A method and composition is described for prevention or treatment of Type II Diabetes Mellitus and its complications comprising the step of administering to a mammal an amount of seaweed extract in effective doses. The seaweed is selected from the group consisting of brown algae, red algae and green algae, wherein the seaweed extract contains a polysaccharide. Optionally, the polysaccharide is Rhamnose, in approximately 63-78 mole %. The seaweed extract optionally also contains approximately 6.5-9.2 mole % Xylose. Optionally, Rhamnose and Xylose are present in the seaweed extract in amounts in a ratio of approximately 12 Rhamnose to 1 Xylose and 8 Rhamnose to 1 Xylose. Preferably, the Rhamnose (algopolysaccharide) is sulfinated. Optionally, the seaweed extract is mixed with food stuffs such as cereals, bread, drinks, health bars, juices, concentrates, canned food, ice cream, water, staple goods such as wheat, corn, barley, and oat in any form, or taste maskers such as sugar or ascorbic acid.