Seaweed is sustainable and protein-packed, but how much of that protein can you digest?
07 Sep 2026 - Rosie de Laune
Seaweed appears to be a sustainable and nutritious food source, but there can be significant differences between the protein content of a food, and how much your body can absorb. This study is the first to use a multi-length-scale approach to find out whether the proteins in seaweed are accessible by the human body through gastrointestinal digestion and understand the structural changes taking place during this physiological process.
Seaweed is recognised as a sustainable food source as its growth does not require land, freshwater or fertilisers. While they are commonly used in food as thickeners and gelling agents, they also present high protein content, which is not currently taken advantage of. Some varieties contain almost 50% protein when dried, which is higher than the protein content in other plant-based protein sources such as legumes (20-30%) or tofu (5-15%).
However, protein nutritional quality doesn’t just depend on the composition of the raw material, but also on digestibility and bioavailability. Not much is known about this for seaweed, and developing this understanding requires an advanced analytical approach, capable of resolving digestion-induced structural transformations across multiple length scales, from molecular arrangements to nano- and micrometre-scale cellular architecture.
In this study, published in Food Hydrocolloids, the researchers aimed to find out what happens during digestion of Nori seaweed. They used a variety of techniques, combining conventional biochemical analysis with large-scale facility experiments funded by the ReMade@ARI project.
They subjected dehydrated seaweed to in vitro gastrointestinal digestion, producing digested samples effectively taken after the stomach, and after the small intestine. They also considered different bile salt concentrations in the intestinal phase, as this is something that varies between different people and depending on how much they have eaten (if they are in a fasted or fed state).
They used Small Angle Neutron Scattering on SANS2D at ISIS to look at the nanostructural changes caused during the gastric and intestinal stages. By using different mixes of H2O and D2O, they could change the contrast between the different nanoscopic components of the seaweed and the liquid phase.
In the original seaweed sample, they saw evidence of hybrid polysaccharide-protein networks. These were still visible, although much less defined, in the gastric sample and were completely absent after intestinal digestion. This supports the biochemical measurements that suggest a minor fraction of proteins were released from the seaweed during the gastric phase, while most of them were released during the intestinal phase. They also found from their in vitro digestion studies that different bile concentrations had an influence on the level of digestion that took place during the intestinal phase, while bile salts promoting solubilisation of proteins and polysaccharides and increasing the degree of digestion.
Their results show that Nori seaweed is a good alternative non-animal protein source because of its high fibre and protein levels, as well as its low fat content. Crucially, its proportion of essential amino acids is comparable to that found in many animal protein sources, and its protein digestibility is similar to that from widely consumed plant-based sources.
Interestingly, histidine was the amino acid with the smallest concentration, unlike other more popular foods like eggs, meat, fish or soy-based products. So, they would recommend keeping the tofu, eggs or fish on your sushi rather than just eating the Nori outside!
The full paper can be found at DOI: 10.1016/j.foodhyd.2026.113284
Access to the large-scale facilities for this study was funded by ReMade@ARI, part of the EU Commission’s Horizon Europe programme and co-funded by UK Research and Innovation (UKRI) and by the Swiss State Secretariat for Education, Research and Innovation. The project provides scientists who are working on the design of new recyclable materials with analytical tools that enable them to explore the properties and the structure of their material in smallest details up to atomic resolution.
