Silicon is an essential element for some lower forms of life. However, it is not generally considered an essential nutrient for mammals and the mechanisms underlying its potential essentiality remain partially unknown. In recent years, a possible association between the aluminum and silicon levels in drinking water and Alzheimer's disease (AD) has been suggested. It has been reported that silicon might have a protective effect for limiting oral aluminum absorption. This review is focused primarily on the potential role of silicon in preventing oral aluminum absorption and retention in mammals. The results of a number of studies suggest that dietary silicon supplementation could be of therapeutic value for preventing chronic aluminum accumulation in the brain, and hence, be a potential therapy for AD. However, it must be noted that controversy remains about whether aluminum accumulation in the brain is a cause or a consequence of AD. It is suggested that further investigation of this issue is warranted.