Dietary Reference Intakes for Calcium and Vitamin D
Calcium and vitamin D are two essential nutrients long known for their role in bone health. Over the last ten years, the public has heard conflicting messages about other benefits of these nutrients—especially vitamin D—and also about how much calcium and vitamin D they need to be healthy.
To help clarify this issue, the U. S. and Canadian governments asked the Institute of Medicine (IOM) to assess the current data on health outcomes associated with calcium and vitamin D. The IOM tasked a committee of experts with reviewing the evidence, as well as updating the nutrient reference values, known as Dietary Reference Intakes (DRIs). These values are used widely by government agencies, for example, in setting standards for school meals or specifying the nutrition label on foods. Over time, they have come to be used by health professionals to counsel individuals about dietary intake.
The committee provided an exhaustive review of studies on potential health outcomes and found that the evidence supported a role for these nutrients in bone health but not in other health conditions. Overall, the committee concludes that the majority of Americans and Canadians are receiving adequate amounts of both calcium and vitamin D. Further, there is emerging evidence that too much of these nutrients may be harmful.
Health Effects of Vitamin D and Calcium Intake
The new reference values are based on much more information and higher-quality studies than were available when the values for these nutrients were first set in 1997. The committee assessed more than one thousand studies and reports and listened to testimony from scientists and stakeholders before making its conclusions. It reviewed a range of health outcomes, including but not limited to cancer, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls, immune response, neuropsychological functioning, physical performance, preeclampsia, and reproductive outcomes. This thorough review found that information about the health benefits beyond bone health—benefits often reported in the media—were from studies that provided often mixed and inconclusive results and could not be considered reliable. However, a strong body of evidence from rigorous testing substantiates the importance of vitamin D and calcium in promoting bone growth and maintenance.
Dietary Reference Intakes
The DRIs are intended to serve as a guide for good nutrition and provide the basis for the development of nutrient guidelines in both the United States and Canada. The science indicates that on average 500 milligrams of calcium per day meets the requirements of children ages 1 through 3, and on average 800 milligrams daily is appropriate for those ages 4 through 8 (see table for the Recommended Dietary Allowance—a value that meets the needs of most people). Adolescents need higher levels to support bone growth: 1,300 milligrams per day meets the needs of practically all adolescents. Women ages 19 through 50 and men up to 71 require on average 800 milligrams daily. Women over 50 and both men and women 71 and older should take in 1,000 milligrams per day on average to ensure they are meeting their daily needs for strong, healthy bones.
Determining intake levels for vitamin D is somewhat more complicated. Vitamin D levels in the body may come from not only vitamin D in the diet but also from synthesis in the skin through sunlight exposure. The amount of sun exposure one receives varies greatly from person to person, and people are advised against sun exposure to reduce the risk of skin cancer. Therefore, the committee assumed minimal sun exposure when establishing the DRIs for vitamin D, and it determined that North Americans need on average 400 International Units (IUs) of vitamin D per day (see table for the Recommended Dietary Allowances— values sufficient to meet the needs of virtually all persons). People age 71 and older may require as much as 800 IUs per day because of potential changes in people’s bodies as they age.