Alginate (HM-NA) is a highly viscous polysaccharide in brown algae. Depolymerized alginate (LM-NA) is less viscous with low molecular weight (∼50 kDa). Both alginates inhibited S. Typhimurium adhesion and invasion in HT-29-Luc cells. Both alginates (2%) in the diet suppressed S. Typhimurium infection in mouse liver. LM-NA (2.5%) drinking water inhibited S. Typhimurium infection in liver and spleen.