There are major deficits in our knowledge of vitamin D, and more research, including well-conducted randomized controlled trials, is needed to define optimal intake levels. Nonetheless, the consensus position of Osteoporosis Canada is that the available evidence of safety and the potential benefits for adults justify recommending that optimal vitamin D status represents a serum 25-hydroxyvitamin D level of at least 75 nmol/L. In Canada, exposure to sunlight and dietary intake are insufficient to maintain this level, and use of vitamin D supplementation is therefore indicated for most adults.30–32
The clinical approach can take into account three “settings,” based on suspicion for vitamin D insufficiency and its complications.
People with low risk for vitamin D insufficiency are adults below age 50 years without comorbid conditions affecting vitamin D absorption or action. For these people, supplementation at 10–25 μg (400–1000 IU) is appropriate, and serum 25-hydroxyvitamin D should not be measured (level 3 evidence, grade D recommendation).
People with moderate risk for vitamin D insufficiency are adults 50 years of age or older, with or without osteoporosis, but without comorbid conditions that affect vitamin D absorption or action. For these people, routine supplementation with vitamin D is appropriate, and this should be at a dose of 20–50 μg (800–2000 IU) daily (level 2 evidence, grade B recommendation). Serum 25-hydroxyvitamin D should not be measured routinely in initial assessment of these individuals, but if pharmacologic therapy for osteoporosis is prescribed, 25-hydroxyvitamin D should be measured after three to four months of an adequate supplementation dose (level 3–5 evidence, grade D recommendation).
People at high risk for adverse outcomes from vitamin D insufficiency include those with recurrent fractures or bone loss despite osteoporosis treatment and/or comorbid conditions that affect vitamin D absorption or action. In these cases, serum 25-hydroxyvitamin D should be measured as part of the initial assessment, and supplementation with vitamin D should be based on the measured value. Supplementation dose requirements above the current definition of tolerable upper intake level (50 μg [2000 IU]) may be identified by measuring serum 25-hydroxyvitamin D levels (grade B recommendation).
is the preferred supplementary form for humans, with vitamin D2
being available for large-dose preparations. Calcitriol and its analogs are prescription products with narrow margins of safety. They are not synonymous with vitamin D and are not advised for prevention or routine treatment of osteoporosis. For most adults given a supplement, an initial dose of vitamin D3
of 20–25 μg (800–1000 IU) daily, is likely to raise serum 25-hydroxyvitamin D by approximately 15–30 nmol/L.12,37
To achieve desirable vitamin D status (> 75 nmol/L) many individuals will require doses greater than this minimum dose.
A weekly dose of 250 μg (10 000 IU) vitamin D3 may be more convenient for some patients if available. Some practitioners use vitamin D2 at a dose of 1250 μg (50 000 IU) monthly or more frequently as needed.
Our recommendations for the use of vitamin D are presented in Box 1
. Changes from the 2002 guidelines are related most specifically to dose recommendations and are presented in . A summary of this guideline is also available.85
Recommendations for vitamin D supplementation*
- Adequate vitamin D status, in addition to calcium from diet or supplements, is essential for the prevention of osteoporosis (level 1 evidence, grade A recommendation).
- Administration of vitamin D and calcium should not be used as the sole treatment for osteoporosis (level 1 evidence, grade A recommendation).
- The optimal level of serum 25-hydroxyvitamin D for musculoskeletal benefits is at least 75 nmol/L (level 2 evidence, grade B recommendation).
- Laboratories performing 25-hydroxyvitamin D testing should take part in external proficiency surveys and should demonstrate that values reported for shared samples approximate the consensus of values reported by others (level 4 evidence, grade D recommendation).
- In healthy adults at low risk for vitamin D deficiency (i.e., under age 50, without osteoporosis or conditions affecting vitamin D absorption or action), routine vitamin D supplementation (10–25 μg [400–1000 IU] daily) is recommended. Serum 25-hydroxyvitamin D should not be measured (level 5 evidence, grade D recommendation).
- Adults over 50 years of age are at moderate risk for vitamin D deficiency. Supplementation with at least 20–25 μg (800–1000 IU) of vitamin D3 daily is recommended. To achieve optimal vitamin D status (> 75 nmol/L), many individuals may require supplementation at greater than 25 μg (1000 IU) daily. Doses up to 50 μg (2000 IU) are safe and do not require monitoring (level 3 evidence, grade C recommendation).
- For individuals receiving pharmacologic therapy for osteoporosis, measurement of serum 25-hydroxyvitamin D should follow three to four months of adequate supplementation and should not be repeated if the optimal level is achieved (grade D recommendation).
- Measurement of serum 25-hydroxyvitamin D is recommended for individuals with recurrent fractures, bone loss despite osteoporosis treatment or comorbid conditions that affect vitamin D absorption or action (grade D recommendation). Dose requirements above Health Canada’s current tolerable upper intake level (50 μg [2000 IU]) may be needed, in which case monitoring of serum 25-hydroxyvitamin D levels is required (level 4 evidence, grade D recommendation).
- Exposure to natural sunlight, when used in moderation (avoiding sunburn) and individualized to the person’s skin type, can contribute to summertime vitamin D sufficiency (level 2 evidence, grade B recommendation).
- Research is needed to better define the minimum required daily dose and the optimal dose for musculoskeletal and other health benefits and to better establish the tolerable upper level for vitamin D supplementation (grade D recommendation).
Key changes to the vitamin D guidelines in the 2002 guidelines for the management of osteoporosis