Silicon reduces aluminum accumulation in rats: Relevance to the aluminum hypothesis of Alzheimer disease

In recent years, a possible relation between the aluminum and silicon level s in drinking water and the risk of Alzheimer disease (AD) has been establi shed. It has been suggested that silicon may have a protective effect in li miting oral aluminum absorption. The present study was undertaken to examin e the influence of supplementing silicon in the diet to prevent tissue alum inum retention in rats exposed to oral aluminum. Three groups of adult male rats were given by gavage 450 mg/kg/day of aluminum nitrate nonahydrate 5 days a week for 5 weeks. Concurrently, animals received silicon in the drin king water at 0 (positive control), 59, and 118 mg Si/L. A fourth group (-A l, -Si) was designated as a negative control group. At the end of the perio d of aluminum and silicon administration, urines were collected for 4 conse cutive days, and the urinary aluminum levels were determined. The aluminum concentrations in the brain (various regions), liver, bone, spleen, and kid ney were also measured. For all tissues, aluminum levels were significantly lower in the groups exposed to 59 and 118 mg Sin than in the positive cont rol group; significant reductions in the urinary aluminum levels of the sam e groups were also found. The current results corroborate that silicon effe ctively prevents gastrointestinal aluminum absorption, which may be of conc ern in protecting against the neurotoxic effects of aluminum.