Silica is the most common mineral in the earth's crust and is found in rocks, sand and, in minimal quantities, in mineral water.

In recent years, interest in the potential role of metals in the pathogenesis of Alzheimer's disease (AD) has grown considerably. In particular, aluminum (Al) neurotoxicity was suggested after its discovery in the senile plaques and neurofibrillary tangles that represent the principal neuropathological hallmarks of AD. Al is omnipresent in everyday life and can enter the human body from several sources, most notably from drinking water and food consumption. The evidence supporting association from ingestion of Al from drinking water is somewhat stronger than for its ingestion from food. However, other elements present in drinking water, such as fluoride, copper, zinc, or iron could also have an effect on cognitive impairment or modify any Al neurotoxicity. Some epidemiological studies, but not all, suggested that silica could be protective against Al damage, because it reduces oral absorption of Al and/or enhances Al excretion. Some epidemiological investigations suggested an association between chronic exposure to Al and risk of AD, although this relationship falls short of all the criteria generally attributed to causation. Future studies need to be more rigorous to truly test the validity of previous findings and in doing so attempt to identify dose-response relationships between Al and AD risk which may provide new routes to disease-modifying treatment of AD or possibly some lifestyle modification, to supplement existing symptomatic approaches (1).

The authors of this study examined associations between exposure to aluminum or silica from drinking water and risk of cognitive decline, dementia and Alzheimer’s disease. Subjects were followed-up for 15 years with an active search for incident cases of dementia, aged 65 years and over living in 91 civil drinking water areas in Southern France. Two measures of exposure to aluminum were assessed: a geographical exposure and an individual exposure taking into account the daily consumption of tap and bottled water. A total of 1,925 subjects free from dementia at baseline and with reliable water assessment were analyzed.

Using random effects models, cognitive decline with time was greater in subjects with a higher daily aluminum intake from drinking water (≥ 0.1 mg/day, p = 0.005) or a higher geographical exposure to aluminum. Using a Cox model, a high daily intake of aluminum was significantly associated with increased risk of dementia. Conversely, an increase of 10 mg/day in silica intake was associated with a reduced risk of dementia (adjusted RR = 0.89, p = 0.036). However, the geographical exposure to aluminum or silica from tap water was not associated with dementia. High consumption of aluminum from drinking water may be a risk factor for Alzheimer’s disease (2).

There has been a plausible link between human exposure to aluminum and Alzheimer's disease for several decades. We contend that the only direct and ethically acceptable experimental test of the 'aluminum hypothesis', which would provide unequivocal data specific to the link, is to test the null hypothesis that a reduction in the body burden of aluminum to its lowest practical limit would have no influence upon the incidence, progression, or severity of Alzheimer's disease. This study have provided preliminary evidence that over 12 weeks of silicon-rich mineral water therapy the body burden of aluminum fell in individuals with Alzheimer's disease and, concomitantly, cognitive performance showed clinically relevant improvements in at least 3 out of 15 individuals. This is a first step in a much needed rigorous test of the 'aluminum hypothesis of Alzheimer's disease' and a longer term study involving many more individuals is now warranted (3).

 Silicon has been suggested to exhibit roles in the structural integrity of nails, hair, and skin, overall collagen synthesis, bone mineralization, and bone health and reduced metal accumulation in Alzheimer's disease, immune system health, and reduction of the risk for atherosclerosis (4).

The objective of this study was to investigate at baseline the potential association between the composition of drinking water and the level of cognitive function in women taking part in the Epidemiology of Osteoporosis (EPIDOS) Study and to determine during follow-up the effects of the composition of drinking water on the risk of Alzheimer disease. Silica in drinking water may reduce the risk of developing AD in elderly women. The results corroborate those of another epidemiologic study carried out in France. The potential effect of silica needs to be confirmed in additional investigations (5).

A nutritional-based strategy has been proposed in order to improve cognitive performance of Alzheimer's disease (AD) patients. The strategy requires daily dietary supplementation with magnesium (Mg), folic acid, and vitamins B6 and B12, daily consumption of silicic acid-rich mineral water in order to lower the body burden of Al, and several plasma exchange procedures in order to replace Aβ-bound albumin with fresh albumin. Evidence suggests that the deteriorating cognitive performance associated with AD may be improved by supplementation with either Mg alone or with the combination of the above three B vitamins (B vitamin combo), or by drinking silicic acid-rich mineral water, or by undergoing plasma exchange. However, for the following reasons the combination of all four therapeutic approaches may have a synergistic effect on improving cognitive performance of AD patients (6).

However, when choosing mineral water, it is not prudent to stop at the lower or higher value of an interesting mineral salt, but make sure that there are no excessive amounts of other mineral salts in contrast to the needs of your body. Always ask your doctor.

In this video, the values of the Silica content of 40 Italian Mineral Waters. I would like to remind you that the values of mineral salts in mineral waters change very little over the years.

References_____________________________________________________________

(1) Aluminum in the diet and Alzheimer's disease: from current epidemiology to possible disease-modifying treatment.  Frisardi V, Solfrizzi V, Capurso C, Kehoe PG, Imbimbo BP, Santamato A, Dellegrazie F, Seripa D, Pilotto A, Capurso A, Panza F.  J Alzheimers Dis. 2010;20(1):17-30. doi: 10.3233/JAD-2009-1340. Review.

(2) Aluminum and silica in drinking water and the risk of Alzheimer's disease or cognitive decline: findings from 15-year follow-up of the PAQUID cohort.  Rondeau V, Jacqmin-Gadda H, Commenges D, Helmer C, Dartigues JF. Am J Epidemiol. 2009 Feb 15;169(4):489-96. doi: 10.1093/aje/kwn348. Epub 2008 Dec 8.

(3) Silicon-rich mineral water as a non-invasive test of the 'aluminum hypothesis' in Alzheimer's disease.  Davenward S, Bentham P, Wright J, Crome P, Job D, Polwart A, Exley C.  J Alzheimers Dis. 2013;33(2):423-30. doi: 10.3233/JAD-2012-121231. 

(4) Silicon: the health benefits of a metalloid.  Martin KR.  Met Ions Life Sci. 2013;13:451-73. doi: 10.1007/978-94-007-7500-8_14. Review.

(5) Cognitive impairment and composition of drinking water in women: findings of the EPIDOS Study.  Gillette-Guyonnet S, Andrieu S, Nourhashemi F, de La Guéronnière V, Grandjean H, Vellas B.  Am J Clin Nutr. 2005 Apr;81(4):897-902.

Domingo JL, Gómez M, Colomina MT. Oral silicon supplementation: an effective therapy for preventing oral aluminum absorption and retention in mammals. Nutr Rev. 2011 Jan;69(1):41-51. doi: 10.1111/j.1753-4887.2010.00360.x. 

The potential influence of silica present in drinking water on Alzheimer's disease and associated disorders.  Gillette Guyonnet S, Andrieu S, Vellas B.  J Nutr Health Aging. 2007 Mar-Apr;11(2):119-24. Review.

(6) A multipronged, nutritional-based strategy for managing Alzheimer's disease.  Glick JL, McMillan PA.  Med Hypotheses. 2016 Jun;91:98-102. doi: 10.1016/j.mehy.2016.04.007.