Calcium with vitamin D does not decrease risk of hip fracture and only shows a modest benefit in bone density, according to the latest results from the ongoing Women's Health Initiative (WHI). Moreover, the supplementation results in a 17% increased risk of kidney stones, according to the study, which appears in the February 16, 2006, issue of the New England Journal of Medicine.¹

In the new study of 36,282 postmenopausal women 50 to 79 years of age who were already enrolled in a WHI clinical trial, participants who received 1000 mg of elemental calcium as calcium carbonate with 400 IU of vitamin D daily had a 1% higher hip bone density than their counterparts in the placebo group (P <.01). According to an intention-to-treat analysis, there was no significant effect of calcium with vitamin D supplementation on any of the fracture endpoints, including hip, spine, and total body. The average follow-up period was 7 years.

However, a subgroup analysis of women who largely adhered to the protocol did suggest that calcium with vitamin D supplementation reduces the risk of hip fracture. In fact, women who consistently took the full supplement dose experienced a significant 29% decrease in hip fracture. In addition, women older than 60 had a significant 21% reduction in hip fracture.

"We have to recognize that this is not a calcium-deficient population," points out WHI investigator JoAnn Manson, MD, chief of preventive medicine at Brigham and Women's Hospital and a professor of medicine at Harvard Medical School, both in Boston, Massachusetts. "The women had good dietary intakes of calcium and the study suggested that women who had lower calcium intake were getting the benefit, as were women who were complying with study medication," she says, adding that "the risk of osteoporotic fracture is really low in the 50- to 59-year-old age group, so fractures may not be related to osteoporosis, and that may somehow dilute the effect."

The new findings "suggest that women can't rely on calcium and vitamin D supplements alone and they need to do other things to improve bone health and monitor bone mineral density, including engaging in regular physical activity, not smoking, and having a healthy diet," says Dr. Manson. "The bottom line is that supplementation offers only modest bone benefits and can't be relied on alone to prevent osteoporotic fractures, but that doesn't mean [it is] not doing anything."

Recommendations remain the same

"This arm of the WHI found that calcium and vitamin D did not improve bone mass very much compared to the placebo medication," says CIAOMed editorial board member Nancy E. Lane, MD, director of the Aging Center and distinguished professor of medicine and rheumatology at the University of California at Davis Medical Center in Sacramento, California. "In addition, there was no protection from hip fracture risk in this population of postmenopausal women," she says, adding, "I would not have expected this treatment would alter bone mass any significant degree unless the women treated were calcium deficient."

The new findings do not change Dr. Lane's recommendations for patients. "Calcium and vitamin D are important for bone, muscle, and joint health," she says. "As we age, we do not absorb calcium as efficiently as when we are young; therefore, the addition of vitamin D to calcium supplements assists in calcium absorption. I will continue to prescribe calcium and vitamin D supplements for the benefits of skeletal health and not just for bone. Calcium is a critical ion for most cellular reactions in the body; if the ionized calcium becomes low in the serum, PTH is released to get the calcium quickly out of bone."

Like the prescription for exercise to prevent or reduce heart disease, "calcium and vitamin D supplementation for skeletal health are critical for aging, and this article articulates what experts have been saying for years—the benefits of this supplementation cannot be measured by bone mineral density or fracture risk in the elderly healthy—it is just plain critical for elder health," says Dr. Lane. Moreover, "the best ways to get these minerals is through diet—they are absorbed better that way."

Calcium with vitamin D not sufficient alone

In a related editorial,² Joel S. Finkelstein, MD, an endocrinologist at Massachusetts General Hospital in Boston, Massachusetts, points out that the benefits of calcium with vitamin D in preventing fracture are still not clear. "The WHI was designed with the hope that it would provide clear answers to several important public health issues, including the efficacy of calcium and vitamin D for the prevention of fractures," he writes. "Has the WHI calcium with vitamin D trial succeeded in this regard? Unfortunately, although the trial was well conducted, the results of the current study leave many questions unanswered."

"Calcium with vitamin D supplementation is akin to the ante for a poker game: it is where everyone starts," Dr. Finkelstein says. "If the clinical data suggest that the risk of fracture is significant, however, a woman probably needs something more."

Calcium with vitamin D does not reduce risk of colorectal cancer

In a related study, also from the WHI,³ researchers found that supplementation with calcium with vitamin D does not lower the risk of colorectal cancer in postmenopausal women, as previous studies had suggested. However, study authors point out that the long latency associated with the development of colorectal cancer, along with the seven-year duration of the trial, may have contributed to this null finding.

References

1. Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and risk of fractures. New Engl J Med. 2006;354:669-683.
2. Finklestein JS. Calcium plus vitamin D for postmenopausal women—bone appétit? New Engl J Med. 2006;354:750-752.
3. Wactawski-Wende J, Kotchen JM, Anderson GL, et al. Calcium plus vitamin D supplementation and the risk of colorectal cancer. New Engl J Med. 2006;354:684-696.