Vitamin B(12) concentrations of dried green (Enteromorpha sp.) and purple (Porphyra sp.) lavers nori were determined, in micrograms: 

• green nori: 64 - 69 mcg per 100 g of dry weight,
• purple nori: 32 - 25 mcg per 100 g of dry weight.

Non-coenzyme forms (hydroxo and cyano forms) of vitamin B12 predominate in both. 

Recommended dietary amounts (RDAs) for cobalamin, B12, are 2.4 mcg (micrograms) daily, one can cover it with 4 g of dry green nori. 

The dried lavers contained lesser amounts of dietary iodine (~ 4-6 mg per 100 g of dry weight) relative to other seaweeds, suggesting that excessive intake of the dried lavers is unlikely to result in harmful intake of iodine.

These results indicate that the nori are the best source of vitamin B12 among edible seaweeds, especially for strict vegetarians (vegans).