Clinical Context

Many adults take supplements featuring vitamin D and calcium, but the recommendations for this practice are widely disparate. An editorial by Nestle and Nesheim, which accompanies the new recommendations from the US Preventive Services Task Force (USPSTF) in the Annals of Internal Medicine, reviews these recommendations. In 2011, the Institute of Medicine (IOM) found that calcium and vitamin D overall are important for bone health, and it recommends calcium intake of 800 to 1000 mg/day for low-risk adults. The Institute also recommends vitamin D intake of 400 IU/day for most adults.

The Endocrine Society was more aggressive in its approach to calcium and vitamin D supplements. Its recommendations, also published in 2011, would define vitamin D deficiency more broadly and recommend vitamin D supplements of 1500 to 2000 IU/day for many adults.

The USPSTF weighs into this controversy but focuses its current recommendations on the prevention of fracture risk in adults. The USPSTF also provides separate guidelines to address vitamin D supplementation for fall prevention.

Study Synopsis and Perspective

The USPSTF recommends against daily supplementation with 400 IU or less of vitamin D₃ and 1000 mg or less of calcium for primary fracture prevention in noninstitutionalized postmenopausal women, according to its final recommendation statement with updated guidelines reported in the May 7 issue of the Annals of Internal Medicine.

"In review of the scientific evidence, the question of whether one should supplement in order to prevent fractures is that [the USPSTF doesn't] have enough evidence to make a recommendation about this for anything, except for postmenopausal women, where we have a study that demonstrates that vitamin D supplementation of modest doses potentially does you some harm," USPSTF chair Virginia A. Moyer, MD, MPH, vice president for Maintenance of Certification and Quality for The American Board of Pediatrics, told Medscape Education. "We do not know about higher doses of supplementation. We don't know about men and premenopausal women."

To determine the effects of supplementation on bone health outcomes in community-dwelling adults, the association of vitamin D and calcium levels with bone health outcomes, and the harms of supplementation, the USPSTF commissioned 2 systematic evidence reviews and a meta-analysis on vitamin D supplementation with or without calcium.

The new recommendations are intended only for noninstitutionalized, asymptomatic adults without a history of fractures, and not for persons with osteoporosis or vitamin D deficiency.

"The USPSTF recommends taking vitamin D if you are frail and elderly and at risk for fractures," Robert P. Heaney, MD, professor of medicine, Division of Endocrinology at Creighton University in Omaha, Nebraska, told Medscape Education when asked for an independent comment.

"We [The Endocrine Society] recommend it [vitamin D] for fall prevention," Dr. Heaney said. "It is clearly not a recommendation against vitamin D for frail, elderly individuals. The media headlines interpreted it as a recommendation against vitamin D instead of stating that [the USPSTF] did not find the evidence they wanted to support a recommendation for vitamin D supplementation for fracture risk...and they [USPSTF] are against the use of too little vitamin D to prevent fracture risk."

Updated USPSTF Conclusions and Recommendations

On the basis of its review, the USPSTF determined that current evidence is insufficient to evaluate the balance of the benefits and harms of combined vitamin D and calcium supplementation for the primary prevention of fractures in premenopausal women or in men.

The USPSTF also found that current evidence is insufficient to evaluate the balance of the benefits and harms of daily supplementation with more than 400 IU of vitamin D₃ and more than 1000 mg of calcium for the primary prevention of fractures in noninstitutionalized postmenopausal women. Both of these are I level statements, meaning that the evidence is insufficient to make a recommendation for or against the provision of a preventive service.

"[I]n terms of postmenopausal women, recommending high doses [of vitamin D] is not good practice," Dr. Moyer said. "There is no evidence of benefit but evidence of a slight risk of harm [such as renal stones]. On the other hand, if someone recommends higher doses, the task force would say that there is no evidence to support this."

For the primary prevention of fractures in noninstitutionalized postmenopausal women, the USPSTF recommends against daily supplementation with 400 IU or less of vitamin D₃ and 1000 mg or less of calcium. This recommendation is a D level statement, meaning that moderate or high certainty exists that the service has no net benefit or that the harms outweigh the benefits, and that the USPTSF therefore discourages use of the practice.

Women taking supplemental vitamin D and calcium have a statistically increased incidence of renal stones, according to evidence from the Women's Health Initiative. For every 273 women who received supplementation during a 7-year follow-up period, 1 woman was diagnosed with a urinary tract stone.

Specialty Views on Evidence Base for Updated Recommendations

"The task force does not make a recommendation in the absence of at least moderate certainty about a medicine, meaning the evidence has to be at least of a certain quality," Dr. Moyer said. "Specialty societies, in response to request of its members, make recommendations based on less solid evidence."

She explained that The Endocrine Society focuses on the population from the perspective that most of the population is vitamin D deficient, whereas the IOM takes the view that most people receive the proper amount of vitamin D.

"[The IOM] used a broader group of people to assess this and take a scientific look at the issue," Dr. Moyer said. "The starting point is not focusing on thinking that the entire population is deficient. Specialty societies see things through the lenses of their specialty, and [the USPSTF wants] to take a broader view."

However, Dr. Heaney points out that the issue of fracture prevention with vitamin D and calcium is linked to baseline levels, as he explained last year in an editorial in the New England Journal of Medicine (July 5, 2012; 367:77-78). Unlike drugs, nutrients do not result in a linear response, and if the patient has adequate vitamin D, giving more will have no effect.

"All depends on whether you are starting from a point of deficiency or adequacy in the vitamin D status," Dr. Heaney said. "There is solid evidence that vitamin D and calcium in adequate doses will prevent fractures. The USPSTF may have come to a different conclusion because they used 2 large systematic reviews on which the [IOM] also based their recommendations, and both of those systematic reviews are seriously flawed."

He notes that the criteria for including studies in the review were all methodological and technical and not biological, and that the review therefore cannot answer the question of whether vitamin D can prevent fracture.

Ann Intern Med. 2013;158:691-696, 701-702.

Clinical Implications

• Both the IOM and The Endocrine Society recommend calcium and vitamin D supplements to improve bone health among average-risk adults. The Endocrine Society recommends higher doses of vitamin D compared with the IOM.
• In its current guidelines, the USPSTF does not endorse the routine use of 400 IU or less of vitamin D and 1000 mg or less of calcium for primary prevention of fractures in postmenopausal women. Limited evidence existed to determine the benefits or harms of high doses of calcium or vitamin D supplementation for postmenopausal women. The task force did not find sufficient evidence to give support for or against vitamin D and calcium supplementation to prevent fractures in men and premenopausal women.

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