The association of serum 25-hydroxyvitamin D with indicators of bone quality in men of Caucasian and African ancestry

Dietary intake patterns, nutrient adequacy and associated factors in a multi-ethnic Caribbean population

Background: Diet is a significant contributor to health and wellbeing of individuals. Aim: In this study we investigated patterns of dietary intakes, levels of nutrient inadequacies and associated sociodemographic, anthropometric and lifestyle factors among adults in Trinidad and Tobago. Method: The study was cross-sectional in nature. A convenience sample of 11783 persons from districts throughout Trinidad and Tobago completed a self-administered questionnaire comprising socio-demographic and lifestyle items. Anthropometry was self-reported with 15% of participants having measurements done according to recommended procedures. Dietary patterns were determined by principal component analysis (PCA) while nutrient intakes and adequacy were assessed using the NutriGenie 7.0 software and nutrient adequacy ratio (MAR) respectively. Foods were categorised as unprocessed/minimally processed and processed/ultra-processed. The University of The West Indies Ethics Committee approved the study. Results: Approximately 72.5% of participants met the Goldberg criteria for plausible reporting. The three predominant dietary patterns 'Typical', 'Fruits and Vegetables', and 'High Fat' explained 45% of the total variance in foods consumed. Processed/ultra-processed foods accounted for most of the energy (80%) and nutrients consumed. Nutrient inadequacies were observed for potassium, vitamins B₁₂, D, E, K, fibre, magnesium; and iron among females. The mean adequacy ratio (MAR) for participants was 67%. MAR was positively associated with predominant dietary patterns independent of socioe demographic and lifestyle factors (p < 0.001). Conclusion: Irrespective of their nature, the predominant dietary pattern was associated with nutrient adequacy among participants. Reducing the risk of inadequate nutrient intakes may be addressed by increasing availability, access and consumption of appropriate sources of these micronutrients.

Global Perspective of the Vitamin D Status of African-Caribbean Populations: A Systematic Review and Meta-analysis

BACKGROUND/OBJECTIVES

Vitamin D deficiency remains a global public health issue, particularly in minority ethnic groups. This review investigates the vitamin D status (as measured by 25(OH)D and dietary intake) of the African-Caribbean population globally.

SUBJECTS/METHODS

A systematic review was conducted by searching key databases (PUBMED, Web of Science, Scopus) from inception until October 2019. Search terms included 'Vitamin D status' and 'African-Caribbean'. A random effects and fixed effects meta-analysis was performed by combining means and standard error of the mean.

RESULT

The search yielded 19 papers that included n = 5670 African-Caribbean participants from six countries. A meta-analysis found this population to have sufficient (>50 nmol/L) 25(OH)D levels at 67.8 nmol/L, 95% CI (57.9, 7.6) but poor dietary intake of vitamin D at only 3.0 µg/day, 95% CI (1.67,4.31). For those living at low latitudes 'insufficient' (as defined by study authors) 25(OH)D levels were found only in participants with type 2 diabetes and in those undergoing haemodialysis. Suboptimal dietary vitamin D intake (according to the UK recommended nutrient intake of 10 µg/day) was reported in all studies at high latitudes. Studies at lower latitudes, with lower recommended dietary intakes (Caribbean recommended dietary intake: 2.5 µg/day) found 'sufficient' intake in two out of three studies.

CONCLUSIONS

25(OH)D sufficiency was found in African-Caribbean populations at lower latitudes. However, at higher latitudes, 25(OH)D deficiency and low dietary vitamin D intake was prevalent.

Does the relationship between 25-hydroxyvitamin D status and bone mass vary according to skin color in adults? Results of a Brazilian population-based study

Skin color has been indicated as an important factor in determining serum concentrations of 25-hydroxyvitamin D [25(OH)D], and consequently bone health. However, studies are controversial and scarce for mixed populations.

PURPOSE/INTRODUCTION

To analyze the association of 25(OH)D with bone mineral content (BMC) and bone mineral density (BMD); and to investigate the presence of interaction with skin color in Brazilian adults.

METHODS

This is a cross-sectional, population-based study conducted with adult individuals (20-59 years) of both genders. Bone health was assessed by dual energy radiological absortometry. Vitamin D status was measured using serum 25(OH)D. Skin color and other variables in the adjusted model were collected using a questionnaire and anthropometric assessment. Associations and interactions were evaluated using linear regression models stratified according to gender.

RESULTS

Non-white men with vitamin D deficiency (< 20.0 ng/mL) have less bone mass than those with insufficiency and sufficiency for the femoral neck and hip sites. According to the adjusted regression analysis, the deficient status of 25(OH)D in men was associated with worse bone health for the lumbar spine sites (β = - 0.1; p = 0.006), femoral neck (β = - 0.08; p = 0.006), and hip (β = - 0.08; p = 0.009). No statistically significant associations were observed between 25(OH)D and bone health in women. In addition, no statistical interaction was identified between skin color and vitamin D status in relation to bone health (p > 0.05 for all tests) in either gender and for all bone sites evaluated.

CONCLUSION

Deficient vitamin D status is associated with lower bone mass in adults with differences observed according to gender, but not according to skin color.

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.

Assessing Vitamin D Status in African Americans and the Influence of Vitamin D on Skeletal Health Parameters

In the United States, there is a significant disparity in vitamin D status among individuals of African versus European descent. Despite having lower total 25-hydroxyvitamin D levels compared with white Americans, African Americans have higher bone mineral density and lower fracture risk. This article reviews classical and nonclassical vitamin D physiology, describes whether total versus free 25-hydroxyvitamin D is a better marker of vitamin D status in African Americans, and summarizes the influence of vitamin D status and vitamin D supplementation on markers of vitamin D bioactivity (intestinal calcium absorption, parathyroid hormone secretion, bone mineral density, fracture) in African Americans.

Three doses of vitamin D, bone mineral density, and geometry in older women during modest weight control in a 1-year randomized controlled trial

The effects of higher than recommended vitamin D doses on bone mineral density (BMD) and quality are not known. In this study, higher intakes, in postmenopausal women undergoing weight control over 1 year, had no effect on areal or volumetric BMD but prevented the deterioration in cortical bone geometry.

INTRODUCTION

Studies examining how bone responds to a standard dose of vitamin D supplementation have been inconsistent. In addition, the effects of higher doses on BMD and quality are not known. Postmenopausal women undergoing weight control to improve health outcomes are particularly at risk for bone loss and might benefit from supplemental vitamin D intake above the recommended allowance.

METHODS

This 1-year-long, randomized, double-blind controlled study addresses whether vitamin D supplementation, in healthy overweight/obese older women, affects BMD and bone structural parameters. In addition, bone turnover and serum total, free, and bioavailable 25-hydroxyvitamin D (25OHD) responses to one of three daily levels of vitamin D₃ (600, 2000, 4000 IU) with 1.2 Ca g/day during weight control were examined.

RESULTS

Fifty-eight women (age, 58 ± 6 years; body mass index, 30.2 ± 3.8 kg/m², serum 25OHD, 27.3 ± 4.4 ng/mL) were randomized to treatment. After 1 year, serum 25OHD concentrations increased to 26.5 ± 4.4, 35.9 ± 4.5, and 41.5 ± 6.9 ng/mL, in groups 600, 2000, and 4000 IU, respectively, and differed between groups (p < 0.01). Weight change was similar between groups (-3.0 ± 4.1 %). Cortical (Ct) thickness of the tibia changed by -1.5 ± 5.1 %, +0.6 ± 3.2 %, and +2.0 ± 4.5 % in groups 600, 2000, and 4000 IU, respectively, and each group was significantly different from each other (p < 0.05).

CONCLUSION

The decline in Ct thickness was prevented with higher vitamin D₃ supplementation, but there were no other significant changes due to treatment over 1 year. Whether these findings translate to changes in biomechanical properties leading to reduced fracture risk should be addressed in future studies.

Vitamin D metabolites and bone mineral density: The multi-ethnic study of atherosclerosis

Previous studies demonstrate associations of low 25-hydroxyvitamin D (25(OH)D) concentrations with low bone mineral density (BMD) and fractures, motivating widespread use of vitamin D supplements for bone health. However, previous studies have been limited to predominantly White populations despite differences in the distribution and metabolism of 25(OH)D by race/ethnicity. We determined associations of serum 25(OH)D, 24,25-dihydroxyvitamin D (24,25(OH2)D3), and parathyroid hormone (PTH) with BMD among 1773 adult participants in the Multi-Ethnic Study of Atherosclerosis (MESA) in a staggered cross-sectional study design. Vitamin D metabolites were measured using liquid chromatography-mass spectroscopy and PTH using a 2-site immunoassay from serum collected in 2000-2002. Volumetric trabecular lumbar BMD was measured from computed tomography scans performed in 2002-2005 expressed as g/cm(3). We used linear regression and graphical methods to compare associations of vitamin D metabolite and PTH concentrations with BMD as the outcomes measure among White (n=714), Black (n=353), Chinese (n=249), and Hispanic (n=457) participants. Serum 25(OH)D and 24,25(OH2)D3 concentrations were highest among Whites and lowest among Blacks. BMD was greatest among Black participants. Higher serum 25(OH)D was only associated with higher BMD among Whites and Chinese participants (P-for-interaction=0.054). Comparing the lowest category of 25(OH)D (<20 ng/ml) to the highest (≥30 ng/ml), the adjusted mean difference in BMD was -8.1g/cm3 (95% CI -14.8, -1.4) for Whites; -10.2g/cm3 (-20.4, 0.0) for Chinese vs. 8.8 g/cm3 (-2.8, 20.5) for Black and -1.1g/cm3 (-8.3, 6.2) for Hispanic. Similar results were observed for serum 24,25(OH2)D3. Serum PTH was not associated with BMD. In a multi-ethnic population, associations of 25(OH)D with BMD were strongest among White and Chinese participants and null among Black and Hispanic participants. Further studies are needed to determine optimal biomarkers for bone health for multiple ethnic groups.

Role of vitamin D levels and vitamin D supplementation on bone mineral density in Klinefelter syndrome

This manuscript describes the role of low vitamin D in bone metabolism of Klinefelter subjects. Low vitamin D is frequent in this condition and seems to be more important than testosterone in inducing low bone mineral density (BMD) and osteoporosis. Supplementation with vitamin D restores BMD after 2 years of treatment, whereas testosterone alone seems to be ineffective.

INTRODUCTION

Decreased bone mineral density (BMD) in Klinefelter syndrome (KS) is frequent, and it has been traditionally related to low testosterone (T) levels. However, low BMD can be observed also in patients with normal T levels and T replacement therapy does not necessarily increase bone mass in these patients. Nothing is known about vitamin D levels and supplementation in KS. In this study, we determine vitamin D status and bone mass in KS subjects and compare the efficacy of T therapy and vitamin D supplementation on BMD.

METHODS

A total of 127 non-mosaic KS patients and 60 age-matched male controls were evaluated with reproductive hormones, 25-hydroxyvitamin D, PTH, and bone densitometry by dual-energy X-ray absorptiometry (DEXA). Patients with hypogonadism and/or 25-hydroxyvitamin D deficiency were treated with T-gel 2% and/or calcifediol and re-evaluated after 24 months of treatment.

RESULTS

25-hydroxyvitamin D levels were significantly lower in KS patients with respect to controls, and they had significantly lower lumbar and femoral BMD. The percentage of osteopenia/osteoporosis in subjects with 25-hydroxyvitamin D deficiency was higher with respect to subjects with normal 25-hydroxyvitamin D and was not related to the presence/absence of low T levels. Subjects treated with calcifediol or T + calcifediol had a significant increase in lumbar BMD after treatment. No difference was found in T-treated group.

CONCLUSIONS

These data highlight that low 25-hydroxyvitamin D levels seem to have a more critical role than low T levels in inducing low BMD in KS subjects. Furthermore, vitamin D supplementation seems to be more effective than T replacement therapy alone in increasing BMD.

Femoral volumetric bone density, geometry, and strength in relation to 25-hydroxy vitamin D in older men

Low serum 25-hydroxy vitamin D (25(OH)D) concentrations are associated with increased hip fracture risk and decreased femoral areal bone mineral density (BMD) among elderly men. Structural dimensions of the proximal femur and volumetric BMD in cortical and trabecular compartments are also associated with hip fracture risk. However, associations of volumetric BMD or structural dimensions with serum 25(OH)D concentrations among older men remain unclear. In a random sample of 1608 men aged ≥65 years from the Osteoporotic Fractures in Men Study (MrOS), baseline serum 25(OH)D concentrations were measured by liquid chromatography/mass spectrometry assays. Femoral neck geometry and volumetric BMD derived from quantitative computed tomography included integral, cortical, and trabecular volumetric BMD; cross-sectional area; integral and cortical volume; and cortical volume as a percent of integral volume. We studied 888 men with vitamin D, parathyroid hormone (PTH), femoral neck geometry, and BMD measures. Whole-bone femoral strength and load-strength ratio from finite element (FE) analysis were also available for 356 men from this sample. Multivariable linear regression was used to estimate least square means of each femoral measure within quartiles of 25(OH)D adjusted for age, race, body mass index, height, latitude, and season of blood draw. Tests of linear trend in the means were performed across increasing quartile of serum 25(OH)D levels. Mean cortical volume (p trend = 0.006) and cortical volume as a percent of integral volume (p trend < 0.001) increased across increasing quartile of 25(OH)D level. However, overall femoral neck size (area and integral volume) did not vary by 25(OH)D level. Femoral neck volumetric BMD measures increased in a graded manner with higher 25(OH)D levels (p trend < 0.001). Femoral strength, but not load-strength ratio, increased with increasing 25(OH)D. Adjustment for PTH did not materially change these associations. We conclude that in older men, higher levels of endogenous 25(OH)D may increase whole-bone strength by increasing femoral volumetric BMD and cortical volume.

Serum 25-hydroxyvitamin D below 25 ng/mL is a risk factor for long bone fracture comparable to bone mineral density in Japanese postmenopausal women

There is emergent evidence for divergent associations between 25(OH)D levels and fractures by race and ethnicity, but data on Asian populations are sparse. We investigated this association in a primary care cohort of 1470 postmenopausal Japanese women followed for a mean period of 7.2 years and explored a potential threshold of 25(OH)D. Endpoints were incident vertebral, proximal femur, and long bone fractures. Rate ratios were estimated using multivariate Poisson regression adjusted for lumbar or femur bone mineral density (BMD) less than -2.5 SD of the young adult mean (YAM), age, weight, presence of diabetes mellitus, parathyroid hormone, estimated glomerular filtration rate, prior fracture, back pain, present medications and past medical history. Mean age was 63.7 ± 10.7 years and osteoporosis patients were 41.3 %. The background data of the present participants were almost identical to the subjects participating in the National Health and Nutrition Survey of 2003. Overall, 49.6 % of the subjects had a 25(OH)D value <20 ng/mL and 27.8 % had a 25(OH)D value from 20 to 24 ng/mL. The propensity score for exposure to 25(OH)D < 25 ng/mL in the present and independent community dwelling populations, namely the Miyama and Taiji cohorts, were not significantly different, suggesting no evidence for selection bias. The generalized additive models showed clear decreasing trends in incidence rates of proximal femur and long bone fractures at higher levels of 25(OH)D, and the annual incidence rate of proximal femur fracture was around 0.0005 in women with 25(OH)D > 25 ng/mL, probably leading to the decreasing trend in long bone fracture. Multivariate-adjusted rate ratios of 25(OH)D < 25 ng/mL were 1.01 (95 % confidence interval [CI], 0.84-1.22, p = 0.88) for vertebral fracture, 2.71 (95 % CI 0.94-7.83, p = 0.07) for proximal femur fracture, and 2.20 (95 % CI 1.37-3.53, p < 0.01) for long bone fracture. The respective rate ratios of a BMD level lower than -2.5 SD of the YAM were 1.61 (95 % CI 1.33-1.94, p < 0.01), 1.52 (95 % CI 0.67-3.45, p = 0.32), and 1.54 (95 % CI 1.02-2.33, p = 0.04). In conclusion, 25(OH)D is a leading risk factor for long bone fracture comparable to BMD in Japanese postmenopausal women. The contribution of 25(OH)D to fracture risks is substantial even below 25 ng/mL and is possibly site-specific. We recommend measuring the serum 25(OH)D level in primary care settings.

Fibroblast growth factor 23, vitamin D, and health disparities among African Americans with chronic kidney disease

Compared with Caucasians, African Americans have lower circulating concentrations of 25-hydroxyvitamin D (25(OH)D), the major storage form of vitamin D, leading to the widespread assumption that African Americans are at higher risk of vitamin D deficiency. However, the finding that African Americans maintain better indices of musculoskeletal health than Caucasians throughout their lifespan despite having lower circulating 25(OH)D concentrations suggests that the relationship between vitamin D deficiency and racial health disparities may not be so straightforward. The fairly recent emergence of fibroblast growth factor 23 (FGF23) may help resolve some of this uncertainty. FGF23 strongly modulates both systemic and local activation of 25(OH)D, playing a potentially important role in the degree to which lower 25(OH)D concentrations impact health outcomes, including differences in the incidence and rate of progression of chronic kidney disease by race. This review critically assesses ongoing controversies surrounding the relationship between vitamin D and racial disparities in chronic kidney disease outcomes, and how FGF23 may help to clarify the picture.

Serum 25-hydroxyvitamin D and risk of major osteoporotic fractures in older U.S. adults

Results from previous prospective studies linking serum 25-hydroxyvitamin D (25OHD) with fracture risk have been inconsistent. The present study examined the relationship between serum 25OHD and risk of incident major osteoporotic fracture (hip, spine, radius, and humerus) in older U.S. adults. The study used a pooled cohort of 4749 men and women ages 65 years and older from the third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) and NHANES 2000-2004. Incident fractures were identified using linked mortality and Medicare records that were obtained for participants from both surveys. Serum 25OHD values were measured by radioimmunoassay in both surveys. Cox proportional hazards models were used to estimate the relative risk (RR) of fracture by serum 25OHD level. There were 525 incident major osteoporotic fractures (287 hip fractures) in the sample. Serum 25OHD was a significant linear predictor of major osteoporotic fracture and significant quadratic predictor of hip fracture in the total sample and among those with less than 10 years of follow-up, but it was not related to risk of either fracture type among those with ≥ 10 years of follow-up. Major osteoporotic fracture risk was increased by 26% to 27% for each SD decrease in serum 25OHD among those with less than 10 years of follow-up. Serum 25OHD was significantly related to risk of major osteoporotic fractures as a group and to hip fracture alone in this cohort of older U.S. adults from NHANES III and NHANES 2000-2004. However, the predictive utility of serum 25OHD diminished after 10 years. In addition, the relationship appeared to be linear when major osteoporotic fracture risk was considered but quadratic when hip fracture risk was assessed.

Association between serum 25-hydroxyvitamin d levels, bone geometry, and bone mineral density in healthy older adults

PURPOSE

The association between serum 25-hydroxyvitamin D values and cortical/trabecular bone parameters in older adults has been incompletely explored. This study was designed to investigate the relationship between serum 25-hydroxyvitamin D levels and bone parameters for the tibia and radius using peripheral quantitative computed tomography in free-living healthy older adults.

METHODS

The study involved 134 older adults attending a twice-weekly low-intensity fitness program. In addition to clinical history and serum parameters, we assessed fat-free mass using dual-energy X-ray absorptiometry, total bone and cortical bone cross-sectional areas, and trabecular and cortical bone mineral density for the tibia and radius by peripheral quantitative computed tomography.

RESULTS

After applying multivariate linear regression models, adjusting for sex, age, body mass index, fat mass and fat-free mass, and creatinine, the association between 25-hydroxyvitamin D and bone parameters was significant for total bone and cortical bone cross-sectional areas in the radius (partial R (2) = 0.05 and 0.09, respectively) and for trabecular bone mineral density and cortical bone cross-sectional area in the tibia (partial R (2) = 0.11 and 0.02, respectively).

CONCLUSION

These findings support the idea that serum 25-hydroxyvitamin D levels and bone parameters are linked in older adults. Longitudinal studies are needed to establish whether vitamin D levels over time are associated with changes in these parameters.

Risk factors for subtrochanteric and diaphyseal fractures: the study of osteoporotic fractures

CONTEXT

Patients on long-term bisphosphonate therapy may have an increased incidence of low-energy subtrochanteric and diaphyseal (SD) femoral fractures. However, the incidence and risk factors associated with these fractures have not been well defined.

OBJECTIVE

The objective of the study was to determine the incidence of and risk factors for low-energy SD fractures in the Study of Osteoporotic Fractures (SOF).

DESIGN

Low-energy SD fractures were identified from a review of radiographic reports obtained between 1986 and 2010 in women in the SOF. Among the SD fractures, pathological, periprosthetic, and traumatic fractures were excluded. We assessed risk factors for SD fractures as well as risk factors for femoral neck (FN) and intertrochanteric (IT) hip fractures using both age-adjusted and multivariate time-dependent proportional hazards models. During this follow-up, only a small minority had ever used bisphosphonates.

RESULTS

Forty-five women sustained low-energy subtrochanteric/diaphyseal femoral fractures over a total follow-up of 140 000 person-years. The incidence of SD fracture was 3.2 per 10 000 person-years compared with a total hip fracture incidence of 110 per 10 000 person-years. A total of about 12% of women reported bisphosphonate use at 1 or more visits. In multivariate analyses, age, total hip bone mineral density (BMD), bisphosphonate use, and history of diabetes emerged as independent risk factors for SD fractures. Risk factors for FN and IT fractures included age, BMD, and history of falls or prior fractures. Bisphosphonate use was protective against FN fractures, whereas there was an increased risk of SD fractures (hazard ratio 2.58, P = .049) with bisphosphonate use after adjustment for other risk factors for fracture.

CONCLUSIONS

In SOF, low-energy SD fractures were rare occurrences, far outnumbered by FN and IT fractures. Typical risk factors were associated with FN and IT fractures, whereas only age, total hip BMD, and history of diabetes were independent risk factors for SD fractures. In addition, bisphosphonate use was a marginally significantly predictor although the SOF study has limited ability to assess this association.

Vitamin D and the racial difference in the genotype 1 chronic hepatitis C treatment response

BACKGROUND

African Americans with genotype 1 chronic hepatitis C attain a sustained virologic response (SVR) at only approximately one-half the rate of whites after peginterferon and ribavirin treatment. The serum concentration of 25-hydroxyvitamin D [25(OH)D] has recently been established as a predictor of treatment response. Therefore, the low serum concentrations of 25(OH)D found among African Americans may contribute to the low response rate; however, to our knowledge, none of the studies of vitamin D in chronic hepatitis C treatment have included a significant number of black patients.

OBJECTIVE

The objective was to compare the relation between the 25(OH)D concentration and genotype 1 chronic hepatitis C treatment response in African Americans with that in whites.

DESIGN

This cross-sectional analysis included 106 African American and 65 white patients with genotype 1 chronic hepatitis C.

RESULTS

Consistent with previous studies, we found that the SVR rate in the white patients increased significantly with an increasing serum concentration of 25(OH)D [SVR rates were 20%, 46%, and 70% for 25(OH)D serum concentrations <20, 20-35, and >35 ng/mL, respectively; P-trend = 0.008]; however, there was no relation between the SVR rate and 25(OH)D serum concentration in the African American patients [SVR rates were 32%, 28%, and 33% for 25(OH)D serum concentrations <20, 20-35, and >35 ng/mL, respectively; P-trend = 0.832]. We also found an analogous racial difference in the relation between the extent of liver fibrosis and the 25(OH)D concentration.

CONCLUSION

Racial differences in vitamin D physiology or race-specific factors that modify the effects of vitamin D may affect the immune response to genotype 1 hepatitis C virus.

Calciotropic hormones and the risk of hip and nonspine fractures in older adults: the Health ABC Study

The effects of vitamin D and parathyroid hormone (PTH) levels on incident fracture remain uncertain. To test the hypothesis that increasing serum 25-hydroxyvitamin D [25(OH)D] and decreasing PTH levels are associated with decreased risk of hip and any nonspine fracture, we conducted a prospective cohort study among 2614 community-dwelling white and black participants, aged ≥70 years, from the Health, Aging and Body Composition (Health ABC) Study. Serum and plasma samples were drawn at year 2, which formed the baseline for this analysis. Serum 25(OH)D and intact PTH (1-84) were measured using radioimmunoassay with DiaSorin reagents and EDTA plasma with a two-site immunoradiometric assay kit, respectively. Incident fractures (hip and any nonspine) were assessed after year 2, every 6 months, by self-report and validated by radiology reports. The median (interquartile range) follow-up times for hip and any nonspine fractures were 6.4 (6.1-6.5) and 6.4 (5.5-6.5) years, respectively. Cox proportional hazards regression was used to estimate the hazard ratios (HR) with 95% confidence intervals (CI) for fracture. There were 84 hip and 247 nonspine fractures that occurred over the follow-up period. The multivariable adjusted HRs (95% CIs) of hip fracture for participants in the lowest (≤17.78 ng/mL), second (17.79 to 24.36 ng/mL), and third quartiles (24.37 to 31.94 ng/mL) of 25(OH)D were 1.92 (0.97 to 3.83), 0.75 (0.32 to 1.72) and 1.86 (1.00 to 3.45), respectively, compared with participants in the highest 25(OH)D quartile (>31.94 ng/mL) (p trend = 0.217). Additional adjustment for IL-6 (p = 0.107), PTH (p = 0.124), and hip areal bone mineral density (p = 0.137) attenuated HRs of hip fracture in the lowest quartile by 16.3%, 17.4%, and 26.1%, respectively. There was no evidence of an association between 25(OH)D and any nonspine fractures, or between PTH and hip or any nonspine fractures. We found limited evidence to support an association between calciotropic hormones and hip and nonspine fractures in older men and women.

Recent insights into racial differences in bone and mineral metabolism

PURPOSE OF REVIEW

This study reviews recent insights into racial differences in bone from 2010 to 2011.

RECENT FINDINGS

Recent studies have focused on expanding our current understanding of responsible mechanisms for racial differences in osteoporotic fracture risk. Using newer, three-dimensional imaging techniques, these studies demonstrated that racial differences in bone mass and structure are apparent early in adolescence, even when accounting for differences in bone size and muscle mass by race. In addition, recent studies using genetic admixture analysis showed that greater percentage of African admixture was independently associated with higher bone mass and more favorable parameters of bone strength in children and adults. Furthermore, recent studies showed that the relationships between 25-hydoxyvitamin D and bone outcomes differed by race, with lower 25-hydroxyvitamin D levels being associated with lower bone quality and higher fracture risk in whites but not blacks.

SUMMARY

Racial differences in bone mass and strength are apparent early in life, are independently associated with genetic ancestry, and may be partly explained by differences in the relationships between vitamin D and bone metabolism. Further studies are needed to explore these findings, with the ultimate goal of better defining molecular and cellular mechanisms underlying racial differences in bone quality.