Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Nori
Raw seaweed is 85% water, 6% protein, 5% carbohydrates, and has negligible fat (table). In a 100 gram reference amount, seaweed is a rich source (20% or more of the Daily Value, DV) of vitamin A, vitamin C, riboflavin, and folate (table). Seaweed is a moderate source (less than 20% DV) of niacin, iron, and zinc. Seaweed has a high content of iodine, providing a substantial amount in just one gram. A 2014 study reported that dried purple laver ("nori") contains vitamin B12 in sufficient quantities to meet the RDA requirement (Vitamin B12 content: 77.6 μg /100 g dry weight).