis, and neurological function. The body cannot produce it, and it is primarily obtained through animal products in the diet or via supplementation. The term 'vitamin B12' refers to a group of compounds, but the forms vary significantly in their origin, conversion, and bioavailability.

The Natural, Non-Synthetic Forms

Several forms of vitamin B12 are considered natural and non-synthetic, as they are found in nature, particularly in animal-based foods. These are also the active forms of the vitamin that the human body uses for metabolic processes.

Methylcobalamin: Often referred to as 'activated B12', methylcobalamin is one of the two active coenzyme forms of vitamin B12 in the body. It is primarily involved in methylation reactions, which are critical for DNA synthesis, cognitive function, and homocysteine metabolism. It is found in animal products like meat, eggs, and fish and is a popular supplement choice due to its high bioavailability. Some people believe methylcobalamin is superior to the synthetic form because it does not require conversion, making it more readily available for use by the body's cells.
Adenosylcobalamin: The other active coenzyme form, adenosylcobalamin, is predominantly found in the mitochondria, the powerhouse of cells. It plays a crucial role in energy production, specifically in the metabolism of fatty acids and amino acids. Both adenosylcobalamin and methylcobalamin are essential for overall health and are often combined in high-quality supplements to provide comprehensive B12 support.
Hydroxocobalamin: Found naturally in foods, hydroxocobalamin is produced by bacteria in the digestive tract. It is efficiently converted into the active forms (methylcobalamin and adenosylcobalamin) within the body and is a common form used for prescription B12 injections, particularly for treating severe deficiencies. It is considered highly bioavailable.

The Synthetic Form: Cyanocobalamin

Cyanocobalamin is the most common form of vitamin B12 used in dietary supplements and fortified foods due to its stability and lower cost. However, it is a synthetic compound not found in significant amounts in nature. The key characteristics include:

Conversion Required: The body must convert cyanocobalamin into the active coenzyme forms, methylcobalamin and adenosylcobalamin, before it can be used. This process is efficient for most healthy individuals, but it may be less effective for those with certain genetic variations or impaired detoxification pathways.
Contains a Cyanide Molecule: Cyanocobalamin contains a small, non-toxic cyanide molecule. While the amount is negligible for most people, the body must still remove and detoxify this compound, requiring extra metabolic effort. For individuals with compromised health, such as smokers with high cyanide exposure, natural forms are often preferred.
Cost-Effectiveness and Stability: Its chemical stability makes it resistant to degradation from heat and light, which is why it is often used in multivitamin supplements and for food fortification.

Comparison of Non-Synthetic vs. Synthetic B12


Feature	Methylcobalamin	Adenosylcobalamin	Hydroxocobalamin	Cyanocobalamin
Origin	Natural, found in food	Natural, found in food	Natural, found in food	Synthetic, not natural
Body Conversion	Active coenzyme, no conversion needed	Active coenzyme, no conversion needed	Converts to active forms	Converts to active forms
Bioavailability	High, readily absorbed	High, well-absorbed	High, used for injections	Good absorption, but lower retention
Retention	Retained well by tissues	High retention	Excellent retention	High urinary excretion
Stability	Less stable; sensitive to light	Less stable; sensitive to light	Good stability	Most stable; less affected by heat, light
Side Chain	Methyl group	5'-deoxyadenosyl group	Hydroxyl group	Cyanide group
Cost	Generally more expensive	Generally more expensive	Varies	Least expensive

Sources of Natural Vitamin B12

The primary source of naturally occurring, non-synthetic vitamin B12 is animal products. This is because bacteria in the digestive tracts of animals produce cobalamin, which is then concentrated in their tissues.

Meats and Poultry: Beef, liver, and poultry are excellent sources.
Fish and Seafood: Clams, mussels, salmon, and tuna are exceptionally rich in B12.
Dairy Products: Milk, yogurt, and cheese contain moderate amounts.
Eggs: A good source, particularly the yolk.
Certain Algae and Mushrooms: Some plant sources, such as dried purple laver (nori) and certain mushrooms like shiitake, have been found to contain bioavailable vitamin B12. However, the content can be highly variable and may not be sufficient to meet all needs, especially for vegans.

Choosing the Right Form

The choice between natural and synthetic B12 often depends on individual needs and health status. While the body can effectively convert cyanocobalamin, those who are sensitive to methylated nutrients or have certain genetic mutations may prefer non-methylated, natural forms. Some researchers suggest that natural forms like methylcobalamin may offer higher retention rates. Conversely, cyanocobalamin is a reliable and cost-effective option for many.

For Vegans and Vegetarians: Since B12 is primarily found in animal products, fortification and supplementation are essential for those following plant-based diets. Nutritional yeast and fortified breakfast cereals are common sources, but supplements are often necessary to ensure adequate intake. Natural forms like methylcobalamin are popular choices for vegan supplements.
For Medical Conditions: In specific medical cases, such as those with certain genetic disorders affecting B12 metabolism, hydroxocobalamin injections may be recommended. For those with impaired absorption due to digestive issues, injections or high-dose oral supplements may be necessary.

For anyone considering a new supplement, it is best to consult a healthcare professional to determine the most appropriate form and dosage.

Conclusion

Understanding which vitamin B12 is non synthetic, namely methylcobalamin, adenosylcobalamin, and hydroxocobalamin, helps consumers make informed decisions about supplementation. These natural forms are readily utilized by the body and are abundant in animal-based food sources. The synthetic alternative, cyanocobalamin, is stable and widely available but requires metabolic conversion. While both natural and synthetic forms can be effective, individual needs related to diet, genetics, and health conditions can influence the best choice for supplementation. Consulting a healthcare provider is the most reliable way to navigate these options and address any potential deficiency.

Frequently Asked Questions

The natural, non-synthetic forms of vitamin B12 are methylcobalamin, adenosylcobalamin, and hydroxocobalamin. These forms are found in animal products and are the same ones used by the human body for metabolic functions.

Methylcobalamin is a naturally occurring, active form of B12, while cyanocobalamin is a synthetic form created in a lab. Cyanocobalamin must be converted by the body into an active form, while methylcobalamin can be used directly.

For most people, cyanocobalamin is safe and effective. However, the body must convert it to active forms, and it contains a trace amount of cyanide that needs to be detoxified. Some individuals may have lower absorption or higher excretion rates with cyanocobalamin compared to natural forms.

Excellent sources of natural vitamin B12 include animal products like beef liver, clams, fish (salmon, tuna), meat, eggs, and dairy products. Some fortified foods, like cereals and nutritional yeast, also contain B12.

Yes, because natural vitamin B12 is found almost exclusively in animal products, vegans and vegetarians are at a higher risk of deficiency and often need to take a supplement or consume fortified foods to meet their needs.

Adenosylcobalamin is the form of vitamin B12 stored in the mitochondria, where it plays a critical role as a coenzyme in the metabolism of fatty acids and amino acids for energy production.

Hydroxocobalamin, a natural and highly bioavailable form of vitamin B12, is often used for medical injections to treat severe deficiencies, as it is readily converted into active B12 forms by the body.