The Journal of Nutrition
Nutritional Epidemiology
Vitamin D Status in Montréal Preschoolers Is
Satisfactory Despite Low Vitamin D Intake1,2
Jessy El Hayek,3,4 Thu Trang Pham,3 Sarah Finch,3 Tom J. Hazell,3 Sonia Jean-Philippe,3
Catherine A. Vanstone,3 Sherry Agellon,3 Celia Rodd,5 Frank Rauch,6 and Hope A. Weiler3*
3
School of Dietetics and Human Nutrition, McGill University, Montréal, QC, Canada; 4Faculty of Nursing and Health Sciences, Notre
Dame University, Zouk Mikael, Lebanon; 5The Montréal Children’s Hospital, Montréal, QC, Canada; and 6Shriners Hospital, Montréal,
QC, Canada
Abstract
The 2007 to 2009 Canadian Health Measures Survey reported vitamin D status in a representative sample of Canadians
supplements, sun exposure, and biological vitamin D status of children ages 2 through 5 y in Montréal (latitude 45°N).
Preschoolers (n = 508) were recruited between June 2010 and 2011 in a random sample of licensed daycares in the
regions of greater Montréal, Canada in a cross-sectional study. The total plasma 25-hydroxyvitamin D [25(OH)D]
concentration was measured using a chemiluminescence assay (Liaison, Diasorin). Dietary intake was assessed during
one 24-h period plus a 30-d FFQ. Socioeconomic, demographic, anthropometry, and sun exposure data were collected.
Plasma 25(OH)D was $50 nmol/L in 88% of children, whereas 49.4% had concentrations $75 nmol/L during the 1-y
study. Almost 95% of preschoolers had vitamin D intakes less than the Estimated Average Requirement (EAR), and 4.8%
of preschoolers #3.9 y and 25.9% of preschoolers $4 y had calcium intakes less than the EAR. Plasma 25(OH)D was
different across age, income, sun index, milk intake, and dietary and supplemental vitamin D intake tertiles. Despite
vitamin D intakes less than the EAR, the vitamin D status of Montréal preschoolers attending daycare is mostly
satisfactory even in winter, suggesting that the EAR value is too high in the context of typical exogenous intakes of
vitamin D in North America. J. Nutr. 143: 154–160, 2013.
Introduction
The Institute of Medicine (IOM)7 revised the recommendations
for vitamin D status and intake based on an exhaustive literature
review (1). Serum 25-hydroxyvitamin D [25(OH)D] concentrations <30 nmol/L defined risk of deficiency. Concentrations of
40 nmol/L were aligned with the Estimated Average Requirement (EAR) of 10 mg/d, and 50 nmol/L with the RDA of 15 mg/d
for children >1 y, assuming minimal sun exposure (1–3). Based
on data from the National Center for Health Statistics, 10% of
children aged 1–8 y in the UShad serum 25(OH)D <50 nmol/L
(4). The Canadian Pediatric Society suggests that young Canadian children are at elevated risk for low vitamin D status (5),
but national data are unavailable.
1
Supported by Dairy Farmers of Canada, Agriculture and Agri-Food Canada, and
the Canadian Dairy Commission in addition to scholarships from the Canadian
Institutes for Health Research (S.F., T.T.P.) and a salary award from the Canada
Research Chairs Program (H.A.W.).
2
Author disclosures: J. El Hayek, T. Trang Pham, S. Finch, T. J. Hazell,
S. Jean-Philippe, C. A. Vanstone, S. Agellon, C. Rodd, F. Rauch, and H. A. Weiler,
no conflicts of interest.
7
Abbreviations used: BSA, body surface area; CCHS, Canadian Community Health
Survey; CHMS, Canadian Health Measures Survey; EAR, Estimated Average
Requirement; IOM, Institute of Medicine; 25(OH)D, 25-hydroxyvitamin D.
* To whom correspondence should be addressed. E-mail: [email protected].
154
National data from the 2004 Canadian Community Health
Survey (CCHS) showed that the median vitamin D intake (5.6
mg/d) of children 1–8 y of age (n = 5655) (6) was less than the
EAR, causing concern about low vitamin D status. The plasma
25(OH)D concentrations of Canadians in the 2007 to 2009
Canadian Health Measures Survey (CHMS) was not measured
in children <6 y. However, 14% of children aged 6–11 y (n = 131)
had a plasma 25(OH)D concentration <50 nmol/L (3). The only
random sampling of Canadian preschoolers was conducted in
the extreme north (Nunavut) and found a median summer
plasma 25(OH)D concentration of 48.3 nmol/L (7). Although
other Canadian studies have examined preschoolers, sampling
was not large enough or across seasons (8,9).
Therefore, the objective of the current study was to assess
vitamin D intake from food, supplements, and sun exposure in
association with the plasma 25(OH)D concentration in preschoolers at randomly selected daycares in the Montréal region.
Participants and Methods
Daycares and participants. Preschoolers (age 2–5 y) were studied
between June 2010 and June 2011 in a random sample of licensed
daycares (n = 77) in greater Montréal, Canada (73°W, 45°N). Ten
percent of all daycares (n = 733) licensed with the Ministère de la Famille
et des Ainés were selected, representing 91% of the regions in greater
ã 2013 American Society for Nutrition.
Manuscript received September 5, 2012. Initial review completed October 3, 2012. Revision accepted November 9, 2012.
First published online December 19, 2012; doi:10.3945/jn.112.169144.
Downloaded from jn.nutrition.org at MCGILL UNIVERSITY on May 30, 2013
(6–79 y); however, children <6 y were not assessed. Our objective was to measure vitamin D intake from food and
Montréal. The selection of children was done proportionally by season
to obtain n $500 children (Fig. 1). Inclusion criteria included healthy
term-born children. Exclusion criteria included diseases associated with
disturbances of bone metabolism, known or suspected serious chronic
illness of childhood, use of medications known to affect bone metabolism in the past 3 mo, history of prior treatment for vitamin D
deficiency, and severe anemia.
Ethics. This study was approved by the McGill University Faculty of
Medicine Institutional Review Board. All daycares agreed in writing to
facilitate the study and all parents or legal guardians provided written
informed consent prior to the study.
Data collection. Data collection took place for 2 d at each daycare. On
d 1 dietary intake was observed by a registered dietitian while at the
daycare; dietary intake at home was collected by subsequent, telephonebased, parental recall. On d 2 anthropometric measurements, skin
pigmentation, and a capillary blood sample were collected.
Other questionnaires. Telephone surveys with parents or legal guardians were used to estimate socioeconomic status (education and household
income). Child sun exposure was assessed by interviewing each daycare
director and parents or legal guardians. Data regarding sun exposure
during the previous month were collected as a percentage of body surface
area (BSA) exposed, frequency of sunscreen use, and total hours spent in
FIGURE 1 Daycare and participant recruitment.
Vitamin D status of Montréal preschoolers
155
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Dietary data. Dietary data were collected by observation, dietary recall,
and a FFQ. The study protocol consisted of collecting dietary data at and
outside of daycare for one 24-h period. A registered dietitian observed
and recorded all food and beverages consumed during daycare hours
(0700–1600 h). To complete a 24-h dietary intake assessment, a
registered dietitian telephoned the parents or legal guardians and used
a multiple-pass recall method to record foods eaten outside of daycare on
the same day. This method is validated for this age group (10). The 30-d
FFQ was completed by a registered dietitian who examined the daycareÕs
menu and interviewed both the childÕs educator and parent/legal
guardian. The semiquantitative FFQ including the frequency of consumption and portion size (11) was adapted to capture intake of
vitamin D and calcium from 13 sources commonly consumed by children
(including milk, baby food cereals, soy or rice beverage or orange juice
with added calcium or vitamin D, eggs and egg dishes, fish including
type, margarine including brand, yogurt including brand, cheeses
including type and brand, ice cream and frozen desert, breast milk and
infant formula, cod or halibut liver oil, supplements or multivitamins
containing vitamin D) based on CCHS data (6). Reproducibility (n = 53,
median 9 d apart) of vitamin D (median 9.9 vs. 10.2 mg/d) and calcium
(median 1160 vs. 1224 mg/d) intakes was high.
Same day observation of food intake at daycare and parental dietary
recall data (i.e., as per protocol) were collected for 318 children. For 126
children, parental recall was delayed due to difficulty reaching the parents.
Thirty-five preschoolers were not observed at daycare, but their parent or
legal guardian completed a full 24-h recall on a weekend day (n = 16) or
weekday (n = 19). Dietary intake for a 24-h period was repeated in a
subsample (n = 76) to adjust for day-to-day variation in nutrient intake and
compared with the EAR using the NRC method (12,13). Missing data for
either assessment were due to parental refusal or inability to contact parents.
All food intake data were analyzed using Nutritionist Pro (Axxya
Systems) and the Canadian Nutrient File 2010b. Brand names, product
details, and percentage daily value on nutrition labels were used to
determine the nutrient content of foods. When the brand was unknown,
the mean nutrient content of all brands reported in the study was used.
Foods were categorized into 4 groups as defined in CanadaÕs Food Guide
to Healthy Eating (14) and ‘‘other foods.’’ Composite meals were
proportionally assigned to the appropriate food groups.
direct sunlight per day. Sun index was calculated for each child by
multiplying the percent BSA exposed by the time spent outside (minutes
per day) based on the Lund and Browder chart (15). This index does not
consider the use of sun block.
Anthropometry. Height was measured using a portable stadiometer
(Seca 213, Seca Medical Scales and Measuring Systems) and body weight
was measured using a digital scale (Home Collection 63–8711–0, Trileaf
Distribution) with the child wearing light clothing and no shoes. Head
circumference was measured using a nonstretchable measuring tape
(Seca 212, Seca Medical Scales and Measuring Systems). Z-scores were
calculated using the WHO 2007 growth standards for children < and >5 y
(WHO AnthroPlus).
Statistical analysis. All statistical analysis was conducted using SAS
(v9.2). Variables were checked for normality using the Shapiro-Wilk test;
non-normal distributions were transformed accordingly. Paired t tests
were used to determine whether total, daycare, or home vitamin D and
calcium intakes from both 24-h and FFQ were different if parental
survey was delayed; these were not and were thus combined. StudentÕs t
tests were used to determine whether the plasma 25(OH)D concentration differed by supplement consumption. ANOVA was used to
determine if the plasma 25(OH)D concentration was different based on
selected characteristics, followed by BonferroniÕs post hoc tests whenever
appropriate. ANCOVA was used to adjust for covariates. Chi-square
was used to compare vitamin D status groups by synthesizing (April 1 to
Oct 31) (16) and nonsynthesizing periods. Values are presented as
percent (95% CI), means 6 SD, or medians with IQR.
Results
The age range of the 508 children included in the study was from
1.8 to 5.8 y (Table 1). Of the mothers, 45.6% had an unTABLE 1 Selected characteristics of preschool age children
attending daycare in the Montréal area1
Characteristic
Age, y
Male, %
Ethnicity, % white
History of fracture, % yes
Weight, kg
Weight-for-age Z-score
Height, cm
Height-for-age Z-score
BMI, kg/m2
BMI-for-age Z-score2
Head circumference, cm
Plasma 25(OH)D, nmol/L
Vitamin D supplement,3 % yes
Calcium supplement,3 % yes
1
n
Percent or median (IQR)
508
245
271
11
503
503
507
507
503
503
507
508
131
41
3.7 (2.9–4.5)
48.2
53.3
2.1
16.0 (14.3–18.1)
0.30 (20.30–0.89)
101.0 (94.2–106.9)
20.02 (20.7–0.68)
16.0 (15.1–16.9)
0.4 (20.2–1.1)
50.7 (49.6–51.8)
74.4 (60.3–93.5)
27.7
8.7
Values are percent or median (IQR). 25(OH)D, 25-hydroxyvitamin D.
According to the WHO.
3
Derived from FFQ.
2
156
El Hayek et al.
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Laboratory analysis. A nonfasted, 1-mL capillary blood sample
(lithium heparin) was collected via finger lance at daycares between
0800 and 1200 h to control for diurnal variation. Samples were stored on
ice for transportation to the laboratory, centrifuged at 3000 3 g and 4°C
for 20 min, and plasma aliquots stored at 280°C until analysis. The
plasma total 25(OH)D concentration was measured using a chemiluminescence assay (Liaison, Diasorin). The inter- and intra-assay CVs were
7.3 and 5.1% for the low 25(OH)D control (39.8 nmol/L) and 7.1 and
2.8% for the high 25(OH)D control (130.3 nmol/L). Accuracy, using the
mid-range of the manufacturerÕs specifications, was 95.6%.
dergraduate degree and 15.6% had a graduate degree. Median
family income was within the range of 60,000–74,999 Canadian
dollars. Sunscreen use was prevalent among 79.4% (n = 397) in
summer and 3% (n = 14) in winter. Sunscreen use varied by
income; the proportion of children using sunscreen was 45.9%
in the first income bracket (#$15,000), 68.2% in the second
bracket ($15,000–29,999), and 87.2% in the highest bracket
($ $75,000) (P < 0.01). FFQ data showed that preschoolers
consumed a daily median of 2.4 (IQR: 1.6–3.3) servings of fluid
milk (250 mL) and 3.8 (IQR: 3.0–5.0) servings of dairy
products, including fluid milk, whereas 24-h recall data yielded
a median of 1.7 (IQR: 1.0–2.3) servings of fluid milk and 2.5
(IQR: 1.7–3.3) servings of dairy products including fluid milk.
The median vitamin D supplement dosage was 7.1 (IQR:
3.2–10.0) mg/d. Home vitamin D intake provided 71.6% (FFQ)
and 62.1% (24-h assessment) of total vitamin D intake. Median
vitamin D intake from either the FFQ or the 24-h intake was less
than the EAR (Table 2). Based on the adjusted vitamin D intake
for day-to-day variation, 95.1% of preschoolers had intakes less
than the EAR. Using the chi-square test, the prevalence of
preschoolers having vitamin D intakes less than the EAR was
lower among those who did not take any vitamin D supplements
(2.4%) compared with supplement consumers (11.5%) (P < 0.01).
The median calcium supplement dosage was 160 (IQR: 100–
200) mg/d. Home calcium intake provided 67.4% (FFQ) and
59.0% (24-h period) of total calcium intake. Median calcium
intake from either the FFQ or the 24-h intakes exceeded the EAR
of 500 mg (1–3 y) and 800 mg (4–8 y) (Table 2). Based on the
adjusted calcium intake for day-to-day variation, 4.8% of
preschoolers #3.9 y and 25.9% of preschoolers $4.0 y had
intakes less than the EAR.
The 2 major contributors to vitamin D intake from both the
24-h assessment and the FFQ were milk (66.1 and 72.1%) and
fish (9.9 and 14.2%) and the third contributor based on 24-h
data was composite meals (3.7%) and the FFQ was yogurt
(6.7%). The 3 major contributors to calcium intake from both
dietary methods were milk (49.3 and 59.7%), cheese (14.8 and
22.3%), and yogurt (7.7 and 12.8%).
The median plasma 25(OH)D concentration was 74.4 (95%
CI: 60.3–93.5 nmol/L). Only 4.5% (95% CI: 2.7–6.3) of children
had a 25(OH)D concentration <40 nmol/L. Plasma 25(OH)D
concentrations were significantly higher in the synthesizing
period (79.8 6 1.4 nmol/L) than in the nonsynthesizing period
(69.7 6 1.4 nmol/L) (P < 0.01). Using the chi-square test, there
was no difference in the proportion of children meeting
the 25(OH)D cutoffs set by either the IOM (50 nmol/L) (2)
or Canadian Pediatric Society (75 nmol/L) (5) in the synthesizing
compared with the nonsynthesizing period (P > 0.05) (Table 3).
The plasma 25(OH)D concentration did not differ by ethnicity (white vs. non-white) or BMI tertiles, even when controlled
for age, sex, and sunscreen use and by milk or fish consumption
(FFQ data), dairy (FFQ and 24-h data), and vitamin D intake
(FFQ; P = 0.06; between 1 and 3 tertiles) (data not shown).
Plasma 25(OH)D concentrations differed by age tertiles (P < 0.01).
However, once adjusted for weight and vitamin D intake, these
results became nonsignificant (Table 4). Similarly, plasma 25(OH)
D concentrations differed by income groups. However, once
adjusted for vitamin D intake and sun exposure, these results
became nonsignificant (Table 4). On the other hand, plasma 25
(OH)D concentrations were higher among preschoolers who
consumed vitamin D supplements (Table 4). The prevalence of a 25
(OH)D concentration <50 nmol/L was lower among vitamin D
supplement consumers (6.1%) than among nonconsumers (13.8%)
(P = 0.02 by chi-square test).
TABLE 2 Median total, daycare, and home vitamin D and
calcium intakes from the 24-h assessment and FFQ1
24-h Assessment
n
Nutrient
Vitamin D intake, mg/d
Total2
Daycare3
Home3
Calcium intake, mg/d
Total2
Daycare3
Home3
Median (IQR)
FFQ
n
Median (IQR)
479
444
444
5.9 (3.8–8.0)
1.8 (1.0–2.8)
3.7 (2.1–5.8)
477
472
472
9.9 (7.1–13.2)
2.6 (1.7–3.5)
7.0 (4.6–10.2)
479
444
444
950 (748–1228)
348 (234–492)
591 (375–807)
477
472
472
1216 (943–1565)
373 (264–472)
836 (587–1139)
1
Values are median (IQR).
Total number of dietary assessments (24-h or FFQ data).
Number of dietary assessments collected as per study protocol (daycare and home in
one 24-h period).
2
3
This report of vitamin D status of preschoolers attending
daycare in a large urban center in Canada suggests that >85%
had a plasma 25(OH)D concentration above the cutoff suggested by the IOM (50 nmol/L). The annual prevalence of
plasma 25(OH)D <50 nmol/L (11.9%) is similar to that for
children aged 1–8 y in the US (4). The proportion of children
with 25(OH)D values <75 nmol/L (50.6%) was lower than in
other Canadian studies among this age group (7,8,17) but
closely aligns with the CHMS in older children (6–11 y), where
51.4% had a plasma 25(OH)D concentration <75 nmol/L (18).
Our data therefore closely align with other population-level
studies and provide new knowledge regarding vitamin D status
in young children <6 y of age.
Endogenous synthesis is thought to be a major contributor to
vitamin D status (1), yet plasma 25(OH)D concentrations in our
sample were only 10 nmol/L higher in the synthesizing period
than in the nonsynthesizing period. Similar seasonal differences
in plasma 25(OH)D were also observed among participants
12–39 y of age in the CHMS (18) as well as in other studies in
TABLE 3 Prevalence of plasma 25(OH)D concentration by targets of the IOM and Canadian Pediatric
Society and synthesizing and nonsynthesizing periods1
Plasma 25(OH)D, (nmol/L)
All seasons, n = 508
Percent (CI)
Median [IQR]
n
Nonsynthesizing, n = 2154,5
Percent (CI)
Median [IQR]
n
Synthesizing, n = 2934,5
Percent (CI)
Median [IQR]
n
,30.02
30.0–49.92
$50.02
$75.03
0.6 (0.07–1.2)
24.9 [23.1–25.0]
3
10.6 (7.9–13.3)
42.6 [37.9–46.8]
54
88.8 (86.0–91.5)
79.1 [66.2–96.3]
451
49.4 (45.0–53.8)
93.7 [84.0–113.0]
251
0.9 (0.3–2.2)
24.1 [23.6–24.5]
2
14.0 (9.3–18.6)
42.3 [37.9–45.0]
30
85.1 (80.3–89.9)
75.5 [65.1–88.5]
183
43.3 (36.7–50.0)
87.6 [81.4–101.0]
93
0.3 (0.4–1.0)
N/A
1
8.2 (5.0–11.3)
45.1 [38.9–47.7]
24
91.5 (88.3–94.7)
83.6 [66.7–103.0]
268
53.9 (48.4–59.8)
97.9 [87.8–121.9]
158
1
IOM, Institute of Medicine; 25(OH)D, 25-hydroxyvitamin D.
IOM (1,2).
Canadian Pediatric Society (5).
4
Synthesizing vitamin D period in Montréal is estimated to extend from April 1 to Oct 31.
5
Chi-square test.
2
3
Vitamin D status of Montréal preschoolers
157
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Discussion
children (7) and adults (19). Furthermore, preschoolers in the
first tertile of the sun index had only a 8.7-nmol/L lower plasma
25(OH)D concentration compared with those in the third tertile,
similar to other studies that report a positive relationship
between sun exposure and vitamin D status among children
(20,21). A possible explanation for the robust vitamin D status
in our study and others in 6–11 y olds (18) might relate to higher
endogenous synthesis capacity for vitamin D in young children
compared with adults (22), even though sunscreen use was
widely prevalent among this group. Alternatively, based on adult
trials, sunscreen use does not alter vitamin D status during summer
(23), whereas it blocks endogenous synthesis in controlled settings
(24). These studies suggest that sunscreen is not adequately applied
in the general population. To our knowledge, no studies exist for
children and research is therefore required to clarify the contribution of endogenous synthesis to vitamin D status.
It is remarkable that in our study, vitamin D status was very
good despite mean vitamin D intakes being lower than the EAR
in 95% of the children. Vitamin D and calcium intakes in the
current study were similar to those reported in a representative
sample of Canadian children 1–8 y old (n = 5655) assessed in the
CCHS (6), suggesting that our 24-h intakes were also representative. Children who had vitamin D intakes above the median
for our study had higher vitamin D status than those with an
intake less than the median, even when adjusted for age, sex,
energy intake, and vitamin D-synthesizing period. Similarly,
other studies have associated higher vitamin D intakes with
better vitamin D status among Canadian children (7,9). Milk
was the main source of both vitamin D and calcium. Milk
consumption, derived from the 24-h recall in the current study
(1.7 serving), was similar to the intake of 1- to 3-y-old (1.7
serving) and slightly higher than the intake of 4- to 8-y-old
children (1.3 serving) reported in the CCHS (25). Children in the
first tertile of milk consumption had a significantly lower plasma
25(OH)D concentration than those in the third tertile. These
results are in agreement with CHMS, as children (6–11 y old)
who did not consume milk at all had a lower vitamin D status
than children who consumed milk more than once per day (18).
This relationship has also been reported in adults (18) and
children <9 y (6). Interestingly, the median total calcium intakes
TABLE 4
Selected characteristics of preschoolers as related to plasma 25(OH)D concentration1
Characteristic
n
Plasma 25(OH)D
P value
nmol/L
169
169
170
81.4 6 1.4
73.7 6 1.4
70.1 6 1.4
240
239
71.5 6 1.4a
78.0 6 1.4b
159
159
160
69.4 6 1.4a
76.7 6 1.4a,b
78.3 6 1.4b
341
131
71.5 6 1.4a
82.3 6 1.4b
38
44
53
53
58
212
71.5 6
68.0 6
68.0 6
80.6 6
75.2 6
76.7 6
165
165
165
70.1 6 1.4a
75.9 6 1.4a,b
79.8 6 1.4b
1.5
1.4
1.5
1.4
1.4
1.4
0.51
,0.01
0.02
,0.01
0.06
,0.01
1
Values are geometric means 6 SD. Means with superscripts without a common letter differ. BSA, body surface area; 25(OH)D,
25-hydroxyvitamin D.
2
Adjusted for body weight and vitamin D intake.
3
24-h assessment.
4
Adjusted for age, sex, energy, and vitamin D-synthesizing period.
4
BSA (exposed).
5
Adjusted for vitamin D intake and sun exposure.
from either the FFQ or the 24-h data were above the EAR and
many met or exceeded the RDA (79.6% #3.9 y and 47.3%
$4 y). The prevalence of calcium inadequacy in preschoolers
#3.9 y (4.8%) and $4 y (25.9%) in the current study were
similar to those reported in CCHS in 2004 among children 1–3 y
(<5%) and 4–8 y (23.3%) (26). It is thus possible that the robust
intakes of calcium partially contributed to the higher vitamin D
status (27,28), because utilization of vitamin D for calcium
homeostasis would be lessened.
Other variables that are known to influence vitamin D status
were also explored in an attempt to explain the very good
vitamin D status in our study despite low dietary vitamin D
intakes. Plasma 25(OH)D varied inconsistently across income
categories; however, once adjusted for vitamin D intake and sun
exposure, these results became nonsignificant. Both positive (21)
and negative associations (29) have been reported between
socio-economic status and plasma 25(OH)D. On the other
hand, those who consumed vitamin D supplements had higher
plasma 25(OH)D concentrations than those who did not by only
10.8 nmol/L, regardless of season, age, sex, and energy intake.
This is similar to the 15.2-nmol/L difference among children in
CHMS who used supplements in winter compared with
nonusers (3) and similar to other studies among children and
infants (30,31). We also examined age, because it is a predictor
of vitamin D status among youth (2–21 y) in North America
(9,32). Although we observed that children in the first age tertile
had higher plasma 25(OH)D than those in the second and third
158
El Hayek et al.
tertiles, the difference (up to 11.5 nmol/L) was not ascribed to a
lower vitamin D intake or a lower sun index. It is likely that
dietary requirements for vitamin D are a function of growth rate
or body mass, because once the analysis was adjusted for weight,
the difference in plasma 25(OH)D between age groups disappeared (P = 0.51).
The EAR value was clearly set based on minimal exposure to
UVB and in support of 40 nmol/L of 25(OH)D (2). Based on our
study, the EAR seems to overestimate dietary requirements of
preschool children in the general population, because vitamin D
intake was less than the EAR in 95% of our sample and
variation in plasma 25(OH)D across seasons was not very large.
Even in the Canadian Arctic (51–70°N), children 3–5 y with low
vitamin D intake (6.3 mg/d or 252 IU/d) have a median plasma
25(OH)D concentration of 48.3 (range 32.7–71.4) nmol/L in
summer and 37.7 (21.4–52.0) in winter (7). Our data suggest
that endogenous synthesis might account for a greater proportion
of vitamin D than anticipated and that future DRI values may
have to be positioned in the context of safe and typical amounts of
UV radiation exposure. The importance of such qualification is
that without assessment of vitamin D status based on biomarkers,
clinicians may be inclined to recommend a supplement or elevate
food fortification to ensure achievement of the EAR or RDA
value, whereas these may be unnecessary practices.
The major strength of this study was the comprehensive
assessment of vitamin D status and a wide range of anthropometric, dietary, socio-economic, and sun behavior variables
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Age (range),2 y
Tertile 1 (1.8–3.2)
Tertile 2 (3.2–4.2)
Tertile 3 (4.2–5.8)
Dietary vitamin D intake (range),3,4 mg/d
#Median (0–5.9)
.Median (5.9–31.1)
Fluid milk intake (range),3,4 servings/d
Tertile 1 (0.3–2.0)
Tertile 2 (2.0–3.0)
Tertile 3 (3.0–7.0)
Supplement intake
No
Yes
By income brackets,5 Canadian dollars
#15,000
15,000–29,999
30,000–44,499
45,000–59,999
60,000–74,999
$75,000
Sun index (range),4 min/d x % BSA
Tertile 1 (0.1–1.7)
Tertile 2 (1.7–8.8)
Tertile 3 (8.8–19.8)
Acknowledgments
The nursing assistance of Sandra DellÕElce (B.Sc.N., McGill
University, casual employee) is greatly appreciated. All authors
contributed to the manuscript preparation; S.A., J.E.H., T.J.H.,
S.F., T.T.P., S.J.-P., C.A.V., and H.A.W. collected the samples or
data or contributed to analysis of data; H.A.W., S.F., F.R., and
C.R. designed the study and secured grant funding; J.E.H. and
H.A.W. had full access to all the data in the study and take
responsibility for the integrity of the data and accuracy of the data
analysis. All authors read and approved the final manuscript.
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across seasons. Dietary intake was assessed by observation by a
registered dietitian combined with recall by parents or legal
guardians for time outside of daycare, a validated method for
this age group (10). Milk, vitamin D, and calcium intakes were
overestimated by the FFQ compared with the 24-h recall, which
could be attributed to both underreporting during the 24-h recall
or difficulty in comparing standardized FFQ portion sizes to
usual portion consumed. Our data were based on food observation for a considerable portion of the day; thus, underestimation is of lesser concern. Food (33) and nutrient (34) intakes are
commonly overestimated by FFQ compared with other dietary
methods. Nonetheless, our results are limited to children
attending daycare in Montréal and not those staying at home
or residing in other regions in Canada. Daycares in Montréal are
regulated in terms of providing milk; milk policies are likely the
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Finally, capillary sampling in adults may overestimate plasma
25(OH)D by 20% compared with venous samples (35). Although the sampling bias has not been tested in young children,
it is possible that our study underestimated the prevalence of
vitamin D deficiency. If we assume venous values are higher
by 20%, then 36.4 and 73.2% of children would have had
25(OH)D values <50 and <75 nmol/L, respectively. However,
vitamin D status was almost identical to venous values for
children in Canada (6–11 y) (18) and the US (1–8 y) (4),
suggesting our data are valid.
Despite vitamin D intakes less than the EAR, 95.5%
of Montréal preschoolers attending daycare had a plasma
25(OH)D concentration $40 nmol/L. This suggests that ambient sunlight exposure made an important contribution to
vitamin D status and/or that the EAR value for vitamin D is
too high for this age group. In summary, our data in a large
sample of preschool-age children suggest that the EAR value is
too high in the context of typical exogenous intakes of vitamin D
and minimal seasonal variation in vitamin D status in a large
urban center in North America. Future longitudinal studies will
be required to clarify recommendations.
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