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

Abstract

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 2 y. 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 Ȁ SD spine BMD loss in the placebo group (1.8 Ȁ 3.9%) did not differ significantly from that in the treatment groups (2.1 Ȁ 3.2%; P ҃ 0.88). Hip BMD loss in the placebo and low-dose potassium citrate groups was 1.3 Ȁ 2.3% and 2.2 Ȁ 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.

No evidence that the skeletal non-response to potassium alkali supplements in healthy postmenopausal women depends on blood pressure or sodium chloride intake

“…The bone loss observed for NE Scotland for the 24-h urine subset was similar to that already reported for the full data set. 11 This is the first time the Californian data relating to bone health have been shown. The percentage bone loss was less compared with NE Scotland, which may be because the Californian women were more than 5 years past the menopause.…”

“…Subjects for this retrospective study were a subset of postmenopausal women living in the Aberdeen area who provided 24-h urine samples during a dietary intervention trial. 11 Exclusion criteria for the original study, which was registered at http://www.controlled-trials.com as ISRCTN86186352, were the lowest 10% of estimated dietary acidity (NEAP calculated from the food frequency questionnaires), 33 and any condition or medication that would affect bone metabolism and potassium-sparing diuretics. Women taking other types of diuretics or hypertension tablets and women on thyroxine treatment provided their thyroid function was stable (as assessed by free T4 and TSH) and their dose had not changed in the year before study entry were included in the study.…”

“…9 However, a recent cohort study that retrospectively measured net acids in frozen 2-h urine specimens did not show an association with BMD or fractures 10 and a 2-year intervention study demonstrated no improvement in BMD in subjects treated with dietary alkali. 11 Salt intake and bone effects Dietary salt may affect bone metabolism via a number of mechanisms. In healthy men, increasing Na intake from 10 to 1500 mmol (0.5-65 g/day) on a fixed calcium intake increased the filtered load of calcium and fractional calcium excretion (Po0.001).…”

Associations between dietary flavonoid intakes and bone health in a scottish population

“…The subjects completed 4-day estimated portion size food diaries and the FFQ 9 months apart as a measure of compliance in a fruit and vegetable intervention trial. (8) Assessment of potential confounders…”

“…A recent 2-year randomized, controlled trial found that supplementation with potassium citrate or three additional portions of fruit and vegetables a day did not reduce bone turnover or increase BMD, suggesting that any long-term benefits of fruit and vegetable intake on bone are not due to the provision of alkaline salts. (8) Animal studies have shown that ovariectomy-induced bone resorption can be inhibited by onions and other vegetables commonly eaten by humans (9) and that this effect is independent of their base-balancing properties, (10) indicating that the protective effects of fruit and vegetables may be found in the nutrients they contain.…”