The effect of a high-protein, high-sodium diet on calcium and bone metabolism in postmenopausal women and its interaction with vitamin D receptor genotype

Abstract

The influence of a high-Na, high-protein (calciuric) diet on Ca and bone metabolism was investigated in postmenopausal women (aged 50 -67 years) who were stratified by vitamin D receptor (VDR) genotype. In a crossover trial, twenty-four women were randomly assigned to a diet high in protein (90 g/d) and Na (180 mmol/d) or a diet adequate in protein (70 g/d) and low in Na (65 mmol/d) for 4 weeks, followed by crossover to the alternative dietary regimen for a further 4 weeks. Dietary Ca intake was maintained at usual intakes (about 20 mmol (800 mg)/d). Urinary Na, K, Ca, N and type I collagen cross-linked N-telopeptide (NTx; a marker of bone resorption), plasma parathyroid hormone (PTH), serum 25-hydroxycholecalciferol (25(OH)D 3 ), 1,25-dihydroxycholecalciferol (1,25(OH) 2 D 3 ), osteocalcin and bonespecific alkaline phosphatase (B-Alkphase) were measured in 24 h urine samples and fasting blood samples collected at the end of each dietary period. The calciuric diet significantly (P,0·05) increased mean urinary Na, N, K, Ca and NTx (by 19 %) compared with the basal diet, but had no effect on circulating 25(OH)D 3 , 1,25(OH) 2 D 3 , PTH, osteocalcin or B-Alkphase in the total group (n 24). There were no differences in serum markers or urinary minerals between the basal and calciuric diet in either VDR genotype groups. While the calciuric diet significantly increased urinary NTx (by 25·6 %, P, 0·01) in the f þ VDR group (n 10; carrying one or more ( f ) Fok I alleles), it had no effect in the f 2 VDR group (n 14; not carrying any Fok I alleles). It is concluded that the Na-and protein-induced urinary Ca loss is compensated for by increased bone resorption and that this response may be influenced by VDR genotype.

Effect of a high-protein, high-salt diet on calcium and bone metabolism in postmenopausal women stratified by hormone replacement therapy use

“…Urinary NTx excretion was about 25% higher in postmenopausal women in the ÀHRT group when consuming the calciuric diet compared to basal diet, whereas there was no change in urinary NTx in women in the þ HRT group. While there are no comparable human data in the literature on the combined effect of increased Na and protein intake on markers of bone resorption in postmenopausal women on HRT, we have recently reported a comparable increase in urinary NTx/creatinine levels (B19%) in response to increased dietary Na and protein in postmenopausal women not taking HRT (Harrington et al, 2004). In addition, increased Na intake has been reported to increase markers of bone resorption (urinary DPD (Evans et al, 1997) and NTx (Sellmeyer et al, 2002)) in two out of the three published crossover intervention studies in postmenopausal women not receiving HRT (Evans et al, 1997;Lietz et al, 1997;Sellmeyer et al, 2002; for a review, see Cashman & Flynn, 2003).…”

“…Women in the þ HRT and ÀHRT groups were randomly assigned to the calciuric diet (ie, high in Na (180 mmol/day) and protein (90 g/day)) or the basal diet (ie, adequate in protein (70 g/ day) and low in Na (65 mmol/day)) for 4 weeks, followed by crossover to the alternative dietary regimen for a further 4 weeks. Information on the calciuric diet as well as the methodology for assessment of urinary NTx, Ca, Na, potassium (K), nitrogen (N), serum bone-specific alkaline phosphatase, osteocalcin, 25-hydroxyvitamin D (25 OH D 3 ) or 1,25-dihydroxyvitamin D (1,25 (OH) 2 D 3 ) and plasma parathyroid hormone (PTH) levels are described in detail elsewhere (Harrington et al, 2004).…”

“…We have recently shown that a calciuric diet (ie, a diet high in sodium (Na) and protein) increased urinary type I collagen crosslinked N-telopeptides (NTx) excretion in postmenopausal women (not receiving hormone replacement therapy (HRT), and stratified by vitamin D receptor genotype) as a consequence of poor adaptation to the increased urinary Ca loss (Harrington et al, 2004). Similarly, increasing Na intake has been shown to significantly increase biomarkers of bone resorption in some (Evans et al, 1997;Sellmeyer et al, 2002), but not all studies of postmenopausal women (Lietz et al, 1997).…”

Effect of dietary supplementation with conjugated linoleic acid on markers of calcium and bone metabolism in healthy adult men

“…Study compliance was 98% using a pill count and was also measured by the incorporation of the cis-9,trans-11 isomer of CLA into total plasma lipids. The duration of the intervention (8 weeks) was chosen on the basis that most of the studies that have investigated the effect of CLA on body composition, plasma lipids, and glucose, insulin and/or leptin levels (see review by Terpstra, 2004) were of 4-12 weeks in duration, together with the fact that we and others have shown that levels of biochemical markers of bone turnover can be altered by dietary intervention/supplementation in as little as 2-4 weeks (Ginty et al, 1998a, b;Lin et al, 2003;Harrington et al, 2004).…”

Bone health, genetics, and personalised nutrition

“…Rapuri et al [23] showed that postmenopausal women with the tt genetic variant of VDR appeared to be at a greater risk for the deleterious effect of a high caffeine intake ([300 mg/d) on vertebral bone loss over 3 years, compared to women with the TT VDR genotype. Harrington et al [24] recently showed an interaction between VDR genotype and the effect of a high sodium-high protein intake on the rate of bone resorption in postmenopausal women.…”