At the request of the US and Canadian governments, the Institute of Medicine (IOM) undertook a massive study of available data on health outcomes associated with calcium and vitamin D. The IOM committee was tasked with determining what benefits calcium and vitamin D might offer, given a slew of often-conflicting messages that the public has received in the past decade about these nutrients.
In November, the IOM released its nearly-500–page report, Dietary Reference Intakes for Calcium and Vitamin D. In it, the committee recommends 600 IU/d of vitamin D for most people and 1,000 to 1,200 mg/d of calcium for most adults. Furthermore, the committee determined, through a review of nearly 1,000 published studies, that most claims of benefits beyond skeletal health are unsupported by evidence.
“At this time, the scientific data available indicate a key role for calcium and vitamin D in skeletal health,” the committee wrote in the closing remarks of their summary. “The data do not, however, provide compelling evidence that either nutrient is causally related to extra-skeletal health outcomes or that intakes greater than those established … have benefits for health.”
Recommended Amounts
The IOM committee determined that most Americans (and their Canadian counterparts) get enough calcium and vitamin D. On average, total intake of vitamin D is actually below the median requirement, but blood levels are above the 20 ng/mL that the committee determined is sufficient for good bone health. The difference may be sun exposure; persons with dark skin pigmentation or those who are elderly and residing in institutional settings may have different needs in terms of vitamin D intake.
The committee established recommended dietary allowances (RDAs)—values that meet the needs of most people—for calcium and vitamin D. The RDAs for vitamin D are simpler:
• 600 IU/d is recommended for everyone ages 1 to 70, including girls and women who are pregnant or lactating
• 800 IU/d is recommended for persons older than 70.
The RDAs for calcium vary more:
• 700 IU/d for children ages 1 to 3
• 1,000 IU/d for children ages 4 to 8, adults ages 19 to 50 (including women who are pregnant or lactating), and men ages 51 to 70
• 1,200 IU/d for women ages 51 to 70 and all adults older than 70
• 1,300 IU/d for children ages 9 to 18, including girls ages 14 to 18 who are pregnant or lactating.
Proceed With Caution
Without overstating the matter, the IOM committee also established “tolerable upper levels” for calcium and vitamin D intake. These recommendations “represent the safe boundary at the high end of the scale and should not be misunderstood as amounts people need or should strive to consume.”
The upper intake levels for vitamin D are as follows:
• 4,000 IU/d for those ages 9 and older, including girls and women who are pregnant or lactating
• 3,000 IU/d for children ages 4 to 8
• 2,500 IU/d for children ages 1 to 3
• 1,500 IU/d for infants ages 6 months to 12 months
• 1,000 IU/d for infants up to 6 months of age.
For calcium, the upper intake levels are:
• 3,000 IU/d for those ages 9 to 18, including girls who are pregnant or lactating
• 2,500 IU/d for adults ages 19 to 50 (including women who are pregnant or lactating) and children ages 1 to 8
• 2,000 IU/d for adults 51 and older
• 1,500 IU/d for infants ages 6 months to 12 months
• 1,000 IU/d for infants up to 6 months of age.
The IOM committee cautions that “kidney stones have been associated with taking too much calcium from dietary supplements,” and very high levels of vitamin D—above 10,000 IU/d—“are known to cause kidney and tissue damage.” Furthermore, as people use more supplements and eat more fortified foods, “it becomes more likely that people consume high amounts” of calcium and vitamin D.
A Final Note
When it came to assessing the role of calcium and vitamin D in areas other than bone health, the committee found that the available data was neither convincing nor adequate. “Outcomes related to cancer/neoplasms, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders, infections, neuropsychological functioning, and preeclampsia, could not be linked reliably with calcium or vitamin D intake and were often conflicting,” the committee wrote.