Can vegans get sufficient vitamin B12 from kombucha alone?

Answer: Probably not (unless you’re drinking a B12 fortified kombucha).

One of my friends, who is a vegan, mentioned recently that kombucha might be a good source of vitamin B12. Confusingly, when we went to a local market, we encountered numerous brands of kombucha that did not mention vitamin B12 on the nutrition label. Only a single brand had a substantial amount of Kombucha (Humm). We couldn’t figure out why this brand was different – if it was a special SCOBY they used or some other production secret.

As a brief introduction, kombucha is tea fermented with co-cultures of yeast and bacteria. The specific yeast and bacteria vary from study to study but almost always include the bacteria Komagataeibacter xylinus (formerly Gluconacetobacter xylinus). This bacteria ferments alcohols produced by other yeasts into organic acids such as acetic acid, which increases kombucha acidity and limits ethanol content. For those interested Jayabalan et al. review the microbiology and composition of kombucha. In their review, Jayabalan et al. discuss an older study by Bauer-Petrovska et al. quantifying water-soluble vitamins in kombucha. This study showed that kombucha made with black tea and sucrose contained ” vitamin B₁ 74 mg/100 mL, vitamin B₆ 52 mg/100 mL, vitamin B₁₂ 84 mg/100 mL, and vitamin C 151 mg/100 mL.” A typical 16 fluid ounce container of kombucha is around 500 mL (473.2 mL), for an estimated 400 mg of vitamin B12 per bottle. The recommended daily allowance of vitamin, B12 is 2.4 mcg/day so a bottle should exceed the RDA by an astounding 166,000 times. A more recent study from Turkey by Arikan et al. determined that the mechanism was biologically plausible; Komagataeibacter indeed “carrries complete pathways for the biosynthesis of vitamin B1, vitamin B7, vitamin B12 “

Wanting to investigate this further, we directly contacted Humm. To our surprise, we actually received a reply! It turns out that “due to inconsistencies in the vitamin levels that naturally occur in our kombucha, we add Vitamin B12 to provide 1,000% of recommended daily intake of Vitamin B12.  Accurate labeling is extremely important to us, as is the consistency and quality of our kombucha.” It’s like the natural variability was also too high from other brands that did not supplement vitamin B12 to make any claims on the nutrition label. The full reply from Humm is below:

Of course, this doesn’t indicate whether or not kombucha is a good source of B12 in practice. A small study (n=42) from Romania by Zugravu et al. compared different strategies of vitamin B12 supplementation in vegans. This study found that vitamin B12 supplementation was superior to supplementation with alternative products (algae, kombucha, other fermented products).

My overall conclusion is that for vegans, vitamin B12 supplements are probably still superior to drinking kombucha alone. Although the mechanism of vitamin B12 in kombucha is plausible, the response from Humm suggests that actual vitamin B12 levels in Kombucha vary wildly in practice. Furthermore, the limited clinical evidence seems to suggest that vitamin B12 supplements are superior to alternative strategies of supplementation.

Note: Humm’s email also mentions they supplement with the “natural” form of vitamin B12, methylcobalamin. Cyanocobalamin (often derided as “synthetic” B12) is readily converted to methylcobalamin in the body. Per Zugravu et al., cyanocobalamin supplementation was actually superior to methylcobalamin supplementation for maintaining serum B12 levels.

References:

1. https://www.reddit.com/r/Kombucha/comments/6op8kd/why_does_humm_kombucha_have_such_insane_amounts/
2. Jayabalan R, Malbaša RV, Lončar ES, Vitas JS, Sathishkumar M. A Review on Kombucha Tea-Microbiology, Composition, Fermentation, Beneficial Effects, Toxicity, and Tea Fungus. Compr Rev Food Sci Food Saf. 2014 Jul;13(4):538-550. doi: 10.1111/1541-4337.12073. PMID: 33412713.
3. Arıkan M, Mitchell AL, Finn RD, Gürel F. Microbial composition of Kombucha determined using amplicon sequencing and shotgun metagenomics. J Food Sci. 2020;85(2):455-464. doi:10.1111/1750-3841.14992
4. Zugravu CA, Macri A, Belc N, Bohiltea R. Efficacy of supplementation with methylcobalamin and cyancobalamin in maintaining the level of serum holotranscobalamin in a group of plant-based diet (vegan) adults. Exp Ther Med. 2021;22(3):993. doi:10.3892/etm.2021.10425