In 2012, the European food safety authority (EFSA) evaluated vitamin D for safety and set a so-called Tolerable Upper Intake Level (UL). This UL was confirmed by EFSA in 2018 in a summary table. The UL reflects the safe maximum amount of a micronutrient (vital substance) that does not cause any side effects when taken daily from all sources for a lifetime.
| The maximum safe daily intake for vitamin D is 100 µg.100 µg of vitamin D is equivalent to 4,000 I.U. (International Units).The maximum safe daily intake for vitamin D is 20 times the EU recommended daily intake (Nutrient Reference Value, NRV). |
This value applies to adult men, women, and children 11 years of age and older, as well as pregnant and nursing women. For infants 0 to less than 6 months of age, the safe daily intake limit (UL) is 25 µg, and for infants 6 to less than 12 months of age, this value is 35 µg. For children from 1 year of age to under 11 years of age, the UL is 50 µg.
The NOAEL (No Observed Adverse Effect Level) – the highest dose of a substance that has no detectable and measurable adverse effects even with continued intake – has been set by EFSA at 250 µg. This makes the highest dose at which no adverse effects could be detected more than twice the safe daily intake limit for vitamin D.
Data from the NVS II (National Nutrition Survey II, 2008) on daily intake of vitamin D from all sources (conventional diet and supplements) indicate that the safe maximum level of 100 µg is not reached.
The undesirable effects of a permanently too high vitamin D intake lie in the vitamin D-dependent increased calcium absorption in the intestine and the increased mobilization (release) of calcium from the bones. This can lead to hypercalcemia. Prolonged high blood calcium concentrations can lead to metastatic calcification of soft tissues, including the kidneys, blood vessels, heart, and lungs.
In one study, hypercalcemia occurred only at levels of 15,000 µg of vitamin D (equivalent to 150 times the safe daily maximum) every 3 months. Increased blood calcium concentration does not necessarily lead to metastatic soft tissue calcification, but it is a risk factor. Another study showed no increase in blood calcium concentration in healthy adults with daily intake of 250 µg vitamin D for 6 weeks. Similarly, single doses of up to 10,000 µg of vitamin D were tolerated by older adults without side effects.