Quote:
Originally Posted by johnt
I've not done one of these geographical associations for some time. I find them useful not so much as proof, which of course they aren't - there is no rigorous statistical analysis, nor does it take into account any of a myriad of confounding issues - but to kick-out obviously flawed hypotheses.
Compare:
A. The geographical prevalence of PD in the US [1].
B. Zinc in the soil in the US [2].
Eye-balling the maps I suspect that there is a small negative association between the two. Thus, we can't throw out the hypothesis that low levels of zinc are linked to PD.
I would suspect that the causal mechanism by which zinc levels in the body associate with those in the soil is through the food chain and the water supply.
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Interesting points. There is an antagonistic relationship between copper and zinc. In fact, many homes have water pipes that are made from copper.