Ethnicity, bone status, and the calcium requirement

Vitamin D/Bone Mineral Density and Triglyceride Paradoxes Seen in African Americans: A Cross-Sectional Study and Review of the Literature

Vitamin D is known to have a positive effect on bone health. Despite the greater frequency of vitamin D deficiency in African Americans (AA), they have a higher bone mineral density (BMD) compared to whites, demonstrating a disconnect between BMD and vitamin D levels in AA. Another intriguing relationship seen in AA is the triglyceride (TG) paradox, an unusual phenomenon in which a normal TG status is observed even when patients house conditions known to be characterized by high TG levels, such as Type II diabetes. To the best of our knowledge, no study has examined whether these two paradoxical relationships exist simultaneously in AA subjects with Type II diabetes. In this study, we compared levels of blood markers, including HbA1c, TG, and vitamin D, measured as serum 25-hydroxyvitamin D [25(OH)VD] µM/mL, [25(OH)VD]/TG, calcium, and BMD in AA (n = 56) and white (n = 26) subjects with Type II diabetes to see whether these relationships exist concurrently. We found that AA subjects had significantly lower TG and [25(OH)VD] levels and a significantly higher BMD status compared to white subjects, even when the ages, BMI, duration of diabetes, HbA1c, and calcium levels were similar between the two groups. This demonstrates that these two paradoxical relationships exist simultaneously in Type II diabetic AA subjects. In addition to these findings, we discuss the current hypotheses in the literature that attempt to explain why these two intriguing relationships exist. This review also discusses four novel hypotheses, such as altered circulating levels and the potential role of estrogen and hydrogen sulfide on BMD and HMG-CoA reductase as a possible contributor to the TG paradox in AA subjects. This manuscript demonstrates that there are still many unanswered questions regarding these two paradoxical relationships and further research is needed to determine why they exist and how they can be implemented to improve healthcare.

Parathyroid Hormone in Pregnancy: Vitamin D and Other Determinants

We aimed to assess the parathyroid hormone (PTH) concentration in pregnant women at the beginning of pregnancy (1st trimester) and within days before delivery (3rd trimester) and evaluate its determinants. From September 2014 through December 2015 in a cross-sectional study, 204 women in the 1st trimester of pregnancy and 203 women in the 3rd trimester of pregnancy were recruited. Blood samples were collected to measure PTH and circulating 25-hydroxy-vitamin D (25(OH)D) concentrations. Lifestyle and demographic data were collected using a questionnaire. Serum 25(OH)D and PTH were inversely correlated in both early and late pregnancy. Our analyses suggest that in the 3rd trimester of pregnancy, a 25(OH)D level of 18.9 ng/mL (47.3 nmol/L) could serve as an inflection point for the maximal suppression of PTH. Statistically significant determinants of PTH concentrations in multiple regression were 25(OH)D concentrations, season, multiparity and education of the partner (all p < 0.05) in early pregnancy. In late pregnancy, 25(OH)D concentrations and country of origin were statistically significant determinants of PTH concentrations (all p < 0.05). These factors and their effect on PTH appear to be vastly determined by 25(OH)D; however, they might also affect PTH through other mechanisms besides 25(OH)D.

Physiological Need for Calcium, Iron, and Folic Acid for Women of Various Subpopulations During Pregnancy and Beyond

Women tend to supplement their diets with multivitamin/mineral (MVM) supplements more often than men, and reports indicate that more than 90% of pregnant women in the United States supplement their diets with prenatal MVMs. Given the widespread use of MVMs among women and given the increasing efforts to unveil the importance of phenotype-specific health determinants, it seems imperative to review what is known about variations in nutrient physiology among women from different ethnic and racial groups and at different reproductive stages of life. In this study, we embark on an assessment of the scientific evidence and knowledge gaps that impact the precise determination of nutrient levels (specifically calcium, iron, and folic acid) that confer benefits to various subpopulations of women in the United States.

Body Mass Index, Lean Mass, and Body Fat Percentage as Mediators of the Relationship between Milk Consumption and Bone Health in Young Adults

Identifying environmental factors that influence bone health is crucial for developing effective intervention strategies that maximize peak bone mass. The aim of this study was to estimate the relationship between milk consumption and bone mineral density (BMD) in young adults, and to examine whether this relationship is mediated by body mass index (BMI) and total lean and fat mass. A cross-sectional study involving college students (n = 239) from a Spanish public university was performed. Data on milk consumption and anthropometric and body composition variables were collected. The Pearson correlation coefficients among total body BMD, body composition variables, and milk consumption ranged from -0.111 to -1.171, most of them statistically significant (p < 0.05). The ANCOVA (analysis of covariance) models showed that those with higher regular milk consumption had less total body BMD than those with lower regular milk consumption (p < 0.05), even after controlling for different sets of confounders. In the mediation analysis, BMI and lean and fat mass turned out to act as full mediators of the relationship between regular milk consumption and total body BMD (z = -1.7148, -1.3208, and -1.8549, respectively; p ≤ 0.05). In conclusion, milk consumption, per se, does not seem to have a direct effect on bone development, because its association seems to be fully mediated by body composition variables in young adults.

Is calcium supplementation always needed in patients with hypoparathyroidism?

Oral calcium salts are recommended for the treatment of chronic hypoparathyroidism (HypoPT), although dosimetry is variable between individual patients and clinicians. However, patient feedback on calcium salts can be negative, particularly due to gastrointestinal side effects and hypercalciuria-related complications. We begin with a clinical case of a HypoPT patient taking oral calcium salts following thyroid surgery, who requested support in reducing her dose of these with a view to stopping entirely. To evaluate her request, we first describe the usual treatment of HypoPT according to current guidance and then present data from (a) a case note review of a cohort of 24 HypoPT patients managed with a "no calcium" treatment regimen by single physician (b) a comprehensive online survey of HypoPT patients' treatment and experiences (n = 330). The case note review found that target range serum calcium levels were successfully achieved in all 24 patients since transitioning to a "no calcium" regimen, without any breakthrough hypocalcaemia-related symptoms, the development of new renal stones, the occurrence of calcium-related hospital admissions or the finding of significant hypercalciuria. The online survey identified 36% of HypoPT patients who continued to take activated vitamin D, but had discontinued calcium supplements. HypoPT patients not currently taking calcium reported a significantly lower prevalence of adverse effects and outcomes, both compared with their previous experiences whilst taking calcium and also compared with the 64% of patients who continued to take oral calcium. We conclude that, subject to methodological limitations, there are significant issues of tolerability arising from conventional calcium-based treatment regimens for patients with chronic HypoPT. For selected patients, it may be reasonable to facilitate a managed therapeutic transition to "no calcium" regimen, and we also propose that calcium-based regimes be prospectively evaluated against calcium-free (or calcium-low) alternatives.

Inter-population variation of histomorphometric variables used in the estimation of age-at-death

Population variation of several microscopic structures used in age-at-death estimation was assessed for three different population samples. The aim of the study was to determine if the need exists for population-specific standards when dealing with individuals of African and European origin. A total sample 223 bone sections from the anterior cortex of the femur (n = 99 black South Africans, n = 94 white South Africans and n = 30 Danish individuals) were analysed using a stereological protocol. Variables assessed included the average number of osteons per grid area (OPD), osteon size and Haversian canal size. ANCOVA was employed for assessment of statistically significant differences. The results indicated that OPD differed significantly between the three groups, but that osteon size was similar for all individuals. Haversian canal size showed unpredictable changes with age and high levels of variation, making it unsuitable to use for age estimation as a single factor. As there are conflicting opinions in the literature on whether to use population-specific equations for the estimation of age-at-death or not, this paper provided additional insight into the use of specific variables and its related variation between groups.

Calcium Intake and Survival after Colorectal Cancer Diagnosis

PURPOSE

Although evidence suggests an inverse association between calcium intake and colorectal cancer incidence, the influence of calcium on survival after colorectal cancer diagnosis remains unclear.Experimental Design: We prospectively assessed the association of postdiagnostic calcium intake with colorectal cancer-specific and overall mortality among 1,660 nonmetastatic colorectal cancer patients within the Nurses' Health Study and the Health Professionals Follow-up Study. Patients completed a validated food frequency questionnaire between 6 months and 4 years after diagnosis and were followed up for death. Multivariable hazard ratios (HRs) and 95% confidence intervals (95% CI) were calculated using Cox proportional hazards regression.

RESULTS

Comparing the highest with the lowest quartile intake of postdiagnostic total calcium, the multivariable HRs were 0.56 (95% CI, 0.32-0.96; P _trend = 0.04) for colorectal cancer-specific mortality and 0.80 (95% CI, 0.59-1.09; P _trend = 0.11) for all-cause mortality. Postdiagnostic supplemental calcium intake was also inversely associated with colorectal cancer-specific mortality (HR, 0.67; 95% CI, 0.42-1.06; P _trend = 0.047) and all-cause mortality (HR, 0.71; 95% CI, 0.54-0.94; P _trend = 0.008), although these inverse associations were primarily observed in women. In addition, calcium from diet or dairy sources was associated with lower risk in men.

CONCLUSIONS

Higher calcium intake after the diagnosis may be associated with a lower risk of death among patients with colorectal cancer. If confirmed, these findings may provide support for the nutritional recommendations of maintaining sufficient calcium intake among colorectal cancer survivors.

Dietary Acid Load, IGF-1 Single Nucleotide Polymorphism and Bone Resorption among Postmenopausal Chinese Women

The interaction of dietary and genetic factors may affect the development of bone deterioration. This study investigated whether the effects of dietary acid load (DAL) on bone loss in postmenopausal Chinese women were moderated by the insulin-like growth factor-1 (IGF-1) single nucleotide polymorphism, a known gene that plays a role in the regulation of bone formation and bone remodeling. A total of 217 healthy participants were recruited from the National Council of Senior Citizens Organizations Malaysia. Serum collagen type 1 cross-linked C-telopeptide was used as a surrogate bone marker to assess bone resorption and Agena^® MassARRAY genotyping analysis was used to identify the signaling of IGF-1 rs35767. The dietary acid load was measured by potential renal acid load score while physical activity was ascertained using the Global Physical Activity Questionnaire. Hierarchical regression was applied to test the main and interaction effects of DAL and IGF-1 genotypes in bone resorption. The result supported the diet-dependent acid-base balance theory that higher DAL was positively associated with bone resorption (β = 0.152, p = 0.031, F_(6,207) = 2.11, sig-F = 0.036, R² = 0.079). However, the results indicated that there was no significant correlation between IGF-1 and bone resorption, or any significant interaction between DAL and IGF-1. In conclusion, there was no moderating effect of IGF-1 on the relationship between DAL and bone resorption.

Ethnic Variations in Serum 25(OH)D Levels and Bone Ultrasound Attenuation Measurements in Blacks and Whites

Vitamin D deficiency is more common in Blacks, yet Blacks have lower prevalence of bone fragility fractures or osteoporosis than Whites. Broadband ultrasound attenuation (BUA) has been used to explore the association between serum 25(OH)D levels and bone quality in White and non-white populations. We investigated serum 25(OH)D status with corresponding BUA measurements assessed cross sectionally in a cohort of 232 Blacks and 260 Whites, aged 30-95 years who were part of the calibration study of the large Adventist Health Study-2 (AHS-2). At the calibration clinics, calcaneal BUA was measured and blood drawn for serum 25(OH)D assessment. In multivariable analyses, BUA was negatively associated with age (β-coefficient = -0.38; p < 0.0001) and positively associated with body mass index (BMI) (p _(trend) < 0.0001) and positively, but non-significantly, associated with serum 25(OH)D levels. Also, as expected, females had lower BUA (β-coefficient = -5.19; p < 0.05) and Blacks had higher BUA (β-coefficient = 4.26; p < 0.05). Gender and race modified the relationship of serum 25(OH)D on BUA with a positive association in males (p _(trend) ≤ 0.05), but no significant association in females after also controlling for menopausal status and hormone therapy. After also controlling for serum 25(OH)D levels, Black males had higher BUA than White men, but such differences were not found among the females. When stratifying on race, a positive association between serum 25(OH)D levels and BUA (p _(trend) ≤ 0.05) was found in Blacks, but not among Whites. Further studies are needed to understand how racial/ethnic differences in serum 25(OH)D levels influence bone health.

Safety assessments of subcutaneous doses of aragonite calcium carbonate nanocrystals in rats

Calcium carbonate nanoparticles have shown promising potentials in the delivery of drugs and metabolites. There is however, a paucity of information on the safety of their intentional or accidental over exposures to biological systems and general health safety. To this end, this study aims at documenting information on the safety of subcutaneous doses of biogenic nanocrystals of aragonite polymorph of calcium carbonate derived from cockle shells (ANC) in Sprague-Dawley (SD) rats. ANC was synthesized using the top-down method, characterized using the transmission electron microscopy and field emission scanning electron microscope and its acute and repeated dose 28-day trial toxicities were evaluated in SD rats. The results showed that the homogenous 30 ± 5 nm-sized spherical pure aragonite nanocrystals were not associated with mortality in the rats. Severe clinical signs and gross and histopathological lesions, indicating organ toxicities, were recorded in the acute toxicity (29,500 mg/m²) group and the high dose (5900 mg/m²) group of the repeated dose 28-day trial. However, the medium- (590 mg/m² body weight) and low (59 mg/m²)-dose groups showed moderate to mild lesions. The relatively mild lesions observed in the low toxicity dosage group marked the safety margin of ANC in SD rats. It was concluded from this study that the toxicity of CaCO₃ was dependent on the particulate size (30 ± 5 nm) and concentration and the route of administration used.

Differential effects of calcium- and vitamin D-fortified milk with FOS-inulin compared to regular milk, on bone biomarkers in Chinese pre- and postmenopausal women

PURPOSE

To compare the effects of a high-calcium vitamin D-fortified milk with added FOS-inulin versus regular milk on serum parathyroid hormone, and bone turnover markers in premenopausal (Pre-M) and postmenopausal (PM) women over 12 weeks.

METHODS

Premenopausal women (n = 136, mean age 41 (±5) years) and postmenopausal women [n = 121, mean age 59 (±4) years] were recruited, and each age group randomised into two groups to take two glasses per day of control = regular milk (500 mg calcium per day) or intervention (Int) = fortified milk (1000 mg calcium for pre-M women and 1200 mg calcium for PM women, 96 mg magnesium, 2.4 mg zinc, 15 µg vitamin D, 4 g FOS-inulin per day). At baseline, week 4 and week 12 serum minerals and bone biochemical markers were measured and bone density was measured at baseline.

RESULTS

Mean 25-hydroxyvitamin D [25(OH) vitamin D3] levels among groups were between 49 and 65 nmol/L at baseline, and over the 12 weeks of supplementation, the fortified milk improved vitamin D status in both Int groups. CTx-1 and PINP reduced significantly in both Pre-M and PM groups over the 12 weeks, with the changes in CTx-1 being significantly different (P < 0.035) between PM control and PM Int groups at week 12. Parathyroid hormone levels were significantly reduced in all groups over time, except for control PM group where levels increased at 12 weeks.

CONCLUSION

The overall pattern of responses indicates that while both regular milk and fortified milk reduce bone resorption in young and older women, fortified milk is measurably more effective.

Protective effects of low calcium intake and low calcium absorption vitamin D receptor genotype in the California Collaborative Prostate Cancer Study

BACKGROUND

High calcium intake is consistently associated with increased prostate cancer risk in epidemiologic studies. We previously reported that the positive association between calcium intake and risk of aggressive prostate cancer was modified by the single-nucleotide polymorphism (SNP) in the CDX-2 binding site of the vitamin D receptor (VDR) gene, among African American men.

METHODS

We expanded our previous study to include White men, a population with a higher calcium intake and a higher prevalence of the low absorption allele. We also examined VDR polymorphisms at other loci unrelated to calcium absorption. The study included 1,857 prostate cancer cases (1,140 with advanced stage at diagnosis, 717 with localized stage) and 1,096 controls. OR were estimated using conditional logistic regression.

RESULTS

Among both Blacks and Whites, we observed a threshold for calcium intake (604 mg/d) below which prostate cancer risk declined sharply. Low calcium intake was most strongly associated with decreased risk among men with the VDR Cdx2 low calcium absorption genotype (P for interaction = 0.001 and P = 0.06 for Whites and African Americans, respectively). Among all men with this genotype, those in the lowest quartile of calcium intake (≤604 mg/d) had a 50% reduction in risk as compared with those in the upper three quartiles [OR = 0.49; 95% confidence interval (CI), 0.36-0.67]. The association between calcium intake and prostate cancer risk was not modified by genotype at other VDR loci.

CONCLUSIONS

Our findings support the hypothesis that genetic determinants of calcium absorption influence prostate cancer risk.

IMPACT

The differences between African Americans and Whites in calcium absorption and dietary calcium intake may contribute to racial disparities in prostate cancer incidence and mortality rates.

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.

High-calcium, vitamin D fortified milk is effective in improving bone turnover markers and vitamin D status in healthy postmenopausal Chinese women

BACKGROUND/OBJECTIVES

Risk for developing osteoporosis increases in Asia. The purpose of the study was to evaluate the impact of a high-calcium vitamin D fortified milk (HCM) intervention on parathyroid hormone (PTH) levels, vitamin D status and markers of bone turnover in postmenopausal Chinese women.

SUBJECTS/METHODS

Sixty three women (>55 years) were assigned to receive two servings of either a calcium/vitamin D fortified milk or a control drink for 12 weeks. PTH, serum 25 (OH)D levels, C-telopeptide of type I collagen (CTX) levels and procollagen type I N-terminal propeptide (PINP) were measured at baseline, 2, 8 and 12 weeks of supplementation.

RESULTS

Daily calcium intake at baseline ranged between 260 and 482 mg for the HCM, and 252 and 692 mg for the control group. HCM improved serum 25 (OH)D levels significantly (33.13-39.49 nmol/l), while remaining similar in the control group (29.27-28.21 nmol/l). The difference between the groups were significant at week 2, 8 and 12. The percentage change in PTH levels in the HCM group was significant from week 2 onwards compared to the control drink (P<0.017, P<0.05 and P<0.001 at weeks 2, 8 and 12, respectively). Plasma CTX of the HCM group reduced by 25% between weeks 0 and 2, remaining significantly lower and at similar levels up to week 12. The difference between the HCM and control group for PINP reached significance at weeks 8 (P=0.011) and 12 (P=0.003).

CONCLUSIONS

The HCM intervention significantly improved vitamin D status and reduced bone turnover over 12 weeks in postmenopausal Chinese women.

The prevalence of self-reported lactose intolerance and the consumption of dairy foods among African American adults are less than expected

OBJECTIVE

To determine the self-reported incidence of lactose intolerance and its influence on dairy choices among African American adults.

DESIGN, SETTING, AND PARTICIPANTS

An online survey closely matched to the 2000 US Census was administered to a nationally representative sample of African Americans (2016 adults) and a comparison sample of the general population (1084 adults). Statistical analyses performed included pairwise t tests for proportion conducted on percent responses at the 95% confidence level.

RESULTS

African Americans were more likely to eat fewer dairy foods, experience physical discomfort after consumption, and believe they were lactose intolerant. While 49% of African Americans had ever experienced "some type of physical discomfort" after eating dairy foods, 24% believed they were lactose intolerant. Within this group, 85% of African Americans would be willing to consume more dairy products if they could avoid lactose intolerance symptoms.

CONCLUSIONS AND IMPLICATIONS

Dairy food, calcium, and vitamin D intake in African Americans and the general population are below US recommendations. Deficiencies of these nutrients are associated with chronic diseases that disproportionately affect African Americans. In the United States, dairy foods are the primary source of calcium and vitamin D, and lactose intolerance can be a significant barrier to dairy food intake. However, self-described lactose intolerance is less than commonly reported in African American populations. Low dairy intake may reflect concerns about lactose intolerance, other factors such as learned food habits and cultural preferences. Nutrition recommendations for African Americans and the general population should focus on the health benefits of dairy foods, provide culturally sensitive dietary options, and strategies to increase tolerance.

The effect of a fortified milk drink on vitamin D status and bone turnover in post-menopausal women from South East Asia

Calcium and vitamin D are essential for bone growth; milk is an appropriate vehicle to be fortified with calcium, vitamin D and other minerals. The purpose of the current study was to compare the effect of supplementing with a high calcium milk drink with added vitamin D, magnesium and zinc (HCM) versus a placebo drink on serum parathyroid hormone (PTH) and vitamin D status as well as markers of bone formation/resorption in postmenopausal women living in South East Asia (Jakarta, Indonesia and Manila, the Philippines) over a period of 4 months. Calcium intake at baseline was 237 mg (median; 176-316, interquartile range) for Indonesia and 353 mg (median; 222-480, interquartile range) for the Filipino women per day. Fortified milk supplementation reduced the percentage of women that were insufficient in 25 (OH) vitamin D(3) (<50 nmol/L) from 70% to 22% in the Indonesian women and 20% to 0% in the Filipino women. Fortified milk supplementation significantly reduced parathyroid hormone levels (PTH) by week 2 (22% and 11%), C-telopeptide of type I collagen (CTX) by week 2 (34% and 27%), osteocalcin (OC) by week 8 (18% and 25%) and procollagen type I N-propeptide (PINP) by week 8 (15% and 21%), in women from Indonesia and the Philippines, respectively. Thus, the HCM intervention was able to significantly improve vitamin D status, lower PTH levels and reduce bone turnover in two groups of South East Asian women.

Cross-sectional study of vitamin D and calcium supplementation effects on chronic periodontitis

BACKGROUND

A low dietary intake of vitamin D and calcium hastens bone loss and osteoporosis. Because vitamin D metabolites may also alter the inflammatory response and have antimicrobial effects, we studied whether the use of vitamin D and calcium supplements affects periodontal disease status.

METHODS

A cohort of 51 subjects receiving periodontal maintenance therapy was recruited from two dental clinics; 23 were taking vitamin D (>or=400 IU/day) and calcium (>or=1,000 mg/day) supplementation, and 28 were not taking such supplementation. All subjects had at least two interproximal sites with >or=3 mm clinical attachment loss. Daily calcium and vitamin D intake (from food and supplements) were estimated by nutritional analysis. The following clinical parameters of periodontal disease were recorded for the mandibular posterior teeth: gingival index, probing depth, cemento-enamel junction-gingival margin distance (attachment loss), bleeding on probing, and furcation involvement. Posterior photostimulable-phosphor bitewing radiographs were taken to determine cemento-enamel junction-alveolar crest distances (alveolar crest height loss). Data were analyzed with a repeated-measures multivariate analysis of variance.

RESULTS

Compared to subjects who did not take vitamin D and calcium supplementation, supplement takers had shallower probing depths, fewer bleeding sites, lower gingival index values, fewer furcation involvements, less attachment loss, and less alveolar crest height loss. The repeated-measures analysis indicated that collectively these differences were borderline significant (P = 0.08).

CONCLUSIONS

In these subjects receiving periodontal maintenance therapy, there was a trend for better periodontal health with vitamin D and calcium supplementation. More expanded longitudinal studies are required to determine the potential of this relationship.

Calcium, vitamin D supplements with or without alendronate and supragingival calculus formation in osteoporotic women: a preliminary study

OBJECTIVES

Long-term calcium intake is related to the formation of urinary stones. Structure and composition of kidney and gallstones are similar to dental calculus. Saliva is the source of calcium for supragingival dental calculus formation. The aim of this preliminary study was to evaluate the possible effects of long-term calcium and vitamin D supplementation with or without alendronate administration on salivary electrolyte concentrations and supragingival calculus formation in osteoporotic women.

METHODS

Thirty-one female patients with osteoporosis for at least 3 years participated in this study. Eighteen women were taking calcium plus vitamin D plus alendronate, while 13 women were taking only calcium plus vitamin D supplements. Eleven systemically healthy women volunteered for the control group. Whole saliva samples were collected from all women before initiation of any periodontal intervention. Plaque index, probing depth, clinical attachment level, bleeding on probing, and calculus index were recorded at six sites/tooth. Salivary concentrations of ionic calcium, potassium, magnesium and sodium were determined by atomic absorption spectrophotometer. Results were evaluated statistically by non-parametric tests.

RESULTS

No significant differences were found in clinical parameters or results of saliva analysis between the study groups (p > 0.05).

CONCLUSION

Within the limits of this preliminary study, it is suggested that long-term calcium and vitamin D supplementation with or without alendronate does not appear to have a significant effect on supragingival calculus formation or saliva total calcium, potassium, magnesium and sodium concentrations. Larger-scale studies investigating the possible effects of various treatment modalities of osteoporosis on supragingival calculus formation are required to better clarify this issue.

African Americans, 25-hydroxyvitamin D, and osteoporosis: a paradox

African Americans have lower serum 25-hydroxyvitamin D concentrations and a lower risk of fragility fractures than do other populations. I review the evidence on factors other than vitamin D that might explain this paradox and the calcium economy in different life stages. Researchers are actively trying to explain this genetically programmed advantage. Factors that could protect African Americans against fracture include their higher peak bone mass, increased obesity rates, greater muscle mass, lower bone turnover rates, and advantageous femur geometry. In addition, bone histomorphometry in young adults shows longer periods of bone formation. Although African Americans fall as frequently as do whites, the direction of their falls and their manner of breaking falls could protect them from fractures. African American girls accrue more calcium than do white girls during adolescence as the result of increased calcium absorption and superior renal calcium conservation. In adulthood, higher parathyroid hormone concentrations do not result in increased bone loss in African Americans because of their skeletal resistance to parathyroid hormone, and their superior renal conservation of calcium persists. These advantages diminish in the elderly, in whom further increases in parathyroid hormone result in increased bone turnover and bone loss. Ultimately, I explain the paradox by multiple factors associated with fracture risk and calcium economy in African Americans. Despite African Americans' reduced risk of osteoporotic fractures, such fractures remain an important public health problem for this population that vitamin D intervention studies have not addressed.

Plasma 1,25(OH)2D levels decrease in postmenopausal women with hypovitaminosis D

OBJECTIVE

Although calcitriol (1,25(OH)2D) is considered the biologically active vitamin D metabolite, several studies have shown that calcidiol (25OHD) is the vitamin D metabolite that is most closely linked to parathyroid function and indices of calcium homeostasis. Moreover, low levels of 25OHD have been associated with increased risk of different diseases including cancer, diabetes, and myopathy.

DESIGN

Cross-sectional study.

METHODS

We studied relations between plasma concentrations of 25OHD, 1,25(OH)2D, and parathyroid hormone (PTH) in fasting plasma samples from 315 healthy postmenopausal women randomly selected from the local background population.

RESULTS

P-1,25(OH)2D levels varied in a concentration-dependent manner with P-25OHD levels (P<0.001). Thus, P-1,25(OH)2D levels were the lowest in women with vitamin D insufficiency, i.e., P-1,25(OH)2D levels were reduced by approximately one-third in subjects with P-25OHD levels below 25 nmol/l compared with levels above 80 nmol/l (P<0.01). The association was most pronounced at P-25OHD concentrations below 80 nmol/l, whereas no major increase in P-1,25(OH)2D was observed at P-25OHD concentrations above 80 nmol/l. In multiple regression analysis, PTH was a minor although significant predictor of P-1,25(OH)2D levels.

CONCLUSIONS

In normal postmenopausal women, the conversion of 25OHD to active vitamin D depends on the substrate concentration. Our data support that vitamin D insufficiency should be considered at P-25OHD levels below 80 nmol/l.

Dose response to vitamin D supplementation among postmenopausal African American women

BACKGROUND

Reports on the dose response to vitamin D are conflicting, and most data were derived from white men and women.

OBJECTIVE

The objective was to determine the response of serum 25-hydroxyvitamin D [25(OH)D] to oral vitamin D(3) supplementation in an African American population.

DESIGN

Healthy black postmenopausal women (n = 208) participated in a vitamin D(3) supplementation trial for a period of 3 y. Analyses were done in the vitamin D supplementation arm (n = 104) to quantify the response in serum 25-hydroxyvitamin D concentrations at a steady state vitamin D input. The participants received 20 microg/d (800 IU) oral vitamin D(3) for the initial 2 y and 50 microg/d (2000 IU) for the third year.

RESULTS

Supplementation with 20 microg/d (800 IU/d) vitamin D(3) raised the mean serum 25(OH)D concentration from a baseline of 46.9 +/- 20.6 nmol/L to 71.4 +/- 21.5 nmol/L at 3 mo. The mean (+/-SD) concentration of serum 25(OH)D was 87.3 +/- 27.0 nmol/L 3 mo after supplementation increased to 50 microg/d (2000 IU/d). All participants achieved a serum 25(OH)D concentration >35 nmol/L, 95% achieved a concentration >50 nmol/L, but only 60% achieved a concentration >75 nmol/L. All patients had concentrations <153 nmol/L. On the basis of our findings, an algorithm for prescribing vitamin D so that patients reach optimal serum concentrations was developed. The algorithm suggests a dose of 70 microg (2800 IU/d) for those with a concentration >45 nmol/L and a dose of 100 microg (4000 IU/d) for those with a concentration <45 nmol/L.

CONCLUSIONS

Supplementation with 50 microg/d (2000 IU/d) oral vitamin D(3) is sufficient to raise serum 25-hydroxyvitamin D concentrations to >50 nmol/L in almost all postmenopausal African American women. However, higher doses were needed to achieve concentrations >75 nmol/L in many women in this population.

Calcium intake and disease prevention

While the fundamental metabolic function of calcium is to serve as a second messenger, coupling intracellular responses to extracellular signals, nutritional deficiency of calcium is manifested at a higher level of organization: 1) depletion of the calcium nutrient reserve; 2) inadequate complexation of digestive byproducts; and 3) collateral effects of hormones produced primarily to compensate for low calcium intake. The first mechanism contributes to the osteoporosis problem, the second to kidney stones and colon cancer, and the third to hypertension, preeclampsia, obesity, and insulin resistance, among others. Adequate calcium intakes (10001500 mg/d) in adults have been shown in controlled trials to lower the risk of osteoporotic fractures, kidney stones, obesity, and hypertension. The best source of calcium is dairy foods, largely because the disorders concerned depend upon multiple nutrients, not just calcium, and dairy provides a broad array of essential nutrients in addition to calcium, and at low cost.

Role of Dietary Sodium in Osteoporosis

Sodium, in the form of sodium chloride, elevates urinary calcium excretion and, at prevailing calcium intakes, evokes compensatory responses that may lead to increased bone remodeling and bone loss. The calciuria is partly due to salt-induced volume expansion, with an increase in GFR, and partly to competition between sodium and calcium ions in the renal tubule. Potassium intakes in the range of current recommendations actually reduce or prevent sodium chloride-induced calciuria. At calcium intakes at or above currently recommended levels, there appear to be no deleterious effects of prevailing salt intakes on bone or the calcium economy, mainly because adaptive increases in calcium absorption offset the increased urinary loss. Such compensation is likely to be incomplete at low calcium intakes. Limited evidence suggests equivalent bone-sparing effects of either salt restriction or augmented calcium intakes. Given the relative difficulty of the former, and the ancillary benefits of the latter, it would seem that the optimal strategy to protect the skeleton is to ensure adequate calcium and potassium intakes.

Low calcium intake among African Americans: effects on bones and body weight

This review was performed to summarize and integrate the evidence relating calcium intake to health status in African Americans, with special attention to bone and fat. Despite lower average calcium intakes, African Americans typically have skeletons more massive than those of whites. This is the result of a relative resistance of the bony resorptive apparatus to parathyroid hormone, which forces better urinary conservation of calcium and, at some life stages, more efficient intestinal calcium absorption as well. This adaptation, however, has other costs and appears to contribute to a greater risk in African Americans for several chronic diseases, including cardiovascular disease and stroke, obesity, and the insulin resistance syndrome. Higher calcium intakes not only support the skeleton in African Americans, just as they do in whites, but reduce the disease burden for other chronic diseases as well.

Newer Perspectives on Calcium Nutrition and Bone Quality

It is now generally accepted that an adequate calcium intake is important for building and maintaining a skeleton that expresses quantitatively the full genetic program and reduces lifetime fracture risk. In this brief review we focus mainly on a new and growing body of evidence indicating a benefit of adequate calcium intake on qualitative features of the skeleton that, independent of the quantity of bone, themselves influence skeletal strength and fragility. Change in bone mass and size during growth are dependent on both calcium intake and exercise, with the largest differences being observed in prepubertal children who have both high exercise levels and high calcium intakes. Much of this benefit is expressed as increased bone diameter (and hence stiffness). Fracture risk peaks at about the time of puberty and is inversely related to bone mass. However, even prepubertally, children with low calcium intakes have been reported to have a fracture rate 2.7x that of their birth cohort. Bone remodeling triples from age 50 to 65 in typical women and is now recognized to have primarily a homeostatic basis. While remodeling improves bone strength by repairing acquired defects, homeostatic remodeling, while necessary to maintain blood calcium levels, contributes only structural weakness to bone. High calcium intakes in postmenopausal and older women reduce this homeostatic remodeling to approximately pre-menopausal values and improve bone strength immediately, well prior to any appreciable change in bone mass.

Calcium supplementation does not augment bone gain in young women consuming diets moderately low in calcium

In earlier observational work, the dietary calcium:protein ratio was directly related to bone accrual in healthy postadolescent women. In this study, we sought to test the hypothesis that augmented calcium intake would increase postadolescent skeletal consolidation, using a double-blind, randomized, placebo-controlled design. We recruited 152 healthy young women (age 23.1 +/- 2.7 y, BMI 22.5 +/- 3.0 kg/m2); their usual diets, as assessed by 7-d food diaries, were low in calcium (605 +/- 181 mg/d; 15.1 +/- 4.5 mmol/d) and in the calcium:protein ratio (10.1 +/- 2.0 mg/g). The subjects were randomly assigned to supplemental calcium [500 mg calcium (12.5 mmol) as the carbonate, 3 times/d, with meals] or placebo capsules identical in appearance; all participants also took a daily multivitamin, and they were followed for up to 36 mo with bone densitometry (dual energy X-ray absorptiometry; DXA) at 6-mo intervals. A total of 121 subjects remained in the study for at least 12 mo (median time in the study, 35 mo), with a mean compliance level (observed/expected tablet consumption) of 87.7%. DXA data for these 121 subjects indicated modest but significant mean rates of increase (i.e., 0.24 to 1.10%/y) in bone mineral content (BMC; total body, total hip, and lumbar spine) and in lumbar spine bone mineral density (BMD) but no change in total hip BMD. None of these rates of change differed by group, i.e., calcium supplementation did not have any measurable effect on bone mass accrual. By midstudy, the calcium content of the subjects' usual diets for both groups had risen by approximately 15%. The combined effect of improved intakes of dietary calcium and the small amount of calcium added by the multivitamin tablets resulted in a mean calcium intake for the control group > 800 mg (20 mmol)/d, possibly at or near the threshold beyond which additional calcium has no further effect on bone accrual.

Two-year changes in bone and body composition in young children with a history of prolonged milk avoidance

No previous longitudinal studies of calcium intake, anthropometry and bone health in young children with a history of avoiding cow's milk have been undertaken. We report the 2-year changes of a group of 46 Caucasian children (28 girls, l8 boys) aged 8.1+/-2.0 years (mean +/- SD) who had low calcium intakes at baseline and were short in stature, with elevated body mass index, poor skeletons and lower Z scores for both areal bone mineral density (BMD, in grams per square centimeter) and volumetric density (bone mineral apparent density, BMAD, in grams per cubic centimeter), compared with a reference population of milk drinkers. At follow-up, adverse symptoms to milk had diminished and modest increases in milk consumption and calcium intake had occurred. Total body bone mineral content (BMC) and bone area assessed by dual energy X-ray absorptiometry had increased (P<0.05), and calcium intake from all sources was associated with both these measures (P<0.05). However, although some catch-up in height had taken place, the group remained significantly shorter than the reference population (Z scores -0.39+/-1.14), with elevated body mass index (Z scores 0.46+/-1.0). The ultradistal radius BMC Z scores remained low (-0.31+/-0.98). The Z scores for BMD had improved to lie within the normal range at predominantly cortical sites (33% radius, neck of femur and hip trochanter) but had worsened at predominantly trabecular sites (ultradistal radius and lumbar spine), where values lay below those of the reference group (P<0.05). Similarly, although volumetric BMAD Z scores at the 33% radius had normalized, BMAD Z scores at the lumbar spine remained below the reference population at follow-up (-0.67+/-1.12, P<0.001). Our results demonstrate persisting height reduction, overweight and osteopenia at the ultradistal radius and lumbar spine in young milk avoiders over 2 years of follow-up.

Effect of Vitamin D and Calcium on Periodontitis

The anthropological record indicates that we are exposed to considerably less ultraviolet radiation (required for the synthesis of vitamin D) and consume considerably less calcium than did our early ancestors. Most U.S. citizens have calcium intakes and serum levels of vitamin D far below recommended values. This is despite there having been extensive evidence that optimal calcium and vitamin D intakes not only benefit our postcranial bone health but also have many other health benefits. Numerous articles indicate that vitamin D and calcium deficiencies result in bone loss and increased inflammation, which are well recognized symptoms of periodontal disease. For more than 40 years, investigators have suggested that calcium intake may be associated with alveolar bone resorption, and more recently there have been a number of studies in which investigators have suggested that calcium and vitamin D may benefit periodontal health, and it has been suggested that calcium deficiency may be a risk factor for periodontal disease. There has not, however, been a vitamin-D-calcium-periodontitis clinical trial in which randomization and masking were carefully controlled, the periodontal disease status of patients known, periodontal disease measures were the primary outcomes, and levels of intake optimized to produce maximal effects. Such research might demonstrate that calcium and vitamin D are important adjuncts to standard treatments for preventing and treating periodontal disease.

Do young New Zealand Pacific Island and European children differ in bone size or bone mineral?

Although Pacific Island adults have been shown to have larger bones and greater bone mineral density than caucasians, no previous studies have been undertaken to determine whether differences are present in prepubertal children. Forty-one Pacific Island children (both parents of Pacific Island descent) and 38 European children, aged 3 to 7 years, living in New Zealand were studied. Heights and weights were determined by simple anthropometry and body mass index (BMI, kg/m2) was calculated. Body composition, bone size, and bone mineral content (BMC, g) were measured by dual energy X-ray absorptiometry (DXA) of the total body and the non-dominant forearm. Compared to European children, in data adjusted for age and gender, Pacific Island children had significantly greater (P < 0.05) BMC in the total body (12%), the ultradistal radius (16%), and the 33% radius (8%), and also greater total body bone area (10%). Bone mineral density (BMD, g/cm2) was higher only at the ultradistal radius (11%). However, after adjustment for body weight, in particular lean mass, no differences were seen between Pacific Island and European children in any bone measure. The larger bone area and BMC of young Pacific Island children can be explained by their greater height and weight. Therefore, this study has shown that prepubertal Pacific Island children do not have greater bone size or BMC for their weight.

Multiple sources of dietary calcium-some aspects of its essentiality

The increasing recognition of the important role of calcium in the myriad regulation of cellular processes in the health and well being throughout one's lifetime has focused on the need to ensure a sufficiency of its intake for nutritional, physiological, and medical reasons. Additionally, the recognition of the dynamic dietary changes and preferences of various populations in terms of their consumption of calcium-containing products coupled with large variations of food patterns and availability of calcium, highlights the need to consider and evaluate multiple sources of calcium (dairy, non-dairy, fortified foods, and supplemental). Aspects of the essentiality of calcium are thus considered via an initial consideration of: the salient aspects of absorption and bioavailability, changes in individual and societal dietary habits and preferences and the evaluation of various RDAs, AIs, and DRIs for calcium.

Long-latency deficiency disease: insights from calcium and vitamin D

Nutrient intake recommendations and national nutritional policies have focused primarily on prevention of short-latency deficiency diseases. Most nutrient intake recommendations today are based on prevention of the index disease only. However, inadequate intakes of many nutrients are now recognized as contributing to several of the major chronic diseases that affect the populations of the industrialized nations. Often taking many years to manifest themselves, these disease outcomes should be thought of as long-latency deficiency diseases. Sometimes they come about by the same pathophysiologic mechanism that produces the index disease, but sometimes the mechanisms are completely different. Well-documented examples of both short- and long-latency deficiency states involving calcium and vitamin D are described briefly. Then, the insights derived from these nutrients are tentatively applied to folic acid. Discerning the full role of nutrition in long-latency, multifactorial disorders is probably the principal challenge facing nutritional science today. The first component of this challenge is to recognize that inadequate intakes of specific nutrients may produce more than one disease, may produce diseases by more than one mechanism, and may require several years for the consequent morbidity to be sufficiently evident to be clinically recognizable as "disease." Because the intakes required to prevent many of the long-latency disorders are higher than those required to prevent the respective index diseases, recommendations based solely on preventing the index diseases are no longer biologically defensible.

Racial differences in the effect of early milk consumption on peak and postmenopausal bone mineral density

Studies of the effect of milk consumption on bone density have focused on white women. The applicability to other races is unclear. This study of 4316 women found a racial difference in the effect of early milk consumption on bone. Further study is required to evaluate the etiology of this difference.

INTRODUCTION

Early milk consumption has been found to influence bone mineral density positively throughout life. Previous studies leading to this finding focused on white women; there are no data to support the view that black women also gain an equivalent benefit from early milk consumption.

MATERIALS AND METHODS

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), we analyzed the relationship between reported childhood and teenage milk consumption and current hip bone mineral density at four sites (femoral neck, trochanter, intertrochanter, and total hip) among postmenopausal and 20- to 39-year-old non-Hispanic white (NHW) and black (NHB) women. Potential confounding variables were accounted for in the analysis.

RESULTS

Controlling for age and body mass index, teenage milk consumption was significantly associated with higher bone mineral density at all four sites among both postmenopausal and 20- to 39-year-old white women, but was not associated with bone mineral density at any site among black women. A similar pattern was observed for childhood milk intake. The interaction between race and teenage milk consumption significantly explained postmenopausal bone mineral density at all sites, whereas the interaction between race and teenage milk consumption was significant at two of the four sites among the 20- to 39-year-old women.

CONCLUSION

The results show racial differences in the effect of early milk consumption on peak and postmenopausal bone mineral density.

Normalizing calcium intake: projected population effects for body weight

Published data describing the inverse relationship between calcium intake and body weight in 564 women were evaluated for their dispersion around their means, and the fraction above any given weight or rate of weight gain was calculated from the parameters of the normal distribution for the variable concerned. At the 25th percentile of calcium intakes, 15% of young women were overweight, and that fraction fell to only 4% at calcium intakes in the range of currently recommended values. Similarly, obesity prevalence in this cohort fell from 1.4 to 0.2% across the same difference in calcium intakes. At midlife, women at the 25th percentile of intakes gained weight, on average, at a rate of 0.42 kg/y. This gain dropped to -0.011 kg/y at currently recommended calcium intakes. Although calcium intake explains only a small fraction of the variability in weight or weight gain, shifting the mean of the distributions downward by increasing calcium intake can be estimated to reduce the prevalence of overweight and obesity by perhaps as much as 60-80%.