Vitamin D status and body fat measured by dual-energy X-ray absorptiometry in a general population of Japanese children

Vitamin D and obesity

An inverse association between vitamin D status and obesity has been reported across diverse populations and age groups in humans. In animal model of diet-induced obesity, dysregulation of vitamin D metabolism has been observed. However, the causal relationship between vitamin D status and obesity is not conclusive. Several explanations, such as volumetric dilution, sequestration of vitamin D into adipose tissue, and limited sunlight exposure, have been suggested as the underlying mechanisms linking poor vitamin D status and obesity. Vitamin D can modulate adipose tissue biology, spanning from adipocyte differentiation to adipocyte apoptosis and energy metabolism, indicating its potential impact on adiposity. In this chapter, we will review the prevalence of vitamin D deficiency and determinants of vitamin D deficiency among different populations, as well as changes in vitamin D metabolism associated with obesity. Additionally, we will review vitamin D's regulation of adipogenesis and lipogenesis at the cellular level in order to gain a deeper understanding of the underlying mechanisms linking vitamin D levels and obesity.

Associations between Body Composition and Vitamin D Status in Children with Overweight and Obesity Participating in a 1-Year Lifestyle Intervention

Background: To examine associations between body composition and vitamin D status in children participating in a lifestyle intervention. Methods: Children (6−12 y, n = 101) with a body mass index (BMI)-for-age >85th percentile were randomized to six dietitian-led behavior counselling sessions or no intervention. Plasma 25-hydroxyvitamin D (25(OH)D), anthropometry, and body composition using dual-energy X-ray absorptiometry were assessed every 3 months for 1 year. For each anthropometry variable (z-scores), tertiles were created to test for differences in 25(OH)D over time (tertile-by-time), and for changes in the z-score (loss, maintain, gain)-by-time, and according to fat patterning (android vs. gynoid) using mixed effects models. Results: The baseline plasma 25(OH)D was 62.2 nmol/L (95%CI: 58.7−65.7), and none < 30 nmol/L. At 6 mo, children with gynoid fat patterning had higher 25(OH)D concentrations than in those with android fat patterning (64.5 ± 1.1 nmol/L vs. 50.4 ± 1.0 nmol/L, p < 0.003, Cohen’s f = 0.20). Children with the lowest lean mass index z-score at 9 mo had higher plasma 25(OH)D concentrations than children with the highest z-score at baseline, 3 mo, and 6 mo (p < 0.05, Cohen’s f = 0.20). No other significant differences were observed. Conclusion: In this longitudinal study, vitamin D deficiency was not present in children 6−12 y of age with obesity. Reductions in adiposity did not alter the vitamin D status.

Associations between serum levels of insulin-like growth factor-I and bone mineral acquisition in pubertal children: a 3-year follow-up study in Hamamatsu, Japan

BACKGROUND

Epidemiological data regarding the association between serum levels of IGF-I and bone mineral acquisition during childhood are scarce. Here, we investigated the association between serum levels of IGF-I and bone status during puberty.

METHODS

We analyzed prospective 3-year follow-up data of 254 community-dwelling children who completed both baselines (at age 11.2 years) and follow-up (at age 14.2 years) surveys in Hamamatsu, Japan. Total body (TB) bone area and bone mineral parameters were assessed using dual-energy X-ray absorptiometry.

RESULTS

During the 3-year follow-up period, there were significant (P < 0.05) increases in total body less head (TBLH) areal bone mineral density (aBMD), TBLH bone mineral content (BMC), and TB bone area, and a significant decrease in TB bone mineral apparent density (BMAD, volumetric bone mineral density, vBMD). IGF-I levels showed significant positive relationships with TBLH BMC and TBLH aBMD at both baseline and follow-up. TBLH aBMD in boys and TB BMAD in girls at follow-up showed significant increases from the lowest to highest quartiles of baseline IGF-I levels after adjusting for confounding factors. Similarly, changes in TBLH aBMD in boys and TB BMAD in girls during the 3-year follow-up period showed significant increases from the lowest to highest quartiles of baseline IGF-I levels after adjusting for confounding factors.

CONCLUSIONS

These results suggest that pubertal children with high levels of serum IGF-I tended to have high bone mineral acquisition later on.

Widespread vitamin D deficiency and its sex-specific association with adiposity in Chinese children and adolescents

OBJECTIVES

Vitamin D is involved in various physiologic and pathologic processes in the human body. The aim of this study was to determine the prevalence of vitamin D deficiency and the association of adiposity indicators with 25-hydroxyvitamin D (25[OH]D) in Chinese children and adolescents.

METHODS

This was a population-based, nationwide, multicenter cross-sectional study involving 10 696 participants (51.2% boys) 6 to 18 y of age. Total body fat mass was assessed by dual-energy x-ray absorptiometry, and measures of body mass index (BMI), fat mass index (FMI), fat mass percentage (FMP), and plasma 25(OH)D concentrations were obtained.

RESULTS

The adjusted mean of 25(OH)D was 39.3 nmol/L for all participants, 40.7 nmol/L for boys, and 37.9 nmol/L for girls. Of the children, 30% had vitamin D deficiency (25[OH]D <30 nmol/L) and 80% had vitamin D insufficiency (25[OH]D <50 nmol/L). The prevalence rates of vitamin D deficiency and insufficiency were higher in girls (31%, 83.4%, respectively) than in boys (22.8%, 78.7%, respectively). An L-shape relationship between age and 25(OH)D was observed in all children, with a threshold age of 14 y. Also, there was an inverted U-shaped association of BMI with 25(OH)D, and multivariable linear models shown FMI and FMP were inversely associated with 25(OH)D concentrations, particularly in boys (β = -0.86 and -0.83, respectively, all P < 0.05).

CONCLUSIONS

Vitamin D deficiency was widespread and its sex-specific association with an excess of body fat in Chinese children and adolescents. The findings indicate that targeted screening and treatment guidelines may be useful.

Association of Vitamin D Status and Metabolic Syndrome Components in Iranian Children

Background:

Recently, it has been found that Vitamin D can affect cardiometabolic risk factors. However, these findings have not been confirmed in younger population. We aimed to assess the associations of serum 25-hydroxyvitamin D (25(OH)D) and metabolic syndrome (MetS) components in Iranian children.

Methods:

This cross-sectional study was conducted on 240 children aged 6–9 years old. Anthropometric indices (weight, height, waist circumference, and body fat), biochemical parameters (low-density lipoprotein, high-density lipoprotein, triglyceride [TG], fasting blood sugar, and serum 25(OH)D), systolic blood pressure (SBP) and diastolic blood pressure (DBP) blood pressure, and dietary intake and physical activity were measured. Multivariate linear regression analysis was used to assess the association of MetS components and serum 25(OH)D.

Results:

Mean age of children was 7.8 ± 1.06 year. Mean serum 25(OH)D concentration was 14.6 ± 10.64 ng/ml, and the prevalence of Vitamin D deficiency (serum 25(OH)D lower than 10 ng/ml) was 41.66%. Dietary intake of Vitamin D was 1.91 ± 1.8 mcg/day. Serum 25(OH)D was inversely associated with TG (β = −0.16; CI: −0.27, −0.04) after adjusting by age, gender, body mass index, physical activity, and some dietary components. Serum 25(OH)D was negatively associated with SBP (β = −0.02; CI: (−0.05, −0.004), and DBP (β = −0.02; CI: −0.05, −0.003); however, it was not significant anymore after adjustment for sodium, potassium, and fiber.

Conclusions:

Vitamin D deficiency is alarming among Iranian children. Among the components of MetS, lower serum Vitamin D concentration was only associated with TG that could contribute in onset and progression of cardiometabolic disorders later in life.

Risk factors of vitamin D deficiency among 15-year-old adolescents participating in the Malaysian Health and Adolescents Longitudinal Research Team Study (MyHeARTs)

Background

This study is to determine the prevalence and risk factors of vitamin D deficiency (vitamin D ≤ 50 nmol/L) among 15-year-old Malaysian adolescents. By identifying potential risk factors, prevention strategies and interventions can be carried out to improve the vitamin D status in adolescents.

Methods and findings

Stratified random sampling design was used to select adolescents from 15 urban and rural secondary schools in Selangor, Perak and Kuala Lumpur, Malaysia. Data collection was carried out from 1^st April 2014 to 30^th June 2014. Information regarding socio-demographic characteristics, sun exposure and sun protective behaviours, clinical data and environmental factors were collected. Blood for total vitamin D was sampled. Descriptive and multivariate logistic regressions were performed. Total 1061 participants were analyzed (62% were female; mean age 15.1 ± 0.4 years). The prevalence of vitamin D deficiency was 33%. Mean vitamin D was lower in female (53 ± 15 nmol), obese (body fat percentage (≥25%^m; ≥33.8%^f) (56 ± 16 nmol/L), Malays (58 ± 18 nmol/L) and Indians (58 ± 15 nmol/L). In multivariate analysis, female (OR = 5.5; 95% CI: 3.4–7.5), Malay (OR = 3.2; 95% CI: 1.3–8.0), Indian (OR = 4.3; 95% CI: 1.6–12.0) and those always wearing long sleeve (OR = 2.4; 95% CI: 1.1–5.4) were more likely to have vitamin D deficiency. For female participants, ethnicity {Malays (OR = 6.7; 95% CI: 2.0–18.5), Indian (OR = 4.5; 95% CI: 1.8–19.3)} was an important risk factors. Cloud cover, school residence, skin pigmentation, sun-exposure and sun-protective behaviours were not significant risk factors. The limitation of this study was recall bias as it relied on self-reported on the sun exposure and protective behaviours. The diet factors were not included in this analysis.

Conclusions

The prevalence of Vitamin D deficiency among Malaysian adolescents was considerable. Gender, ethnicity and clothing style were important risk factors.

High Prevalence of Insufficient Vitamin D Intake and Serum 25-Hydroxyvitamin D in Chinese School-Age Children: A Cross-Sectional Study

Despite the importance of vitamin D in early stages of life, data are lacking on the levels of vitamin D intake and serum 25-hydroxyvitamin D (25-(OH)D) among Chinese school-age children. The aims of this study were to investigate the vitamin D intake and serum 25-(OH)D concentration of children aged 7 to 12 years in China, and to measure the associations between vitamin D status and children's growth and development parameters. We obtained data on vitamin D intake, serum 25-(OH)D concentration, and anthropometric measurements from a cross-sectional study on school-aged children in China. Multiple linear regression and multivariable logistic regression analyses assessed the associations mentioned above. A total of 563 children (9.5 ± 1.6 years) from six areas of China were included. Among them, 86.1% had a vitamin D intake below the recommended nutrient intake (10 μg/day), and 54.7% had vitamin D deficiency (serum 25-(OH)D <15 ng/mL). We also found that high vitamin D intake was inversely associated with the risk of vitamin D deficiency (OR = 0.836, 95% confidence interval: 0.713, 0.980), and serum 25-(OH)D concentration was positively associated with the intelligence score and body mass index-for-age Z-score (BAZ) (p < 0.05). Insufficient vitamin D intake and serum 25-(OH)D are prevalent among Chinese school-aged children. A negative association was observed between vitamin D intake and the risk of vitamin D deficiency. Moreover, vitamin D status was positively associated with intelligence and BAZ, which await confirmation in future studies.

Role of Vitamin D in urogenital health of geriatric participants

INTRODUCTION

Role of Vitamin D is very well known for the functioning of many body organs. However, its role in the postmenopausal women in relation to various genitourinary disorders has been recognized recently. The main objective of this study was to evaluate role of Vitamin D in vaginal health, prolapse, bladder and bowel function, and bacterial vaginosis (BV).

MATERIALS AND METHODS

This was a randomized controlled study in which 200 geriatric female patients of 65-78 years of age divided into two groups comprising study and control group with 100 participants in each. Detailed obstetrical, gynecological, and clinical history was elicited. Detailed examination regarding the prolapse, urinary and bowel functions, and bacterial infections was done followed by follow-up of 3 and 6 months each. Chi-square and independent t-test used for data analysis.

RESULTS

Mean modified vaginal health index (MVHI) among patients with pelvic floor diseases was statistically significant with P = 0.0472. There was a visible increasing trend in Vitamin D deficiency with increase in time since menopause (P = 0.1193). Patients with pelvic floor disease had mean Vitamin D statistically significant with P = 0.0462. With increase in Vitamin D levels, MVHI was found to be better. The association of mean Vitamin D levels among patients with urinary incontinence as compared to controls was significant with P = 0.0460. Association of mean Vitamin D levels in patients with fecal incontinence and BV as compared to controls was not statistically significant with P = 0.6304 and 0.79, respectively. Low Vitamin D levels were associated with high mean parathyroid hormone (PTH) levels statistically significant with P = 0.034. MVHI was found to increase significantly with Vitamin D supplementation at 3 and 6 months' follow-up. There was increase in Vitamin D and calcium levels and fall in serum PTH levels at 3 and 6 months.

CONCLUSIONS

Vitamin D levels were associated with a decreased risk of pelvic floor disorders, improved MVHI in women in geriatric age group.

Dietary vitamin D dose-response in healthy children 2 to 8 y of age: a 12-wk randomized controlled trial using fortified foods

BACKGROUND

Vitamin D is fundamental for bone health. A high proportion of Canadian 2- to 8-y-olds do not meet the Estimated Average Requirement (EAR) of 400 IU/d.

OBJECTIVE

The objective was to determine whether vitamin D intakes consistent with the EAR or Recommended Dietary Allowance (RDA), through fortification of additional dairy products, would result in higher vitamin D status in young children.

DESIGN

Participants aged 2-8 y (n = 77; Montreal, Canada) were randomly assigned to 1 of 3 dietary vitamin D targets (control; EAR: 400 IU/d; or RDA: 600 IU/d) for 12 wk (January to April 2014). Anthropometric measurements, demographic characteristics, dietary intakes, fasting serum parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], and ionized calcium were compared by using mixed-model ANOVA.

RESULTS

Participants' mean ± SD age was 5.1 ± 1.9 y; 54.5% were boys with body mass index z scores of 0.50 ± 0.85. Compliance was 85% overall. No differences were observed in baseline dietary vitamin D intakes or serum 25(OH)D. At 12 wk, the EAR and RDA groups had significantly higher vitamin D intakes [median (IQR): control, 227 (184-305) IU/d; EAR, 410 (363-516) IU/d; and RDA, 554 (493-653) IU/d; P < 0.05] and serum 25(OH)D concentrations (control: 55.8 ± 12.3 nmol/L; EAR: 64.1 ± 10.0 nmol/L; and RDA: 63.7 ± 12.4 nmol/L; P < 0.05) than the control group. Ninety-six percent of children in the EAR and RDA groups and 67% of the control group had 25(OH)D concentrations ≥50 nmol/L.

CONCLUSION

Increasing the vitamin D intakes of young children through fortification of alternative dairy products results in significantly higher serum concentrations of 25(OH)D and a significantly greater proportion of children with serum 25(OH)D ≥50 nmol/L during periods of minimal ultraviolet B radiation exposure. This trial was registered at clinicaltrials.gov as NCT02097160 and had Health Canada Temporary Marketing Authorization Letters for both products (TM-13-0432 and TM-13-0433).

Clinical implications of vitamin D deficiency

Vitamin D deficiency is a common medical problem worldwide and its prevalence rises along with latitude, obesity, sedentary lifestyle, limited sunlight exposure and aging. A great body of evidence has shown that patients with vitamin D deficiency have increased cardiovascular risks and total mortality. Conversely, the presence of comorbidities progressive with age such as abdominal obesity, insulin resistance, type 2 diabetes and hypertension places the patients at an increased risk of vitamin D deficiency. The multidirectional effect of vitamin D deficiency is present in different phases of the aging process. Based on the literature review, the risk factors for vitamin D insufficiency most often found in post-menopausal women include limited sun exposure and time spent outdoors, inadequate dietary vitamin D intake, winter season and increased age. Vitamin D supplementation in this group might offer prevention of falls and fractures and may be beneficial for cardiovascular health, what may be especially important in osteoporotic and elderly populations. Prevention and treatment processes involve education regarding sunlight exposure and pharmacological cholecalciferol supplementation according to the recommendations for Central Europe. This manuscript reviews the role of vitamin D and its deficiency and considers their clinical implications, with particular regard to peri- and postmenopausal women.

Decrease in vitamin D status in the Greenlandic adult population from 1987-2010

Background

Low vitamin D status may be pronounced in Arctic populations due to limited sun exposure and decreasing intake of traditional food.

Objective

To investigate serum 25(OH)D3 as a measure of vitamin D status among adult Inuit in Greenland, predictors of low serum 25(OH)D3 concentrations and the trend from 1987 to 2005–2010.

Design

A total of 2877 randomly selected Inuit (≥18 years) from the Inuit Health in Transition study were included. A sub-sample (n = 330) donated a blood sample in 1987 which allowed assessment of time trends in vitamin D status.

Results

The geometric mean serum 25(OH)D3 (25[OH]D2 concentrations were negligible and not reported) in 2005–2010 was lowest among the 18–29 year old individuals (30.7 nmol/L; 95% CI: 29.7; 31.7) and increased with age. In all age-groups it decreased from 1987 to 2005–2010 (32%–58%). Low 25(OH)D3 concentrations (<50 nmol/L) were present in 77% of the 18–29 year old and decreased with age. A characteristic seasonal variation in 25(OH)D3 concentrations was observed (range 33.2–57.1 nmol/L, p<0.001), with the highest concentrations in August to October. Age (2.0% per year increase; CI: 1.7, 2.2), female gender (7.1%; CI: 2.0; 12.5), alcohol intake (0.2% per increase in drinks/week; 0.0; 0.4), and traditional diet (10.0% per 100 g/d increase; CI: 7.9; 12.1) were associated with increased serum 25(OH)D3, whereas smoking (−11.6%; CI: −16.2; −6.9), BMI (−0.6%; CI: −1.1; −0.2) and latitude (−0.7% per degree increase; CI: −1.3; −0.2) were associated with decreased concentrations.

Conclusion

We identified a remarkable decrease in vitamin D status from 1987 to 2005–2010 and a presently low vitamin D status among Inuit in Greenland. A change away from a traditional diet may well explain the observed decline. The study argues for the need of increased dietary intake of vitamin D and supplementation might be considered.

Interaction between vitamin D receptor gene polymorphisms and 25-hydroxyvitamin D concentrations on metabolic and cardiovascular disease outcomes

AIM

25-hydroxyvitamin D (25OHD) concentrations have been shown to be associated with major clinical outcomes, with a suggestion that individual risk may vary according to common genetic differences in the vitamin D receptor (VDR) gene. Hence, we tested for the interactions between two previously studied VDR polymorphisms and 25OHD on metabolic and cardiovascular disease-related outcomes in a large population-based study.

METHODS

Interactions between two previously studied VDR polymorphisms (rs7968585 and rs2239179) and 25OHD concentrations on metabolic and cardiovascular disease-related outcomes such as obesity- (body mass index, waist circumference, waist-hip ratio (WHR)), cardiovascular- (systolic and diastolic blood pressure), lipid- (high- and low-density lipoprotein, triglycerides, total cholesterol), inflammatory- (C-reactive protein, fibrinogen, insulin growth factor-1, tissue plasminogen activator) and diabetes- (glycated haemoglobin) related markers were examined in the 1958 British Birth cohort (n up to 5160). Interactions between each SNP and 25OHD concentrations were assessed using linear regression and the likelihood ratio test.

RESULTS

After Bonferroni correction, none of the interactions reached statistical significance except for the interaction between the VDR SNP rs2239179 and 25OHD concentrations on waist-hip ratio (WHR) (P=0.03). For every 1nmol/L higher 25OHD concentrations, the association with WHR was stronger among those with two major alleles (-4.0%, P=6.26e(-24)) compared to those with either one or no major alleles (-2.3%, P≤8.201e(-07), for both) of the VDR SNP rs2239179.

CONCLUSION

We found no evidence for VDR polymorphisms acting as major modifiers of the association between 25OHD concentrations and cardio-metabolic risk. Interaction between VDR SNP rs2239179 and 25OHD on WHR warrants further confirmation.

Vitamin D status among pulmonary TB patients and non-TB controls: a cross-sectional study from Mwanza, Tanzania

BACKGROUND

Little is known about vitamin D status in low-income populations burdened with infectious diseases. Hence, there is a need for data on correlates of serum 25-hydroxy vitamin D (S-25(OH)D) and its validity during infections.

OBJECTIVE

To assess the role of pulmonary TB (PTB) and HIV as correlates of S-25(OH)D.

DESIGN

Age-sex-matched cross-sectional study among PTB patients and non-TB controls.

METHODS

PTB patients were categorized as sputum negative (PTB-) and positive (PTB+) by culture. Non-TB controls were randomly selected among age-sex-matched neighbours to PTB+ patients. Height, weight, arm circumference and triceps skinfold were measured, and body mass index (BMI), arm fat (AFA) and muscle area (AMA) computed. HIV status, and S-25(OH)D, C-reactive protein (S-CRP) and α1-acid glycoprotein (S-AGP) were determined. Linear regression analysis with controls and PTB patients combined was used to identify correlates of S-25(OH)D.

RESULTS

S-25(OH)D data were available on 97.8% (1570) of 1605 participants. Mean (SD) S-25(OH)D was 84.4 (25.6) nmol/L with 39.6% <75 nmol/L among 347 non-TB controls. Time of recruitment, sex, PTB and HIV, and elevated S-AGP were correlates of S-25(OH)D. S-25(OH)D was 24.8 (95% CI 18.6;30.9) nmol/L higher in PTB compared to controls among females, but only 9.8 (95% CI:4.5;15.2) nmol/L among males (interaction p<0.0001). Females had 13.8 (95% CI:8.2;21.9) nmol/L lower S-25(OH)D than males, and HIV infected individuals had 8.5 (95% CI:4.9;12.1) higher S-25(OH)D compared to uninfected. Elevated S-AGP was a positive correlate of S-25(OH)D. Low BMI was associated with S-25(OH)D, but not with infections or S-AGP in the model.

CONCLUSION

While S-25(OH)D may decline transiently during a mild acute phase response, it may increase if the acute phase response leads to loss of fat. The validity of S-25(OH)D as a marker of vitamin D status may be affected by infections.