The Association Among Vitamin D status, Bone Geometry and Muscle Structure in 14 to 18 y Female Adolescents with Usual Intake of < 2 Servings of Milk and Alternatives per Day
Authors: Slim May A , Vanstone Catherine A , Morin Suzanne , Rahme Elham , Weiler Hope 
Published: November 2023

The associations among vitamin D status, based on serum 25‐hydroxyvitamin D (25OHD), and bone geometry and muscle structure in adolescents is under investigated. The objective was to explore the relationships among serum 25OHD and bone and muscle parameters of the lower leg and forearm in female adolescents with usual intake of < 2 servings of milk and alternatives per day. Healthy adolescents (14 to 18 y, n=50) from the Greater Montreal area participating in a trial (NCT02236871) were divided into three groups according to serum 25OHD level (<50, n=15; 50–74.9, n= 25; and ≥75 nmol/L, n=10) at baseline. Trabecular and cortical volumetric bone mineral density (vBMD), cortical thickness (CT) and bone area (BA) of the radius (4% and 66% sites), the tibia (4%, 38% and 66% sites) and muscle cross‐sectional area and density (66% sites) were obtained using peripheral quantitative computed tomography (pQCT, XCT‐2000; Stratec). Fasted venous blood was sampled to measure serum 25OHD concentration (Liaison, Diasorin). Lean mass and fat mass were acquired using dual‐energy X‐ray absorptiometry (DXA; Hologic Discovery QDR series). This was followed by standardized anthropometry, individual topological angle (ITA) as well as 24‐hour recall for dietary calcium, vitamin D, total energy and protein intake. All data reflect baseline only. Differences among 25OHD level groups for bone and muscle parameters were tested using mixed model ANOVA with post‐hoc Bonferroni adjustment. Data are presented as mean ± SD unless otherwise stated. Multivariate linear regression models, adjusting for age, height, fat mass, lean mass, ethnicity, skin color and vitamin D intake, were applied to evaluate the association between 25OHD and bone parameters. Participants (n= 50) had a mean age of 16.4 ± 1.5 y and a BMI of 21.7 ± 3.1 kg/m2 (Table 1). No significant differences among the groups were obtained for any of the bone parameters except for trabecular vBMD at the 4% tibia, where the group with 25OHD levels of >75 nmol/L revealed greater vBMD values than the group with less than 50 nmol/L (Figure 1). Muscle parameters did not differ among vitamin D status groups. After applying multivariate linear regression models, the association between 25OHD and bone parameters remained significant for trabecular vBMD of the 4% tibia (Table 2). Findings of this study support a beneficial role of vitamin D status in skeletal health of female youth. Further longitudinal studies are needed to determine whether changes in vitamin D status over time associates with peak bone mass.

Support or Funding Information

Supported by a contribution from the Dairy Research Cluster Initiative (Dairy Farmers of Canada, Agriculture and Agri‐food Canada, the Canadian Dairy Network and the Canadian Dairy Commission), Canada Foundation for Innovation and Canada Research Chairs Program

Descriptive characteristics of the study population

25OHD Levels (nmol/L)

Total Sample, n= 50
< 50, n=15Means ± SD
50 – 74.9, n= 25Means ± SD
≥ 75, n= 10Means ± SD

25OHD (nmol/L)
63.7 ± 27.8
38.9 ± 7.6a
60.3 ± 6.4b
109.2 ± 25.4c

Age (y)
16.4 ± 1.5
16.6 ± 1.4
16.4 ± 1.7
16.1 ± 1.3

Ethnicity, white (%)1
66
40
66.7
100

Height (cm)
165.0 ± 7.0
165.9 ± 7.1
164.0 ± 7.3
166.3 ± 6.3

Weight (kg)
60.7 ± 10.8
62.8 ± 12.6
58.8 ± 10.2
62.5 ± 9.9

BMI (kg/m2)
22.2 ± 3.2
22.7 ± 3.5
21.8 ± 3.1
22.6 ± 3.1

Fat Mass (kg)
16.9 ± 5.6
18.0 ± 5.1
15.9 ± 5.6
17.7 ± 6.4

Lean Mass (kg)
42.5 ± 6.9
42.4 ± 7.8
40.6 ± 5.7
42.6 ± 4.7

Vitamin D Intake (IU/d)
108.7 ± 118.4
128.7 ± 106.1
133.6 ± 88.9
128.1 ± 95.2

Calcium Intake (mg/d)
741.4 ± 445.9
705.2 ± 469.6
727.5 ± 449.5
830.8 ± 435.0

Protein Intake (g/d)
73.3 ± 38.6
65.3 ± 36.1
77.8 ± 43.4
74.2 ± 30.4

Total Energy Intake (kcal/d)
1849.8 ± 677.7
1814.7 ± 803.5
1963.2 ± 658.3
1630.4 ± 497.6

Calcium per 1000 kcal
402.8 ± 204.5
371.9 ± 218.3
371.9 ± 192.0
494.3 ± 206.6

Physical Activity (min/wk)
386.6 ± 242.9
318.5 ± 197.1
392.0 ± 215.5
475.6 ± 346.8

Groups with different superscripts are significantly different from each other using a mixed model ANOVA (p<0.0001). Data are expressed as mean ± SD.

Ethnicity was defined as 1= white and 2=non‐white including Asian, African and Hispanics.

Multiple regression analysis to evaluate the relation between vitamin D status and 4% tibial trabecular volumetric bone mineral density

Dependent Variable
Regression Model (n=50)
R‐square
β
SE
p‐value

4% Tibia Trabecular vBMD (mg/cm3)1

0.20

25OHD (nmol/L)

1.6
0.8
0.04

Age (years)

−21.2
15.7
0.2

Whole body fat mass (kg)

0.007
0.004
0.09

Whole body lean mass (kg)

−0.0006
0.004
0.99

Height (cm)

−1.5
3.7
0.7

Vitamin D intake (IU/d)

0.02
0.2
0.9

Ethnicity (white)2

56.8
54.3
0.4

Multiple linear regression models were used with a stepwise forward procedure to assess the independent association among the bone parameters at each bone site and the 25‐OHD values, including the following covariates (age, height, fat mass, lean mass, ethnicity and vitamin D intake). R‐Square was used as a fit criterion. A variance inflation factor was computed for each independent variable in the model to test for multicollinearity: Values more than 2 were used to indicate a multicollinearity problem in the model. In all analyses, a p‐value less than .05 was considered statistically significant.

Ethnicity was defined as 1= white and 2=non‐white including Asian, African and Hispanics.