[Show abstract][Hide abstract] ABSTRACT: It has been assumed that the increase in urine calcium (UCa) that accompanies an increase in dietary protein was due to increased bone resorption. However, studies using stable Ca isotopes have found that dietary protein increases Ca absorption without increasing bone resorption.
To investigate the impact of a moderately-high protein diet on bone mineral density (BMD).
A randomized, double-blind, placebo-controlled trial of protein supplementation daily for 18 months.
Two institutional research centers.
Two hundred and eight older women and men with a BMI between 19 and 32 kg/m(2) and a self-reported protein intake between 0.6 and 1.0 g/kg.
Subjects were asked to incorporate either a 45 g whey protein or isocaloric maltodextrin supplement into their usual diet for 18 months.
BMD by dual-energy x-ray absorptiometry (DXA), body composition, and markers of skeletal and mineral metabolism were measured at baseline, 9 and 18 months.
There were no significant differences between groups for changes in L-spine BMD (primary outcome) or the other skeletal sites of interest. Truncal lean mass was significantly higher in the protein group at 18 months (p = 0.048). CTX (p = 0.0414), insulin-like growth factor-1 (IGF-1, p = 0.0054) and urinary urea (p <0.001) were also higher in the protein group at the end of the study period. There was no difference in eGFR at 18 months.
Our data suggest that protein supplementation above the RDA (0.8 g/kg) may preserve fat-free mass without adversely affecting skeletal or renal function in healthy older adults.
The Journal of Clinical Endocrinology and Metabolism 04/2015; 100(6):jc20143792. DOI:10.1210/jc.2014-3792 · 6.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We compared circulating levels of Wnt inhibitors among patients with high bone mass mutations in LRP5, unaffected kindred, and unrelated normal controls. Inhibitors were unchanged in affected and unaffected kindred. We saw no meaningful differences between controls and affected individuals. LRP5 signaling may not influence circulating levels of these inhibitors.
Osteoporosis International 06/2014; 25(10). DOI:10.1007/s00198-014-2767-5 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objectives: Objectives
Sarcopenia, the involuntary loss of skeletal muscle with age, affects up to onequarter of older adults. Evidence indicates a positive association between dietary protein intake and lean muscle mass and strength among older persons, but information on dietary protein’s effect on physical performance in older adults has received less attention.
Cross-sectional observational analysis of the relationship of dietary protein on body composition and physical performance.
Clinical research center.
387 healthy women aged 60–90 years (mean 72.7 ± 7.0 y).
Measures included body composition (fat-free mass, appendicular skeletal mass and fat mass) via dual x-ray absorptiometry (DXA), physical performance (Physical Performance Test [PPT] and Short Physical Performance Battery [SPPB]), handgrip strength, Physical Activity Scale in the Elderly (PASE), quality of life measure (SF-8), falls, fractures, nutrient and macromolecule intake (four-day food record). Independent samples t-tests determined mean differences between the above or below RDA protein groups.
Analysis of covariance was used to control for body mass index (BMI) between groups when assessing physical performance, physical activity and health-related quality of life.
The subjects consumed an average of 72.2 g protein/day representing 1.1 g protein/kg body weight/day. Subjects were categorized as below the recommended daily allowance (RDA) for protein (defined as less than 0.8 g protein/kg) or at or above the RDA (equal to or higher than 0.8 g protein/kg). Ninety-seven subjects (25%) were in the low protein group, and 290 (75%) were in the higher protein group. Women in the higher protein group had lower body mass, including fat and lean mass, and fat-to-lean ratio than those in the lower-protein group (p <0.001). Composite scores of upper and lower extremity strength were impaired in the group with low protein intake; SPPB score was 9.9±1.9 compared to 10.6±1.6 in those with higher protein intake and PPT was 19.8± 2.9 compared to 20.9±2.1 in the low and higher protein groups, respectively. The results were attenuated by correction for BMI, but remained significant. The physical component of the SF-8 was also lower in the low protein group but did not remain significant when controlling for BMI. No significant differences were found in hand grip strength or reported physical activity.
Healthy, older postmenopausal women consumed, on average, 1.1 g/kg/d protein, although 25% consumed less than the RDA. Those in the low protein group had higher body fat and fat-to-lean ratio than those who consumed the higher protein diet. Upper and lower extremity function was impaired in those who consumed a low protein diet compared to those with a higher protein intake. Protein intake should be considered when evaluating the multi-factorial loss of physical function in older women.
The Journal of Nutrition Health and Aging 02/2014; 18(2). DOI:10.1007/s12603-013-0391-2 · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Increasing dietary protein within a physiologic range stimulates intestinal calcium absorption, but it is not known if specific amino acids or dietary protein as a whole are responsible for this effect. Therefore, we selectively supplemented a low-protein (0.7 g/kg) diet with either the calcium-sensing receptor-activating amino acids (CaSR-AAAs) L-tryptophan, L-phenylalanine, and L-histidine, or the dibasic amino acids (DAAs) L-arginine and L-lysine, to achieve intakes comparable to the content of a high-protein diet (2.1 g/kg) and measured intestinal calcium absorption. Fourteen young women took part in a placebo-controlled, double-blind, crossover feeding trial in which each participant ingested a 6-d low-protein diet supplemented with CaSR-AAAs, DAAs, or methylcellulose capsules (control) after an 11-d adjustment period. All participants ingested all 3 diets in random order. Intestinal calcium absorption was measured between days 5 and 6 using dual-stable calcium isotopes ((42)Ca, (43)Ca, and (44)Ca). There was no difference in calcium absorption between the diet supplemented with CaSR-AAAs (22.9 ± 2.0%) and the control diet (22.3 ± 1.4%) (P = 0.64). However, calcium absorption tended to be greater during the DAA supplementation period (25.2 ± 1.4%) compared with the control diet period (22.3 ± 1.4%) (P < 0.10). Larger and longer clinical trials are needed to clarify the possible benefit of arginine and lysine on calcium absorption.
Journal of Nutrition 01/2014; 144(3). DOI:10.3945/jn.113.185009 · 3.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To determine the usefulness of urinary urea as an index of dietary protein intake, 10 postmenopausal women were enrolled in and completed a randomized, double-blind, cross-over feeding trial from September 2008 to May 2010 that compared 10 days of a 45-g whey supplement with 10 days of a 45-g maltodextrin control. Urinary nitrogen, urinary calcium, urinary urea, and bone turnover markers were measured at days 0, 7, and 10. Paired sample t tests, Pearson's correlation statistic, and simple linear regression were used to assess differences between treatments and associations among urinary metabolites. Urinary nitrogen/urinary creatinine rose from 12.3±1.7 g/g (99.6±13.8 mmol/mmol) to 16.8±2.2 g/g (135.5±17.8 mmol/mmol) with whey supplementation, but did not change with maltodextrin. Whey supplementation caused urinary calcium to rise by 4.76±1.84 mg (1.19±0.46 mmol) without a change in bone turnover markers. Because our goal was to estimate protein intake from urinary nitrogen/urinary creatinine, we used our data to develop the following equation: protein intake (g/day)=71.221+1.719×(urinary nitrogen, g)/creatinine, g) (R=0.46, R(2)=0.21). As a more rapid and less costly alternative to urinary nitrogen/urinary creatinine, we next determined whether urinary urea could predict protein intake and found that protein intake (g/day)=63.844+1.11×(urinary urea, g/creatinine, g) (R=0.58, R(2)=0.34). These data indicate that urinary urea/urinary creatinine is at least as good a marker of dietary protein intake as urinary nitrogen and is easier to quantitate in nutrition intervention trials.
Journal of the American Academy of Nutrition and Dietetics 03/2013; 113(3):447-51. DOI:10.1016/j.jand.2012.11.002 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Proton pump inhibitors (PPIs) are the most potent gastric acid suppressing drugs available, and their use is widespread. An emerging concern about chronic PPI therapy is whether these drugs impair intestinal calcium absorption, resulting in a negative calcium balance and thereby potentially causing bone loss. The objective of this study was to evaluate the acute effect of the PPI esomeprazole or placebo on intestinal calcium absorption in healthy adults. Twelve young adults participated in a placebo-controlled, double-blind, crossover study. There were two 3-week interventions that included a 14-day adjustment period (designed to stabilize calcium homeostasis) followed by 6 days of a diet containing 800 mg of calcium and 2.1 g/kg of protein (intervention). During the last 3 days of the adjustment period and throughout the intervention period, subjects consumed esomeprazole or placebo. Half the subjects underwent 24-hour continuous gastric acid pH monitoring. Intestinal calcium absorption was measured using dual-stable calcium isotopes at the end of each intervention. Treatment with esomprazole significantly increased gastric pH (mean pH on PPI 5.38 +/- 0.13, mean pH on placebo 2.70 +/- 0.44, p = .005). Neither calcium absorption (PPI 34.2% +/- 2.4%, placebo 31.5% +/- 2.1%, p = .24) nor urinary calcium (PPI 321 +/- 38 mg/34 hours, placebo 355 +/- 37 mg/34 hours, p = .07) differed between the PPI and placebo groups. It is concluded that short-term gastric acid suppression by PPIs does not attenuate intestinal calcium absorption in healthy young adults.
Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 10/2010; 25(10):2205-11. DOI:10.1002/jbmr.108 · 6.83 Impact Factor