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More than 4000 beard samples were collected from a single person every morning over a 12-year period and analyzed using a standard-free method. We detected significant annual variations in the concentrations of magnesium and calcium in the study period, although significant monthly and seasonal variations were not noted. Calcium tends not to be obtained from season-specific foods or drinks, so its variations may be affected by changes in the metabolism of the body. In contrast, however, potassium showed marked long-term variations with significant seasonal differences. As our previous studies confirmed that green vegetables contain large quantities of potassium and that their supply and consumption increase from May to July, the seasonal variations in potassium concentration were attributed to the ingestion of green vegetables. Although magnesium is also contained in green vegetables in large quantities, its principle supply sources are diverse and its concentration did not show any clear seasonal changes.

To evaluate a participatory role of environmental minerals in the pathogenesis of amyotrophic lateral sclerosis (ALS) in the Kii Peninsula of Japan, one of the three high-incidence foci, elemental and neuropathological investigations of lumbar spinal cord and hippocampal tissues were conducted, using particle-induced x-ray emission (PIXE) spectrometry and histomorphometric analysis. The PIXE analysis revealed extremely high contents of Al in both tissues of Kii ALS cases as compared with sporadic ALS and control cases. Morphometric analysis in the hippocampus showed abundant Alzheimer’s neurofibrillary tangles (NFTs) in the Kii ALS cases as compared with the other cases. Al content significantly correlated with the density of NFTs in all ALS cases (r=0.765, p < 0.0001). Interestingly, both Al content and density of NFTs in the hippocampus of all ALS cases significantly and negatively correlated with Ca and Mg contents in the birthplace area’s rivers. The extremely low Ca and Mg content in the focus rivers was confirmed along with the high ratio of Al₂O₃/CaO in the soil. Thus, Kii ALS patients may reflect the geochemical environment of their birthplace, i.e., long term Ca and Mg deficiencies and excess Al accumulation along with widespread NFT formation in the brain.