Effects of Hydration and Calcium Supplementation on Urine Calcium Concentration in Healthy Postmenopausal Women.

OBJECTIVE: The aim of this study was to determine whether calcium supplementation, compared with placebo, increases urine calcium concentrations to levels indicative of increased renal stone risk, and the role that fluid intake, as indicated by urine volume, may play in mitigating this risk. METHODS: This is a secondary analysis of data from a randomized placebo-controlled trial of 500 mg/d calcium supplementation to prevent bone loss. Subjects were 240 white postmenopausal women age 40 to 70 years in good general health. Effects of supplementation on 1-year changes in 24h urine calcium concentration and urine volume were examined. RESULTS: Both treatment group and urine volume were strong independent predictors of urine calcium concentration (p < 0.001). Among subjects with urine volume under 2 L/24 h, more than half of placebo subjects were at lowest risk for renal stones compared with less than 35% of calcium-supplemented subjects. Among those with higher urine volumes, all placebo subjects and more than 80% of calcium supplemented subjects were at lowest risk. CONCLUSIONS: The increased risk of renal stones with calcium supplement use may be largely eliminated with adequate fluid intake, but older adults may not spontaneously consume adequate fluids to minimize this risk and should be counseled to do so.

Predictors of Weight Loss in African Americans with Prediabetes or Early Diabetes.

ACKNOWLEGMENT: This study was supported by Clinical Research Grant (7-08-CR-27) from the American Diabetes Association and by a contract (58-1950-7-707) with the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University. This article does not necessarily reflect the views or policies of the U.S. Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government. PURPOSE: This analysis was undertaken to describe healthcare seeking, weight loss efforts and predictors of weight loss among African Americans recently identified with prediabetes or early diabetes METHODS: A secondary analysis was conducted on data collected from 89 participants who completed a previously published 12-week randomized placebo-controlled trial testing the benefit of vitamin D supplementation on blood measures predictive of diabetes risk. Information about care seeking, weight loss strategies and weight loss effort was collected by questionnaire at three data collection visits. Weight was measured by trained staff at each visit. RESULTS: More than half of the participants saw a healthcare provider during the study, but few recalled receiving advice about diet, physical activity or other strategies for weight loss. Thirty-seven % of participants maintained their weight within 1 kg of their baseline weight. Of the remaining participants, half gained >1 kg and half lost >1 kg during the study period. Age-adjusted independent predictors of weight loss included a visit to a healthcare provider for preventive care, dietary restrictions, and consistent weight loss effort. Vitamin D supplementation had no effect on weight change. CONCLUSIONS: This study reinforces the importance of preventive healthcare and sustainable changes in diet and physical activity. It also suggests that physicians need better tools for motivating and supporting their patients to adopt behaviors that can reduce diabetes risk. For the millions of Americans who are trying to lose weight to reduce their risk for chronic disease, this study reinforces the importance of sustained effort.

An evaluation of the reliability of muscle fiber cross-sectional area and fiber number measurements in rat skeletal muscle.

BACKGROUND: The reliability of estimating muscle fiber cross-sectional area (measure of muscle fiber size) and fiber number from only a subset of fibers in rat hindlimb muscle cross-sections has not been systematically evaluated. This study examined the variability in mean estimates of fiber cross-sectional area as a function of the number of fibers measured, and tested whether counting a subset of fibers in a cross-section could predict total fiber number in middle-aged rats. RESULTS: Soleus and extensor digitorum longus (EDL) muscle cross-sections from 23-month-old, male Fisher 344 x Brown Norway rats were stained for myofibrillar ATPase activity to identify muscle fiber type (either type I [slow-twitch] or II [fast-twitch]) and laminin to facilitate fiber cross-sectional measurements. We outlined the circumference of 1000 to 1600 single muscle fibers for measurement of fiber cross-sectional area within muscle sections. Mean type I fiber cross-sectional area was based on soleus muscle sections which were predominantly composed of type I muscle fibers. Mean type II fiber cross-sectional area was based on EDL muscle sections which were predominantly composed of type II muscle fibers. A bootstrapping resampling technique demonstrated that variability in sampling distribution of mean type I and II fiber cross-sectional areas decreased and gradually stabilized as the number of fibers measured increased with large declines in variability occurring at numbers below 150 fibers. Coefficients of variation for bootstrapped mean type I fiber cross-sectional areas were lower than for type II. In the same muscle sections, total fiber number was compared to fiber numbers within 1, 2, 3, and 4 fixed field areas (10x magnification; 1000 x 1500 pixels in size/field) on the cross-section. Fiber numbers from 3 to 4 fields (approximating 15 to 20% of the cross-section) provided a reasonably predictive value of total fiber number (r=0.57-0.59, P=0.003). CONCLUSIONS: These data describe a pattern of improved precision in estimating mean fiber cross-sectional area as sample size of fibers measured increases to at least 150 in this rat model. Counting 15-20% of the fibers in cross-sections provides a reasonably reliable estimate of the total fiber number.

Vitamin D and its role in skeletal muscle.

This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated with risk of falling. Clinical trials of vitamin D supplementation in older adults with low vitamin D status mostly report improvements in muscle performance and reductions in falls. The underlying mechanisms are probably both indirect via calcium and phosphate and direct via activation of the vitamin D receptor (VDR) on muscle cells by 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. VDR activation at the genomic level regulates transcription of genes involved in calcium handling and muscle cell differentiation and proliferation. A putative membrane-associated VDR activates intracellular signaling pathways also involved in calcium handling and signaling and myogenesis. Additional evidence comes from VDR knockout mouse models with abnormal muscle morphology and physical function, and VDR polymorphisms which are associated with differences in muscle strength. Recent identification of CYP27B1 bioactivity in skeletal muscle cells and in regenerating adult mouse muscle lends support to the direct action of both 25-hydroxyvitamin D and 1,25(OH)(2)D in muscle. Despite these research advances, many questions remain. Further research is needed to fully characterize molecular mechanisms of vitamin D action on muscle cells downstream of the VDR, describe the effects on muscle morphology and contractility, and determine whether these molecular and cellular effects translate into clinical improvements in physical function.

Serum 25-hydroxyvitamin D concentration and physical function in adult men.

OBJECTIVE: Recent reports suggest that vitamin D status influences musculoskeletal health; yet, there are limited data in adult men. This study investigated whether serum 25-hydroxyvitamin D [25(OH)D] concentration was associated with lean body mass, muscle strength and physical performance in men. DESIGN: Population-based, observational survey. PARTICIPANTS: 1219 black, Hispanic and white randomly selected men aged 30-79 years from the Boston Area Community Health/Bone Survey. MEASUREMENTS: Lean body mass by dual-energy X-ray absorptiometry, hand grip strength, a composite physical function score (chair stand and walking speed), 25(OH)D, parathyroid hormone (PTH), testosterone, age, race, body mass index, socioeconomic status, education, smoking, arthritis, self-reported health, calcium intake, physical activity. RESULTS: The distributions of serum 25(OH)D quartiles differed by race/ethnicity, education and smoking status. After adjustment for multiple lifestyle factors, serum 25(OH)D was not related to lean body mass, grip strength or the composite physical function score (all P>0.20). There was no variation in the associations between 25(OH)D level and outcomes by race/ethnicity. The relationship between PTH and the outcomes revealed similar results. CONCLUSION: In this population-based sample of adult men with a broad age range, there was no association between serum 25(OH)D concentration and lean body mass, muscle strength and physical function after controlling for multiple lifestyle factors.

Evaluation of an inexpensive calcium absorption index in healthy older men and women.

OBJECTIVE: Calcium absorption is an important determinant of calcium retention and bone metabolism. However, most methods of measuring calcium absorption, including the well-established dual stable isotope method, are costly and cumbersome to implement. We evaluated whether an oral calcium tolerance test (OCTT), which involves measuring calcium excretion in a fasting 2-h urine collection and two 2-h collections following an oral calcium dose, may be a useful index of calcium absorption in older adults consuming a fixed calcium intake of 30 mmol/day. DESIGN: After a 10-day metabolic diet containing 30 mmol/day of calcium, subjects had calcium absorption measured using the dual stable isotope method and the OCTT. PARTICIPANTS: Eleven healthy subjects aged 54-74 years. MEASUREMENTS: Fractional calcium absorption (FCA), calcium excretion in a fasting 2-h urine collection and two 2-h collections in response to a 10-mmol calcium dose (total intake 30 mmol/day). RESULTS: Calcium excretion from several combinations of the urine collections was examined in relation to FCA. The most predictive of FCA was calcium excretion 4 h following the calcium dose. This measure was significantly correlated with FCA (r = 0.735, P = 0.010), fitting 54% of the variability in FCA. CONCLUSION: Urinary calcium excretion during the 4 h after a 10-mmol calcium dose is a useful index of calcium absorption among older adults consuming recommended calcium intakes. This test is inexpensive, easy to implement and potentially useful in large clinical studies.

Three-phase model harmonizes estimates of the maximal suppression of parathyroid hormone by 25-hydroxyvitamin D in persons 65 years of age and older.

The concentration or threshold of 25-hydroxyvitamin D [25(OH)D] needed to maximally suppress intact serum parathyroid hormone (iPTH) has been suggested as a measure of optimal vitamin D status. Depending upon the definition of maximal suppression of iPTH and the 2-phase regression approach used, 2 distinct clusters for a single 25(OH)D threshold have been reported: 16-20 ng/mL (40-50 nmol/L) and 30-32 ng/mL (75-80 nmol/L). To rationalize the apparently disparate published results, we compared thresholds from several regression models including a 3-phase one to estimate simultaneously 2 thresholds before and after adjusting for possible confounding for age, BMI, glomerular filtration rate, dietary calcium, and season (April-September vs. October-March) within a single data set, i.e. data from the Tufts University Sites Testing Osteoporosis Prevention/Intervention Treatment study, consisting of 181 men and 206 women (total n = 387) ages 65-87 y. Plasma 25(OH)D and serum iPTH concentrations were (mean +/- SD) 22.1 +/- 7.44 ng/mL (55.25 +/- 18.6 nmol/L) and 36.6 +/- 16.03 pg/mL (3.88 +/- 1.7 pmol/L), respectively. The 3-phase model identified 2 thresholds of 12 ng/mL (30 nmol/L) and 28 ng/mL (70 nmol/L); similar results were found from the 2-phase models evaluated, i.e. 13-20 and 27-30 ng/mL (32.5-50 and 67.5-75 nmol/L) and with previous results. Adjusting for confounding did not change the results substantially. Accordingly, the 3-phase model appears to be superior to the 2-phase approach, because it simultaneously estimates the 2 threshold clusters found from the 2-phase approaches along with estimating confidence limits. If replicated, it may be of both clinical and public health importance.

Treatment with potassium bicarbonate lowers calcium excretion and bone resorption in older men and women.

CONTEXT: Bicarbonate has been implicated in bone health in older subjects on acid-producing diets in short-term studies. OBJECTIVE: The objective of this study was to determine the effects of potassium bicarbonate and its components on changes in bone resorption and calcium excretion over 3 months in older men and women. DESIGN, PARTICIPANTS, AND INTERVENTION: In this double-blind, controlled trial, 171 men and women age 50 and older were randomized to receive placebo or 67.5 mmol/d of potassium bicarbonate, sodium bicarbonate, or potassium chloride for 3 months. All subjects received calcium (600 mg of calcium as triphosphate) and 525 IU of vitamin D(3) daily. MAIN OUTCOME MEASURES: Twenty-four-hour urinary N-telopeptide and calcium were measured at entry and after 3 months. Changes in these measures were compared across treatment groups in the 162 participants included in the analyses. RESULTS: Bicarbonate affected the study outcomes, whereas potassium did not; the two bicarbonate groups and the two no bicarbonate groups were therefore combined. Subjects taking bicarbonate had significant reductions in urinary N-telopeptide and calcium excretion, when compared with subjects taking no bicarbonate (both before and after adjustment for baseline laboratory value, sex, and changes in urinary sodium and potassium; P = 0.001 for both, adjusted). Potassium supplementation did not significantly affect N-telopeptide or calcium excretion. CONCLUSIONS: Bicarbonate, but not potassium, had a favorable effect on bone resorption and calcium excretion. This suggests that increasing the alkali content of the diet may attenuate bone loss in healthy older adults.

Potassium bicarbonate attenuates the urinary nitrogen excretion that accompanies an increase in dietary protein and may promote calcium absorption.

CONTEXT: Protein is an essential component of muscle and bone. However, the acidic byproducts of protein metabolism may have a negative impact on the musculoskeletal system, particularly in older individuals with declining renal function. OBJECTIVE: We sought to determine whether adding an alkaline salt, potassium bicarbonate (KHCO3), allows protein to have a more favorable net impact on intermediary indices of muscle and bone conservation than it does in the usual acidic environment. DESIGN: We conducted a 41-d randomized, placebo-controlled, double-blind study of KHCO3 or placebo with a 16-d phase-in and two successive 10-d metabolic diets containing low (0.5 g/kg) or high (1.5 g/kg) protein in random order with a 5-d washout between diets. SETTING: The study was conducted in a metabolic research unit. PARTICIPANTS: Nineteen healthy subjects ages 54-82 yr participated. INTERVENTION: KHCO3 (up to 90 mmol/d) or placebo was administered for 41 d. MAIN OUTCOME MEASURES: We measured 24-h urinary nitrogen excretion, IGF-I, 24-h urinary calcium excretion, and fractional calcium absorption. RESULTS: KHCO3 reduced the rise in urinary nitrogen excretion that accompanied an increase in protein intake (P = 0.015) and was associated with higher IGF-I levels on the low-protein diet (P = 0.027) with a similar trend on the high-protein diet (P = 0.050). KHCO3 was also associated with higher fractional calcium absorption on the low-protein diet (P = 0.041) with a similar trend on the high-protein diet (P = 0.064). CONCLUSIONS: In older adults, KHCO3 attenuates the protein-induced rise in urinary nitrogen excretion, and this may be mediated by IGF-I. KHCO3 may also promote calcium absorption independent of the dietary protein content.

Reduced sun exposure does not explain the inverse association of 25-hydroxyvitamin D with percent body fat in older adults.

CONTEXT: Greater adiposity is associated with lower blood levels of 25-hydroxyvitamin D [25(OH)D]. The extent to which this results from reduced sun exposure among heavier individuals is unknown. OBJECTIVES: This analysis was conducted to determine whether sun exposure habits differ according to percent body fat (%FAT) in older adults and to what extent they explain the inverse association of adiposity with 25(OH)D in that population. DESIGN: We performed a cross-sectional analysis of baseline data from a randomized trial of calcium and vitamin D supplementation to prevent bone loss. SETTING: The study was performed at the Metabolic Research Unit at the Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University. PARTICIPANTS: A total of 381 generally healthy male and female volunteers age 65 and older participated in the study. Exclusion criteria included vitamin D and calcium supplement use, and medical conditions and medications known to affect bone metabolism. INTERVENTION: There were no interventions. Measurements for this analysis were made before participants received trial supplements. MAIN OUTCOME MEASURES: Plasma 25(OH)D, an indicator of vitamin D status, was measured. RESULTS: Sunscreen use, hours spent outside per week, and percent of skin exposed did not differ across quartiles of %FAT (P > 0.43). 25(OH)D decreased across %FAT quartiles (P < 0.05) and was about 20% lower in the highest compared with the lowest quartile of %FAT after adjustments for age, sex, season, and vitamin D intake. Further adjustment for sun exposure habits had little effect on estimates of 25(OH)D. CONCLUSIONS: In older adults, sun exposure habits do not vary according to adiposity and do not appear to explain lower 25(OH)D concentrations with increasing adiposity.

Prevalence of vitamin D deficiency in uninsured women.

BACKGROUND: Vitamin D deficiency, an important risk factor for osteoporosis and other chronic medical conditions, is epidemic in the United States. Uninsured women may be at an even higher risk for vitamin D deficiency than others owing to low intake of dietary and supplemental vitamin D and limited sun exposure. OBJECTIVE: Our goal was to determine the prevalence of vitamin D deficiency in this vulnerable population. SETTING AND PARTICIPANTS: We enrolled 145 uninsured women at a County Free Medical Clinic in urban Michigan. Questionnaires were used to obtain information about demographics, medical history, vitamin supplementation, sunlight exposure, and dietary vitamin D intake. RESULTS: The 96 women who were tested for vitamin D status ranged in age from 21 to 65 years (mean 48 +/- 11), and 67% were vitamin D deficient as indicated by a 25-hydroxyvitamin D [25(OH)D)] level <50 nmol/L (20 ng/mL). Non-Caucasians were 3 times more likely than Caucasians to be vitamin D deficient (P = .049). Mean dietary vitamin D intake was low (125 +/- 109 IU/d) and only 24% of the participants used any supplemental vitamin D. Participants with total vitamin D intake <400 IU/day from diet and supplements were 10 times more likely to be vitamin D deficient than others (P < .001). CONCLUSIONS: These results demonstrate a high prevalence of vitamin D deficiency in an uninsured, medically underserved female population. Uninsured women should be strongly encouraged to increase their vitamin D intake.

Testosterone, dehydroepiandrosterone, and physical performance in older men: results from the Massachusetts Male Aging Study.

OBJECTIVE: This manuscript examines the relationships of total testosterone (T), bioavailable T, dehydroepiandrosterone (DHEA), and DHEA sulfate (DHEAS) to measures of physical performance in a large, population-based, random sample of men. METHODS: In the most recent wave of the Massachusetts Male Aging Study, measures of strength and physical performance [seven-item physical performance test (PPT), timed chair stand test, and grip strength] were made in 684 men, aged 55-85 yr. Complete hormone data were also obtained. Initial graphical exploration of performance outcomes as a function of hormone levels showed linear increases in physical performance up to certain threshold hormone concentrations, beyond which the associations were diminished. Regression models were used to estimate threshold locations and standardized regression coefficients quantifying the association between hormones and strength. RESULTS: All hormones exhibited significant age-adjusted positive association with PPT score below, but not necessarily above, the thresholds. DHEA was positively associated with chair stand score below, but was not above the threshold. None of the hormones studied was significantly associated with grip strength. CONCLUSION: Up to certain critical concentrations, elevated levels of TT, total T, bioavailable T, DHEA, and DHEA sulfate are associated with increased physical performance, as indicated by the PPT. However, levels beyond those critical concentrations, as might be achieved through exogenous supplementation, do not appear to confer any additional benefit. In general, hormone concentrations do not appear to be meaningfully associated with grip strength or chair stand scores.

Dietary fat increases vitamin D-3 absorption.

BACKGROUND: The plasma 25-hydroxyvitamin D response to supplementation with vitamin D varies widely, but vitamin D absorption differences based on diet composition is poorly understood. OBJECTIVES: We tested the hypotheses that absorption of vitamin D-3 is greater when the supplement is taken with a meal containing fat than with a fat-free meal and that absorption is greater when the fat in the meal has a higher monounsaturated-to-polyunsaturated fatty acid ratio (MUFA:PUFA). DESIGN: Open, three-group, single-dose vitamin D-3 comparative absorption experiment. PARTICIPANTS/SETTING: Our 1-day study was conducted in 50 healthy older men and women who were randomly assigned to one of three meal groups: fat-free meal, and a meal with 30% of calories as fat with a low (1:4) and one with a high (4:1) MUFA:PUFA. After a 12-hour fast, all subjects took a single 50,000 IU vitamin D-3 supplement with their test breakfast meal. MAIN OUTCOME MEASURES: Plasma vitamin D-3 was measured by liquid chromatography-mass spectrometry before and 10, 12 (the expected peak), and 14 hours after the dose. STATISTICAL ANALYSES PERFORMED: Means were compared with two-tailed t tests for independent samples. Group differences in vitamin D-3 absorption across the measurement time points were examined by analysis of variance with the repeated measures subcommand of the general linear models procedure. RESULTS: The mean peak (12-hour) plasma vitamin D-3 level after the dose was 32% (95% CI 11% to 52%) greater in subjects consuming fat-containing compared with fat-free meals (P=0.003). Absorption did not differ significantly at any time point in the high and low MUFA and PUFA groups. CONCLUSIONS: The presence of fat in a meal with which a vitamin D-3 supplement is taken significantly enhances absorption of the supplement, but the MUFA:PUFA of the fat in that meal does not influence its absorption.

Potassium Bicarbonate Supplementation Lowers Bone Turnover and Calcium Excretion in Older Men and Women: A Randomized Dose-Finding Trial.

The acid load accompanying modern diets may have adverse effects on bone and muscle metabolism. Treatment with alkaline salts of potassium can neutralize the acid load, but the optimal amount of alkali is not established. Our objective was to determine the effectiveness of two doses of potassium bicarbonate (KHCO3 ) compared with placebo on biochemical markers of bone turnover, and calcium and nitrogen (N) excretion. In this double-blind, randomized, placebo-controlled study, 244 men and women age 50 years and older were randomized to placebo or 1 mmol/kg or 1.5 mmol/kg of KHCO3 daily for 3 months; 233 completed the study. The primary outcomes were changes in 24-hour urinary N-telopeptide (NTX) and N; changes in these measures were compared across the treatment groups. Exploratory outcomes included 24-hour urinary calcium excretion, serum amino-terminal propeptide of type I procollagen (P1NP), and muscle strength and function assessments. The median administered doses in the low-dose and high-dose groups were 81 mmol/day and 122 mmol/day, respectively. When compared with placebo, urinary NTX declined significantly in the low-dose group (p = 0.012, after adjustment for baseline NTX, gender, and change in urine creatinine) and serum P1NP declined significantly in the low-dose group (p = 0.004, adjusted for baseline P1NP and gender). Urinary calcium declined significantly in both KHCO3 groups versus placebo (p < 0.001, adjusted for baseline urinary calcium, gender, and changes in urine creatinine and calcium intake). There was no significant effect of either dose of KHCO3 on urinary N excretion or on the physical strength and function measures. KHCO3 has favorable effects on bone turnover and calcium excretion and the lower dose appears to be the more effective dose. Long-term trials to assess the effect of alkali on bone mass and fracture risk are needed.

Effect of dietary protein supplements on calcium excretion in healthy older men and women.

Currently there is no consensus on the impact of dietary protein on calcium and bone metabolism. This study was conducted to examine the effect of increasing protein intake on urinary calcium excretion and to compare circulating levels of IGF-I and biochemical markers of bone turnover in healthy older men and women who consumed either a high or a low protein food supplement for 9 wk. Thirty-two subjects with usual protein intakes of less than 0.85 g/kg.d were randomly assigned to daily high (0.75 g/kg) or low (0.04 g/kg) protein supplement groups. Isocaloric diets were maintained by advising subjects to reduce their intake of carbohydrates. Selected biochemical measurements were made at baseline and on d 35 and either d 49 or 63. Changes in urinary calcium excretion in the two groups did not differ significantly over the course of the study. The high protein group had significantly higher levels of serum IGF-I (P = 0.008) and lower levels of urinary N-telopeptide (P = 0.038) over the period of d 35-49 or 63. We conclude that increasing protein intake from 0.78 to 1.55 g/kg.d with meat supplements in combination with reducing carbohydrate intake did not alter urine calcium excretion, but was associated with higher circulating levels of IGF-I, a bone growth factor, and lowered levels of urinary N-telopeptide, a marker of bone resorption. In contrast to the widely held belief that increased protein intake results in calcium wasting, meat supplements, when exchanged isocalorically for carbohydrates, may have a favorable impact on the skeleton in healthy older men and women.

Calcium intake influences the association of protein intake with rates of bone loss in elderly men and women.

BACKGROUND: There is currently no consensus on the effect of dietary protein intake on the skeleton, but there is some indication that low calcium intakes adversely influence the effect of dietary protein on fracture risk. OBJECTIVE: The objective of the present study was to determine whether supplemental calcium citrate malate and vitamin D influence any associations between protein intake and change in bone mineral density (BMD). DESIGN: Associations between protein intake and change in BMD were examined in 342 healthy men and women (aged > or = 65 y) who had completed a 3-y, randomized, placebo-controlled trial of calcium and vitamin D supplementation. Protein intake was assessed at the midpoint of the study with the use of a food-frequency questionnaire and BMD was assessed every 6 mo by dual-energy X-ray absorptiometry. RESULTS: The mean (+/-SD) protein intake of all subjects was 79.1 +/- 25.6 g/d and the mean total calcium intakes of the supplemented and placebo groups were 1346 +/- 358 and 871 +/- 413 mg/d, respectively. Higher protein intake was significantly associated with a favorable 3-y change in total-body BMD in the supplemented group (in a model containing terms for age, sex, weight, total energy intake, and dietary calcium intake) but not in the placebo group. The pattern of change in femoral neck BMD with increasing protein intake in the supplemented group was similar to that for the total body. CONCLUSION: Increasing protein intake may have a favorable effect on change in BMD in elderly subjects supplemented with calcium citrate malate and vitamin D.

Precision of single vs bilateral hip bone mineral density scans.

This study was performed to determine and compare the precision of single and bilateral hip bone mineral density (BMD) measurements and to determine the precision of spinal and total body measurements by dual-energy X-ray absorptiometry (DXA). Precision (group root-mean-square average coefficient of variation) was determined in 6 subjects scanned six times each at the spine, both hips, and total body, with repositioning after each scan. Mean percentage coefficients of variance (%CVs) in BMD for single and bilateral hip scans were, respectively: 0.65% and 0.67% for the total hip, 1.16% and 1.03% for the trochanter, and 1.66% and 1.31% for the femoral neck, respectively. Mean %CV was 1.04% for spine BMD (L2-L4), 0.67% for total body BMD, 1.12% for total body bone mineral content (BMC), 0.94% for total body fat tissue, and 0.77% for total body nonfat soft tissue. We conclude that precision overall is excellent and that femoral neck precision can be improved with bilateral compared with the traditional single hip scans.

The effect of calcium consumption on iron absorption and iron status.

Recent increases in recommended calcium intakes recognize the important role of calcium in skeletal health, but many Americans, especially women, consume far less than recommended amounts. A potential drawback to encouraging increased calcium intake is suggested by the extensive literature showing an adverse effect of high calcium intake on dietary iron absorption, at least in short, highly controlled, experimental studies. However, the applicability of short-term studies involving test meals to long-term iron absorption and iron status is limited given the variety of foods and food combinations in self-selected diets and the ability of individuals to adapt to reduced iron intake. In general, studies of whole diets and studies conducted over several weeks tend to show no effect of increased calcium intake on iron absorption. In addition, experimental studies of calcium and iron status measures such as serum ferritin show no long-term effect of calcium supplementation on iron status. Prevention and treatment of iron deficiency should emphasize adequate consumption of iron-rich foods and, when indicated, the use of iron supplements. Recommended calcium intakes are important for skeletal health and do not appear to increase the risk for iron deficiency in healthy people.

Ability of vitamin D to reduce inflammation in adults without acute illness.

In vitro studies and some clinical studies suggest that vitamin D plays an important role in reducing inflammation. The objective of this review was to examine recent evidence that vitamin D status influences the level of inflammation in adults without acute illness or injury. Five large cross-sectional studies and two randomized controlled trials are the focus of this review. Associations between 25-hydroxyvitamin D (25OHD) and inflammation markers are significant and inverse in study populations with low 25OHD levels (<21 ng/mL). They are also inverse in adults with relatively high inflammation levels. These associations in the few available randomized controlled vitamin D intervention trials have been null; this may be because they were not examined in populations with sufficiently low levels of 25OHD or high levels of inflammation.