Overview

• The BfR advises against intermittent high single doses of vitamin D, citing moderate-quality evidence of increased falls and fractures as well as the risk of elevated calcium levels.
• Regulators say bolus products can invite dosing errors, so high-dose regimens and combinations such as vitamin D with K2 should be used only under medical instruction pending further research.
• For pregnancy, the DGE recommends 20 micrograms daily when sunlight is insufficient and warns that regular intake above 100 micrograms can trigger kidney stones or calcifications, with consumer checks flagging variable supplement quality.
• Studies and official estimates indicate widespread under-supply in Germany, with more than 40% to about 60% inadequately supplied overall and particularly high deficiency rates among pregnant women in past research.
• The DGE notes vitamin D can support intestinal magnesium uptake but the overall effect on magnesium balance remains unclear, and leading medical societies do not endorse routine supplementation or testing for healthy adults, with large trials showing no clear protection against respiratory infections.