A new literature review from the US suggests that long-term daily intake of up to and including 10,000 IU of vitamin D is safe.
To examine the safety of daily consumption of vitamin D, a detailed literature search was conducted, which summarized primary and secondary sources of original data, meta-analyses and systematic reviews (1). The analysis showed that long-term daily intake, up to and including 10,000 IU of vitamin D, does not produce signs or symptoms of vitamin D toxicity and is safe for the entire general population of otherwise healthy adults. Even daily vitamin D intake of 2,000 IU allows for the often cited and excessively conservative five-fold safety factor.
The researcher commented that a large body of scientific evidence would demonstrate that long-term daily intake of 600 to 800 IU of vitamin D is insufficient to achieve and sustain vitamin D adequacy ( serum 25-hydroxyergocalciferol + 25-hydroxycholecalciferol concentration above 75 nmol/L). Furthermore, it would require daily vitamin D intake of at least 1500 IU to maximize the physiologic benefits of vitamin D to the musculoskeletal system, the central and peripheral nervous systems, the heart and central and peripheral cardiovascular systems, the respiratory system, the skin, the eyes, dentition, glucoregulation, immuno-regulation, and disease resistance.