• Proceedings of the Korean Nutrition Society Conference
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• 2004.11a
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• pp.22-33
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• 2004

It has been more than three decades since the first assay assessing circulating 25(OH)D in human subjects was performed. That publication as well as several that followed it defined 'normal' nutritional vitamin D status in human populations. Recently, the wisdom by which 'normal' circulating 25(OH)D levels in human subjects were assigned in the past has come under question. It appears that sampling human subjects, who appear to be free from disease, and assessing 'normal' circulating 25(OH)D levels by plotting a Gaussian distribution is grossly inaccurate. There are many reasons why this method is inaccurate, including race, lifestyle habits, sunscreen usage, age, latitude, and inappropriately low dietary recommendations for vitamin D. For instance, a 400IU/day. AI for vitamin D is insignificant when one considers that a 10-15 minute whole body exposure to peak summer sun will generate and release up to 20,000 IU vitamin $D_3$ into the circulation. Recent studies, which orally administered up to 10,000 IU/day vitamin $D_3$ to human subjects for several months, have successfully elevated circulating 25(OH)D levels to those observed in individuals from sun-rich environments. Further, we are now able to accurately assess sufficient circulating 25(OH)D levels utilizing specific biomarkers instead of guessing what an adequate level is. These biomarkers include intact parathyroid hormone (PTH), calcium absorption, bone mineral density (BMD), insulin resistance and pancreatic beta cell function. Using the data from these biomarkers, vitamin D deficiency should be defined as circulating levels of $25(OH)D{\leq}30ng/mL$. In certain cases, such as pregnancy and lactation, significantly higher circulating 25(OH)D levels would almost certainly be beneficial to both the mother and recipient fetus/infant.

• Journal of Nutrition and Health
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• v.49 no.6
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• pp.437-446
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• 2016

Purpose: The purpose of this study was to estimate dietary intake of vitamin D and the relationship between serum 25-hydroxyvitamin D (25OHD) concentration and bone mineral density (BMD) in Korean adults using the 2011 data from the Korea National Health and Nutrition Examination Survey. Methods: Daily intake of vitamin D and ratio of subjects that consumed less vitamin D than adequate intake (AI) were estimated in 4,879 Korean adults. The relationship between daily intake of vitamin D and serum 25OHD and BMD were analyzed. Results: Average daily intakes of vitamin D were $3.84{\pm}0.23{\mu}g/day$ for men and $2.22{\pm}0.11{\mu}g/day$ for women. Approximately 72~97% of men and 80~99% of women consumed less than the AI of vitamin D for Koreans. Serum 25OHD concentration increased with age, and the ratios of serum vitamin D deficiency (< 20 ng/mL) were 47.8~81.1% for men and 59.4~92.8% for women. Average intake of vitamin D was higher in subjects aged < 50 yr than in those ${\geq}50yr$, but lower in serum 25OHD concentration. In subjects aged < 50 yr, serum 25OHD was higher in subjects that consumed $10{\mu}g/day$ of vitamin D than in those that consumed less than $5{\mu}g/day$. In female subjects aged ${\geq}50yr$, average intake of vitamin D was associated with higher bone mineral density. Conclusion: It was found that dietary intake of vitamin D could increase serum 25OHD concentration in young adults and bone mineral density in old women. Therefore, nutrition policies for enriched foods with vitamin D and nutrition education to consume more vitamin D-rich foods are needed to ameliorate vitamin D status of the Korean population. Adequate intake for Korean population aged < 50 yr might be adjusted upwardly up to $10{\mu}g/day$.

• Clinical and Experimental Pediatrics
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• v.56 no.10
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• pp.417-423
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• 2013

Vitamin D is an essential component of bone and mineral metabolism; its deficiency causes growth retardation and skeletal deformities in children and osteomalacia and osteoporosis in adults. Hypovitaminosis D (vitamin D insufficiency or deficiency) is observed not only in adults but also in infants, children, and adolescents. Previous studies suggest that sufficient serum vitamin D levels should be maintained in order to enhance normal calcification of the growth plate and bone mineralization. Moreover, emerging evidence supports an association between 25-hydroxyvitamin D (25[OH]D) levels and immune function, respiratory diseases, obesity, metabolic syndrome, insulin resistance, infection, allergy, cancers, and cardiovascular diseases in pediatric and adolescent populations. The risk factors for vitamin D insufficiency or deficiency in the pediatric population are season (winter), insufficient time spent outdoors, ethnicity (non-white), older age, more advanced stage of puberty, obesity, low milk consumption, low socioeconomic status, and female gender. It is recommended that all infants, children, and adolescents have a minimum daily intake of 400 IU ($10{\mu}g$) of vitamin D. Since the vitamin D status of the newborn is highly related to maternal vitamin D levels, optimal vitamin D levels in the mother during pregnancy should be maintained. In conclusion, given the important role of vitamin D in childhood health, more time spent in outdoor activity (for sunlight exposure) and vitamin D supplementation may be necessary for optimal health in infants, children, and adolescents.

• Clinical and Experimental Pediatrics
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• v.58 no.8
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• pp.283-287
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• 2015

Purpose: We assessed the relationships between iron and vitamin D statuses in breastfed infants and their mothers and evaluated the determinants of iron and vitamin D deficiencies in breastfed infants. Methods: Seventy breastfed infants aged 4-24 months and their mothers participated in this study from February 2012 to May 2013. Complete blood counts, total iron binding capacity, and levels of C-reactive protein, iron, ferritin, calcium, phosphate, alkaline phosphatase, and 25-hydroxyvitamin D (25(OH)D) in infants and their mothers were measured. Results: A history of maternal prepregnancy anemia was associated with lower ferritin and 25(OH)D levels in both infants and their mothers. The 25(OH)D level of infants correlated with maternal 25(OH) D levels. The independent risk factors for iron deficiency in breastfed infants were the duration of breastfeeding (odds ratio [OR], 6.54; 95% confidence interval [CI], 1.09-39.2; P=0.04) and infant body weight (OR, 2.65; 95% CI, 1.07-6.56; P=0.04). The determinants for vitamin D deficiency were the infant's age (OR, 0.15; 95% CI, 0.02-0.97; P=0.046) and maternal 25(OH)D level (OR, 0.74; 95% CI, 0.59-0.92; P=0.01). Conclusion: A maternal history of prepregnancy anemia requiring iron therapy was associated with lower current ferritin and 25(OH)D levels in both infants and their mothers. Therefore, physicians should monitor not only iron but also vitamin D levels in infants who are breastfed by mothers who had prepregnancy anemia.

• Journal of Nutrition and Health
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• v.51 no.4
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• pp.287-294
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• 2018

Purpose: This study was conducted to evaluate the association between serum 25-hydroxyvitamin D (25(OH)D) levels and dental caries experience in Korean adolescents based on the 2010 ~ 2014 Korean National Health and Nutrition Examination Surveys. Methods: The study subjects were 2,655 Korean adolescents aged 10 to 18 years. Subjects were classified into four groups according to their serum 25(OH)D levels. We used logistic regression to evaluate the relationship between vitamin D and for dental caries experience after adjusting for age, household income level, recipient of basic livelihood, tooth brushing and visiting dental clinics. Result: Multiple logistic regression analysis showed that serum 25(OH)D insufficiency (20 ng/mL ${\leq}25(OH)D$ < 30 ng/mL) was associated with increased odd ratios (ORs) for dental caries experience in boys (OR = 2.577, 95% CI = 1.013-6.557), compared with serum 25(OH)D sufficiency (25(OH)D ${\geq}30ng/mL$). Conclusion: The serum 25(OH)D levels were found to be related to risk of dental caries experience in Korean adolescent boys.

• Clinical and Experimental Pediatrics
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• v.56 no.10
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• pp.439-445
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• 2013

Purpose: Previous studies suggest that the concentration of 25-hydroxyvitamin D [25(OH)D] in cord blood may show an inverse association with respiratory tract infections (RTI) during childhood. The aim of the present study was to examine the influence of 25(OH)D concentrations in cord blood on infant RTI in a Korean birth cohort. Methods: The levels of 25(OH)D in cord blood obtained from 525 Korean newborns in the prospective COhort for Childhood Origin of Asthma and allergic diseases were examined. The primary outcome variable of interest was the prevalence of RTI at 6-month follow-up, as diagnosed by pediatricians and pediatric allergy and pulmonology specialists. RTI included acute nasopharyngitis, rhinosinusitis, otitis media, croup, tracheobronchitis, bronchiolitis, and pneumonia. Results: The median concentration of 25(OH)D in cord blood was 32.0 nmol/L (interquartile range, 21.4 to 53.2). One hundred and eighty neonates (34.3%) showed 25(OH)D concentrations less than 25.0 nmol/L, 292 (55.6%) showed 25(OH)D concentrations of 25.0-74.9 nmol/L, and 53 (10.1%) showed concentrations of ${\geq}75.0$ nmol/L. Adjusting for the season of birth, multivitamin intake during pregnancy, and exposure to passive smoking during pregnancy, 25(OH)D concentrations showed an inverse association with the risk of acquiring acute nasopharyngitis by 6 months of age (P for trend=0.0004). Conclusion: The results show that 89.9% of healthy newborns in Korea are born with vitamin D insufficiency or deficiency (55.6% and 34.3%, respectively). Cord blood vitamin D insufficiency or deficiency in healthy neonates is associated with an increased risk of acute nasopharyngitis by 6 months of age. More time spent outdoors and more intensified vitamin D supplementation for pregnant women may be needed to prevent the onset of acute nasopharyngitis in infants.

• Clinical and Experimental Pediatrics
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• v.56 no.5
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• pp.205-210
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• 2013

Purpose: The aim of this study was to recognize the state of vitamin D among healthy infants aged 1 to 6 months in South Korea, and also to identify the risk factors affecting the level of vitamin D. Methods: A total of 117 infants were enrolled in this study for 12 months, from March 1, 2011 to February 29, 2012. Serum levels of 25-hydroxyvitamin D (25[OH]D), calcium, phosphorus, and alkaline phosphatase were measured and data including birth weight, body weight, sex, feeding pattern, delivery mode, siblings and maternal age and occupation were collected. Data was mainly analyzed with independent t-test model. Results: We determined that the prevalence of vitamin D deficiency (serum 25[OH]D<20 ng/mL [50 mmol/L]) was 48.7% in the population investigated. Particularly in breastfed infants, the prevalence of vitamin D deficiency was strikingly high (90.4%). The mean serum level of 25(OH)D in breastfed infants was lower than that of formula fed infants (9.35 ng/mL vs. 28.79 ng/mL). Also female infants showed lower mean serum level of 25(OH)D than male. Mean serum values of calcium and phosphorus had positive correlation with vitamin D state (P<0.001). Conclusion: Vitamin D deficiency was found to be very common in infants aged 1 to 6 months in South Korea, and breast feeding was the most critical risk factor of vitamin D deficiency. Therefore we suggest to start vitamin D supplementation in South Korea, as soon as possible, to all infants, including breastfed and female infants.

• Clinical and Experimental Pediatrics
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• v.55 no.6
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• pp.206-211
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• 2012

Purpose: The increasing prevalence of breast feeding has led to concerns about vitamin D deficiency (VDD) and iron deficiency anemia (IDA) in children. We evaluated the prevalence of VDD in a population of Korean children with IDA and assessed the risk factors for VDD in these children. Methods: A total of 79 children who were diagnosed with IDA were prospectively surveyed from April 2010 to March 2011. Data were collected by questionnaire, medical assessment, and laboratory tests, including measurement of 25-hydroxyvitamin D (25OHD), hemoglobin, and wrist radiography. Results: The median age was 22 months and 30% of the subjects were female. Over a half of subjects (58%) had subnormal vitamin D level (25OHD<30 ng/mL), and VDD (25OHD<20 ng/mL) was present in 39% of children. There was no difference in serum hemoglobin level between IDA patients with VDD and those without VDD. Most subjects (89%) were currently or had recently been breastfed and almost all subjects (97%) who had VDD received breastfeeding. Children with VDD were more likely to be younger than 2 years, to have been breastfed, and to have been tested in winter or spring. Multivariable analysis indicated seasonal variation was a significant independent risk factor for VDD in our IDA patients. Conclusion: Our results demonstrated that VDD has a high prevalence in Korean children with IDA. Primary care physicians should be aware of the possibility of VDD in children with IDA and should supplement the vitamin D as well as iron.

• Journal of Environmental Health Sciences
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• v.44 no.2
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• pp.188-195
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• 2018

Objectives: This study aimed to investigate the association between vitamin D deficiency and the risk of diabetes mellitus, and also examined whether their association is differed by sex and age. Methods: We analyzed the data from 28,135 subjects ${\geq}20years$ old who were registered for the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2014. Vitamin D was measured using serum 25-hydroxyvitamin D (25(OH)D) concentrations. Results: After adjusting for potential confounders (age, sex, education, income, total energy intake, smoking, physical activity, body mass index, and waist circumference), lower vitamin D was dose-dependently associated with a higher risk of diabetes mellitus (p-trend=0.004). When compared with the sufficient group (25(OH)D ${\geq}30ng/mL$), the severe deficient group (25(OH)D <10 ng/mL) had 1.46 (95% CI 1.11-1.94) odds ratio for the risk of diabetes mellitus. This association was markedly strong in men and adults aged ${\geq}40$, whereas no significant association was observed in women and adults aged <40. Conclusions: We found that vitamin D deficiency may be associated with an increased risk for diabetes mellitus in Korean adults. Our findings suggest that intake of higher vitamin D may help reduce the risk of diabetes mellitus.

• Clinical and Experimental Pediatrics
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• v.60 no.8
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• pp.248-253
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• 2017

Purpose: Vitamin D plays a key role in immune function. Vitamin D deficiency may play a role in the pathogenesis of infections, and low levels of circulating vitamin D are strongly associated with infectious diseases. In this study, we aimed to evaluate the effects of low vitamin D levels in cord blood on neonatal sepsis in preterm infants. Methods: One hundred seventeen premature infants with gestational age of <37 weeks were enrolled. In the present study, severe vitamin D deficiency (group 1) was defined as a 25-hydroxyvitamin D (25(OH)D) concentration <5 ng/mL; vitamin D insufficiency (group 2), 25(OH)D concentration ${\geq}5ng/mL$ and <15 ng/mL; and vitamin D sufficiency (group 3), 25(OH)D concentration ${\geq}15ng/mL$. Results: Sixty-three percent of the infants had deficient levels of cord blood vitamin D (group 1), 24% had insufficient levels (group 2), and 13% were found to have sufficient levels (group 3). The rate of neonatal sepsis was higher in group 2 than in groups 1 and 3. Conclusion: There was no significant relationship between the cord blood vitamin D levels and the risk of neonatal sepsis in premature infants.