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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