The Controversial Status of Seaweed and Vitamin B12
For many on a plant-based diet, finding reliable sources of vitamin B12 can be a challenge. Seaweed has long been touted as a potential natural source, but the scientific community has historically remained cautious due to the presence of inactive B12 analogues, or 'pseudovitamin B12,' in some species. However, more recent, robust studies have begun to clarify this picture, revealing that not all seaweeds are created equal when it comes to delivering this vital nutrient.
B12 in Nori: A Promising Source
Dried purple laver, more commonly known as nori and used for sushi, is one of the most promising seaweeds for B12. Multiple studies have confirmed that nori contains significant amounts of bioavailable B12. One study found that dried purple laver products contained approximately 30–60 μg of B12 per 100g dry weight, and a clinical trial showed that daily consumption improved B12 status in vegetarians.
Chlorella and Spirulina: The Cautionary Tales
In contrast to nori, other algae and seaweeds are less reliable. Both chlorella and spirulina are often marketed as B12 sources, but research shows significant issues with their content.
- Spirulina: Studies have consistently shown that spirulina contains a high proportion of inactive B12 analogues (pseudovitamin B12) that cannot be used by the human body. While some recent findings claim to have found active B12, the variability and risk of relying on a source with high pseudovitamin content make it an unreliable option.
- Chlorella: Some chlorella supplements have been shown to contain active B12, but its reliability and source are questionable. It is believed that chlorella absorbs B12 from its environment, often due to bacterial contamination during production, which makes the content highly variable.
Other Seaweed Varieties
Beyond nori, spirulina, and chlorella, other seaweeds offer little or no reliable B12. Varieties such as wakame, hijiki, kelp, and kombu are reported to contain none or only trace amounts of B12. This highlights the need for a nuanced understanding of each specific type of seaweed rather than treating them all as a single food group for B12 content.
Practical Considerations for Using Seaweed as a B12 Source
Even with promising research on nori, relying on seaweed for all your B12 needs carries some practical challenges and risks. The variability in B12 content due to factors like harvesting location, drying process, and season remains a concern. Furthermore, excessive consumption of seaweed can lead to harmful levels of iodine intake, which can negatively affect thyroid function. For consistent and optimal B12 status, especially for those on long-term vegetarian or vegan diets, a combination of fortified foods and reliable supplementation is generally recommended by health experts. Nori can be a supportive addition to a B12-conscious diet but should not be the sole foundation.
Conclusion
To conclude, how much B12 is in seaweed depends entirely on the type. While species like dried purple laver (nori) contain substantial and bioavailable amounts of B12, others such as spirulina contain mostly inactive pseudovitamin B12. Western nutritional bodies remain cautious about recommending seaweed as a sole source due to inconsistencies and the risk of consuming inactive analogues. Recent human trials, particularly with roasted nori, are promising, but until more conclusive evidence emerges, relying on fortified foods and supplements for B12 is the safest approach for those with dietary restrictions. Including nori in moderation can contribute to your intake, but a balanced strategy is best for maintaining optimal B12 health. For further reading on the bioavailability of B12 from different sea vegetables, refer to sources from reputable nutrition organizations and recent scientific studies like those found on PubMed. Additional information on plant-based B12 sources can be found on {Link: Vegan Health website https://veganhealth.org/vitamin-b12/vitamin-b12-plant-foods/}.
