Drinking Water and Alzheimer's

Summarized by Robert W. Griffith, MD
July 13, 2005

Introduction

Alzheimer's continues to be seen more frequently as people survive to greater age. In spite of great efforts, the cause of the condition is still obscure. Genetic factors play a role in some cases, and other risk factors (obesity, lack of cerebral activity, smoking, and so on) are well recognized.

The concentration of aluminum in drinking water has been a popular risk factor, although somewhat discounted in recent years as epidemiological studies have yielded conflicting results. This may have been because the relationship between aluminum in drinking water and dementia is very dependant on the presence of silica and the acidity of the water. When the aluminum and the acidity is high and the silica is low, the risk of dementia is increased; conversely, a high aluminum level with low acidity and a high silica level is linked to lessened risk of dementia. A study done in Toulouse, France, has recently been reported in the American Journal of Clinical Nutrition; here's a summary of the publication.

What was done

Five centers (Amiens, Lyon, Montpellier, Paris, and Toulouse) recruited more than 7500 women over 75. Their mental function was assessed using a 10-item questionnaire that tested memory, concentration, and other aspects of possible cognitive impairment. Scores ranged from 10 (normal) to 0 (severely impaired).

The food-frequency questionnaire used contained specific questions about the daily consumption of tap water (including that used to make tea or coffee) and the brand of mineral water most often drunk. Standard water composition was obtained for the tap water in each city.

Numerous other pieces of information were obtained at baseline. Follow-up included questionnaires every 4 months, for 5 years, regarding changes to health.

Although all the women were followed for at least 5 years, the 1400 women in the Toulouse center were examined in detail over a 7-year period, in order to detect all cases of possible dementia. Information was gathered by interviews in the home by trained investigators. Mental functioning was assessed by a battery of tests that included the 10-item questionnaire and the Mini Mental State Exam.

What was found in the Toulouse sample

The composition of tap water varied considerably among the cities, with Toulouse having one of the lower levels of silica. On the other hand, Toulouse water had a relatively high aluminum content. The mineral waters used had relatively high silica contents - much more than tap water. But in general, Toulouse women drank less mineral water than those from other cities.

Women who had a normal score on mental function testing at baseline had a high total water intake and a high daily silica intake. This was independent of the type of water drunk - tap or mineral. Aluminum and calcium intake was without effect on mental function scores.

After adjusting for a number of possibly interfering factors - age, study center, income, education, history of stroke - it was found that there was a clear association between silica intake and mental functioning - the higher the silica, the better the score.

Those women who developed Alzheimer's disease during the 7-year follow-up period had been exposed to significantly lower silica levels at baseline. And women with Alzheimer's were 2.7 times as likely to have a daily silica intake of 4 mg daily or less than non-demented women.

What this may mean

As with all studies, there are sometimes limitations that have to be considered before too much weight is given to the results. First, the women were all volunteers, and may not have accurately represented the entire population at risk. Second, only half the women in the original Toulouse group were re-examined after 7 years; this meant the actual occurrence rate of Alzheimer's could not be assessed adequately. Nevertheless, the findings were sufficiently strong to allow one to echo the conclusion voiced by the doctors, namely: "silica in drinking water may reduce the risk of developing Alzheimer's disease in elderly women".

Obviously, the effects of drinking silica-containing mineral water for some time need to be studied in comparison to those in subjects drinking low-silica water, to see if a protective effect can be demonstrated. In the meantime, until such a study is done, you can continue to drink your mineral water without any qualms. At least one company has realized the possibilities - see the third link below!

Source

• Cognitive impairment and composition of drinking water in women; findings of the EPIDOS study. S. Gillette-Guyonnet, S. Andrieu, F. Nourhashemi,  et al., Am J Clin Nutr, 2005, vol. 81, pp. 897--902

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