How to use calcium supplements correctly: evidence for bone density and key precautions

A meta-analysis of 1,806 postmenopausal women (Shea et al., 2002) found that calcium supplementation significantly attenuated bone mineral density loss at the spine and hip. Effects were most pronounced in those with low baseline dietary calcium intake, while additional benefit was limited when intake was already adequate.

1,806 participants

Meta-analysis sample size

Significant attenuation

BMD change at spine and hip

Vitamin D is essential for intestinal calcium absorption. Without adequate vitamin D, supplemented calcium cannot be efficiently absorbed and bone benefits are diminished. Research indicates that combined calcium and vitamin D supplementation tends to produce greater improvements in bone mineral density than calcium alone.

Intestinal absorption ~30–40%

Estimated calcium absorption with sufficient vitamin D

Some studies have suggested that long-term high-dose calcium supplementation (over 1,000 mg/day) may be associated with elevated cardiovascular disease risk—a concern not typically seen with dietary calcium. Caution is especially warranted when taking large single doses via supplements. A practical approach is to cover only the shortfall from diet with supplemental calcium.

600–800 mg/day

Reference calcium intake for Japanese adults

>1,000 mg/day warrants caution

Supplementation level associated with possible cardiovascular risk