Long-term and season-specific changes in the body concentrations of magnesium, potassium and calcium by means of quantitative analyses of beard samples collected every day: A case study

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.