Firstly, a multinational analysis of older multimorbid individuals shows that mismanagement of vitamin D is common: one-third did not receive D despite indications (“underuse”), while about 10 percent supplemented without indication (“overuse”). Polypharmacy and hospital stays were associated with both mismanagement issues – a plea for more precise, indication-based administration instead of blanket supplementation ^[1]. Secondly, case reports and market analyses document the risks of unregulated high doses: vitamin A supplements sometimes exceed recommendations, with known hepatotoxic and teratogenic effects ^[2]; misdosed vitamin D products led to life-threatening hypercalcemia and kidney damage in children ^{[3] [4]}. Relevance: Supplements are not automatically safe – especially fat-soluble vitamins require dose discipline and quality control. Thirdly, nutrition is emerging as a smart carrier: fermented foods can provide bioavailable forms of K2 and certain B vitamins; the food matrix and microbial strains affect absorption – a hint that diversity and processing can modulate vitamin effects ^[5].

- Prioritize vitamin C from foods: Incorporate citrus fruits, peppers, or broccoli daily – ideally spread throughout the day to consistently support skin barrier and immune defense ^[6].