Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies was asked to re-evaluate the safety in use of vitamin D and to provide, if necessary, revised Tolerable Upper Intake Levels (ULs) of vitamin D for all relevant population groups.
Vitamin D derives from the diet but can also be synthesised in the skin under the influence of UV‑B radiation. Serum 25(OH)D concentration is a good marker of vitamin D status, but can only be used as a biomarker of vitamin D intake in people with low exposure to sunlight. Following ingestion of large doses of vitamin D, the concentration of 25(OH)D in serum increases, while that of the active metabolite 1,25(OH)2D is unchanged or even reduced. Very high serum 25(OH)D concentrations may lead to hypercalcaemia, which is considered the critical effect of excess intake of vitamin D. Hypercalciuria can be associated with hypercalcaemia, but it can also occur without.
For the derivation of the UL, the occurrence of hypercalcaemia and hypercalciuria has been assessed in studies using daily or weekly supplementation of vitamin D for several weeks to months. The shorter-term studies were generally performed in seasons of low sun exposure. Study populations were not generally vitamin D-deficient, and two studies were conducted in subjects with a high vitamin D status at baseline. Study populations included whites, African Americans, young men, pre- and postmenopausal women, elderly nursing home residents, and overweight and obese adults. It was concluded that vitamin D at doses up to 275 µg/day does not lead to persisting hypercalcaemia or hypercalciuria in adults.
Long-term health outcomes (all-cause mortality, cardiovascular disease, cancer, fractures and kidney stones) were also considered, but no studies reported an association between vitamin D intake and increased risk for adverse long-term health outcomes. Studies reporting on an association between 25(OH)D concentration and all-cause mortality or cancer were inconsistent. When 25(OH)D concentrations were associated with an increased risk for adverse long-term health outcomes in some studies, there was a wide variation in 25(OH)D concentrations associated with the adverse effect. It was considered that 25(OH)D concentrations cannot be used to characterise the risk for adverse long-term health outcomes.
In adults, a daily vitamin D dose of 250 µg/day (range 234-275 µg/day) was considered to reflect a no observed adverse effect level (NOAEL). This value was based on only two studies of short duration (up to five months) in small samples of healthy young men with minimal sun exposure. To take into account the uncertainties associated with this value, an uncertainty factor of 2.5 was chosen, and the UL was established at 100 µg/day. It was considered that the UL of 100 µg/day for adults also applies to pregnant and lactating women. This UL is supported by two studies in pregnant and lactating women, both using doses of vitamin D2 or D3 up to 100 µg/day for several weeks to months, which did not report adverse events for either the mothers or their offspring.
For infants, there is historical evidence on retarded growth from a study in which infants received various regimens of vitamin D exceeding 45 µg/day up to one year of age, although another small study using doses up to 54 µg vitamin D/day until about five months of age did not show such an effect. More recent intervention studies using doses up to 25 µg vitamin D/day (plus the amount ingested via fortified infant formula) for up to five months after birth did not indicate that these intakes are associated with hypercalcaemia in infants. As new data from intervention studies in healthy infants have not become available since the previous risk assessment by the SCF (2003), it was decided that the UL of 25 µg vitamin D/day previously derived for infants from 0 to 12 months of age should be retained.
For children and adolescents aged 10-17 years, there is limited evidence from two studies showing that vitamin D intakes at doses up to 50 µg/day do not lead to hypercalcaemia. While there are no studies at higher intakes, it was considered that there is no reason to believe that adolescents in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults, and a UL of 100 µg/day for adolescents aged 11-17 years was proposed.
For children aged 1-10 years, no new data from intervention studies have emerged since the previous risk assessment. It was considered that there is no reason to believe that children aged 1-10 years in the phase of rapid bone formation and growth have a lower tolerance for vitamin D compared to adults, and, by taking into account their smaller body size, a UL for vitamin D of 50 µg/day was proposed.
Data from European populations indicate that vitamin D intakes from all sources in high consumers are below the UL for all population subgroups (i.e., about 25 %, 75 %, 30 % and 8 % of the UL for adults, infants, children and adolescents, respectively).