Vitamin D intake: We recommend that women at increased risk of osteoporosis and women older than 70 years receive at least 800 IU daily and, potentially, more if necessary to achieve the target 25OHD level.
Although the evidence to date does not support routine achievement of a 25OHD level substantially above 20 ng/mL in most women, many clinicians recommend that women in this higher-risk group maintain a 25OHD level above 30 ng/mL because of the possibly greater (although unproven) skeletal and nonskeletal benefits. As more data become available regarding the benefits and safety of vitamin D doses higher than those recommended by the IOM, these recommendations may be revised.
In 2010, the National Osteoporosis Foundation (NOF) recommended a vitamin D intake of 800 to 1,000 IU daily for all adults 50 years and older. Among persons at risk of deficiency, the NOF also recommended measurement of the serum 25OHD level, with vitamin D supplementation, as necessary, to achieve a 25OHD level of 30 ng/mL or higher.19 Also in 2010, the International Osteoporosis Foundation (IOF) recommended a target 25OHD level above 30 ng/mL for all older adults. The IOF also estimated that the average dosage required to achieve this level in older adults is 800 to 1,000 IU daily, noting that upward adjustment may be required in some people.4 It is unclear whether these guidelines will be revised in the future, based on the IOM report.
We recommend against achieving a 25OHD level above 50 ng/mL, based on evidence suggesting potential adverse health effects above this level.
More isn’t necessarily better
Excessive vitamin D intake should be avoided because of the potential for harm and the lack of evidence from well-designed clinical trials that vitamin D intake beyond the currently recommended amount affords greater skeletal or nonskeletal health benefits. Although moderate vitamin D supplementation has proven skeletal benefits, a “U-shaped” curve for some outcomes has emerged, suggesting that excessive vitamin D supplementation may pose health risks. Notably, a recent clinical trial reported a higher risk of fracture (and falls) among elderly women treated annually with high-dose (500,000 IU) oral vitamin D3 versus placebo.20
A suggestion of adverse effects associated with 25OHD levels above 50 ng/mL has also emerged, from observational studies, for several nonskeletal health outcomes, including pancreatic cancer,21 cardiovascular disease,1 and all-cause mortality.22
Limited evidence is available regarding the safety and overall risk-benefit profile of long-term maintenance of 25OHD levels above the recommended dietary allowance (RDA) range. Therefore, you should remind your patients that, despite the importance of both prevention and treatment of vitamin D insufficiency, more is not necessarily better.
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