Vitamin D and Health

7. Potential adverse effects of high vitamin D intakes/serum
25(OH)D concentration
Vitamin D toxicity
7.1 Cutaneous synthesis of vitamin D is regulated so that prolonged sunshine exposure does not lead to
excess production (see paragraph 2.10). Excessive vitamin D intakes have, however, been shown to
have toxic effects (Vieth, 2006). Vitamin D toxicity results in hypercalcaemia (elevated serum calcium)
caused by increased intestinal calcium absorption and mobilisation of calcium from the bone (Jones,
2008). Hypercalcaemia can result in deposition of calcium in soft tissues, diffuse demineralisation of
bones, and irreversible renal and cardiovascular toxicity.
7.2 Other adverse effects that have been linked with high vitamin D intakes or high serum 25(OH)D
concentration include an increased incidence of falls and fractures, increased rates of pancreatic and
prostate cancer and increased total mortality (i.e., from all causes combined). Evidence for these
associations is less robust and consistent than that relating to hypercalcaemia.
Supplemental sources of vitamin D
7.3 Food supplements containing up to 250 µg (10,000 IU) of vitamin D per daily dose are available. Most
multi-vitamin food supplements contain 5 µg (200 IU) of vitamin D per daily dose.
Recommended upper intake levels for vitamin D
UK
7.4 In 2003, the Expert Group on Vitamins and Minerals (EVM) reported on the safety of vitamin and
mineral supplements and recommended maximum advisable levels of intake. Safe Upper Levels
(SULs) were established when supported by sufficient data. The SUL represents an intake that can be
consumed daily over a lifetime without significant risk to health. A Guidance Level (GL) was set when
the evidence base was inadequate to establish an SUL. GLs represent an approximate indication of
intakes that would not be expected to cause adverse effects; they are less secure than SULs because
they are derived from limited data.
7.5 The EVM found insufficient data to establish an SUL for vitamin D. Based on data relating to
hypercalcaemia, a GL for supplemental vitamin D intake (i.e., in addition to dietary intake) of 25 µg/d
(1000 IU) was set for adults. Scaling on a body weight basis to children and infants was not considered
appropriate because of concerns that it might lead to the recommended intake for an infant not being
met.
USA
7.6 The IOM (2011) selected onset of hypercalcaemia and related toxicity as the basis for establishing a
Tolerable Upper Intake Level (UL) for all age groups except infants (0-12m). Retarded linear growth
was used as the basis for establishing the UL for infants. The UL is defined as the highest average daily
intake of a nutrient that is likely to pose no risk of adverse health effects to nearly all persons in the
population. It applies to intakes on a chronic basis among free-living persons.
7.7 A UL of 100 µg/d (4000 IU) was set for adults ≥ 19y of age. A UL of 25 µg/d (1000 IU) was set for
infants 0-6m and 38 µg/d (1520 IU) for infants aged 6-12m. The UL for pregnant and lactating women
was the same as that for adults.
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