Seaweed (unspecified species) has some scientific evidence supporting its use for supporting the large intestines (colon) body system, mainly due to its high content of dietary fibers known as polysaccharides (such as alginates, fucoidans, and carrageenans). These fibers are largely indigestible by human enzymes but can be fermented by gut microbiota in the colon, leading to the production of short-chain fatty acids (SCFAs) like butyrate, which support colonic health and have anti-inflammatory properties.

Several studies have shown that seaweed-derived fibers can act as prebiotics, enhancing the growth of beneficial bacteria in the gut. For example, a 2016 review in Marine Drugs outlined that seaweed polysaccharides can modulate gut microbiota composition and improve intestinal barrier function. Animal and some human studies suggest potential benefits like improved bowel regularity, reduced risk of colorectal cancer, and mitigation of inflammatory bowel disease symptoms. However, most clinical trials are small or preliminary, and the effects may vary by seaweed species and preparation.

In summary, while traditional use also exists in some cultures for digestive health, the justification for seaweed supporting colon health is primarily based on emerging scientific evidence related to its fiber content and prebiotic effects. More large-scale, controlled human studies are needed for stronger conclusions.