Based on our recent re-analysis of vitamin B12 needs, Vitamin B12: Rationale for Recommendations, in which we determined that MMA levels below 270 nmol/l were not necessary for someone to have adequate B12 status, we revisited a 2015 clinical trial using chlorella.
In that trial, B12 levels in the B12-deficient vegan and vegetarian participants decreased from 441 nmol/l at baseline to 301 nmol/l after 30 days of taking chlorella, which we believe shows meaningful B12 activity. The study was funded by the Sun Chlorella Corporation of Japan, and the lead author of the study is a paid consultant by the company.
While it’s too soon to recommend chlorella as a reliable source of B12 for vegans, it’s not out of the question if future, independent research confirms these findings. More details can be found in the Chlorella section of our article B12 in Plant Foods.