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

Randomized controlled trial in healthy postmenopausal women, approximately 55 to 65 years old, recruited from the community in Aberdeen, Scotland. Participants were followed for 2 years and assessed for bone turnover markers and bone mineral density.

Participants were randomized to oral potassium citrate capsules at either a high dose of 2.16 g daily (55.5 mEq alkali) or a low dose of 0.72 g daily (18.5 mEq alkali) for 2 years, or to a dietary intervention targeting an additional 300 g per day of fruit and vegetables. Potassium citrate was taken in divided capsule doses; the diet arm used nutritionist-calculated portions. Placebo capsules served as the comparator for the potassium citrate arms.

Overall, neither potassium citrate supplementation nor increased fruit and vegetable intake produced sustained improvements in bone turnover or bone mineral density over 2 years. Time-by-arm interactions were not significant for P1NP, CTX, or fDPD/Cr across follow-up, and the authors concluded that alkali provision from fruits and vegetables does not explain long-term bone benefits. A short-term effect was seen only for fDPD/Cr at 4 to 6 weeks, where the high-dose and low-dose potassium citrate groups differed after Bonferroni post hoc testing (P=0.047), but this was not sustained. Baseline P1NP also differed across groups (P=0.02), which complicates interpretation of that marker.

Each active arm was modest in size (high-dose n=70, low-dose n=70, diet n=66), limiting power for small effects. Baseline P1NP differed between groups (P=0.02), and some biomarker data were missing at baseline and follow-up. The dietary arm relied on self-reported intake, and the findings apply mainly to healthy postmenopausal women from one UK region.