An activist brought to my attention the article B12 Deficiencies in Vegans? Not True! at Flaming Vegan. I was surprised to read the article and the comments, and so I posted some comments of my own below it.

Another reader brought my attention to a page claiming that miso is a source of vitamin B12 and that chlorella is the “best source” of vitamin B12.

As for miso, the two published studies that have measured vitamin B12 in miso have found none. As for chlorella, two studies have found vitamin B12 in batches of chlorella while one study found practically none. Chlorella might be a source of vitamin B12, but there has yet to be any studies in the scientific literature to determine if chlorella can improve vitamin B12 status (see B12 in Tempeh, Seaweeds, Organic Produce, and Other Plant Foods for citations).

It is not clear why chlorella would have vitamin B12 – whether through contamination or because it actually produces it, and because of this, multiple batches from different locations should be tested before there is any certainty that it is a reliable source.

It should also be noted that the second link above lists romaine and arugula as sources of calcium. According to the USDA, one cup of shredded romaine has only 15 mg of calcium and one cup of arugula has 32 mg of calcium. So if you are going to rely on either for calcium, you will need to eat many servings.