Chlorella Shown to Have B12 Activity in Humans—Caution Warranted

I have updated the article B12 in Plant Foods with a new study on B12 activity in Chlorella:

In a 2015 (USA) study, Merchant et al. fed 17 B12-deficient vegans and vegetarians a Chlorella pyrenoidosa supplement for 60 days (1). Average serum MMA levels decreased from 441 nmol/L at baseline to 301 nmol/L at 30 days and 297 nmol/L at 60 days. Average serum homocysteine levels decreased from 10.0 µm/L at baseline to 9.5 µmol/L at 30 days and 9.0 µmol/L at 60 days. No adverse effects were noted from the chlorella regimen.

Some caveats:

• Average serum MMA levels appeared to stabilize on this regimen at above recommended levels. B12 deficiency is generally defined as serum MMA levels above 270 nmol/L, the same standard used in this study by Merchant et al.

• The study was funded by Sun Chlorella Corporation of Japan and the lead author of the study is a paid consultant.

• A daily regimen of 45 Sun Chlorella A tablets (totaling 9 g) were used in this study. That amount of tablets would be quite costly. While it might require fewer than 45 tablets to achieve the same results, we can’t tell from this study.

In summary, it appears that at least some batches of chlorella have vitamin B12 activity, but it’s too soon to know how much chlorella vegans would require for optimal B12 status.


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1. Merchant RE, Phillips TW, Udani J. Nutritional Supplementation with Chlorella pyrenoidosa Lowers Serum Methylmalonic Acid in Vegans and Vegetarians with a Suspected Vitamin B(12) Deficiency. J Med Food. 2015 Oct 20. [Epub ahead of print] | link

4 Responses to “Chlorella Shown to Have B12 Activity in Humans—Caution Warranted”

  1. Christian Koeder Says:

    Yes, the 45 chlorella tablets per day seems unrealistic and expensive. But maybe this will make some vegans happy, so we can say “we could take chlorella, but cyanocobalamin is cheaper” 😉

    Also the chlorella “treatment” seemed to work for some, but not for others –>

    15 of 17 participants had MMA >271 nmol/L at baseline –> 9 (participants #1, 4, 6, 8, 12, 13, 14, 16, 17) out of these 15 could lower their MMA below 271 nmol/L

    – Note that MMA for participant #17 was lower at 30 days than at 60 days, i.e. inspite of increased intake of chlorella, MMA went up again but it stayed within the normal range.

    – Note that in all of these above participants with successful “MMA-response” (participants #1, 4, 6, 8, 12, 13, 14, 16, 17) the vitamin B12 serum concentration also increased.

    – Note that in 4 out of these 9 participants with good “MMA-response” homocysteine concentration was also corrected (went from above to below 10 µmol/L).

    7 of 17 participants had Hcy >10 µmol/L at baseline –> 4 (participants #1, 8, 14, 17) out of these 7 could lower their Hcy below 10 µmol/L

    That means only 15 of the 17 participants had increased MMA at the beggining, and out of those 9 could lower their MMA and 4 of could lower both MMA and Hcy by taking the 45 chlorella tablets.

  2. Jack Norris RD Says:


    Thanks for pointing this out. The chlorella seemed to make no difference for MMA levels for two of the participants who started out with elevated MMA levels. Participant #9 seems to have something odd going on given that he or she started with a very high B12 level and it went down over the course of the study. Participant #10’s B12 levels went up quite a bit, but so did their MMA levels; so they might have something else going on besides B12 deficiency causing their MMA levels to be elevated.

  3. soren Says:

    it might be a good idea to have a more prominent disclaimer when reporting small “n” reports that are not medically relevant.

    thanks for being evidence-based, jack!

  4. Linda Says:

    It sounds like participant 9 quit a B12 supplement in favor of the chlorella for the study. B12 tablets give a falsely high B12 serum blood test, showing only what is in the blood from the supplement and not what has reached the cells. When stopping B12 supplements, the falsely high serum level decreases over time. Chlorella (with active B12) may have increased the B12 level at cellular level, while not giving a falsely high serum level. See

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