A supplementation trial starting with 224 postmenopausal women provided with adequate vitamin D and Ca was conducted to determine whether increased Cu and Zn intakes would reduce the risk for bone loss. Healthy women aged 51–80 years were recruited for a double-blind, placebo-controlled study. Women with similar femoral neck T scores and BMI were randomly assigned to two groups of 112 each that were supplemented daily for 2 years with 600 mg Ca plus maize starch placebo or 600 mg Ca plus 2 mg Cu and 12 mg Zn. Whole-body bone mineral contents, densities and T scores were determined biannually by dual-energy X-ray absorptiometry, and 5 d food diaries were obtained annually. Repeated-measures ANCOVA showed that bone mineral contents, densities and T scores decreased from baseline values to year 2. A priori contrasts between baseline and year 2 indicated that the greatest decreases occurred with Cu and Zn supplementation. Based on 5 d food diaries, the negative effect was caused by Zn and mainly occurred with Zn intakes ≥ 8·0 mg/d. With Zn intakes < 8·0 mg/d, Zn supplementation apparently prevented a significant decrease in whole-body bone densities and T scores. Food diaries also indicated that Mg intakes < 237 mg/d, Cu intakes < 0·9 mg/d and Zn intakes < 8·0 mg/d are associated with poorer bone health. The findings indicate that Zn supplementation may be beneficial to bone health in postmenopausal women with usual Zn intakes < 8·0 mg/d but not in women consuming adequate amounts of Zn.