Although calcium supplementation is routinely recommended, evidence from the Women's Health Initiative showed that calcium supplementation did not reduce fracture risk in healthy postmenopausal women, and other research has highlighted potential risks of calcium supplementation.
2. Calcium plus Vitamin D
The USPSTF recommendations state that the evidence is insufficient (Grade I) to assess the balance of benefits and harms for the combination of vitamin D and calcium for primary prevention of fractures in men or premenopausal women. For noninstitutionalized postmenopausal women, there is insufficient evidence for daily supplementation with more than 400 international units of vitamin D3 and 1000 mg of calcium; supplementation with less than 400 international units of vitamin D3 and 1000 mg calcium is not recommended. Recommended calcium intake for women younger than 50 years is 1000 mg/day and for women aged 51 and over, it is 1200 mg/day. Dietary calcium is the preferred route for calcium intake because calcium supplements have been associated with an increased risk of myocardial infarction, although there has not been an increase in either cardiovascular or all-cause mortality. Calcium supplements, if they are taken, can be given as either calcium citrate or calcium carbonate and should be combined with vitamin D. Taking calcium supplementation with meals may reduce the risk of nephrolithiasis. Regular weight-bearing exercise has also been associated with an increase in bone density, although the effect is lost when the exercise is not continued.
Vitamin D is important for bone health. Vitamin D can be given as either D2 or D3 formulations. Recommendations are that women aged 70 and younger should consume 600 international units of vitamin D per day, whereas women aged 71 and older should consume 800 international units per day. Individuals with vitamin D deficiency (defined by the National Academy of Medicine as a 25-OH vitamin D less than 20 mg/mL) may require higher doses, although most recommendations for vitamin D supplementation are based on achieving a serum 25-OH vitamin D concentration of 20 mg/mL or more, rather than on a clinical outcome. Whether women should be routinely screened for vitamin D deficiency remains an ongoing question. However, given the association of vitamin D and fractures and falls, checking a 25-OH vitamin D level in women with osteopenia or osteoporosis or at high fall risk is appropriate.