Relation between milk-fat percentage, vitamin D, and BMI z score in early childhood

ABSTRACT

Background: Fortified cow milk is a material contributor of vitamin D and dietary fat in children. Recommendations for children >2 y of age advise reduced milk-fat consumption to reduce childhood obesity, yet the relation between lower milk fat, vitamin D stores, and body mass index (BMI) is unclear.

Objectives: The primary objective was to explore the association between milk-fat percentage and both BMI z score (zBMI) and venous 25-hydroxyvitamin D [25(OH)D]; the secondary objective was to assess whether milk volume consumed modified this relation.

Design: This was a cross-sectional analysis. Healthy urban children aged 12–72 mo were recruited from 9 primary health care practices within The Applied Research Group for Kids (TARGet Kids!) research group in Toronto, Canada. We used adjusted bivariate linear regression to examine the relation between milk-fat percentage and child 25(OH)D and zBMI concurrently. Effect modification by milk volume consumed on the evaluated relations was explored with the use of an interaction term in the statistical model.

Results: Among the 2745 included children there was a positive association between milk-fat percentage and 25(OH)D (P = 0.006) and a negative association between milk-fat percentage and zBMI (P < 0.0001). Participants who drank whole milk had a 5.4-nmol/L (95% CI: 4.32, 6.54) higher median 25(OH)D concentration and a 0.72 lower (95% CI: 0.68, 0.76) zBMI score than children who drank 1% milk. Milk volume consumed modified the effect of milk-fat percentage on 25(OH)D (P = 0.003) but not on zBMI (P = 0.77).

Conclusions: Whole milk consumption among healthy young children was associated with higher vitamin D stores and lower BMI. Longitudinal and interventional studies are needed to confirm these findings. TARGet Kids! was registered at clinicaltrials.gov as NCT01869530.

pediatrics, milk, vitamin D, obesity, zBMI

INTRODUCTION

Vitamin D is essential for healthy bone development and the prevention of rickets (1, 2). In North America, the main dietary contributor of vitamin D is fortified cow milk. Legislation requires all cow milk to be fortified to ~100 IU/250-mL cup (3–6). The National Institutes of Health, Health Canada, and the American Academy of Pediatrics recommend that children between 1 and 2 y old consume whole cow milk. For children >2 y, 2 servings of low fat (1% or 2%) milk are recommended each day to limit fat intake and reduce the incidence of childhood obesity (4, 7–9). The main indicator and chief circulating form of vitamin D in the blood is 25-hydroxyvitamin D concentration [25(OH)D]⁹ (10).

Childhood obesity in North America has tripled in the past 30 y (11), yet children’s consumption of whole cow milk (3.25% fat) has halved during the same period (12). Several studies have suggested a relation between higher milk-fat consumption and lower risk of childhood obesity (13–17). Furthermore, adiposity and vitamin D stores are known to manifest in an inverse relation in several studies of children (18–24). Evidence supports a relation between higher dietary fat consumption and vitamin D stores (25, 26); however, the milk-fat concentration that maximizes 25(OH)D and minimizes adiposity in children is unknown. Similar studies that have evaluated nutritional trade-offs related to milk consumption, such as the inverse relation between iron and vitamin D stores, have been clinically useful (27).

The primary aim of our study was to determine the relation between milk-fat percentage and both 25(OH)D concentration and BMI in healthy preschool-age children. The secondary objective was to analyze how the milk volume that children consumed might modify the relation between milk-fat percentage, 25(OH)D, and adiposity.

METHODS

Study design

Our cross-sectional study was conducted on 2745 children through The Applied Research Group for Kids (TARGet Kids!) Collaboration. TARGet Kids! is a partnership between the University of Toronto’s Faculty of Medicine and clinicians in the university’s Departments of Pediatrics and Family and Community Medicine (28).

Trained research assistants recruited children aged 12–72 mo during health supervision visits between September 2008 and August 2014 at 9 primary care clinics in Toronto, Canada. Exclusion criteria were growth-altering disorders (e.g., failure to thrive), chronic conditions (excluding asthma), or substantial developmental impairment.

Exposures and outcomes

Parents answered a standardized data collection instrument adapted from the Canadian Community Health Survey (29), which was used to collect clinical data; research assistants gathered anthropometric measurements from children. Trained phlebotomists obtained venous blood, which was sent daily in chilled batches to the Mount Sinai Services laboratory in Toronto.

The primary exposure was the milk-fat percentage consumed by each child and was measured as a continuous variable by asking the parent, “Please specify your child’s diet for the past 3 days: skim, 1%, 2%, or whole milk.” The mean value was calculated for subjects consuming >1 type of milk.

There were 2 primary outcomes: serum 25(OH)D, and BMI z score (zBMI). Serum 25(OH)D was quantified by use of a 2-step competitive chemiluminescence assay from venous blood (LIAISON 25 OH Vitamin D TOTAL; DiaSorin) (30), which has an intra-assay inaccuracy of 7.2% at 213 nmol/L and an interassay inaccuracy of 4.9% at a concentration of 32 nmol/L, 8.9% at 77 nmol/L, and 17.4% at 213 nmol/L. These measurements are within adequate limits for biochemical analyses (31, 32). The Vitamin D External Quality Assessment Scheme was used to evaluate vitamin D testing (30). Children’s weight (in kilograms) was divided by height (square meters) to determine BMI. zBMI is based on the WHO growth standards, which represent optimal children’s growth and are age- and sex-standardized measures of adiposity in children (33–35). Height measurements were obtained through use of a standardized length board for participants ≤2 y and a stadiometer for those >2 y (SECA). A precision digital scale was used to quantify weight (±0.025%; SECA).

Biologically plausible factors that may affect the relation between milk-fat percentage and both serum 25(OH)D and zBMI were determined a priori based on existing scientific data and used as potential confounding variables. These factors included age, sex, daily vitamin D supplementation, minutes per day of both outdoor free play and screen time, milk volume (in 250-mL cups) consumed daily, volume of sugar-sweetened beverages consumed daily, maternal BMI (measured at clinic visit), skin pigmentation, after-tax median neighborhood family income, maternal self-reported ethnicity, and date of serum collection. Children consuming a vitamin D supplement and/or multivitamin each day were considered to supplement daily with vitamin D. All Canadian children’s supplements that contain vitamin D have 400 IU (10 μg) as a daily dose (36). Daily outdoor free play was measured by the question, “On a typical weekday, how much time does your child spend outside in ‘unstructured free play’?” Daily screen time was quantified with the question, “On a typical day, how many minutes did your child spend in a room with a TV, video games, computer games, or handheld device games on?” Milk volume and sugar-sweetened beverages consumed daily were quantified by asking, “How many cups of each drink does your child have currently in a typical day?” Trained personnel measured maternal BMI at the time of child primary care visits by use of the standard formula (33, 34). Skin pigmentation was evaluated with the Fitzpatrick scale, which is commonly used in dermatological research (37, 38). We determined after-tax median neighborhood family income by collecting postal codes and using the Postal Code Conversion File from Statistics Canada, which used the 2011 census of Canada (39). Maternal ethnicity was classified into 1 of 6 geography-based categories (40).

Statistical analysis

To examine the association between milk-fat percentage (primary exposure) and the 2 primary outcomes, serum 25(OH)D and zBMI, we used bivariate multivariable linear regression, which allowed modeling of 2 simultaneously occurring outcomes in each individual. This method is ideal when the 2 outcomes may be correlated; should this prove true, statistical power is maximized (41). This model was adjusted for sociodemographic, dietary, and environmental covariates determined a priori (listed above), all of which remained in the model irrespective of statistical significance, to eliminate incorrect SEs and biased R² values (42). To make a clinically relevant comparison, we compared the bivariate outcomes in children who consumed whole milk (3.25%) to those in children who consumed 1% milk [a small proportion of children within the sample consumed skim (0.1% fat) milk] using bivariate logistic regression. Residual plot examination of 25(OH)D revealed a positive skew, which normalized with log transformation. Date values were manipulated by use of a sinusoidal function to adjust for the seasonal influence on 25(OH)D.

For the secondary analysis, an interaction term tested at the α = 0.05 significance level, between-volume and fat percentage of milk each child drank were added to the primary model to explore possible effect modification by the milk volume consumed. Multicollinearity was evaluated through use of the variance inflation factor; the variance inflation factor of all covariates remained under 2 (43). Because data were expected to be missing at random, multiple imputation was used to reduce bias from performing complete case analysis; none of the variables had >11% missing data. Fifty data sets were computer generated and the results were recombined (42, 44). All of the analyses were completed by use of R version 3.1.1 (R Foundation) (45). The research ethics boards of The Hospital for Sick Kids and St. Michael’s Hospital approved this study, and permission was obtained from every parent or guardian.

RESULTS

Of the 5301 children in TARGet Kids!, 2745 had venous blood samples taken and underwent 25(OH)D testing (Figure 1). Participants eligible and ineligible for the study were clinically alike (Table 1). The mean age was 2.8 y, and 53% were boys. The mean serum 25(OH)D concentration was 87 nmol/L, and the mean zBMI was 0.2 (SD 1.0). The mean daily milk consumption was 2.1 cups (1 cup = 250 mL)/child, and 56% of participants took a daily vitamin D supplement. Forty-nine percent of the children drank whole milk (3.25% fat); 35% consumed 2% milk, 12% drank 1% milk, and 4% consumed skim milk (0.1% fat). More than one type of milk was consumed by 122 children; the milk-fat percentage was averaged for these subjects. Overweight children (zBMI >1) constituted 21% of the sample and 5% were obese (zBMI >2) (46). A total of 38% of children had a serum 25(OH)D concentration <75 nmol/L, whereas 5.9% had a serum 25(OH)D concentration <50 nmol/L (47, 48).

FIGURE 1

Participant selection. zBMI, BMI z score.

TABLE 1

Participant and nonparticipant characteristics¹

Covariates	Children with 25(OH)D measured (N = 2745)	Children without 25(OH)D measured (N = 2556)
Age, mo	33.9 ± 16.52	35.9 ± 16.6
Male	1448 (53)	1327 (52)
Child 25(OH)D, nmol/L	87.0 ± 30.0	N/A
Milk-fat percentage consumed,3
Skim (0.1%)	123 (4)	111 (4)
1%	335 (12)	316 (12)
2%	954 (35)	1002 (39)
Whole (3.25%)	1333 (49)	1127 (44)
Child zBMI	0.2 ± 1.0	0.22 ± 1.0
<−1	315 (11)	279 (11)
−1 to <1	1860 (68)	1755 (69)
1 to <2	435 (16)	406 (16)
≥2	128 (5)	111 (4)
Skin pigmentation, Fitzpatrick scale ≤3	2213 (83)	2005 (87)
Cow milk consumption vol, 250-mL cups/d	2.1 ± 1.1	2.0 ± 1.0
Child vitamin D supplementation/d	1491 (56)	1361 (55)
Maternal ethnicity4
Mixed Western	1830 (72)	1873 (77)
Mixed Western and Non-Western	128 (5)	98 (4)
East and Southeast Asian	266 (10)	264 (10)
Southwest Asian	193 (8)	142 (6)
African and Caribbean	109 (4)	72 (3)
Other	11 (0)	6 (0)
Median neighborhood family income,5 $
<30,000	167 (7)	130 (5)
30,000–79,999	2039 (80)	1851 (78)
80,000–150,000	319 (12)	369 (15)
>150,000	23 (1)	32 (1)
Screen time, h/d	1.2 ± 1.3	1.2 ± 1.1
Free play, h/d	1.0 ± 1.0	0.9 ± 0.9

1

Values are n (%) unless otherwise specified. N/A, not applicable; vol, volume; zBMI, BMI z score; 25(OH)D, 25-hydroxyvitamin D.

2

Mean ± SD (all such values).

3

Milk-fat consumption in children 1–2 y old was similar to consumption in children >2 y old.

4

The number of children with reported maternal ethnicity was n = 2537 for those with 25(OH)D measured and n = 2455 for those without.

5

After-tax values. The number of children with reported median neighborhood family income was n = 2548 for those with 25(OH)D measured, and n = 2382 for those without.

Regression results are shown in Table 2 and Figure 2. In the bivariate linear regression model, adjusted for clinically relevant potential confounders, there was a positive relation between milk-fat percentage and 25(OH)D (P = 0.006) and a negative relation between milk-fat percentage and zBMI (P < 0.0001). Children’s median 25(OH)D was 1.67 nmol/L (95% CI: 1.01, 3.05) higher with every 1% increase in milk fat consumed. The average child who consumed whole milk had a median 25(OH)D concentration of 5.43 nmol/L (95% CI: 4.32, 6.54) higher than a child who drank 1% milk. Furthermore, children had a 2.25-fold lower odds (95% CI: 1.28, 3.99) of 25(OH)D <50 nmol/L if they drank whole milk compared to those who drank 1% milk. As Table 2 shows, higher milk volume consumption and vitamin D supplements taken daily both were positively related to 25(OH)D concentration (P = 0.0001); southwest Asian maternal ethnicity was negatively related to 25(OH)D (P = 0.01).

TABLE 2

Bivariate multivariable linear regression results showing association between milk-fat percentage (primary exposure), 25(OH)D, and zBMI (primary outcomes), adjusted for clinically relevant covariates¹

Child characteristics	Difference in median 25(OH)D, nmol/L (95% CI)	Difference in 25(OH)D, % (95% CI)	P	Parameter estimate of zBMI (95% CI)	P
Milk-fat percentage consumed per 1% increase	1.67 (1.01, 3.05)	2.04 (0.82, 2.50)	0.006	−0.221 (−0.26, −0.18)	<0.0001
Age, mo	0 (−0.07, 0.08)	0 (−0.06, 0.07)	0.95	−0.0003 (0, 0)	0.80
Sex, male	−1.70 (−3.92, 0.40)	−2.08 (−3.22, 0.33)	0.10	0.110 (0.03, 0.19)	0.005
Date of serum collection	0.74 (−0.80, 2.63)	0.90 (−0.65, 2.16)	0.33	−0.0083 (−0.062, 0.0454)	0.76
Skin pigmentation, Fitzpatrick scale ≤3	3.52 (2.02, 10.52)	4.29 (1.66, 8.62)	0.05	0.037 (−0.09, 0.16)	0.57
Milk volume consumed, 250-mL cups/d	2.84 (2.02, 5.13)	3.46 (1.66, 4.20)	<0.0001	0.065 (0.03, 0.10)	0.0007
Child vitamin D supplementation/d	9.26 (8.33, 13.88)	11.29 (6.83, 11.38)	<0.0001	−0.113 (−0.19, −0.03)	0.005
Maternal ethnicity
Mixed Western	Reference	Reference		Reference
Mixed Western and Non-Western	−1.38 (−7.69, 4.08)	−1.69 (−6.30, 3.35)	0.58	−0.105 (−0.29, 0.08)	0.26
East and Southeast Asian	−1.46 (−5.82, 4.08)	−1.78 (−4.78, 1.66)	0.35	−0.019 (−0.13, 0.10)	0.74
Southwest Asian	−5.70 (−12.19, −1.00)	−6.95 (−10.00, −0.82)	0.01	−0.156 (−0.33, 0.02)	0.08
African and Caribbean	−2.18 (−9.52, 4.08)	−2.66 (−7.80, 3.35)	0.45	0.184 (−0.03, 0.40)	0.09
Median neighborhood family income,2 $
<30,000	−2.42 (−7.69, 3.05)	−2.96 (−6.30, 2.50)	0.34	0.073 (−0.09, 0.23)	0.37
30,000–79,999	Reference	Reference		Reference
80,000–150,000	3.26 (0.07, 8.33)	3.98 (0.06, 6.83)	0.05	0.036 (−0.08, 0.15)	0.56
>150,000	−1.86 (−14.79, 11.63)	−2.27 (−12.12, 9.53)	0.74	−0.271 (−0.69, 0.15)	0.21
Screen time, h/d	−0.48 (−1.48, 0.49)	−0.60 (−1.80, 0.60)	0.48	−0.06 (−0.10, −0.02)	0.005
Free play, h/d	0.98 (−0.02, 1.94)	1.20 (−0.02, 2.38)	0.16	0.03 (−0.005, 0.07)	0.17
Sugar-sweetened beverages, cups/d	−1.46 (−5.82, 2.02)	−1.78 (−4.78, 1.66)	0.39	0.068 (−0.06, 0.19)	0.28
Maternal BMI	−0.16 (−0.50, 0.20)	−0.20 (−0.41, 0.16)	0.36	0.033 (0.02, 0.04)	<0.0001
Milk-fat percentage × milk volume consumed3	−1.59 (−2.62, −0.55)	−1.94 (−3.20, −0.67)	0.003	0.006 (−0.01, 0.03)	0.77

1

zBMI, BMI z score; 25(OH)D, 25-hydroxyvitamin D.

2

After-tax values.

3

The effect of the interaction between milk-fat percentage and milk volume consumed was statistically significant on 25(OH)D concentration but not on zBMI.

FIGURE 2

Adjusted [for age, sex, date of serum collection, skin pigmentation, daily vitamin D supplementation, milk volume consumption (cups per day), maternal ethnicity, screen time (minutes per day), outdoor play (minutes per day), maternal BMI, sugar-sweetened beverage consumption (250-mL cups per day), and median neighborhood family income] bivariate regression between milk-fat percentage (represented by various line types), 25-hydroxyvitamin D (y axis), and zBMI (x axis); 4% (n = 123) of children consumed skim milk (0.1% fat), 12% (n = 335) consumed 1% milk, 35% (n = 954) consumed 2% milk, and 49% (n = 1333) consumed whole milk (3.25% fat). The dashed line denotes the 95% CI. zBMI, BMI z score.

A 0.22 (95% CI: 0.18, 0.26) lower zBMI was associated with each 1% higher milk fat consumed. For example, the average child who drank whole milk had a 0.72-U (95% CI: 0.68-, 0.76-U) lower zBMI score than a child who consumed 1% milk. Furthermore, participants who drank whole milk had a 2.43-fold (95% CI: 1.69, 3.49) lower odds of being overweight and a 3.21-fold (95% CI: 1.76, 5.88) lower odds of obesity than participants who drank 1% milk. Factors positively associated with zBMI in the adjusted model included male sex (P = 0.005), higher milk volume consumption (P = 0.0007), and higher maternal BMI (P < 0.0001); covariates negatively associated with zBMI included daily vitamin D supplementation (P = 0.005) and higher daily screen time (P = 0.005).

For the secondary analysis, we evaluated whether the volume of milk that children drank modified the relation between milk-fat percentage and both 25(OH)D and zBMI by use of an interaction term between volume and milk-fat percentage consumed (Table 2). This interaction held statistical significance for 25(OH)D (P = 0.003) but not zBMI (P = 0.77) (Table 2). Each cup of milk consumed was related to a 4.97-nmol/L (95% CI: 3.09, 6.92) higher 25(OH)D and a statistically nonsignificant 0.08-U (95% CI: 0.01, 0.14) higher zBMI for a given fat content of milk (Figure 3). Children who consumed 1 cup whole milk/d had a 25(OH)D that was comparable to children who consumed 2.9 cups 1% milk/d (95% CI: 2.85, 3.04 cups 1% milk/d) but had a zBMI score 0.79 U (95% CI: 0.64, 0.94 U) lower.

FIGURE 3

Adjusted [for age, sex, date of serum collection, skin pigmentation, daily vitamin D supplementation, milk volume consumption (cups per day), maternal ethnicity, screen time (minutes per day), outdoor play (minutes per day), maternal BMI, sugar-sweetened beverage consumption (250-mL cups per day), and median neighborhood family income] bivariate regression between milk-fat percentage (represented by various line types); on the y axes: 25-hydroxyvitamin D (A) and zBMI (B); with effect modification by milk volume, in 250-mL cups, consumed on the x axis; 4% (n = 123) of children consumed skim milk (0.1% fat), 12% (n = 335) consumed 1% milk, 35% (n = 954) consumed 2% milk, and 49% (n = 1333) consumed whole milk (3.25% fat). The interaction between milk volume and milk-fat percentage was statistically significant for 25-hydroxyvitamin D but not statistically significant for zBMI. Skim milk, solid line; 1% milk, dotted line; 2% milk, dotted-dashed line; whole milk, dashed line. zBMI, BMI z score.

DISCUSSION

We have described a relation between milk-fat percentage and both 25(OH)D and zBMI during early childhood. Those who consumed whole milk (3.25% fat) had a median serum 25(OH)D 5.4 nmol/L higher than those who consumed 1% milk, which is a similar change in 25(OH)D as 1 additional cup milk/d (27). Children who drank a given volume of whole milk also had a 0.72-U lower zBMI score (equivalent to a 0.9 lower BMI in a 3-y-old boy) than children who drank 1% milk, which is comparable to the difference between healthy weight and overweight (49). Interventions for childhood obesity have considered a 0.5 change in zBMI to be meaningful, suggesting that the magnitude of this association may be clinically important (50, 51). It also appeared that milk-fat percentage modified the association between milk volume consumed and 25(OH)D but not zBMI. When analyzing the outcomes associated with either 1% milk or whole milk (3.25% fat), participants who drank 1 cup whole milk/d had a 25(OH)D concentration comparable to participants who drank 2.9 cups 1% milk/d but a 0.79-U lower zBMI.

Suggestions made by the National Institutes of Health, Health Canada, and the American Academy of Pediatrics state that people >2 y should drink 2 servings/d of reduced fat milk (1% or 2%) to reduce fat in their diet. Our findings raise the possibility that this recommendation may paradoxically decrease children’s vitamin D status and increase their adiposity, which may not be desirable outcomes. Several mechanisms have been described, which may explain our findings. The positive association observed between milk fat and serum 25(OH)D could be attributed to increased intestinal absorption of vitamin D because of its fat solubility (26). This was observed in our previous analysis on a similar cohort of children, which did not analyze zBMI as a simultaneous outcome as the current study did (25). Alternatively, this positive association may be a reflection of children’s adiposity, because adiposity and vitamin D stores have an inverse relation in children (18–24, 52). The negative association between milk-fat consumption and adiposity may be the result of heightened satiety following higher milk-fat consumption, thus reducing total caloric intake as reported by others (14, 17). Alternatively, a reverse-causality scenario may exist in which overweight children transition to lower-fat milk to reduce further gains in adiposity (14). The degree of adiposity in overweight or obese children may be underestimated by parents, however; thus they may not intervene (53).

Our findings raise the possibility that reduced-fat milk may compromise both serum 25(OH)D and zBMI. Should these relations prove to be causal, young children may benefit from consuming higher fat content milk (i.e., whole milk) rather than low fat milk (1% or skim) to maximize vitamin D stores and minimize risk of overweight (13–17). Because both vitamin D status and adiposity have a substantial impact on children’s growth and development, these findings may have important implications for health maintenance at a population level.

The strengths of our analysis include a broad, healthy, culturally diverse cohort of young children with data on milk consumption, vitamin D status, and adiposity. In addition, the sample size allowed sufficient power to conduct the proposed analysis. Simulations reveal that the sample size required to have 80% power to detect associations of the observed magnitude was ~200 children; therefore, 2745 children were sufficient to control for a broad range of potential confounders with the available clinical data. Furthermore, the analytic approach allowed modeling both 25(OH)D and zBMI as simultaneous outcomes, which coexist in children.

The limitations of our analysis include the study design; in a cross-sectional analysis, causality and its direction cannot be established between the exposure and outcomes. Data collection for milk consumption was by parent report, which may be subject to recall bias. Potential additional sources of dietary vitamin D were not accounted for in this study; however, cow milk has been identified as the main dietary source of vitamin D in children in North America (3–5). Other sources were considered to contribute a negligible amount of vitamin D to children’s diets. Our population of healthy urban North American children may not be representative of all urban children; specifically, 56% regularly consumed a vitamin D–containing supplement.

The present guidelines for reduced milk-fat consumption in children >2 y are intended to decrease the risk of childhood obesity, but they may have the paradoxical effect of limiting 25(OH)D concentration and increasing adiposity. If these findings prove causal, then consumption of milk with higher fat content may be helpful in optimizing both vitamin D stores and adiposity. Longitudinal and intervention studies are needed to confirm these findings and examine clinical outcomes related to both serum 25(OH)D concentrations and adiposity in children.

The members of the TARGet Kids! Collaboration are as follows: Co-Leads: Catherine S Birken, Jonathon L Maguire; Advisory Committee: Eddy Lau, Andreas Laupacis, Patricia C Parkin, Michael Salter, Peter Szatmari, Shannon Weir; Scientific Committee: Kawsari Abdullah, Yamna Ali, Laura N Anderson, Imaan Bayoumi, Catherine S Birken, Cornelia M Borkhoff, Sarah Carsley, Shiyi Chen, Yang Chen, Denise Darmawikarta, Cindy-Lee Dennis, Karen Eny, Stephanie Erdle, Kayla Furlong, Kanthi Kavikondala, Christine Koroshegyi, Christine Kowal, Grace Jieun Lee, Jonathon L Maguire, Dalah Mason, Jessica Omand, Patricia C Parkin, Navindra Persaud, Lesley Plumptre, Meta van den Heuvel, Shelley Vanderhout, Peter Wong, Weeda Zabih; Site Investigators: Murtala Abdurrahman, Barbara Anderson, Kelly Anderson, Gordon Arbess, Jillian Baker, Tony Barozzino, Sylvie Bergeron, Dimple Bhagat, Nicholas Blanchette, Gary Bloch, Joey Bonifacio, Ashna Bowry, Anne Brown, Jennifer Bugera, Douglas Campbell, Sohail Cheema, Elaine Cheng, Brian Chisamore, Ellen Culbert, Karoon Danayan, Paul Das, Mary Beth Derocher, Anh Do, Michael Dorey, Kathleen Doukas, Anne Egger, Allison Farber, Amy Freedman, Sloane Freeman, Keewai Fung, Sharon Gazeley, Donna Goldenberg, Charlie Guiang, Dan Ha, Curtis Handford, Laura Hanson, Hailey Hatch, Teresa Hughes, Sheila Jacobson, Lukasz Jagiello, Gwen Jansz, Paul Kadar, Tara Kiran, Lauren Kitney, Holly Knowles, Bruce Kwok, Sheila Lakhoo, Margarita Lam-Antoniades, Eddy Lau, Fok-Han Leung, Alan Li, Jennifer Loo, Joanne Louis, Sarah Mahmoud, Roy Male, Vashti Mascoll, Rosemary Moodie, Julia Morinis, Maya Nader, Sharon Naymark, Patricia Neelands, James Owen, Jane Parry, Michael Peer, Kifi Pena, Marty Perlmutar, Navindra Persaud, Andrew Pinto, Tracy Pitt, Michelle Porepa, Vikky Qi, Nasreen Ramji, Noor Ramji, Jesleen Rana, Alana Rosenthal, Katherine Rouleau, Janet Saunderson, Rahul Saxena, Vanna Schiralli, Michael Sgro, Hafiz Shuja, Susan Shepherd, Hafiz Shuja, Barbara Smiltnieks, Cinntha Srikanthan, Carolyn Taylor, Suzanne Turner, Fatima Uddin, Joanne Vaughan, Thea Weisdorf, Sheila Wijayasinghe, Peter Wong, Anne Wormsbecker, Ethel Ying, Elizabeth Young, Michael Zajdman, Ian Zenlea; Research Team: Charmaine Camacho, Arthana Chandraraj, Dharma Dalwadi, Ayesha Islam, Thivia Jegathesan, Tarandeep Malhi, Megan Smith, Laurie Thompson; Applied Health Research Centre: Christopher Allen, Bryan Boodhoo, Judith Hall, Peter Juni, Gerald Lebovic, Karen Pope, Jodi Shim, Kevin Thorpe; Mount Sinai Services laboratory: Azar Azad.

The authors’ responsibilities were as follows—SMV and JLM: designed the research study, performed the initial statistical analyses, drafted the manuscript, had primary responsibility for the final manuscript content, and had full access to all of the data in the study; CSB, PCP, and DLO: assisted in the research design and reviewed and revised the manuscript; GL and YC: reviewed and revised the statistical analysis and the manuscript; and all authors: read and approved the final manuscript. None of the authors had a conflict of interest related to the study.

FOOTNOTES

1

Funding for the TARGet Kids! Collaboration was provided by the Canadian Institutes of Health Research (CIHR) Institute of Human Development, Child and Youth Health grant no. MOP-106532, the CIHR Institute of Nutrition, Metabolism and Diabetes, and the St. Michael’s Hospital Foundation. The Paediatric Outcomes Research Team is supported by a grant from The Hospital for Sick Children Foundation.

2

The funding agencies had no role in study design; the collection, analysis, and interpretation of data; the writing of the report; or the decision to submit the article for publication.

ABBREVIATIONS

 
• TARGet Kids!

  The Applied Research Group for Kids

 
• zBMI

  BMI z score

 
• 25(OH)D

  25-hydroxyvitamin D