Calcium from mineral water are absorbed in the same amounts as they are from milk, whole-grain bread, or nutritional supplements. The varying levels of other minerals present in mineral waters have no impact on the bioavailability of calcium and magnesium. https://www.foh.uni-hannover.de/en/research/research-at-the-institute/nutrition-physiology-human-nutrition/kmh/news-details/news/bioverfuegbarkeit-von-calcium-und-magnesium-aus-mineralwasser Calcium-rich water strengthens bones and prevents bone loss. https://www.focus.de/gesundheit/ratgeber/kalziumreiches-wasser-staerkt-knochen-und-beugt-schwund-vor_e5d85d30-8976-4e54-9a98-48afd9feeb17.html