IOM Report: Most North Americans Receive Enough Calcium, Vitamin D

November 30, 2010

November 30, 2010 ( UPDATED December 1, 2010 ) — Most North Americans receive enough calcium and vitamin D, according to a report containing updated dietary reference intakes (DRIs) that was released today by the Institute of Medicine.

Catharine Ross, PhD, from Pennsylvania State University, in State College, chaired a committee of 14 experts appointed by the Institute of Medicine to assess current data of health outcomes associated with calcium and vitamin D intake.

In the report issued today, the committee reviewed studies on the metabolism and physiology of calcium and vitamin D and their influence on health. DRIs were determined using the estimated average requirement (EAR; the level at which 50% of the population's needs are met), recommended dietary allowance (level at which 95% of the population's needs are met), tolerable upper intake level, and adequate intake level.

The suggested daily calcium EAR is 500 mg for children aged 1 to 3 years and 800 mg for those aged 4 to 8 years. Adolescents should consume at least 1100 mg calcium daily to support bone growth (the recommended dietary allowance for this age group is 1300 mg calcium/day). The EAR for women aged 19 to 50 years and men up to 71 years of age is 800 mg daily; for women older than 50 years and men older than 71 years, the EAR is 1000 mg, and the recommended dietary allowance is 1200 mg.

The only group that did not meet EARs for calcium intake was girls aged 9 to 18 years. In contrast, most postmenopausal women met or exceeded recommendations with calcium supplementation; the report expresses concern that older women taking calcium supplements may be at increased risk for kidney stones. All groups met the EAR for vitamin D of 400 IU daily when considering dietary intake together with cutaneous synthesis from sun exposure, but not from food intake alone. As the committee highlights, this poses a challenging concern because of the risk for skin cancer from sun exposure.

Increase in Dietary Vitamin D Requirements

Because of this potential public health hazard, the committee estimated dietary vitamin D requirements based on minimal sunlight exposure. The new recommended recommended daily allowance for vitamin D is 400 IU for children aged 1 year or younger, 600 IU for North Americans older than age 1 year and up to age 70 years, and up to 800 IUs for those aged 71 years and older. This represents a significant increase from the 1997 DRIs for vitamin D.

The committee determined that risk for harm increases when consuming more than 2000 mg calcium or more than 4000 IU vitamin D daily.

Several studies have reported widespread vitamin D deficiency in North American populations, which the committee attributes to inconsistent serum 25-hydroxyvitamin D cut-points that are often too high. The committee suggests that serum 25-hydroxyvitamin D levels of 50 nmol/L (20 ng/mL) are sufficient for all persons.

The group concluded that there is insufficient evidence to link vitamin D intake with cancer, cardiovascular disease, type 2 diabetes, obesity, immune response, neuropsychological functioning, physical performance, falls, preeclampsia, or reproductive outcomes. However, this "does not mean that future research will not reveal a compelling relationship between vitamin D and another health outcome," the committee writes.

No Link Between Vitamin D and Chronic Disease

"We could not find solid evidence that consuming more of either nutrient would protect the public from chronic disease ranging from cancer to diabetes to improved immune function," said Dr. Ross during a press conference about the new report. "On the other hand, regarding bone health the amount of evidence that has been accumulating is really quite impressive."

According to Dr. Ross, the take-home message to physicians is that now there has been a systematic, evidence-based review, and there is new evidence on which they should base their recommendations to patients.

"We are still very enthusiastic about [vitamin D] that regulates hundreds or even thousands of genes in the body," said panelist Glenville Jones, PhD, from the Queen's University, in Kingston, Ontario, Canada, during the press conference. "What's missing is...a lack of translation of that information into public health recommendations.

"We have been quite amazed that the positive effects of vitamin D haven't been nearly as clear-cut as the advocates have suggested," he added.

Dr. Ross pointed out that the recommendations are for total intake, both through diet and supplements. "We think that many individuals will be able to obtain these recommended dietary allowances from diet, but we are not really specifying the source. A supplement may be appropriate for some age groups," she added.

"The major implications of this report are that after an extensive review of the data, the panel concluded that the strongest evidence was for the fact that vitamin D is helpful for bone health and reduction of fractures," said Sundeep Khosla, MD, president of the American Society on Bone and Mineral Research, in a telephone interview with Medscape Medical News.

According to Dr. Khosla, the main thing clinicians can tell their patients is that there are now some very clear guidelines about calcium and vitamin D intake that are based on solid evidence. "Vitamin D is hard to get from the diet, and the committee did not really advocate sun exposure because of risk of skin cancer, but it can be obtained through a multivitamin."

Dr. Khosla added that it is important to note that "the calcium level of 1000 to 1200 mg/day is to be obtained through diet plus supplement, and that each serving of a dairy product counts for 200 to 300 mg/day. If a patient is getting 4 servings of dairy product, they are probably getting enough calcium."

Future research should focus on understanding the role of vitamin D in nonbone outcomes, he said.

The study was sponsored by the Agricultural Research Service, US Department of Agriculture Center for Nutrition Policy and Promotion, US Department of Agriculture; Department of the Army, US Department of Defense; FDA, US Department of Health and Human Services; Health Canada; Office of Disease Prevention and Health Promotion, US Department of Health and Human Services; and US Department of Health and Human Services, National Institutes of Health (Division of Nutrition Research Coordination, National Institute on Aging, National Institute of Arthritis and Musculoskeletal and Skin, National Cancer Institute, and Office of Dietary Supplements).

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