Should healthy people take calcium and vitamin D to prevent fractures? What the US Preventive Services Task Force and others say
WHAT OTHER ORGANIZATIONS SAY
Both the National Osteoporosis Foundation and the American Society of Bone and Mineral Research suggest following the 2010 recommendations of the Institute of Medicine8 on calcium and vitamin D instead of those of the USPSTF, as the former address the overall health benefits of calcium and vitamin D in healthy individuals rather than only fracture prevention.
Neither the Institute of Medicine nor the USPSTF, however, addresses vitamin D requirements of people at high risk, such as those with vitamin D deficiency due to very little sun exposure, dark skin, problems absorbing dietary fat, or medications that interfere with vitamin D absorption, or those with osteoporosis.
The Institute of Medicine suggests that, for healthy adults under age 71, an adequate vitamin D intake is 600 IU daily, and for healthy adults age 71 and older it is 800 IU daily. They state that the safe upper limit for daily intake of vitamin D is 4,000 IU. As for adequate calcium intake, the daily recommendation is 1,200 mg for women ages 50 through 70, and 1,200 mg for all adults age 71 and older. As I have already discussed, the Institute of Medicine recommendations are based on the overall health benefits of calcium and vitamin D rather than solely on fracture prevention. Monitoring of vitamin D levels is not recommended unless the patient has osteoporosis or is at risk for vitamin D deficiency.
Risks of calcium supplementation
Much has been written recently about the risks of calcium supplementation.
This concern was first raised in 2008 by Bolland et al7 in a post hoc analysis of data collected to evaluate the effect of calcium supplements on bone density and fracture.7 More myocardial infarctions occurred in the calcium supplement group than in the placebo group, but the difference was not statistically significant, and the events occurred only in those who took more than 1,000 mg of calcium daily.
The same group reanalyzed data from the Women’s Health Initiative and found a 24% higher risk of myocardial infarction in women who took calcium with or without vitamin D, but only in those women assigned to take calcium supplementation who had not taken calcium supplements before the study began.9
More recently, Xiao et al10 evaluated the effect of both dietary and supplemental calcium on cardiovascular disease mortality rates.10 This was a prospective study of 388,229 men and women who participated in the National Institutes of Health-American Association of Retired Persons Diet and Heart Study. Supplemental calcium intake was associated with an elevated risk of cardiovascular disease in men, but not in women. Dietary calcium intake was unrelated to cardiovascular death.
The latest study to address this issue was from the Swedish Mammography Cohort, a population-based cohort that included 61,433 women born between 1914 and 1948, with a mean follow-up of 19 years.11 Diet was evaluated by food frequency questionnaires. A daily dietary intake of calcium below 600 mg was associated with higher risks of all-cause mortality, cardiovascular disease, ischemic heart disease, and stroke. However, compared with women whose daily calcium intake was between 600 and 999 mg, a dietary intake of more than 1,400 mg/day was associated with a higher death rate, with a hazard ratio for all-cause mortality of 1.40, cardiovascular disease 1.49, and ischemic heart disease 2.14.
Unfortunately, none of these studies were designed to assess the risk of cardiovascular disease related to calcium supplementation. Like the USPSTF, both the National Osteoporosis Foundation and the American Society of Bone and Mineral Research state that this type of study is needed to clarify both the benefit and risk of calcium supplementation.
Until these data are available, the American Society of Bone and Mineral Research has advised doctors and their patients “to discuss the best strategy for each individual patient, putting supplements as the last resort for healthier adults if they cannot reach recommended levels through the intake of calcium and vitamin rich foods.” For adults who cannot tolerate dairy products, calcium can be obtained from calcium-supplemented foods such as orange juice and Jello and from nondairy sources such as leafy green vegetables, almonds, garbanzo beans, tofu, and eggs.12
The National Osteoporosis Foundation suggests following the Institute of Medicine recommendations for adequate calcium and vitamin D rather than the USPSTF recommendations, most likely because the former are based on the overall health benefits of calcium and vitamin D rather than fracture prevention only. However, it reminds us that the Institute of Medicine recommendations do not apply to patients who are at the highest risk of fracture, ie, those with osteoporosis and vitamin D deficiency.
TAKE-HOME POINTS
- All medications, including those available over the counter, have benefits and risks.
- Even the USPSTF states that for a healthy lifestyle, the diet should contain adequate calcium and vitamin D intake.
- When following guidelines, practitioners should be certain that the guidelines pertain to the population they are treating—for example, not to apply the Institute of Medicine recommendations to a woman with a hip fracture, but that a healthy premenopausal woman who is taking calcium supplements should be advised to stop the supplements and focus on dietary sources of calcium.
- Only if individuals cannot obtain the recommended amount of calcium in their diet is it advisable for them to take a calcium supplement.
My recommendations
Based on the information summarized above, I recommend that my patients obtain as much calcium as possible from their diet—between 600 and 1,200 mg daily—and to take a calcium supplement only if they cannot obtain that amount of calcium in the diet. However, 24-hour calcium excretion is not recommended as a marker of calcium intake.
I also advise my patients to take a vitamin D supplement, per the Institute of Medicine report for overall good health. The USPSTF recommendations concerning vitamin D and calcium address only fracture prevention. As I am responsible for the overall health of my patients, not just fracture prevention, I choose to follow the National Osteoporosis Foundation and Institute of Medicine recommendations, not those of the USPSTF.
