Is Duckweed a Source of Vitamin B12?

Reports of a new plant source of vitamin B12 are making the rounds on the internet. The plant in question is duckweed, an aquatic plant also known as water lentils. One company in Florida has announced that the duckweed grown in their ponds was found to contain vitamin B12 and that the B12 is also found in their commercial product Lentein.

We want to advise a little caution before you ditch your B12 supplements.

At this time, the B12 sourced from duckweed hasn’t been studied to determine if it has actual vitamin B12 activity. Without research showing that the vitamin B12 from duckweed can reverse deficiency, we can’t say anything about its value for humans. The company agrees that these tests are needed.

Right now, the research on duckweed as a source of vitamin B12 is limited. Only one published study has measured the amount of vitamin B12 in duckweed (1). In this study, male subjects consumed a cutlet made from duckweed that reportedly contained 2.81 micrograms of vitamin B12 per serving, which is just a little bit more than the RDA. However, the food wasn’t tested for overall B12 activity (2, 3). This is always necessary to absolutely determine if the B12 found in a food is active for humans and that no inactive B12 analogs are interfering with its activity.

While it’s common for aquatic plants to be contaminated with bacteria that can produce vitamin B12, these researchers suggested that bacteria inside the plant are producing vitamin B12 (1, 3), which is a unique finding. But we don’t know if all duckweed contains these bacteria. And given that only a few strains of bacteria produce vitamin B12, it seems unlikely that one of these types of bacteria just happens to be living inside duckweed plants. And if so, there is the possibility that the bacteria also produce analogs, which could interfere with B12 activity.

None of this is to say that it’s not possible that duckweed will turn out to be a source of vitamin B12. But right now, we need much more information before we can conclude that it’s a reliable source of the vitamin. Multiple batches of duckweed need to be tested for B12 content and we need studies to determine if the B12 is active.

Even if duckweed turns out to be a reliable source of B12 for vegans, it probably doesn’t change much in terms of advice for vegans, because it’s unlikely that all vegans will start eating duckweed products on a regular basis as a way to get vitamin B12. Most of us will still choose to get vitamin B12 from supplements and fortified foods given that these approaches are simple, accessible, and proven to support healthy B12 status.

We’ll be watching the story on duckweed and have added a section on the topic to the Vegan Health website.

References

1. Kaplan A, Zelicha H, Tsaban G, et al. Protein bioavailability of Wolffia globosa duckweed, a novel aquatic plant – A randomized controlled trial. Clin Nutr. 2019 Dec;38(6):2576-2582.

2. Jahreis G, Appenroth KJ, Sree KS, Dawczynski C. Letter to original article by Kaplan et al. 2018 – Protein bioavailability of Wolffia globosa duckweed, a novel aquatic plant, A randomized controlled trial. Clin Nutr. 2019 Oct;38(5):2463. 

3. Kaplan A, Lapidot M, Sela I, Shai I. RE: Protein bioavailability of Wolffia globosa duckweed, a novel aquatic plant, a randomized controlled trial. Clin Nutr. 2019 Oct;38(5):2464.