Factors associated with calcium absorption efficiency in pre- and perimenopausal women

Association between Phytochemical Index and Osteoporosis in Women: A Prospective Cohort Study in Korea

Osteoporosis is a prevalent issue among postmenopausal women, who have a higher incidence of the condition than men. This study aimed to examine the relationship between phytochemical-rich food intake and osteoporosis incidence in premenopausal and postmenopausal women. The data analyzed included 4600 women aged 40–69 who were free of osteoporosis at baseline, with dietary intake evaluated through a semi-quantitative food frequency questionnaire and osteoporosis prevalence determined using interviewer-administered questionnaires and bone mineral density tests. The phytochemical index (PI) was calculated to reflect the intake levels of phytochemical-rich foods. Postmenopausal women in the highest PI quartile had a 16% lower risk of osteoporosis (95% confidence interval (CI): 0.71 to 0.99, p for trend = 0.02) than those in the lowest quartile, while no significant association was observed among premenopausal women (hazard ratio: 0.98, 95% CI: 0.78 to 1.24, p for trend = 0.8). These findings suggest that consuming phytochemical-rich foods may have a protective effect against osteoporosis in postmenopausal women, offering valuable scientific insights. However, additional research is needed to validate these findings using biochemical data. Overall, this study highlights the potential of dietary interventions to reduce the risk of osteoporosis in postmenopausal women.

Bioavailability of calcium in an enriched postbiotic system compared to calcium citrate in healthy postmenopausal females; A randomized, double-blind, comparator-controlled, crossover study

Introduction

Bioavailability of calcium is an important consideration when designing supplements for achieving adequate calcium intake, mainly in high-risk, and aged populations. Alternative supplementation strategies may be able to circumvent absorption issues commonly seen with calcium supplements. The objective of this study was to assess the bioavailability of a single serving of two calcium formulations vs. comparator product in healthy postmenopausal women.

Methods

A total of 24 participants between 45 and 65 years were enrolled in a randomized, double-blind, three-phase, crossover study, with a 7-day washout period between phases. The bioavailability of calcium from calcium-carrying Saccharomyces cerevisiae (Ca-SC) or calcium-carrying Lactobacillus (Ca-LAB) in the form of postbiotic products versus calcium citrate, a conventional salt-based calcium supplement, was determined. Each product provided 630 mg of calcium and 400 IU of vitamin D3. After a 14-h (overnight) fast followed by a single dose of product with a standard low-calcium breakfast, both serum and urine calcium concentrations were assessed for up to 8 and 24 h, respectively.

Results

Ca-LAB resulted in greater calcium bioavailability, demonstrated by significantly higher area under the curve and peak concentration both in blood and urine, and total calcium mass excreted in urine. The bioavailability of calcium was similar for Ca-SC and calcium citrate except for the peak concentration value that was significantly higher for calcium citrate. Both Ca-LAB and Ca-SC were well tolerated with no significant difference in adverse events between the products during the study.

Discussion

These findings suggest that calcium enriched in a Lactobacillus-based postbiotic system is associated with higher levels of bioavailability as compared to calcium citrate, while a calcium-enriched yeast-based postbiotic does not influence calcium absorption.

Intestinal Calcium Absorption Decreases After Laparoscopic Sleeve Gastrectomy Despite Optimization of Vitamin D Status

CONTEXT

Laparoscopic sleeve gastrectomy (LSG), now the most commonly performed bariatric operation, is a highly effective treatment for obesity. While Roux-en-Y gastric bypass is known to impair intestinal fractional calcium absorption (FCA) and negatively affect bone metabolism, LSG's effects on calcium homeostasis and bone health have not been well characterized.

OBJECTIVE

We determined the effect of LSG on FCA, while maintaining robust 25-hydroxyvitamin D (25OHD) levels and recommended calcium intake.

DESIGN, SETTING, PARTICIPANTS

Prospective pre-post observational cohort study of 35 women and men with severe obesity undergoing LSG.

MAIN OUTCOMES

FCA was measured preoperatively and 6 months postoperatively with a gold-standard dual stable isotope method. Other measures included calciotropic hormones, bone turnover markers, and bone mineral density (BMD) by dual-energy X-ray absorptiometry and quantitative computed tomography.

RESULTS

Mean ± SD FCA decreased from 31.4 ± 15.4% preoperatively to 16.1 ± 12.3% postoperatively (P < 0.01), while median (interquartile range) 25OHD levels were 39 (32-46) ng/mL and 36 (30-46) ng/mL, respectively. Concurrently, median 1,25-dihydroxyvitamin D level increased from 60 (50-82) pg/mL to 86 (72-107) pg/mL (P < 0.01), without significant changes in parathyroid hormone or 24-hour urinary calcium levels. Bone turnover marker levels increased substantially, and areal BMD decreased at the proximal femur. Those with lower postoperative FCA had greater areal BMD loss at the total hip (ρ = 0.45, P < 0.01).

CONCLUSIONS

FCA decreases after LSG, with a concurrent rise in bone turnover marker levels and decline in BMD, despite robust 25OHD levels and with recommended calcium intake. Decline in FCA could contribute to negative skeletal effects following LSG.

Dietary Effects of Nanopowder Eggshells on Mineral Contents, Bone Turnover Biomarkers, and Regulators of Bone Resorption in Healthy Rats and Ovariectomy-Induced Osteoporosis Rat Model

Postmenopausal osteoporosis is a critical issue for female health worldwide. This current study was designed to evaluate the role of nanopowder eggshell (NPES) in healthy and ovariectomy-induced osteoporosis rats. Fifty-six female rats were divided into healthy rats (35) and ovariectomized rats (21). The healthy rats were subdivided into five groups (G1-G5) and received one of the following treatments: saline, 20 or 40 mg/kg of calcium carbonate, and 20 or 40 mg/kg of NPES. The 21 ovariectomized rats were divided into three groups (G6-G8) and received either saline, 40 mg/kg of calcium carbonate, or 40 mg/kg of NPES. Biochemical and histopathological assessments of bone formation and resorption were performed. Biomarkers of bone formation (calcium and osteocalcin (OCN)) and calcium content in left femur ashes were significantly higher in healthy rats given 40-mg/kg NPES than in healthy control rats and healthy rats given 40-mg/kg calcium carbonate. The ovariectomized groups had significantly lower levels of vitamin D3, OCN, and osteoprotegerin (OPG) than the healthy control. Alanine transaminase (ALT), alkaline phosphatase (ALP), and receptor activator of nuclear factor-κB ligand (RANKL) were significantly increased in the ovariectomized group than in the healthy control group. Treatment with NPES and calcium carbonate reduced liver enzymes in ovariectomized rats. NPES treatment significantly increased Vit D3, OCN, OPG, and bone ash mineral content (calcium, magnesium, zinc, and phosphorus) in ovariectomized rats. NPES also increased femur cortical thickness, osteoblast number, and collagen fiber. The current study suggests that NPES can modulate bone turnover biomarkers and increase bone trace elements. Moreover, NPES alleviates bone resorption in ovariectomy-induced osteoporosis.

Calcium prescription by Indian orthopaedic surgeons: A survey and a review of literature

BACKGROUND

Orthopaedic surgeons prefer calcium supplement for various pathologies like fracture, osteoporosis, chronic musculoskeletal pain, yet there is no proper evidence to support the benefits of taking them regularly. The average requirement for calcium is around 500-1000 mg/day for a healthy adult, this amount of calcium is not achieved by diet, especially in developing countries like India. Despite this, the serum calcium level remains unaltered, due to the well-controlled absorption and excretion of calcium by the human body. As there is no clarity over the dose, duration and the prefered calcium salts, we constructed a survey to find the preferred dose, duration, the preferred calcium salts among orthopaedic surgeons, and to give an in-depth review of literature about dose, duration, timing, preferred calcium salt and various other calcium-related queries.

MATERIALS AND METHOD

The survey included 15 pre-structured questionnaires; these questions were formatted and validated by senior surgeons and other specialists after a through a review of calcium-related literature. These questionnaires were used in a pilot study conducted within the department and were later modified and separated into 7 sections. Data were collected by both online survey (google forms) and direct interviews.

RESULT AND CONCLUSION

128 Orthopedic surgeons responded. The total number of response obtained was 2355. Unanswered questions were 152. From the survey, it was found that most orthopaedic surgeons prefer to prescribe calcium routinely (55.46%). The commonly used calcium salt was calcium carbonate (47.65%), followed by citrate (32.8%). 42.18% were not aware of the efficiency of prescribing calcium in divided doses. Most responded that calcium is not to be given for patients with renal stones, but literature shows that calcium prescribed reduces the recurrence of commonest kidney stones, calcium oxalate stones.

A Review of Nonpharmacological Strategies in the Treatment of Relative Energy Deficiency in Sport

Relative energy deficiency in sport (RED-S) can result in negative health and performance outcomes in both male and female athletes. The underlying etiology of RED-S is low energy availability (LEA), which occurs when there is insufficient dietary energy intake to meet exercise energy expenditure, corrected for fat-free mass, leaving inadequate energy available to ensure homeostasis and adequate energy turnover (optimize normal bodily functions to positively impact health), but also optimizing recovery, training adaptations, and performance. As such, treatment of RED-S involves increasing energy intake and/or decreasing exercise energy expenditure to address the underlying LEA. Clinically, however, the time burden and methodological errors associated with the quantification of energy intake, exercise energy expenditure, and fat-free mass to assess energy availability in free-living conditions make it difficult for the practitioner to implement in everyday practice. Furthermore, interpretation is complicated by the lack of validated energy availability thresholds, which can result in compromised health and performance outcomes in male and female athletes across various stages of maturation, ethnic races, and different types of sports. This narrative review focuses on pragmatic nonpharmacological strategies in the treatment of RED-S, featuring factors such as low carbohydrate availability, within-day prolonged periods of LEA, insufficient intake of bone-building nutrients, lack of mechanical bone stress, and/or psychogenic stress. This includes the implementation of strategies that address exacerbating factors of LEA, as well as novel treatment methods and underlying mechanisms of action, while highlighting areas of further research.

Effect of Extra Virgin Olive Oil and Traditional Brazilian Diet on the Bone Health Parameters of Severely Obese Adults: A Randomized Controlled Trial

Dietary interventions can stabilize and/or reverse bone mass loss. However, there are no reports on its effects on bone mineral density (BMD) in severely obese people, despite the vulnerability of this group to bone loss. We examine the effect of extra virgin olive oil supplementation and the traditional Brazilian diet (DieTBra) on BMD and levels of calcium, vitamin D, and parathyroid hormone (PTH) in severely obese adults. A randomized controlled trial followed-up with severely obese adults (n = 111, with mean body mass index 43.6 kg/m2 ± 4.5 kg/m2) for 12 weeks. Study participants received either olive oil (52 mL/day), DieTBra, or olive oil + DieTBra (52 mL/day + DieTBra). BMD was assessed by total spine and hip dual-energy X-ray absorptiometry. After interventions, BMD means for total spine (p = 0.016) and total hip (p = 0.029) were higher in the DieTBra group than in the olive oil + DieTBra group. Final mean calcium levels were higher in the olive oil group compared to the olive oil + DieTBra group (p = 0.026). Findings suggest that DieTBra and extra virgin olive oil have positive effects on bone health in severely obese adults. The major study was registered at ClinicalTrials.gov (NCT02463435).

Changes in bone mineral density and bone turnover markers during treatment with teriparatide in pregnancy- and lactation-associated osteoporosis

CONTEXT

Teriparatide (TPTD) therapy has been proposed as a potential treatment strategy in severe cases of pregnancy- and lactation-associated osteoporosis (PLO) characterized by the occurrence of fragility fractures in the third trimester or early postpartum.

OBJECTIVE

To investigate the changes in bone mineral density (BMD) and bone turnover markers in patients with PLO with and without TPTD treatment.

DESIGN

Retrospective cohort study.

PATIENTS

Thirty-two patients with PLO who presented with multiple vertebral fractures to a tertiary institution between 2007 and 2015 were included.

MEASUREMENTS

Changes in BMD at the lumbar spine (LSBMD) and proximal femur after 12 months of daily subcutaneous injections of 20 μg TPTD (n = 27) were assessed. Subjects who rejected the TPTD treatment were used as controls (n = 5).

RESULTS

LSBMD increased in both subjects treated with TPTD and controls, with greater increases in the TPTD group (15.5 ± 6.6% vs 7.5 ± 7.1%, P = .020) after adjustment for age and baseline LSBMD. During follow-up, serum levels of osteocalcin (OCN) and C-telopeptide of type I collagen (CTX) increased significantly in the TPTD group. In multivariate linear regression models, TPTD treatment (adjusted β = 7.92, P = .032) and younger age (adjusted β = 1.06, P = .046), but not baseline LSBMD, body mass index, serum OCN level and CTX level, were independently associated with greater increases in LSBMD.

CONCLUSIONS

In patients with PLO, LSBMD at 12 months increased in both the TPTD-treated and control groups. TPTD treatment and younger age were associated with greater increases in LSMBD irrespective of baseline LSBMD.

The influence of dietary fat and intestinal pH on calcium bioaccessibility: anin vitrostudy

In vivostudies measuring true fractional calcium (Ca) absorption have shown that dietary fat is a significant predictor of absorption and is influenced by luminal pH levels.

Osteoporosis is associated with metabolic syndrome induced by high-carbohydrate high-fat diet in a rat model

This study aimed to investigate the bone quality in rats induced with metabolic syndrome (MetS) using high-carbohydrate high-fat (HCHF) diet. Male Wistar rats (n = 14) were randomized into two groups. The normal group was given standard rat chow. The MetS group was given HCHF diet. Diet regimen was assigned for a period of 20 weeks. Metabolic syndrome parameters were measured monthly until MetS was established. Left tibiae were scanned using micro-computed tomography at week 0, 8, 12, 16, and 20 to analyze the trabecular and cortical bone structure. At the end of the study, rats were euthanized and their bones were harvested for analysis. Metabolic syndrome was established at week 12 in the HCHF rats. Significant deterioration of trabecular bone was observed at week 20 in the HCHF group (p < 0.05). The HCHF diet also decreased cortical and tissue area significantly (p < 0.05), but did not affect cortical thickness and bone calcium content (p > 0.05). Femur length and width in the HCHF group were significantly shorter than the normal group (p < 0.05). The biomechanical strength test showed that the femur of the HCHF rats could endure significantly lower force, but significantly higher displacement and strain compared to the normal rats (p < 0.05). In conclusion, HCHF diet-induced MetS can cause adverse effects on the bone.

LS, Bruening. KS, Scerpella. TA, Dowthwaite. JN. Relationships among diet, physical activity, and dual plane dual-energy X-ray absorptiometry bone outcomes in pre-pubertalgirls

In pre-pubertal girls, nutrient intakes and non-aquatic organized activity were evaluated as factors in vertebral body bone mass, structure, and strength. Activity, vitamin B₁₂, and dietary fiber predicted bone outcomes most consistently. Exercise and vitamin B₁₂ appear beneficial, whereas high fiber intake appears to be adverse for vertebral body development.

PURPOSE

Childhood development sets the baseline for adult fracture risk. Most studies evaluate development using postero-anterior (PA) dual-energy X-ray absorptiometry (DXA) areal bone mineral density, bone mineral content, and bone mineral apparent density. In a prior analysis, we demonstrated that PA DXA reflects posterior element properties, rather than vertebral body fracture sites, such that loading is associated with subtle differences in vertebral body geometry, not 3D density. The current analysis is restricted to pre-pubertal girls, for a focused exploration of key nutrient intakes and physical activity as factors in dual plane indices of vertebral body geometry, density, and strength.

METHODS

This cross-sectional analysis used paired PA and supine lateral (LAT) lumbar spine DXA scans to assess "3D" vertebral body bone mineral apparent density (PALATBMAD), "3D" index of structural strength in axial compression (PALATIBS), and fracture risk index (PALATFRI). Diet data were collected using the Youth/Adolescent Questionnaire (YAQ, 1995); organized physical activity was recorded via calendar-based form. Pearson correlations and backward stepwise multiple linear regression analyzed associations among key nutrients, physical activity, and bone outcomes.

RESULTS

After accounting for activity and key covariates, fiber, unsupplemented vitamin B₁₂, zinc, carbohydrate, vitamin C, unsupplemented magnesium, and unsupplemented calcium intake explained significant variance for one or more bone outcomes (p < 0.05). After adjustment for influential key nutrients and covariates, activity exposure was associated with postero-anterior (PA) areal bone mineral density, PA bone mineral content, PA width, lateral (LAT) BMC, "3D" bone cross-sectional area (coronal plane), "3D" PALATIBS, and PALATFRI benefits (p < 0.05).

CONCLUSIONS

Physical activity, fiber intake, and unsupplemented B₁₂ intake appear to influence vertebral body bone mass, density, geometry, and strength in well-nourished pre-pubertal girls; high fiber intakes may adversely affect childhood vertebral body growth.

Nutrients intake, and serum calcium and phosphorus levels: An evidence-based study

INTRODUCTION

Dietary calcium and phosphorus appear to be important determinants of dyslipidemia and hypertension. We have investigated (1) the prevalence of hypocalcemia and hypophosphatemia in an Iranian population, and (2) the association between nutrient's intake and serum levels of calcium and phosphorus.

METHODS

A total of 908 individuals were enrolled using a stratified-cluster sampling method from the Mashhad stroke and heart atherosclerosis disorder (MASHHAD) study. Dietplan6 software was used for 24-hour recalls and food frequency questionnaire to investigate macro- and micronutrient intakes of our population, followed by univariate analysis for evaluation of the association of dairy consumption with serum calcium and phosphorus.

RESULTS

We observed that the mean dietary Ca intake was 862.4 mg/d (672.7-1052) for men and 864.2 mg/d (604.5-1123) for women in our population, which is lower than the dietary reference intake for Ca. Moreover, a significant relationship was detected between serum calcium level and dietary intakes of saturated fatty acids, copper, iodine, sucrose, potato, and juices. Of note, we observed a negative association between copper intake, and serum Ca (P˂.01). Also, a significant association was found between serum phosphorus levels and dietary intakes of chicken meat and fresh fruits. Interestingly, we observed an inverse relationship between tea and Ca/P ratio (eg, -r=.098; P=.02).

CONCLUSION

We found that the dietary intake of Ca was not sufficient in our population and was associated with the dietary intake of some macro- and micronutrient, supporting further investigation on clinical impact of this condition on calcium/phosphorus deficiency related diseases.

Effect of Calcium Derived from Lithothamnion sp. on Markers of Calcium Metabolism in Premenopausal Women

A double-blind crossover pilot trial tested the hypothesis that botanically derived calcium could demonstrate greater influence over calcium metabolism markers compared with a nonplant-derived calcium carbonate supplement or placebo. Twelve fasting female subjects received a single oral dose of Aquamin F™ (derived from the marine algal Lithothamnion sp.), or calcium carbonate, or placebo. Blood and urine samples were collected at baseline and over 12 h to evaluate ionized and total calcium and parathyroid hormone (PTH). Subjects treated with Aquamin F demonstrated significantly greater urinary clearance of calcium after 12 h compared with placebo (P = .004). Following a meal at 90 min, subjects treated with Aquamin F demonstrated a more prolonged suppression of serum PTH concentration (significantly lower than placebo at 90, 120, and 240 min). Calcium carbonate provided an intermediate response; urinary clearance was not significantly different from placebo treatment and PTH was only significantly lower than placebo at 90 min. Aquamin F may demonstrate greater influence over these markers of calcium metabolism than calcium carbonate or placebo, as suggested by a greater calciuric response and a more prolonged suppression of serum PTH concentrations following a meal in premenopausal women.

Vitamin D and intestinal calcium transport after bariatric surgery

Bariatric surgery is a highly effective treatment for obesity, but it may have detrimental effects on the skeleton. Skeletal effects are multifactorial but mediated in part by nutrient malabsorption. While there is increasing interest in non-nutritional mechanisms such as changes in fat-derived and gut-derived hormones, nutritional factors are modifiable and thus represent potential opportunities to prevent and treat skeletal complications. This review begins with a discussion of normal intestinal calcium transport, including recent advances in our understanding of its regulation by vitamin D, and areas of continued uncertainty. Human and animal studies of vitamin D and intestinal calcium transport after bariatric surgery are then summarized. In humans, even with optimized 25-hydroxyvitamin D levels and recommended calcium intake, fractional calcium absorption decreased dramatically after Roux-en-Y gastric bypass (RYGB). In rats, intestinal calcium absorption was lower after RYGB than after sham surgery, despite elevated 1,25-dihyroxyvitamin D levels and intestinal gene expression evidence of vitamin D responsiveness. Such studies have the potential to shed new light on the physiology of vitamin D and intestinal calcium transport. Moreover, understanding the effects of bariatric surgery on these processes may improve the clinical care of bariatric surgery patients.

Relationship Between Nutritional Factors and Hip Bone Density in Individuals with Chronic Stroke

The aim of this study was to investigate the relationship between dietary habits and hip bone health in community-dwelling individuals with chronic stroke. The usual dietary intake of 94 individuals with chronic stroke (30 women, mean age: 59.0 years) was assessed by a 3-day food record within a single week. Dual-energy X-ray absorptiometry was used to measure bone mineral density (BMD) at both hips. The results showed that low hip bone mass was found in 59 and 50 of the participants on the affected and unaffected side, respectively. The mean hip BMD was also significantly lower on the affected side than the unaffected side (P < 0.001). The intake of total fat, carbohydrates, calcium, magnesium, iron, zinc, fiber, folic acid, vitamin B1, B2, B3, B6, C, and K was significantly lower than the respective recommended daily intake values (P < 0.05). Multiple regression analyses revealed that after adjusting for the effects of age, sex, body mass index, post-stroke duration, side of paresis, motor impairment, physical activity level, walking endurance, total calories intake, and total number of medications, intake of protein, fiber, and magnesium remained significantly associated with hip T score on the affected side, accounting for 4.2, 4.4, and 3.2% of the variance, respectively. On the other hand, intake of protein and fiber was independently associated with hip T score on the unaffected side, explaining 2.7 and 5.2% of the variance, respectively. The results highlighted the potential relevance of diet modification in maintaining bone health post stroke, which would require further study.

Obesity is a concern for bone health with aging

Accumulating evidence supports a complex relationship between adiposity and osteoporosis in overweight/obese individuals, with local interactions and endocrine regulation by adipose tissue on bone metabolism and fracture risk in elderly populations. This review was conducted to summarize existing evidence to test the hypothesis that obesity is a risk factor for bone health in aging individuals. Mechanisms by which obesity adversely affects bone health are believed to be multiple, such as an alteration of bone-regulating hormones, inflammation, oxidative stress, the endocannabinoid system, that affect bone cell metabolism are discussed. In addition, evidence on the effect of fat mass and distribution on bone mass and quality is reviewed together with findings relating energy and fat intake with bone health. In summary, studies indicate that the positive effects of body weight on bone mineral density cannot counteract the detrimental effects of obesity on bone quality. However, the exact mechanism underlying bone deterioration in the obese is not clear yet and further research is required to elucidate the effect of adipose depots on bone and fracture risk in the obese population.

Calcium Supplementation in Clinical Practice: A Review of Forms, Doses, and Indications

Most Americans do not meet the adequate intake (AI) for calcium; calcium supplements can help meet requirements. Calcium supplementation has been found to be beneficial for bone health in children, young adults, and menopausal women. In addition to calcium, vitamin D is necessary for bone health and is generally deficient in the industrialized world. Calcium from carbonate and citrate are the most common forms of calcium supplements. Calcium carbonate, the most cost-effective form, should be taken with a meal to ensure optimal absorption. Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or protein-pump inhibitors. Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements. Research on hydroxyapatite as a source of calcium is limited, so this form of calcium is not recommended. The maximum dose of elemental calcium that should be taken at a time is 500 mg. U.S. Pharmacopeia-verified calcium supplements meet vigorous manufacturing and quality requirements. Absorption from calcium-fortified beverages varies and in general is not equal to that of milk. Potential adverse effects of calcium supplementation include gastrointestinal complaints. Renal calculi in most studies have not been associated with calcium supplementation. The risk of advanced and fatal prostate cancer has been associated with calcium intakes from food or supplements in amounts >1500 mg/d.

High fat diet enriched with saturated, but not monounsaturated fatty acids adversely affects femur, and both diets increase calcium absorption in older female mice

Diet induced obesity has been shown to reduce bone mineral density (BMD) and Ca absorption. However, previous experiments have not examined the effect of high fat diet (HFD) in the absence of obesity or addressed the type of dietary fatty acids. The primary objective of this study was to determine the effects of different types of high fat feeding, without obesity, on fractional calcium absorption (FCA) and bone health. It was hypothesized that dietary fat would increase FCA and reduce BMD. Mature 8-month-old female C57BL/6J mice were fed one of three diets: a HFD (45% fat) enriched either with monounsaturated fatty acids (MUFAs) or with saturated fatty acids (SFAs), and a normal fat diet (NFD; 10% fat). Food consumption was controlled to achieve a similar body weight gain in all groups. After 8wk, total body bone mineral content and BMD as well as femur total and cortical volumetric BMD were lower in SFA compared with NFD groups (P<.05). In contrast, femoral trabecular bone was not affected by the SFAs, whereas MUFAs increased trabecular volume fraction and thickness. The rise over time in FCA was greater in mice fed HFD than NFD and final FCA was higher with HFD (P<.05). Intestinal calbindin-D9k gene and hepatic cytochrome P450 2r1 protein levels were higher with the MUFA than the NFD diet (P<.05). In conclusion, HFDs elevated FCA overtime; however, an adverse effect of HFD on bone was only observed in the SFA group, while MUFAs show neutral or beneficial effects.

Diets High in Fiber and Vegetable Protein Are Associated with Low Lumbar Bone Mineral Density in Young Athletes with Oligoamenorrhea

BACKGROUND

Associations of bone mineral density (BMD) with specific food components, including dietary fiber and isoflavones (that have a negative association with serum estrogen), are unclear and need to be determined, particularly in populations more likely to consume large amounts of these nutrients (such as young athletes).

OBJECTIVE

To determine dietary intake of specific food components in athletes with oligoamenorrhea (OA) compared to athletes with eumenorrhea (EA) and nonathletes (NA), and associations of the dietary intake of these nutrients with lumbar spine BMD.

DESIGN AND SUBJECTS

This cross-sectional study evaluated 68 OA, 24 EA, and 26 NA individuals aged 14 to 23 years. Measurements included 4-day food records, a dual x-ray absorptiometry scan evaluating lumbar spine BMD and body composition, and hormone levels. Multivariate analysis was used to estimate associations of nutrients with lumbar spine BMD.

RESULTS

Compared with EA and NA, OA had higher intake of fiber, phytic acid, and vegetable protein (all P values <0.0001). Intake of isoflavones, genistein, and daidzein was higher in OA than NA (P=0.003 and P=0.0002, respectively). OA had lower consumption of energy from saturated fatty acids than NA (P=0.002). After controlling for confounders such as body weight, menstrual status (indicative of estrogen status), calcium intake, and serum vitamin D (known BMD determinants), lumbar spine BMD z scores were inversely associated with dietary fiber (β=-.30; P=0.01), vegetable protein (β= -.28; P=0.02), phytic acid (β=-.27; P=0.02), genistein (β=-.25; P=0.01), and daidzein (β=-.24; P=0.01), and positively associated with percent energy from fatty acids (β=.32; P=0.0006).

CONCLUSIONS

Compared with EA and NA, OA had a higher dietary intake of fiber, vegetable protein, and phytic acid, which were inversely associated with lumbar spine BMD z scores. Further studies are needed to assess dietary recommendations for OA to optimize bone accrual.

Influence of vitamin D and estrogen receptor gene polymorphisms on calcium absorption: BsmI predicts a greater decrease during energy restriction

Low calcium absorption is associated with low bone mass and fracture. In this study, we use gold standard methods of fractional calcium absorption (FCA) to determine whether polymorphisms of intestinal receptors, vitamin D receptor (VDR) and estrogen receptor α (ESR1), influence the response to energy restriction. Fractional calcium absorption was measured using dual stable isotopes ((42)Ca and (43)Ca) in women given adequate calcium and vitamin D and examined at baseline and after 6 weeks of energy restriction or no intervention. After genotyping, the relationship between VDR and ESR1 genotypes/haplotypes and FCA response was assessed using several genetic models. One-hundred and sixty-eight women (53 ± 11 years of age) were included in this analysis. The ESR1 polymorphisms, PvuII and XbaI and VDR polymorphisms (TaqI, ApaI) did not significantly influence FCA. The BB genotype of the VDR polymorphism, BsmI, was associated with a greater decrease in FCA than the Bb/bb genotype. Multiple linear regression showed that the BsmI polymorphism or the VDR haplotype, BAt, in addition to changes in weight and vitamin D intake explained ~16% of the variation in changes in FCA. In conclusion, the reduction in calcium absorption due to energy restriction is greatest for those with the BB genotype. Previous candidate gene studies show that VDR polymorphisms are associated with higher risk for osteoporosis, and the current study supports the notion that the BsmI polymorphism in intestinal VDR may be contributing to alterations in bone health.

Intestinal Calcium Absorption Decreases Dramatically After Gastric Bypass Surgery Despite Optimization of Vitamin D Status

Roux-en-Y gastric bypass (RYGB) surgery has negative effects on bone, mediated in part by effects on nutrient absorption. Not only can RYGB result in vitamin D malabsorption, but the bypassed duodenum and proximal jejunum are also the predominant sites of active, transcellular, 1,25(OH)2 D-mediated calcium (Ca) uptake. However, Ca absorption occurs throughout the intestine, and those who undergo RYGB might maintain sufficient Ca absorption, particularly if vitamin D status and Ca intake are robust. We determined the effects of RYGB on intestinal fractional Ca absorption (FCA) while maintaining ample 25OHD levels (goal ≥30 ng/mL) and Ca intake (1200 mg daily) in a prospective cohort of 33 obese adults (BMI 44.7 ± 7.4 kg/m(2)). FCA was measured preoperatively and 6 months postoperatively with a dual stable isotope method. Other measures included calciotropic hormones, bone turnover markers, and BMD by DXA and QCT. Mean 6-month weight loss was 32.5 ± 8.4 kg (25.8% ± 5.2% of preoperative weight). FCA decreased from 32.7% ± 14.0% preoperatively to 6.9% ± 3.8% postoperatively (p < 0.0001), despite median (interquartile range) 25OHD levels of 41.0 (33.1 to 48.5) and 36.5 (28.8 to 40.4) ng/mL, respectively. Consistent with the FCA decline, 24-hour urinary Ca decreased, PTH increased, and 1,25(OH)2 D increased (p ≤ 0.02). Bone turnover markers increased markedly, areal BMD decreased at the proximal femur, and volumetric BMD decreased at the spine (p < 0.001). Those with lower postoperative FCA had greater increases in serum CTx (ρ = -0.43, p = 0.01). Declines in FCA and BMD were not correlated over the 6 months. In conclusion, FCA decreased dramatically after RYGB, even with most 25OHD levels ≥30 ng/mL and with recommended Ca intake. RYGB patients may need high Ca intake to prevent perturbations in Ca homeostasis, although the approach to Ca supplementation needs further study. Decline in FCA could contribute to the decline in BMD after RYGB, and strategies to avoid long-term skeletal consequences should be investigated.

Safety of daily teriparatide treatment: a post hoc analysis of a Phase III study to investigate the possible association of teriparatide treatment with calcium homeostasis in patients with serum procollagen type I N-terminal propeptide elevation

OBJECTIVE

Serum procollagen type I N-terminal propeptide (PINP), a representative marker of bone anabolic action, is strongly related to bone mineral density during teriparatide therapy. This post hoc study analyzed data from a Phase III study (ClinicalTrials.gov identifier NCT00433160) to determine if there was an association between serum PINP elevation and serum calcium concentration or calcium metabolism-related disorders.

RESEARCH DESIGN AND METHODS

Japanese subjects with osteoporosis at high risk of fracture were randomized 2:1 to teriparatide 20 μg/day (n=137) or placebo (n=70) for a 12-month double-blind treatment period, followed by 12 months of open-label teriparatide treatment of all subjects.

MAIN OUTCOME MEASURES

Serum PINP levels were measured at baseline, and after 1, 3, 6, 12, 18, and 24 months of treatment. Serum calcium levels were measured at baseline, and after 1, 3, 6, 9, 12, 15, 18, 21, and 24 months of treatment.

RESULTS

Serum PINP increased from baseline to 1 month of treatment and then remained high through 24 months. Twenty-eight of 195 subjects experienced PINP elevations >200 μg/L during teriparatide treatment. Serum calcium concentration in both the teriparatide and placebo groups remained within the normal range. There was no clinically relevant difference in serum calcium concentration between subjects with PINP >200 μg/L and subjects with PINP ≤200 μg/L. Two subjects experienced hypercalcemia and recovered without altering teriparatide treatment. Adverse events possibly related to calcium metabolism disorders included periarthritis calcarea (one subject) and chondrocalcinosis pyrophosphate (two subjects), but neither was accompanied with a significant increase in PINP or serum calcium concentration.

CONCLUSION

Although the moderate size of this study prevented statistical analysis of any potential association between calcium metabolism-related disorders and elevated PINP, this analysis suggests that there was no association between serum PINP elevation during daily teriparatide treatment and serum calcium concentration or calcium metabolism-related disorders in Japanese subjects.

The effect of probiotics (Lactobacillus rhamnosus HN001, Lactobacillus paracasei LPC-37, and Lactobacillus acidophilus NCFM) on the availability of minerals from Dutch-type cheese

The use of probiotic cultures in the production of Dutch-type cheeses did not lead to significant changes in their chemical composition but it lowered their acidity. The availability of calcium and magnesium analyzed by in vitro enzymatic hydrolysis was 19 and 35%, respectively; the availability of phosphorus was significantly higher, at >90%. The use of probiotic cultures significantly increased the availability of calcium (~2.5%), phosphorus (~6%), and magnesium (~18%). The in vitro method supports accurate determination of the effect of the Lactobacillus spp. cultures on the availability of mineral compounds ingested with Dutch-type cheese.

Gene-by-diet interactions influence calcium absorption and bone density in mice

Dietary calcium (Ca) intake is needed to attain peak bone mineral density (BMD). Habitual low Ca intake increases intestinal Ca absorption efficiency to protect bone mass, but the mechanism controlling, and the impact of genetics on, this adaptive response is not clear. We fed 11 genetically diverse inbred mouse lines a normal (0.5%) or low (0.25%) Ca diet from 4 to 12 weeks of age (n = 8 per diet per line) and studied the independent and interacting effects of diet and genetics on Ca and bone metabolism. Significant genetic variation was observed in all bone, renal, and intestinal phenotypes measured including Ca absorption. Also, adaptation of Ca absorption and bone parameters to low dietary Ca was significantly different among the lines. Ca absorption was positively correlated to femur BMD (r = 0.17, p = 0.02), and distal femur bone volume/tissue volume (BV/TV) (r = 0.34, p < 0.0001). Although Ca absorption was correlated to 1,25 dihydroxyvitamin D (1,25(OH)2 D) (r = 0.35, p < 0.0001), the adaptation of Ca absorption to low Ca intake did not correlate to diet-induced adaptation of 1,25(OH)2 D across the 11 lines. Several intestinal proteins have been proposed to mediate Ca absorption: claudins 2 and 12, voltage gated Ca channel v1.3 (Cav1.3), plasma membrane Ca ATPase 1b (PMCA1b), transient receptor potential vanilloid member 6 (TRPV6), and calbindin D9k (CaBPD9k). Only the mRNA levels for TRPV6, CaBPD9k, and PMCA1b were related to Ca absorption (r = 0.42, 0.43, and 0.21, respectively). However, a significant amount of the variation in Ca absorption is not explained by the current model and suggests that novel mechanisms remain to be determined. These observations lay the groundwork for discovery-focused initiatives to identify novel genetic factors controlling gene-by-diet interactions affecting Ca/bone metabolism.

Factors associated with calcium absorption in postmenopausal women: a post hoc analysis of dual-isotope studies

Reduced calcium absorption is a risk factor for osteoporosis. This study examined factors associated with fractional calcium absorption (FCA) and net calcium absorption in postmenopausal women in a post hoc analysis of three completed dual-isotope studies. Data were analyzed from 50 postmenopausal women undergoing 121 inpatient research visits in three studies evaluating changes in FCA related to correction of vitamin D insufficiency (n=19), use of proton pump inhibitors (n=21), and use of aromatase inhibitors to treat breast cancer (n=10). Net calcium absorption was the product of FCA and total calcium intake in milligrams per day. Variables included subjects' age, race, body mass index, serum calcium, creatinine, parathyroid hormone, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D, and habitual intake of kilocalories, protein, fat, carbohydrate, fiber, calcium, iron, magnesium, oxalate, phosphorus, potassium, and vitamin D based on outpatient diet diaries. In multivariate models, subjects' age, dietary intake of kilocalories, carbohydrates, fat, fiber, calcium, and potassium were significant predictors of FCA. In multiple variable models predicting net calcium absorption, dietary intake of kilocalories, fat, fiber, calcium, potassium, and serum 1,25-dihydroxyvitamin D were significant. The square of the correlation between actual and predicted values (an approximation of R(2)) was 0.748 for FCA and 0.726 for net calcium absorption. Similar to other studies, this study found that age, 1,25-dihydroxyvitamin D, and dietary calcium and fat were associated with calcium absorption. Dietary intake of kilocalories, carbohydrates, and potassium were new factors that were significantly associated with FCA and net calcium absorption. In summary, the study suggests that several dietary habits play a role in calcium absorption, beyond vitamin D and calcium.

Vitamin D supplementation and calcium absorption during caloric restriction: a randomized double-blind trial

BACKGROUND

Weight loss (WL) is associated with a decrease in calcium absorption and may be one mechanism that induces bone loss with weight reduction.

OBJECTIVE

Because vitamin D supplementation has been shown to increase true fractional calcium absorption (TFCA), the goal of this study was to examine the effect of vitamin D during WL or weight maintenance (WM).

DESIGN

A randomized, placebo-controlled, double-blind 6-wk study was conducted in 82 postmenopausal women [BMI (in kg/m(2); ±SD): 30.2 ± 3.7] with 25-hydroxyvitamin D [25(OH)D] concentrations <70 nmol/L during either WL or WM. All women were given 10 μg vitamin D(3)/d and 1.2 g Ca/d and either weekly vitamin D(3) (375 μg) or a placebo equivalent to 63 μg (2500 IU)/d and 10 μg (400 IU)/d, respectively. We measured TFCA with the use of dual-stable isotopes, 25(OH)D, parathyroid hormone, estradiol, calcitriol, and urinary calcium at baseline and 6 wk in weight loss and vitamin D(3)-supplementation (WL-D; n = 19), weight maintenance and vitamin D(3)-supplementation (WM-D; n = 20), weight loss and placebo (n = 22), and weight maintenance and placebo (n = 21) groups.

RESULTS

WL groups lost 3.8 ± 1.1% of weight with no difference between vitamin D(3) supplementation and the placebo. The rise in serum 25(OH)D was greatest in the WL-D group (19.8 ± 14.5 nmol/L) compared with in WM-D (9.1 ± 10.3 nmol/L) and placebo groups (1.5 ± 10.9 nmol/L). TFCA increased with vitamin D(3) supplementation compared with placebo treatment (P < 0.01) and decreased during WL compared with WM. Serum 25(OH)D or 1,25-dihyroxyvitamin D did not correlate with TFCA.

CONCLUSION

These data show that vitamin D supplementation increases TFCA and that WL decreases TFCA and suggest that, when calcium intake is 1.2 g/d, either 10 or 63 μg vitamin D/d is sufficient to maintain the calcium balance. This trial was registered at clinicaltrials.gov as NCT00473031.

Hormonal and dietary influences on true fractional calcium absorption in women: role of obesity

The goal in this study was to examine the hormonal and dietary predictors of true fractional Ca absorption (TFCA) in adult women and to determine whether TFCA differs due to body weight. Results showed that TFCA is higher in obese individuals and dietary fat, estradiol, and 1,25-dihydroxy vitamin D are the most significant positive predictors of TFCA in adult women.

INTRODUCTION

Calcium absorption is an important determinant of calcium balance and is influenced by several factors. Previous studies have identified that age, intake of protein, fat and fiber, and hormones such as 1, 25-dihyroxyvitamin D (1,25(OH)(2)D(3)) influence absorption. The determinants of TFCA using the double isotope method, the gold standard estimate of absorption, have not been examined previously in adult women nor has the role of obesity been addressed.

METHODS

In this study, we examined the hormonal and dietary predictors of TFCA in adult women with a wide range of age, body weights, and nutrient intake. TFCA was measured using dual stable isotope ((42)Ca and (43)Ca) technique. Serum was analyzed for bone-regulating hormones, and dietary information was obtained through food records. The independent dietary factors and hormonal predictors (25-hydroxyvitamin D, 1,25(OH)(2)D(3), parathyroid hormone, and estradiol) of TFCA were analyzed using multiple regression analysis.

RESULTS

Two hundred twenty-nine women aged 54 ± 11 years old (24-75 years) and with BMI of 31 ± 7.0 kg/m(2) were eligible and were categorized into tertiles of body mass index (BMI) into leaner, overweight, and obese. In the entire group of women, total fat intake, estradiol, and 1,25(OH)(2)D(3) are significant positive predictors (p < 0.05). As expected, age is a significant negative predictor of TFCA (R (2) = 26%). TFCA is higher in obese women compared to non-obese women (p < 0.05).

CONCLUSION

Together, these data show that dietary fat is the most significant positive predictor of TFCA which may have implications for dietary intake for non-obese individuals who are more likely to have lower and potentially compromised Ca absorption.

A Mediterranean diet enriched with olive oil is associated with higher serum total osteocalcin levels in elderly men at high cardiovascular risk

BACKGROUND

The intake of olive oil has been related to the prevention of osteoporosis in experimental and in in vitro models. Very few prospective studies have evaluated the effects of olive oil intake on circulating osteocalcin (OC) in humans.

OBJECTIVE

The objective of the study was to examine the longitudinal effects of a low-fat control diet (n=34), a Mediterranean diet enriched with nuts (MedDiet+nuts, n=51), or a Mediterranean diet enriched with virgin olive oil (MedDiet+VOO, n=42) on circulating forms of OC and bone formation markers in elderly men at high cardiovascular risk.

DESIGN

Longitudinal associations between baseline and follow-up (2 yr) measurements of total OC, undercarboxylated osteocalcin, C-telopeptide of type I collagen, and procollagen I N-terminal propeptide (P1NP) concentrations were examined in 127 elderly men randomized to three healthy dietary interventions.

RESULTS

Baseline characteristics (age, body mass index, waist circumference, lipid profile, fasting insulin levels, and bone formation and resorption markers) were similar in all intervention groups. The total osteocalcin concentration increased robustly in the MedDiet+VOO group (P=0.007) in parallel to increased P1NP levels (P=0.01) and homeostasis model assessment-β-cell function (P=0.01) but not in subjects on the MedDiet+nuts (P=0.32) or after the control diet (P=0.74). Interestingly, the consumption of olives was associated positively with both baseline total osteocalcin (r=0.23, P=0.02) and the 2-yr osteocalcin concentrations (r=0.21, P=0.04) in the total cohort.

CONCLUSIONS

Consumption of a Mediterranean diet enriched with virgin olive oil for 2 years is associated with increased serum osteocalcin and P1NP concentrations, suggesting protective effects on bone.

Calcium metabolism and correcting calcium deficiencies

Calcium is the most abundant cation in the human body, of which approximately 99% occurs in bone, contributing to its rigidity and strength. Bone also functions as a reservoir of Ca for its role in multiple physiologic and biochemical processes. This article aims to provide a thorough understanding of the absorptive mechanisms and factors affecting these processes to enable one to better appreciate an individual's Ca needs, and to provide a rationale for correcting Ca deficiencies. An overview of Ca requirements and suggested dosing regimens is presented, with discussion of various Ca preparations and potential toxicities of Ca treatment.

Aromatase inhibitors and calcium absorption in early stage breast cancer

To investigate the effect of aromatase inhibitors (AI) on intestinal calcium absorption, measured using the gold-standard dual stable calcium isotope method. In this pilot study, we recruited 10 postmenopausal women with hormone receptor-positive breast cancer who planned to initiate AI therapy; women receiving chemotherapy were excluded. Women completed two 24 h inpatient calcium absorption study visits, the first prior to AI therapy and the second at least 6 weeks following onset of AI therapy. We calculated total fractional calcium absorption (TFCA) using the dose-corrected fractional recovery of two stable isotopes from 24 h urine collections. Ten postmenopausal women (mean±SD age, 66±7 years; 25(OH)D 40±7 ng/mL, and total calcium intake of 1,714±640 mg/day) exhibited no change in TFCA related to AI therapy (0.155±0.042 prior to and 0.160±0.064 following AI therapy, p=1.0). Subjects exhibited a surprisingly small decline in serum estradiol levels with AI therapy that was not statistically significant. However, there was a significant correlation between duration of AI therapy and the decline in serum estradiol levels (r=-0.65, p=0.040). In this pilot study, AI therapy did not decrease TFCA. Women with early stage breast cancer exhibited an unexpectedly low TFCA, most likely due to their high calcium intake. The null effect of AI therapy on TFCA might relate to the brief duration of AI therapy, the minimal effect of AI therapy on estradiol levels, subjects' high calcium intake or excellent vitamin D status.

Calcium and vitamin D and risk of colorectal cancer: results from a large population-based case-control study in Newfoundland and Labrador and Ontario

BACKGROUND

Previous epidemiological studies have been suggestive but inconclusive in demonstrating inverse associations of calcium, vitamin D, dairy product intakes with risk of colorectal cancer (CRC). We conducted a large population-based comparison of such associations in Newfoundland and Labrador (NL) and Ontario (ON).

METHODS

A case control study design was used. Colorectal cancer cases were new CRC patients aged 20-74 years. Controls were a sex and age-group matched random sample of the population in each province. 1760 cases and 2481 controls from NL and ON were analyzed. Information on dietary intake and lifestyle was collected using self-administered food frequency and personal history questionnaires.

RESULTS

Controls reported higher mean daily intakes of total calcium and total vitamin D than cases in both provinces. In ON, significant reduced CRC risk was associated with intakes of total calcium (OR of highest vs. lowest quintiles was 0.57, 95% CI 0.42-0.77, p(trend) = 0.03), total vitamin D (OR = 0.73, 95% CI 0.54-1.00), dietary calcium (OR = 0.76, 95% CI 0.60-0.97), dietary vitamin D (OR = 0.77, 95% CI 0.61-0.99), total dairy products and milk (OR = 0.78, 95% CI 0.60-1.00), calcium-containing supplements use (OR = 0.76). In NL, the inverse associations of calcium, vitamin D with CRC risk were most pronounced among calcium- or vitamin D-containing supplement users (OR = 0.67, 0.68, respectively).

CONCLUSIONS

Results of this study add to the evidence that total calcium, dietary calcium, total vitamin D, dietary vitamin D, calcium- or vitamin D-containing supplement use may reduce the risk of CRC. The inverse associations of CRC risk with intakes of total dairy products and milk may be largely due to calcium and vitamin D.

Is the metabolic syndrome caused by a high fructose, and relatively low fat, low cholesterol diet?

The metabolic syndrome (MetS) is manifested by a lipid triad which includes elevated serum triglycerides, small LDL particles, and low high-density lipoprotein (HDL) cholesterol, by central obesity (central adiposity), insulin resistance, glucose intolerance and elevated blood pressure, and it is associated with an increased risk of type 2 diabetes and coronary heart disease. We have developed a new hypothesis regarding MetS as a consequence of a high intake in carbohydrates and food with a high glycemic index, particularly fructose, and relatively low intake of cholesterol and saturated fat. We support our arguments through animal studies which have shown that exposure of the liver to increased quantities of fructose leads to rapid stimulation of lipogenesis and accumulation of triglycerides. The adipocytes store triglycerides in lipid droplets, leading to adipocyte hypertrophy. Adipocyte hypertrophy is associated with macrophage accumulation in adipose tissue. An important modulator of obesity-associated macrophage responses in white adipose tissue is the death of adipocytes. Excess exposure to fructose intake determines the liver to metabolize high doses of fructose, producing increased levels of fructose end products, like glyceraldehyde and dihydroxyacetone phosphate, that can converge with the glycolytic pathway. Fructose also leads to increased levels of advanced glycation end products. The macrophages exposed to advanced glycation end products become dysfunctional and, on entry into the artery wall, contribute to plaque formation and thrombosis.

Inflammatory bowel diseases, celiac disease, and bone

The article summarizes the current knowledge on the pathogenesis, clinical aspects and treatment of bone problems in the major inflammatory bowel diseases (Crohn's disease and ulcerative colitis) and celiac disease. It presents the physiological relationship between intestine and bone as well as the alterations determined by disease-disrupted intestinal integrity. Two hypotheses about the pathogenetic mechanisms of bone metabolism derangements and bone loss are discussed: the classical one, that indicates calcium malabsorption as the main culprit, and the new one, that emphasizes the role of inflammation. The article summarizes the available epidemiological data about osteopenia/osteoporosis and fragility fractures in these chronic intestinal diseases and presents the state-of-the-art treatment options.

A physiologically based mathematical model of integrated calcium homeostasis and bone remodeling

Bone biology is physiologically complex and intimately linked to calcium homeostasis. The literature provides a wealth of qualitative and/or quantitative descriptions of cellular mechanisms, bone dynamics, associated organ dynamics, related disease sequela, and results of therapeutic interventions. We present a physiologically based mathematical model of integrated calcium homeostasis and bone biology constructed from literature data. The model includes relevant cellular aspects with major controlling mechanisms for bone remodeling and calcium homeostasis and appropriately describes a broad range of clinical and therapeutic conditions. These include changes in plasma parathyroid hormone (PTH), calcitriol, calcium and phosphate (PO4), and bone-remodeling markers as manifested by hypoparathyroidism and hyperparathyroidism, renal insufficiency, daily PTH 1-34 administration, and receptor activator of NF-kappaB ligand (RANKL) inhibition. This model highlights the utility of systems approaches to physiologic modeling in the bone field. The presented bone and calcium homeostasis model provides an integrated mathematical construct to conduct hypothesis testing of influential system aspects, to visualize elements of this complex endocrine system, and to continue to build upon iteratively with the results of ongoing scientific research.

Human duodenum responses to vitamin D metabolites of TRPV6 and other genes involved in calcium absorption

Calcium absorption by the intestine is necessary for bone mineralization. Much has been learned about this process and the role of vitamin D metabolites in gene transcription from animal studies, but the molecular mechanisms in humans are less well understood. We have used samples of normal human duodenal mucosa, obtained at endoscopy, to investigate the effects of the vitamin D metabolites, 1alpha-dihydroxycholecalciferol [1,25(OH)(2)D(3)] and 25-hydroxycholecalciferol (25OHD), on transcripts on genes involved in calcium absorption and vitamin D metabolism. TRPV6 transcripts were significantly higher after incubation for 6 h with 1,25(OH)(2)D(3) (10(-9) mol/l) than after control incubations (median difference 3.1-fold, P < 0.001). Unexpectedly, TRPV6 expression was also higher (2.4-fold, P < 0.02) after incubation with 25OHD (10(-7) mol/l). Transcripts for the calcium-ATPase, PMCA1, were significantly higher with 1,25(OH)(2)D(3); CYP24 transcripts were reliably detected after incubation with either metabolite, but calbindin-D9k transcripts were unaffected. The response of TRPV6 to 25OHD and the expression of transcripts for CYP27B1, the 25OHD-1alpha-hydroxylase, were significantly correlated (r = 0.82, P < 0.02). Basal duodenal expression of TRPV6 and CYP27B1 were significantly associated (r = 0.72, P < 0.001) in a separate previously reported series of subjects. Multiple regression analysis of the associations with basal duodenal TRPV6 expression identified CYP27B1 expression and serum 1,25(OH)(2)D as major factors. Expression of the CYP27B1 protein was demonstrated immunohistochemically in duodenal mucosa. This study has shown that human duodenal TRPV6, PMCA1, and CYP24 transcripts respond rapidly to 1,25(OH)(2)D(3) and provides evidence suggesting that local duodenal production of 1,25(OH)(2)D(3) by 25OHD-1alpha-hydroxylase may have a role in human calcium absorption.

The effect of vitamin D2 and vitamin D3 on intestinal calcium absorption in Nigerian children with rickets

CONTEXT

Children with calcium-deficiency rickets have high 1,25-dihydroxyvitamin D values.

OBJECTIVE

The objective of the study was to determine whether vitamin D increased calcium absorption.

DESIGN

This was an experimental study.

SETTING

The study was conducted at a teaching hospital.

PARTICIPANTS

Participants included 17 children with nutritional rickets.

INTERVENTION

The participants were randomized to 1.25 mg oral vitamin D(3) (n = 8) or vitamin D(2) (n = 9).

MAIN OUTCOME MEASURE

Fractional calcium absorption 3 da after vitamin D administration was measured.

RESULTS

Mean baseline 25-hydroxyvitamin D concentrations were 20 ng/ml (range 5-31 ng/ml). The increase in 25-hydroxyvitamin D was equivalent after vitamin D(3) (29 +/- 10 ng/ml) or vitamin D(2) (29 +/- 17 ng/ml). Mean 1,25-dihydroxyvitamin D values increased from 143 +/- 76 pg/ml to 243 +/- 102 pg/ml (P = 0.001), and the increase in 1,25-dihydroxyvitamin D did not differ between vitamin D(2) and vitamin D(3) (107 +/- 110 and 91 +/- 102 ng/ml, respectively). The increment in 1,25-dihydroxyvitamin D was explained almost entirely by the baseline 25-hydroxyvitamin D concentration (r(2) = 0.72; P < 0.001). Mean fractional calcium absorption did not differ before (52.6 +/- 21.4%) or after (53.2 +/- 23.5%) vitamin D, and effects of vitamin D(2) and vitamin D(3) on calcium absorption were not significantly different. Fractional calcium absorption was not closely related to concentrations of 25-hydroxyvitamin D (r = 0.01, P = 0.93) or 1,25-dihydroxyvitamin D (r = 0.21, P = 0.24). The effect of vitamin D on calcium absorption did not vary with baseline 25-hydroxyvitamin D values or with the absolute increase in 25-hydroxyvitamin D or 1,25-dihydroxyvitamin D values.

CONCLUSIONS

Despite similar increases in 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with vitamin D(2) or vitamin D(3), fractional calcium absorption did not increase, indicating that rickets in Nigerian children is not primarily due to vitamin D-deficient calcium malabsorption.

Vitamin D insufficiency: disease or no disease?

Vitamin D insufficiency (VDI) is widely reported. In patients with normal PTH, the diagnosis rests on increases in fractional calcium absorption (FCA) when 25(OH)D increases above 30 ng/ml. However, estimates of increased FCA after correction of VDI vary dramatically, depending on study methods. We used a dual stable calcium isotope to clarify the impact of vitamin D repletion on FCA in postmenopausal women with VDI. We hypothesized that FCA would increase with vitamin D repletion. We studied postmenopausal women with VDI [25(OH)D = 16-24 ng/ml] and an estimated calcium intake <or=1100 mg daily. Exclusion criteria included hypercalcemia, hypercalciuria, renal insufficiency, nephrolithiasis, gastrointestinal disorders, osteomalacia, prior adult fragility fracture, baseline T-score < -3.0, and use of medications known to interfere with vitamin D or calcium metabolism. Each woman underwent inpatient FCA studies before and after correction of VDI. We used ergocalciferol 50,000 IU/d for 15 days to achieve vitamin D repletion. During each study, women consumed their typical diet. They ingested (44)Ca orally with breakfast and received (42)Ca intravenously. We collected urine for 24 h and measured its calcium isotope content by mass spectrometry. Eighteen women completed the study; all but two had normal PTH. During the first and second FCA studies, their mean 25(OH)D level was 22 +/- 4 and 64 +/- 21 ng/ml, respectively (p < 0.001). Subjects' average FCA was 24 +/- 7% initially and 27 +/- 6% after vitamin D repletion (p = 0.04). Thus, FCA increased by 3 +/- 1% with correction of VDI. Postmenopausal women with VDI experience small FCA increments with vitamin D therapy. In existing literature, this small change in FCA does not associate with lower fracture rates or consistently higher bone mass. Future studies should ascertain whether small FCA increments favorably affect the skeleton.

The pig as an experimental model for elucidating the mechanisms governing dietary influence on mineral absorption

This review highlights the similarities between pigs and humans and thereby the value of the porcine human nutritional model, and reviews some of the more recent applications of this model for nutritional research.

The health benefits of calcium citrate malate: a review of the supporting science

There has been considerable investigation into the health benefits of calcium citrate malate (CCM) since it was first patented in the late 1980s. This chapter is a comprehensive summary of the supporting science and available evidence on the bioavailability and health benefits of consuming CCM. It highlights the important roles that CCM can play during various life stages. CCM has been shown to facilitate calcium retention and bone accrual in children and adolescents. In adults, it effectively promotes the consolidation and maintenance of bone mass. In conjunction with vitamin D, CCM also decreases bone fracture risk in the elderly, slows the rate of bone loss in old age, and is of benefit to the health and well-being of postmenopausal women. CCM is exceptional in that it confers many unique benefits that go beyond bone health. Unlike other calcium sources that necessitate supplementation be in conjunction with a meal to ensure an appreciable benefit is derived, CCM can be consumed with or without food and delivers a significant nutritional benefit to individuals of all ages. The chemistry of CCM makes it a particularly beneficial calcium source for individuals with hypochlorydia or achlorydia, which generally includes the elderly and those on medications that decrease gastric acid secretion. CCM is also recognized as a calcium source that does not increase the risk of kidney stones, and in fact it protects against stone-forming potential. The versatile nature of CCM makes it a convenient and practical calcium salt for use in moist foods and beverages. The major factor that may preclude selection of CCM as a preferred calcium source is the higher cost compared to other sources of calcium commonly used for fortification (e.g., calcium carbonate and tricalcium phosphate). However, formation of CCM directly within beverages or other fluid foods and/or preparations, and the addition of a concentrated CCM solution or slurry, are relatively cost-effective methods by which CCM can be incorporated into finished food and beverage products.

Association of vitamin D receptor polymorphism with calcaneal broadband ultrasound attenuation in Korean postmenopausal women with low calcium intake

This study investigated the associations among vitamin D receptor (VDR)BsmI polymorphism, calcium intake and bone strength as indicated by the broadband ultrasound attenuation (BUA) measured by calcaneal quantitative ultrasound at the left calcaneus in community-dwelling subjects with a low calcium intake. The VDRBsmI polymorphism was analysed in 335 women older than 65 years residing in rural Asan, Korea. Calcium intake was assessed with a 2 d, 24 h recall method. The distribution of genotypes was similar to that reported in other Asian populations (92 % bb, 7 % Bb and 1 % BB). The calcaneal BUA was significantly higher (P = 0·013) in the bb genotype than in the Bb or BB genotype (Bb and BB genotypes were combined due to the small number of BB subjects) in a multiple regression model after adjusting for age, body weight, height, physical activity and nutritional factors. BUA was not significantly affected by the calcium intake regardless of the genotype, cross-sectionally. The energy-adjusted average calcium intake of this population was 439·6 mg/d (432·5 mg/d for bb and 522·3 mg/d for Bb or BB), and 96 % of the subjects had dietary intakes that were less than the recommended Dietary Reference Intake for Koreans (which for calcium is 800 mg/d for women older than 65 years). In summary, the BUA in older Korean women with a low calcium intake was significantly influenced by the VDR genotype but not by the calcium intake, cross-sectionally.

Effects of two marine dietary supplements with high calcium content on calcium metabolism and biochemical marker of bone resorption

BACKGROUND/OBJECTIVE

Calcium is essential for the bone metabolism but daily calcium requirements are not met in a significant proportion of the population. Fortunately, oral calcium supplementation can help to meet these needs; however, the calcium bioavailability depends on the calcium sources. The calcium absorption and bioavailability of dietary supplements from marine sources are not known. The objectives of this study were to evaluate the effects of two marine dietary supplements with a high calcium content: a fishbone powder (Phoscalim) and a ray cartilage hydrolysate (Glycollagene), in comparison with milk, and a placebo (maltodextrin), on calcium metabolism and a biochemical marker of bone resorption, using the oral calcium tolerance test.

SUBJECTS

Twenty male volunteers were randomized to eat 836 mg of calcium from different sources compared to maltodextrin during a Latin square study. Serum calcium concentrations and other parameters of the calcium metabolism, such as serum intact parathyroid hormone (iPTH) and serum C telopeptides (s-CTX), were measured after an acute oral calcium load based on the Pak protocol.

RESULTS

An increase in serum-corrected calcium areas under the curve (AUC) occurred with Phoscalim and Glycollagene when compared to milk. Significantly lower iPTH concentrations were observed with Glycollagene than with milk at T0+1 h, T0+3 h, T0+6 h and with Phoscalim than with milk at T0+6 h. A significantly lower s-CTX concentration was observed with Glycollagene than with milk and Phoscalim at T0+6 h. Furthermore, the urinary calcium/creatinine ratio increased significantly more with Glycollagen than with milk in T0 h+3 h and T3 h+6 h.

CONCLUSION

These two dietary supplements from marine sources constitute oral calcium sources when compared to milk on calcium absorption and bone resorption markers on short time.

Calcium, dietary, and lifestyle factors in the prevention of colorectal adenomas

BACKGROUND

Many studies have suggested a role for calcium in reducing the risk of colorectal adenomas and cancer but its effectiveness may be dependent on interactions with other dietary and/or lifestyle factors. We examined the association between calcium and prevalence of adenomas and assessed whether the association was stronger in biologically plausible subgroups.

METHODS

Cross-sectional data from 222 cases and 479 adenoma-free controls who underwent colonoscopies and completed food frequency and lifestyle questionnaires were used in the analyses. Multivariable logistic regression was used to estimate the association between calcium and prevalence of adenomas. Stratified analyses and the likelihood ratio test were used to examine effect modification by various demographic, lifestyle, and behavioral factors.

RESULTS

Overall, little association was observed comparing total calcium intake of > or = 900 mg/day to < 500 mg/day (adjusted odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.53-1.37). However, stronger associations were observed in patients with lower fat intake and in those who regularly (> or = 15 times/month) took nonsteroidal antiinflammatory drugs (NSAIDs). Specifically, total calcium intake of > or = 900 mg/day was associated with a lower prevalence of adenomas among patients with lower fat intake (OR = 0.47, 95% CI: 0.25-0.91) but not among those with higher fat intake (OR = 1.20, 95% CI: 0.61-2.35; P-value for interaction = .01). For NSAIDs, the associations were OR = 0.37 (95% CI: 0.16-0.86) for regular NSAID users and OR = 1.27 (95% CI: 0.73-2.22) with infrequent or nonuse of NSAIDs, respectively (P = .06).

CONCLUSIONS

The data suggest that a lower-fat diet and regular NSAID use may enhance calcium's effectiveness as a colorectal cancer preventive agent.

The effects of Vitamin D metabolites on expression of genes for calcium transporters in human duodenum

The role of Vitamin D in the regulation of calcium absorption in the intestine is well recognized but the mechanisms of the effects on human genes are surprisingly poorly understood. We have determined the expression of transcripts of the apical membrane calcium transporter TRPV6, the cytoplasmic calcium binding protein calbindin-D9k, the basolateral plasma membrane Ca(2+)-ATPase (PMCA1) and the Vitamin D receptor (VDR) in normal endoscopic duodenal mucosal biopsies using quantitative real-time RT-PCR and related baseline expression to Vitamin D metabolites. TRPV6 transcript levels have been shown to be significantly correlated with serum 1,25(OH)(2)D levels in men, but not overall in women, where negative effects of age predominate. TRPV6 and VDR expression were significantly related in both men and women, but were significantly lower in older women. Associations with bone mineral density and fractional calcium absorption were also studied. In a second series of subjects, duodenal biopsies were incubated in organ culture for 6h with Vitamin D metabolites. TRPV6 expression was significantly increased by 1,25(OH)(2)D(3) (10(-9)mol/l) as was PMCA1 to a much smaller extent. TRPV6 expression also increased with 25(OH)D(3). CYP27B1 expression was found in all samples, and CYP24 transcripts were detected after incubation with 1,25(OH)(2)D(3) or 25(OH)D(3).

Calcium channel TRPV6 expression in human duodenum: different relationships to the vitamin D system and aging in men and women

Intestinal absorption of calcium affects bone mineralization and varies greatly. In human duodenum, expression of the calcium channel TRPV6 was directly related to blood 1,25-dihydroxyvitamin D in men, but effects of age with lower median vitamin D receptor levels were more significant in women.

INTRODUCTION

The TRPV6 calcium channel/transporter is implicated in animal studies of intestinal calcium absorption, but in humans, its role and relationship to differences in mineral metabolism is unclear. We aimed to characterize TRPV6 expression in human intestine including defining relationships to the vitamin D endocrine system.

MATERIALS AND METHODS

TRPV6 transcript expression was determined in endoscopic mucosal biopsies obtained from normal duodenum. Expression was compared with that in ileum and with in situ hybridization in archival tissues and related to sequence variants in genomic DNA. TRPV6 expression was related in 33 subjects to other transcripts involved in calcium absorption including the vitamin D receptor (VDR) and to blood vitamin D metabolites including 1,25-dihydroxyvitamin D [1,25(OH)(2)D].

RESULTS

TRPV6 transcripts were readily detected in duodenum but not in ileum. Expression was highest in villous epithelial cells. Sequence variants in the coding and upstream regions of the gene did not affect TRPV6 expression. The relationship between duodenal TRPV6 expression and 1,25(OH)(2)D differed in men and women. In men, linear regression showed a strong association with 1,25(OH)(2)D (r = 0.87, p < 0.01), which was unaffected by age. In women, there was no significant overall relationship with 1,25(OH)(2)D, but there was a significant decrease with age (r = -0.69, p < 0.001). Individual expression of TRPV6 and VDR was significantly correlated. The group of older women (>50) had lower median levels of both TRPV6 and VDR transcripts than younger women (p < 0.001 and 0.02, respectively).

CONCLUSIONS

Duodenal TRPV6 expression is vitamin D dependent in men, but not in older women, where expression of TRPV6 and VDR are both reduced. These findings can explain, at least in part, the lower fractional calcium absorption seen in older postmenopausal women.

Bone, body weight, and weight reduction: what are the concerns?

Of the U.S. population, 65% is either overweight or obese, and weight loss is recommended to reduce co-morbid conditions. However, bone mobilization and loss may also occur with weight loss. The risk for bone loss depends on initial body weight, age, gender, physical activity, and conditions of dieting such as the extent of energy restriction and specific levels of nutrient intake. Older populations are more prone to bone loss with weight loss; in women, this is due at least in part to a reduced dietary Ca intake and/or efficiency of absorption. Potential hormonal mechanisms regulating bone loss during weight loss are discussed, including decreases in estrogen, leptin, glucagon-like peptide-2, growth hormone, and insulin-like growth factor-1, or an increase in cortisol. In contrast, the rise in adiponectin and ghrelin with weight reduction should not be detrimental to bone. Combining energy restriction with exercise does not necessarily prevent bone loss, but may attenuate loss as was shown with additional Ca intake or osteoporosis medications. Future controlled weight loss trials should be designed to further address mechanisms influencing the density and quality of bone sites vulnerable to fracture, in the prevention of osteoporosis.

A cross-sectional survey of calcium intake in relation to knowledge of osteoporosis and beliefs in young adult women

This investigation found that young adult women (n = 265) were very likely (80.6%) to have accurate knowledge about osteoporosis but also typically had a low calcium intake (454 mg/day). The women in this study believed that they were at risk of osteoporosis but felt that prevention was difficult. Meanwhile, they held the opinion that osteoporosis is not serious and that taking preventative measures would not be worthwhile. The factors that most strongly affected the intake of calcium by women were, in order, knowledge, number of children, self-rated health score, Body Mass Index, graduation from high school, experience of bone density examination and family history. These seven items accounted for 31.8% of the variation in calcium intake.