The Impact of Vitamin D Status on Glycemic Control in Saudi Children and Adolescents with Type 1 Diabetes Mellitus

Abstract

Objectives

This study aims to assess the 25-hydroxyvitamin D (25-OH VitD) status in children and adolescents with type 1 diabetes mellitus and to identify the correlation between 25-OH VitD levels and glycosylated hemoglobin (HbA1c) levels.

Methods

A cross-sectional study was conducted in the King Abdulaziz Medical City, Jeddah, Saudi Arabia. The study included 146 eligible patients. Serum 25-OH VitD < 50 nmol/L indicated below normal vitamin D level.

Results

All participants were Saudis, 63.0% were children, and 37.0% were adolescents (52.7% were male and 47.3% were female). The mean of HbA1c levels was 9.85 ± 1.79% and 25-OH VitD levels was 35.54 ± 13.88 nmol/L. The prevalence of 25-OH VitD inadequacy was 84.2%, with a mean 25-OH VitD levels of 31.22 ± 9.82 nmol/L. There was no significant correlation between 25-OH VitD levels and HbA1c levels (p = 0.14). On the other hand, the correlation was significantly negative between 25-OH VitD levels and daily insulin dose (p < 0.001), diabetes duration (p < 0.001), age (p < 0.001), and body mass index (p = 0.001), while it was significantly positive with dairy products intake per mL per day (p < 0.001). Furthermore, multiple regression analysis demonstrated that age, daily insulin dose, and gender were the factors that were associated adversely and significantly with 25-OH VitD levels (p = 0.001, p = 0.008, p = 0.002), respectively.

Conclusion

Although vitamin D levels did not correlate significantly with HbA1c levels in this study, the findings of a significant inverse correlation of vitamin D levels with insulin requirements, in addition to a high prevalence of vitamin D levels inadequacy in children and adolescents with T1DM, indicate the importance of maintaining adequate vitamin D levels in this population.

Keywords

type 1 diabetes - vitamin D status - HbA1c - correlation - glycemic control - children - adolescents

Introduction

Vitamin D (25-hydroxyvitamin D [25-OHD]) has immunemodulatory properties, and thus many immunemodulatory diseases, including diabetes.[1] Low 25-OHD concentrations have been suggested to be one of the factors leading to poor glycemic control and diabetes complications. For instance, low levels of 25-OHD were associated with an increased risk of microalbuminuria in patients with type 1 diabetes mellitus[2] (T1DM). It is important to realize that the variation in the estimation of the 25-OH VitD deficiency prevalence rate stands on the cutoff level that is used to define 25-OHD deficiency and adequacy. However, elevated vitamin D deficiency at 25-OHD < 50 nmol/L among children and adolescents with T1DM was documented in Saudi Arabia,[3] [4] [5] and many other countries.[6] [7] [8] Few studies have shown the link between vitamin D levels and glycemic control regarding glycosylated hemoglobin (HbA1c).[8] [9] This study can draw attention to the prevalence of vitamin D deficiency in children and adolescents with T1DM and the link between vitamin D levels and HbA1c in this population, and start for further studies looking toward the efficacy of vitamin D supplementation on glycemic control.

The first objective of this study was to assess the vitamin D status in children and adolescents with T1DM. The second objective was to identify the correlation of 25-OHD with HbA1c levels among the participants.

Patients and Methods

Study Design

This study was a cross-sectional method to assess the 25-OHD status of the study participants. Study participants were recruited from pediatrics diabetes clinics at a hospital in Jeddah, Saudi Arabia. A total number of 146 eligible children and adolescents with T1DM aged 3 to 18 years were selected based on the exclusion criteria. The participants were classified based on their age into two categories; children (2–< 12 years) and adolescents (12–18 years), following the American National Institute of Children's Health Development classification.[10] Patients excluded from the study were those who did not meet the age criteria; patients with abnormalities in liver function, renal function, hereditary vitamin D disorders, intestinal malabsorption, gastric surgery, hyperparathyroidism, blood diseases such as G6PD deficiency, thalassemia, and sickle cell anemia; patients who were on medications known to interact with 25-OHD metabolism such as anticonvulsants and statins; those who were on regular 25-OHD supplementation before recruitment in the study; and those who did not complete their laboratory tests; or refused to participate in the study. The total number of excluded patients was 263 out of 409 patients initially screened.

Data Collection

The required medical data were collected from participants' medical records, including diabetes-related information, laboratory data, medical history, and any other prescribed in-use medications. Body mass index (BMI) (weight divided by height squared; kg/m²) was calculated from the collected height and weight data. BMI for age percentile charts (Centers for Disease Control and Prevention) were used[11] accordingly, the participants were categorized into four groups: underweight at BMI < 5th percentile, normal weight at 5th to < 85th percentile, overweight at BMI 85th to 94th percentile, and obese at BMI ≥ 95th percentile.[12] All laboratory tests were performed in the main hospital's laboratory by collecting two blood samples for routine screening of 25-OH VitD and HbA1c. One plain blood sample was collected for 25-OH VitD and one ethylenediaminetetraacetic acid blood sample for HbA1c.

Following the recommended goal of glycemic control by the American Diabetes Association, for children and adolescents with T1DM at all ages, HbA1c level < 7.5 was considered a good control.[13] Serum level of HbA1c was measured using Tosoh automated glycohemoglobin analyzer HLC-723 G8 (Tosoh Corporation, Tokyo, Japan) as per the manufacturer's instructions.

The serum concentration of 25-OHD was tested to determine the participants' vitamin D status. Following the Institute of Medicine definition of 25-OHD sufficiency (> 50 nmol/L), insufficiency (30–50 nmol/L), deficiency (< 30 nmol/L), and > 125 nmol/L as potentially adverse effects,[14] [15] the participants in the present study were classified accordingly into a group with 25-OHD < 50 nmol/L, including vitamin D insufficiency and deficiency, and a group of vitamin D sufficiency 25-OHD > 50 nmol/L. The quantitative value of serum 25-OHD level was measured by method of chemiluminescent immunoassay (Liaison 25OH vitamin D Total Assay; DiaSorin, Stillater, Minnesota, United States) as per the manufacturer's instructions, which measures total vitamin D [25(OH) Vit.D3] in the range between 10 and 375 nmol/L. The sensitivity of this assay is < 10 nmol/L.

A questionnaire was designed to collect demographic data such as age, gender, nationality, and place of residence. Data related to sun exposure such as sun exposure pattern, use of sunscreen, home type, and school design were collected. Other collected data include physical activity pattern, females' clothing style such as wearing a veil known as abaya when being outside, food allergy, intake of 25-OH VitD supplementation, and frequency intake of milk products (milk, drinking yogurt known as Laban, and yogurt). Additionally, the Fitzpatrick scale chart for skin-colored types was used in the clinic to assess the participants' skin color.

Statistical Data Analysis

First, some questions in the questionnaires were treated (recategorized) for data analysis. The 25-OHD metering unit (ng/mL) used in other studies was converted to mmol/L (1 ng/mL = 2.5 nmol/L) for comparison with the present study.

The data were analyzed by using the Statistical Package for the Social Sciences (SPSS) software, version 20.0 (SPSS Inc. Chicago, Illinois, United States). Descriptive statistics were used to analyze and summarize the participants' demographic and clinical characteristics. The values of categorical variables are presented in the tables as frequency number (N) and percentage (%). Student's t-test was used to compare mean values between groups, and Pearson's correlation test to measure the correlation of 25-OHD levels with other factors. A test of chi-square was used to determine the differences in the proportion of categorical variables, and Fisher's exact test value was used when the count of any cell was below 5. Regression analysis was done to find out the predictors of the 25-OHD level. A p-value of < 0.05 was considered statistically significant. Means and standard deviation were used to describe continuous data.

Results

Demographic and Clinical Characteristics

Participants' demographic characteristics are demonstrated in [Table 1], and clinical characteristics are shown in [Table 2]. All participants were Saudi, known to have T1DM, and none of the participants were found to have a sun allergy.

Table 1 Participants' characteristics (n = 146)

Variables	n (%)	Mean ± SD
Gender
Male	77 (52.7)
Female	69 (47.3)
Age		10.61 ± 3.67
2–< 12 years	92 (63.0)	8.27 ± 2.22
12–18 years	54 (37.0)	14.58 ± 1.68
Skin color type[a]
White	7 (4.9)
Light brown	83 (58.0)
Moderate brown	50 (35.0)
Dark brown and dark brown to black	3 (2.1)
BMI (kg/m2), All		19.46 ± 4.42
2–< 12 years		17.87 ± 3.89
12–18 years		22.17 ± 3.97
Region of residence
Makkah province	136 (93.2)
Al Madinah province	6 (4.1)
Asir province (southern)	4 (2.7)
Female wearing abaya (69 out of 146)
No	31 (44.9)
Yes	38 (55.1)

Abbreviations: BMI, body mass index; SD, standard deviation.

Note: n, number of participants.

^a White color: very fair pale white, often freckled color, and fair white (type I and type II). Brown color: light brown (type III), moderate brown (type IV), and with dark brown and intensely pigmented dark brown to black (type V and VI).

Table 2 Clinical characteristics (n = 146)

Variable	n (%)	Mean ± SD
Age at diagnosis (y)		6.43 ± 3.13
Diabetes duration (y)		4.13 ± 3.37
≤ 1 y	27 (18.5)	0.40 ± 0.29
> 1–< 5 y	75 (51.4)	2.98 ± 1.23
≥ 5 y	44 (30.1)	8.39 ± 2.44
Type of insulin therapy[a]
Conventional	9 (6.2)
Intensive	134 (91.8)
Insulin pump	3 (2.1)
Daily insulin dose (IU/kg)		0.95 ± 0.26
HbA1c levels (%)		9.85 ± 1.79
Good control (HbA1c < 7.5%)	10 (6.8)	6.88 ± 0.45
Poor control (HbA1c ≥ 7.5%)	136 (93.2)	10.07 ± 1.65
HbA1c levels (%)
25-OH VitD deficiency	123 (84.2)	9.91 ± 1.79
25-OH VitD sufficiency	23 (15.8)	9.54 ± 1.78
25-OH VitD levels (nmol/L)[a]		35.54 ± 13.88
25-OH VitD sufficiency (23)	23 (15.8)	59.14 ± 6.47
25-OH VitD insufficiency (123)	23 (84.2)	31.22 ± 9.82

Abbreviations: HbA1c, glycosylated hemoglobin A1c; IU, international unit/kg, kilogram per body weight; 25-OH VitD, 25-hydroxyvitamin D; SD, standard deviation.

Note: n, number of participants.

^a Insufficiency: 25-OH VitD < 50 nmol/L. Sufficiency: 25-OH VitD ≥ 50 nmol/L. Conventional: 2 injection/d; intensive: > 3 injection/d.

Vitamin D Status

The results showed that the majority of participants, 123 (84.2%) out of 146, were below normal vitamin D levels at 25-OHD < 50 nmol/L, and only 23 (15.8%) were found to have sufficient 25OHD levels (50–125 nmol/L).

Correlations with 25-OHD Levels

HbA1c with 25-OHD level: Among all the participants (n = 146), no significant correlation between 25-OHD levels and HbA1c levels was detected in this study (r = –0.12, p = 0.14). Considering the effect of a honeymoon period as well as hyperglycemia in the early stage of diabetes diagnosis on HbA1c level, this correlation was also nonsignificant (r = –0.06, p = 0.46) among participants with T1DM for more than 1 year (n = 119).

Daily Insulin Dose and Diabetes Duration with 25-OHD Level

The correlation of 25-OHD level with daily insulin dose (IU/kg) and diabetes duration was adversely significant, r = –0.36, p < 0.001 (n = 146) and r = –0.28, p < 0.001, respectively.

Age, Gender, BMI, and Skin Color with 25-OHD Level

The correlation was adversely significant between 25-OHD and age (r = –0.45, p < 0.001). Further analysis showed that the mean 25-OHD level was significantly higher among children than adolescents ([Table 3]). The mean 25-OHD level was significantly higher in males than females. Further, girls who were wearing a veil (abaya) showed significantly diminished mean values of 25-OHD level than those who were not ([Table 3]). The correlation was adversely significant between 25-OHD level and BMI (r = –0.27, p = 0.001). Furthermore, an insignificant difference between the mean value of the 25-OHD level of participants with normal weight and those who were obese and overweight was reported. The correlation of 25-OHD status with skin color and sunlight exposure factors is presented in [Table 4].

Table 3 Comparing the means of 25-OH VitD levels across different categories

Variables	25-OH VitD level Mean ± SD		95% CI
		p-Value[a]	Lower	Upper
Age group		< 0.001	6.23	15.00
2–< 12 years (92)	39.47 ± 13.71
12–18 years (54)	28.85 ± 11.47
Gender		0.001	3.18	11.96
Male (77)	39.12 ± 13.19
Female (69)	31.55 ± 13.62
Female wearing abaya		0.001	–16.88	–4.71
Yes (38)	26.70 ± 11.40
No (31)	37.50 ± 13.93
Weight (kg)		0.79
Normal (90)	35.07 ± 14.03
Overweight and obese (50)	35.71 ± 14.21

Abbreviations: CI, confidence interval of the difference; 25-OH VitD, 25-hydroxyvitamin D; SD, standard deviation.

^a p-Value of Student's t-test. p-Value < 0.05 considered significant at two-tailed.

Table 4 Correlation of 25-OH VitD status with skin color and sunlight exposure factors

Variables	25-OH VitD status
	Insufficiency, n (%)[a]	Sufficiency, n (%)[b]	Chi-square	p-Value
Skin color (143)[c]				0.29[d]
Type I and type II (7)	5 (71.4)	2 (28.6)
Type III, IV, V, and VI (136)	116 (85.3)	20 (14.7)
Exposure to sunlight time (142)			4.30	0.12
Between 7 a.m. to 3 p.m. (59)	53 (89.8)	6 (10.2)
After 3 p.m. (12)	8 (66.7)	4 (33.3)
Any time of the day (71)	59 (83.1)	12. (16.9)
Frequency of sun exposure (142)				0.23[d]
≤ 3 times per week (14)	10 (71.4)	4 (28.8)
> 3 times per week (128)	110 (85.9)	18 (14.1)
Duration of sun exposure (141)			0.10	0.74
< 30 min (75)	64 (53.8)	11 (50.0)
≥ 30 min (66)	55 (46.2)	11 (50.0)
Home type (139)			0.15	0.69
With yard or roof (104)	89 (75.4)	15 (71.4)
Without yard or roof (35)	29 (24.6)	6 (28.6)
Shaded school yard (122)			0.15	0.75[d]
Yes (97)	84 (80.0)	13 (76.5)
No (25)	21 (20.0)	4 (23.5)

Abbreviation: 25-OH VitD, 25-hydroxyvitamin D.

Note: Data represented in frequency (%).

^a Deficiency: 25-OH VitD < 50 nmol/L.

^b Sufficiency: 25-OH VitD ≥ 50 nmol/L.

^c Type I and II: Very fair, pale white, often freckled, and fair white. Type III, IV, V, and VI: Light brown, moderate brown, dark brown, and black.

^d p: Fisher's exact test. p-Value < 0.05 considered significant at two-tailed.

Physical Activity with 25-OHD Level and Dairy Products Intake

The 25-OHD status did not correlate significantly with physical activity levels, type, duration, and frequency (p = 1.00, p = 0.25, p = 0.10, and p = 0.43, respectively). Further analysis showed an insignificant difference between the mean value of 25-OHD levels for those who were usually active for less than 1 hour (n = 48) and those who were physically active for more than 1 hour (n = 37), 35.75 ± 13.97 versus 33.21 ± 10.93 nmol/L, respectively, t (83) = 0.91, p = 0.36.

The results have also shown that the mean value of dairy products intake (milk/Laban and yogurt) was 1.39 ± 0.73 serving per day (n = 130), which was equivalent to 268.97 ± 140.58 mL per day. The correlation of 25-OHD levels with dairy products intake per mL per day was significantly positive, r = 0.31, p < 0.001.

Predictors of 25-OHD Level

Multiple linear regression analysis showed the predictors of 25-OHD level ([Table 5]). Furthermore, the modified model showed that the p-value of gender, age, and daily insulin dose were 0.002, 0.001, and 0.015, respectively, and the p-value of analysis of variance was 0.00, so, the model is linear. Else, R ² = 0.293, which means this model explained 29.3% of 25-OHD levels.

Table 5 Predictors for 25-OH VitD level (n = 146)

Predictor	p-Value[a]
HbA1c	0.458
Daily insulin dose (IU/kg)	0.008
Diabetes duration	0.372
Age	0.001
Gender	0.002
BMI	0.769

Abbreviations: BMI, body mass index; HbA1c, glycosylated hemoglobin A1c; IU, international unit; 25-OH VitD, 25-hydroxyvitamin D.

Note: Constant = 0.00. Dependent variable: 25-OH VitD level.

^a p-Value of ANOVA = 0.000. p-Value < 0.05 considered significant. Sex coded as 0 = male and 1 = female.

Discussion

Various studies have identified the vitamin D status of children and adolescents with T1DM in Saudi Arabia. However, few studies investigated the relationship between vitamin D levels and glycemic control, including HbA1c levels and insulin requirements among this population. Regardless of the cutoff point used, local and global data have shown a high prevalence rate of 25-OHD deficiency in children and adolescents with T1DM. However, elevated vitamin D deficiency at 25-OHD < 50 nmol/L among children and adolescents with T1DM was documented in many studies. In the present study, we focused on the studies that used the cutoff level of 25-OHD < 50 nmol/L to define vitamin D deficiency and/or insufficiency for comparison. In Saudi Arabia, a high prevalence of low vitamin D status (25-OHD levels < 50 nmol/L) in this life stage was reported in several studies, for instance, 97%,[3] 91.7% of 135 participants,[4] 84.0% of 100 diabetic children,[5] and 59.9% of 117 subjects.[16] In Kuwait, the prevalence of 25-OHD deficiency (< 52.2 nmol/L) was 84.0% in the group of newly diagnosed T1DM Kuwaiti children.[6] A high prevalence of 25-OHD deficiency at a level < 50 nmol/L was also reported among a group of children and adolescents with T1DM in Italy (67.2%)[7] and among 71% of 100 subjects in Turkey.[17] In the present study, most of the participants were found to be under sufficient level of 25-OHD (< 50 nmol/L), which indicates a high prevalence of vitamin D deficiency and insufficiency among children and adolescents with T1DM. These results represent a significant health concern in the early life stage and indicate the increase of health burden in diabetic patients.

The existence of some disparities in the prevalence rate of 25-OHD deficiency within a country and between countries can be attributed to many reasons, including the difference in cutoff points used in various studies to define the 25-OHD sufficiency and deficiency. However, the high prevalence rate of 25-OHD deficiency in this country can be attributed to many factors, including lifestyle patterns. Lifestyle in Saudi Arabia is represented mainly in dietary habits and reduced time spent outdoors, including the type of traditional clothes worn outdoors, which cover most of the body parts.

The present study showed an insignificant correlation between 25-OH VitD and HbA1c levels, as shown in many studies of similar population.[5] [8] [9] [18] On the other hand, Talaat et al[19] reported that higher vitamin D levels were negatively correlated with HbA1c levels. The differences in the studies' results can be attributed to many factors that could mediate the relationship between vitamin D levels and HbA1c levels, including age, type of diabetes, and therapy regimen. However, the mean vitamin D level was lower, and HbA1c levels were higher, in addition to a higher sample size[19] than in the present study and other studies.[5] [8] [9] [18] The results of the present study could benefit further exploration of this relation; therefore, more in-depth studies are needed, especially on patients with vitamin D deficiency.

Limited studies evaluated the correlation of vitamin D levels with insulin requirements, and insulin regimen types in this population are available. The finding of a negative correlation between 25-OH VitD level and daily insulin requirements in the present study indicates a significant increase in daily insulin dose (IU/kg) with a decrease in 25-OH VitD levels. As a supporting result, we found that daily insulin dose (DID) is one of the 25-OH VitD level predictors. On the other hand, most of the patients in our study were on intensive insulin therapy. Similarly, the link between vitamin D levels and insulin requirement among children and adolescents with T1DM was signifficant.[17] The result was inconsistent[18] [20] with the present study. Further, one study reported significant lower vitamin D levels in patients treated with multiple insulin injections in the same population. It has been suggested that insulin resistance is linked with vitamin D levels inversely.[21] [22] Data on the effect of vitamin D supplementation on insulin resistance in T1DM are limited. However, the inverse correlation between vitamin D and insulin resistance was reported in obese children and adolescents.[23]

Overall, the data explaining the mechanisms of how vitamin D levels could potentially influence insulin requirement in T1DM are limited. However, the present study result sheds light on the importance of vitamin D levels in the possibility of reducing the insulin dose needed for diabetes control. Therefore, treating vitamin D deficiency might lead to better glycemic control with lower insulin doses. Using lower insulin doses to maintain good glycemic control could reduce the short-term and long-term side effects of insulin therapy. Further studies exploring this effect in-depth on insulin requirement and insulin efficacy are suggested.

In this study, the correlation between 25-OH VitD and diabetes duration was significantly negative, as reported in some studies[5] [18] with similar subjects. In contrast, an insignificant correlation was observed in some other studies,[16] [24] which could be due to the different analytical tests used.

Consistent with the current study, many studies confirmed the significant effect of age on 25-OH VitD levels; for instance, 25-OH VitD levels were significantly lower in adolescents than in children with T1DM.[8] The correlation between 25-OH VitD status and age groups was significant in children and adolescents with T1DM.[24] In the nondiabetic population, a multicenter, school-based study in Saudi Arabia demonstrated a significant correlation between age groups and 25-OH VitD deficiency among students. 25-OH VitD deficiency was more common in adolescents than in younger participants.[25]

A higher 25-OH VitD deficiency among females than males, as shown in this study, could be explained by the female's clothes style outdoors. Since early adulthood, females in Saudi Arabia tend to wear a veil, which is a long dress with long sleeves known as “abaya” that covers most of the female's body parts, with a head-cover known as “Tarah.” In this study, 25-OH VitD levels among those who used to wear abaya were significantly lower than those who did not.

A significantly higher 25-OH VitD deficiency among females than males and a significant correlation between gender and 25-OH VitD status were also reported in other national studies[3] [24] [25] [26] and in another study in Philadelphia.[8] Some studies showed that the mean value of 25-OH VitD was not significantly different between females and males in children and adolescents with T1DM,[11] and 25-OH VitD levels was not correlated with gender.[9] Variance in the results of 25-OH VitD levels correlation with gender may be attributed to many factors, including but not limited to the difference in cultural and religious aspects between the countries.

Although a significant negative correlation was found between 25-OH VitD levels and BMI in the present study and other similar studies,[9] [26] contradictory results had shown no correlation between 25-OH VitD levels and BMI among similar subjects.[5] [18] However, there was a variation between the BMI mean values of the studies. Additionally, the present study did not show a significant difference between the mean of 25-OH VitD levels among participants with normal weight and overweight including obese, which indicates 25-OH VitD deficiency is common among individuals with normal weight as well. A similar finding was reported previously.[8]

There was no significant correlation between 25-OH VitD status and skin color type in the present study. Similarly, skin color did not associate with 25-OH VitD deficiency as reported in a school-based cross-sectional study.[25] The vitamin D levels were significantly lower only in the dark-skin color Saudi boys who showed lesser time to sunshine exposure.[27] Although Saudi Arabia is located inside the zone of high ultraviolet radiation, the correlation of 25-OH VitD status with the frequency, time, and duration of sun exposure was insignificant in our study. Besides insufficient exposure to sunshine for many reasons, many other factors could mediate this result. The location of Saudi Arabia is a suitable location for producing adequate 25-OHD levels when exposing a sufficient body surface, for sufficient time, to the sunshine. Therefore, awareness regarding the importance of sunshine exposure should be raised among this country's population to prevent the occurrence of vitamin D deficiency and its consequences. Furthermore, since sun exposure is a major source of vitamin D, more in-depth studies exploring its correlation with vitamin D levels are suggested.

Very few studies presented data about the role of physical activity on 25-OH VitD levels. Nevertheless, the present study did not show a significant correlation between 25-OH VitD status and physical activity measures such as physical activity level, duration, and frequency. These results were consistent with some studies' findings; for instance, physical activity levels were not associated with 25-OH VitD deficiency.[25] Likewise, an insignificant relationship between 25-OH VitD levels and physical activity was reported.[28] Many studies' results were inconsistent with the current study, such as a multicenter study of healthy Saudi children and adolescents in Riyadh.[29] However, physical activity influence on 25-OH VitD status is not evident until now, with limited available related studies.

Furthermore, the significant relationship of 25-OH VitD levels with a daily dairy intake was shown positively in this study; this confirms the importance of dairy products as a source of vitamin D. Estimated dairy product intake per day in this study was less than the American dietary guidelines (2015–2020) of dairy products intake for children.[30] However, cheese intake was not calculated in this study.

This study was conducted in a single hospital, which may not represent the pediatric and adolescent type 1 diabetic patients in this country. The collected data on dietary intake, sun exposure, and physical activity patterns were based on participants' estimation and recall; therefore, these data have less accuracy. The effect of vitamin D levels on the insulin regimens was not analyzed, but the study focused on its effect on insulin requirement.

Conclusion

Although vitamin D levels did not correlate significantly with HbA1c levels in this study, the findings of a significant inverse correlation of vitamin D levels with insulin requirements, in addition to a high prevalence of vitamin D levels inadequacy in children and adolescents with T1DM, indicate the importance of maintaining adequate vitamin D levels in this population; therefore, a routine 25-OH VitD level screening in children and adolescents with type 1 diabetes is recommended for proper treatment. Further in-depth studies on the relationship of vitamin D levels with HbA1c, insulin therapy regimens, and the efficacy of vitamin D supplementation on glycemic control in patients with T1DM and vitamin D deficiency are recommended.

Conflict of Interest

None declared.

Acknowledgments

We would like to thank the laboratory department staff for their support in laboratory data during our study. We would also like to sincerely thank the patients and their parents for their great contribution in this study.

Authors' Contributions

N.A. contributed to the study design, data collection, data analysis, and manuscript writing and submission. M.E. and N.F. contributed to the study design revision, data collection, and data review. N.K. and A.B. contributed to the data review and the manuscript drafting. N.E. contributed to data analysis and manuscript drafting. A.H. and D.A. contributed to the questionnaire design and the literature searches. All authors reviewed and approved the manuscript.

Compliance with Ethical Principles

The study proposal was approved (IRB# C/098/11) by the International Medical Research Centre board, Jeddah, Saudi Arabia. A written informed content was optioned from all participant's guardians.

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Publication History

Article published online:
23 May 2025