By Reed Mangels, PhD, RD

Vitamin B12 in supplements may be in the form of cyanocobalamin, methylcobalamin, adenosylcobalamin, or hydroxocobalamin. Note that cobalamin means vitamin B12. The cobalamin molecule is bound to different side groups. For example, methylcobalamin has cobalamin attached to methyl (CH₃). Of these, the cyanocobalamin form is the most stable and is least likely to lose potency with time.

When foods are fortified with vitamin B12, it is likely that they are fortified with cyanocobalamin because it is the most stable form of the vitamin (1, 2). Cyanocobalamin is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (3).

References

1. Temova Rakuša Ž, Roškar R, Hickey N, Geremia S. Vitamin B₁₂ in foods, food supplements, and medicines-A review of its role and properties with a focus on its stability. Molecules. 2022;28(1):240.
2. Oh S, Cave G, Lu C. Vitamin B₁₂ (cobalamin) and micronutrient fortification in food crops using nanoparticle technology. Front Plant Sci. 2021;12:668819.
3. 21CFR184.1945. Vitamin B12. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=184.1945

To read more about vitamin B12 see:

Vitamin B12 in the Vegan Diet

Do Vegetarians Have To Take Vitamin B12 Supplements?

Vitamin B12 Myths