This document provides methods and materials for reducing amyloid beta levels within a mammal (e.g. a mammal having Alzheimer's disease). For example, this document provides methods for using compositions containing a potato polysaccharide preparation to reduce one or more symptoms of Alzheimer's disease. In some cases, a composition containing a potato polysaccharide preparation provided herein can be used to increase binding, sequestration, and/or degradation of CNS-derived amyloid beta polypeptides, thereby inhibiting the formation of neurofibrillary plaques.