Effect of potassium citrate supplementation or increased fruit and vegetable intake on bone metabolism in healthy postmenopausal women: a randomized controlled trial

Background: Alkali provision may explain why fruit and vegetables benefit bone health. Objective: We aimed to determine the effects of alkali-providing potassium citrate (double-blind) and fruit and vegetable intake (single-blind) on bone turnover over 2 y. Design: We conducted a randomized placebo-controlled trial in 276 postmenopausal women (aged 55– 65 y). Women were randomly assigned to 4 groups: high-dose potassium citrate (55.5 mEq/d), low-dose potassium citrate (18.5 mEq/d), placebo, and 300 g additional fruit and vegetables/d (equivalent of 18.5 mEq alkali). Serum and fasted urine for bone markers were collected at baseline and at 3, 6, 12, 18, and 24 mo. An additional urine sample was collected at 4 – 6 wk. Bone mineral density (BMD) was measured at baseline and 2y . Results: Repeated-measures ANOVA showed no difference between groups for urinary free deoxypyridinoline cross-links relative to creatinine (fDPD/Cr), serum N-terminal propeptide of type 1 collagen, or beta C-terminal telopeptide, although, at 4 – 6 wk, fDPD/Cr was lower in the high-dose potassium citrate group (P 0.04). Mean SD spine BMD loss in the placebo group (1.8 3.9%) did not differ significantly from that in the treatment groups (2.1 3.2%;P 0.88). Hip BMD loss in the placebo and low-dose potassium citrate groups was 1.3 2.3% and 2.2 2.3%, respectively (P 0.14). Conclusions: Two-year potassium citrate supplementation does not reduce bone turnover or increase BMD in healthy postmenopausal women, which suggests that alkali provision does not explain any long-term benefit of fruit and vegetable intake on bone. Am J Clin Nutr 2008;88:465–74.