Summary of Reccomendations
On November 30th 2010 the Institute of Medicine (IOM) released the Dietary Reference Intakes (DRIs) for calcium and vitamin D. The complete report is available at www.iom.edu/calciumvitamind. The committee made recommendations about recommended nutrient intake, upper limits and optimal serum levels for bone health. The full review is over 1000 pages long.
The IOM determined that while there is evidence supporting the relationship between calcium/vitamin D and bone health, there is inadequate evidence that higher intakes of these nutrients will confer benefit or protect against other chronic diseases including diabetes, cancer, cardiovascular disease, immune function and falls. They do acknowledge the biological plausibility for the role of vitamin D in these conditions; however the final DRI's were set considering only outcomes related to bone health.
Blood level recommendations:
Serum 25-hydroxy vitamin D: the IOM recommends that as a measure of bone health, 50nmol/L would be an acceptable level.
Calcium: The RDA for calcium ranges from 700-1300mg/d while the upper limit ranges from 1000-3000mg/d.
Vitamin D: The DRI's for vitamin D are consistent across most age groups with the RDA for vitamin D set at 600IU per day. Individuals over 70 years of age have an RDA of 800IU per day. These recommendations are based on the assumption of minimal sun exposure.
Both the DRI for vitamin D and the optimal serum level were lower than expected. The IOM suggested that most individuals in Canada and the US would be able to achieve adequate vitamin D (600IU) from diet alone. Dietary sources of vitamin D are very limited and it is challenging to achieve 600IU/d – especially in the Canadian food supply which has fewer and different foods approved for fortification.
The only health outcome that the committee took into account when determining DRIs was bone health. It is important to note that many of the newer studies showing benefits for vitamin D were too small to be included in the evaluation.
A target serum 25-hydroxyvitamin D levels of 50nmol/L is much lower than expected and less than half of what would be seen in sun replete individuals. Using this level, the 2010 Canadian Health Measures Survey (www.statcan.gc.ca/chms) would therefore indicate that the majority of Canadians had vitamin D status adequate for bone health.
In patients receiving Vitamin D sterols, the dose had to stay the same for at least 30 days prior to the start of the study. Exclusion criteria were the use of this bisphosphonates or fluoride in 3 months previous to the study onset.
Impact on Practice
The upper limit reference for calcium ranges from 1000-3000mg per day from all sources. For adults over 50 years, this level is set at 2000mg/d. This is a reduction (in this age group) from the previous tolerable upper limit of 2500mg. The report estimates that at the 50th percentile, most adults achieve an intake of approximately 1000mg/d which suggests that an intake of greater than 1000mg supplemental calcium may exceed the UL. Indeed, the report specifically identified that excess intake of calcium comes from the use of calcium supplements. Calcium based binder usage in the CKD population is often greater than 1000mg/d and often exceed the UL from binder use alone. Vascular and soft tissue calcification were identified as potential indicators of adverse outcomes which is of significant concern to the CKD population.
As GFR falls, renal synthesis of calcitriol declines. Vitamin D recommendations for the general population may not apply to later stages of CKD. In addition, the CKD population has unique challenges when trying to achieve adequate dietary vitamin D from diet alone as milk is generally restricted. This population is at high risk for vitamin D deficiency and dietary assessment and intervention should include the evaluation of vitamin D sufficiency. More research is needed in the CKD population.
Reviewed by Reviewed by June Martin, RD
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