• Journal of Nutrition and Health
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• v.29 no.7
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• pp.747-757
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• 1996

In this study, the serum level of 25-hydroxyvitamin D(25-(OH)D) was measured by high pressure liquid chromatography(HPLC), and factors affecting it were investigated in 72 young adults age ranging from 21 years to 39 years with normal bone density. The mean level of serum 25-(OH)D was 20.0$\pm$6.8ng/ml in males and 26.1$\pm$12.3ng/ml in females, which was significantly higher in females (p<0.01). The serum level of parathyroid hormone(PTH) showed a negative correlation with that of 25-(OH)D(p<0.05). Time spent outdoors in a day correlated positively with the serum level of 25-(OH)D(p<0.01). During the day, a specific time between 12:00 a.m. and 2:00 p.m. showed the most significant correlation with the level of 25-(OH)D(p<0.005). Among the nutrients studied, fat and vitamin D intake were positively correlated with the serum 25-(OH)D level. Stepwise multiple regression analysis showed that the serum level of 25-(OH)D could be fit by vitamin D intake(34.7% explained), serum PTH level (27.3% explained) and the time spent outdoors during the specific time(28.4% explained).1996)

• The Journal of the Korean dental association
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• v.12 no.12
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• pp.919-923
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• 1974

Serum calcium level was decreased by submaxillary gland removal in rate. To investigate the mechanisms involved in the above change, the authors examined the effects of thyroxine, vitamin D₂, and calcium gluconate, which influence the metabolisms of calcium and submaxillary gland, on the serum calcium level of the intact and submaxillary gland removal rats. The results were as follows: 1) Serum calcium level decreased by submaxillary gland removal. 2) Vitamin D₂, increased the serum calcium level significantly. 3) Thyroxine falied to recover the decreased serum calcium level induced by submaxillary gland removal to the control level. 4) In submaxillary gland removal rats, vitamin D₂ failed to increase the serum calcium level. 5) In thyroxine administered rats for 55 days, of which submaxillary glands were removed, vitamin D₂ failed to increase the serum calcium level. 6) The serum calcium level in intact rats was increased slightly, but increased significantly in submaxillary gland removal rats shortly after intravenous injection of calcium gluconate.

• Journal of Nutrition and Health
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• v.39 no.7
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• pp.649-660
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• 2006

This study was performed to estimate serum 2S-hydroxyvitamin D (25-OHD) level in wintertime and to evaluate the relationship between serum 25-OHD level and associated factors in 50 premenopausal working women aged 30-49 y in Busan. The serum 25-OHD level was measured by radioimmunoassay. Data for physiological characteristics, lifestyle factors, physical activity and nutrient intake was assessed by questionnaire including information about outdoor activity time, daily activity diary and 24hr recall method. The mean vitamin D intake was $4.24{\mu}g$, which corresponded to 84.9% of the Korean RDA. The mean level of serum 25-OHD was 25.7 ng/mL. Vitamin D deficiency (25-OHD < 7nmol/L) and toxicity $(25-OHD{\geq}75\;nmol/L)$ were not found in the subjects. However, the prevalence of vitamin D insufficiency (25-OHD < 15 nmol/L) and hypovitaminosis D (25-OHD < 30 nmol/L) were 12% and 60% respectively. The serum 25-OHD level showed positive significant correlations with the duration of outdoor activity per weekdays (p < 0.05). Our findings suggest that hypovitaminosis D was common in the subjects in wintertime. So nutritional education for increasing outdoor activities is needed for premenopausal working women to increase vitamin D status in wintertime.

• Clinical and Experimental Pediatrics
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• v.59 no.7
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• pp.292-297
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• 2016

Purpose: To compare different regimens of vitamin D with respect to its serum increment levels and bone mineral accrual in vitamin D-deficient children. Methods: Children identified as being vitamin D deficient (serum levels<20 ng/mL) were divided into 3 treatment groups by stratified block randomization (group 1, 4,000 IU/day of vitamin D3 plus 50 mg/kg/day calcium for 12 weeks; group 2, 30,000 IU/wk of vitamin D3 plus 50 mg/kg/day calcium for 12 weeks; and group 3, 300,000 IU of vitamin D3 once intramuscularly plus 50 mg/kg/day calcium). After regimen completion, each child received a maintenance dose of 400 IU/day vitamin D3 plus 50 mg/kg/day calcium. Their serum vitamin D level was measured after 3 and 12 months. Total body less head bone mineral concentration (BMC) and total body less head bone mineral density (BMD) were measured after 12 months. Results: The mean increment in serum vitamin D levels from baseline to 3 months was significantly higher in group 3 than in groups 1 and 2, but the levels from 3 to 12 months were almost similar among all 3 groups. There were no significant differences among the 3 groups with respect to percentage increase of BMD and BMC. Conclusion: The injectable form of vitamin D was more efficacious than the oral forms in increasing the serum level to the normal range. All 3 regimens were equally effective in increasing the BMC and BMD. The 400 IU/day maintenance dose was sufficient to keep the serum level within the normal range.

• Journal of the Korean Dietetic Association
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• v.23 no.1
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• pp.39-53
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• 2017

Insufficient vitamin D intake is a major health problem around the world. Recently, many studies have suggested that vitamin D intake may influence insulin resistance. However, little is known about the association between vitamin D and diabetes mellitus. The aim of this study was to investigate the association between serum 25-hydroxy vitamin D (25(OH)D) levels and diabetes mellitus in Korean adults. This study was a cross-sectional analysis of 3,686 participants of the Korean National Health and Nutrition Examination Survey (KNHANES) 2013~2014 aged 19 years and higher. The results showed that the mean serum 25-hydroxy vitamin D (25(OH)D) level in Korean adults was 16.77 ng/mL, and 74.2% of them had an insufficient serum 25-hydroxy vitamin D (25(OH)D) level (below 20 ng/mL). In normal and pre-diabetic groups, the serum 25-hydroxy vitamin D (25(OH)D) level significantly increased with age (P<0.001), but there was no significant difference relative to age in the diabetic group. Low vitamin D levels (25-hydroxy vitamin D < 10 ng/mL) were associated with increased fasting blood glucose levels, compared with optimal vitamin D levels (25-hydroxy vitamin D > 30 ng/mL), after adjusting for variables that may affect fasting blood glucose, but this result was not significant. In conclusion, although no significant association was observed between diabetes prevalence and vitamin D levels in this study, further studies are needed because the effect of vitamin D on diabetes remains controversial. This nutrient plays a crucial role in the body, and levels are insufficient in the Korean population.

• Korean Journal of Exercise Nutrition
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• v.25 no.2
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• pp.20-25
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• 2021

[Purpose] The aim of this review was to discuss the effects of vitamin D on physical performance and musculoskeletal injuries in athletes and provide information on the field applications of vitamin D. [Methods] A systematic review was conducted to identify studies on vitamin D in athletes that assessed serum vitamin D levels, vitamin D and physical performance, vitamin D and musculoskeletal injuries, and practical guidelines for supplementation of vitamin D. [Results] Several studies reported that a high proportion of athletes had vitamin D insufficiency or deficiency. Low serum levels of vitamin D in athletes were more pronounced in winter than in other seasons, and indoor athletes had lower serum vitamin D levels than outdoor athletes. Low vitamin D levels have been demonstrated to have negative effects on muscle strength, power, and endurance; increase stress fractures and other musculoskeletal injuries; and affect acute muscle injuries and inflammation following high-intensity exercises. Therefore, periodic assessment and monitoring of vitamin D levels are necessary in athletes; the recommended serum level of 25(OH)D is > 32 ng/mL and the preferred level is > 40 ng/mL (-1). In those with low levels of vitamin D, exposure to sunlight and an improved diet or supplements may be helpful. Particularly, 2000-6000 IU of supplemental vitamin D3 can be consumed daily. [Conclusion] Vitamin D is a potential nutritional factor that can significantly affect physical performance and musculoskeletal injuries in athletes. The importance and role of vitamin D in athletes should be emphasized, and the current levels of vitamin D should be assessed. Therefore, it is essential to periodically evaluate and monitor serum vitamin D levels in athletes.

• Korean Journal of Community Nutrition
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• v.10 no.1
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• pp.79-90
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• 2005

This study was performed to estimate serum 25-hydroxyvitamin D level and to evaluate the relationship between serum 2S-hydroxyvitamin D level and associated factors. The subjects were 61 premenopausal working women aged 30 - 49 y in Busan. The serum 25-hydroxyvitamin D level was measured by radioimmunoassay. Data for physiological characteristics, lifestyle factors, physical activity and nutrient intake were assessed by questionnaire including information about outdoor activity time, daily activity diary and 24 hr recall method. The mean vitamin D intake was 3.12 ug, which corresponded to $62.5\%$ of the Korean RDA. The mean level of serum 25-hydroxyvitamin D was 31.0 ng/mL. Low 25-hydroxyvitamin D (<25 nmol/L) was not found in the subjects. The serum 2S-hydroxyvitamin D level showed positive significant correlations with exercise hours, daily energy expenditure, hours of outdoor activity per weekdays (p < 0.001, P < 0.05, P < 0.05). Exercise hours were found to be the most important determinant of serum 25-hydroxyvitamin D level. Therefore nutritional education for increasing hours of physical activity including indoor and outdoor exercise, is needed for premenopausal working women to increase vitamin D status.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.8
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• pp.1179-1189
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• 2006

This experiment was designed to examine the effects of supplemental vitamin D on laying performance, metabolic profile and egg quality of hens fed diets containing different fat sources and levels. Lohman strains (n = 480) were assigned to one of 10 diets: basal diet (BD), BD plus 2.5 and 5.0% sunflower oil (SO) or tallow (T) at vitamin D provided $1{\times}$ and $3{\times}$ of the current recommendation. The experiment lasted from week 30 to 44 of age. Each diet was tested in 12 replicate cages of 4 hens. Production, metabolism, and egg quality data were subjected to three-way ANOVA. Both fats decreased feed intake (FI) as compared to BD. Increasing SO and T levels linearly decreased and quadratically increased FI, respectively. The dietary factors did not affect egg production (EP) and egg weight. Vitamin D supplementation increased and decreased EP when diets contained SO and T, respectively. Feed conversion efficiency (FCE) for hens fed SO was lower than for hens fed T. However, increasing T level improved FCE, whereas increasing SO level worsened FCR. Vitamin D supplementation increased serum vitamin D and glucose concentrations. Vitamin D supplementation also caused a decrease and an increase in serum vitamin D concentration when diets contained SO and T, respectively. Serum glucose concentration for hens fed SO was lower than hens fed T. Increasing fat level linearly increased serum triglyceride and VLDL concentrations, regardless of the fat type. Increasing SO level linearly decreased serum cholesterol concentration. Vitamin D supplementation did not alter lipid metabolites. The dietary factors did not affect serum total protein, Ca, and P concentrations. As compared with BD, feeding SO decreased dry tibia and ash weights more than feeding T. Vitamin D supplementation tended to increase dry tibia weight and decrease tibia ash weight. Eggshell strength and thickness, yolk and albumen indexes, and Haugh unit were not responsive to the dietary factors. Eggshell strength quadratically increased with increasing T level. Yolk color for hens fed SO was lower than for hens fed T. The dietary factors did not affect most of yolk fatty acids. Increasing SO level quadratically decreased yolk $C_{18:2}$ concentration. Vitamin D supplementation increased and decreased yolk $C_{18:2}$ concentration when diets contained SO and T, respectively. In conclusion, increasing fat level improved laying performance without altering metabolic profile and egg quality. Vitamin D supplementation had minor alteration effects on laying performance, metabolic profile, and egg quality in response to fat feeding.

• 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.

• Nutrition Research and Practice
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• v.16 no.1
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• pp.120-131
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• 2022

BACKGROUND/OBJECTIVES: Low early pregnancy serum 25-hydroxy vitamin D (25[OH]D) levels can increase gestational diabetes mellitus (GDM) risk, although inconsistent findings related to that association have been reported. This study examined the association of serum vitamin D with GDM and the possible influencers on this association. SUBJECTS/METHODS: This study included 259 pregnant women within the Seremban Cohort Study (SECOST). Blood samples at < 14 weeks of gestation were drawn to determine serum 25(OH)D levels. GDM diagnosis was made at 24 to 32 weeks of gestation using a standard procedure. Association between serum vitamin D and GDM was tested using binary logistic regression. RESULTS: Nearly all women (90%) had mild (68.3%) or severe (32.2%) vitamin D deficiency (VDD). Non-GDM women with mild VDD had a significantly higher mean vitamin D intake than GDM women with mild VDD (t = 2.04, p < 0.05). Women with higher early pregnancy serum vitamin D levels had a greater risk of GDM. However, this significant association was only identified among those with a family history of type 2 diabetes mellitus (T2DM) and in women with a body mass index indicating overweight or obese status. CONCLUSIONS: The high prevalence of VDD in this sample of pregnant women underscores the need for effective preventive public health strategies. Further investigation of this unexpected association between serum vitamin D level and GDM risk in predominantly VDD pregnant women and the potential effects of adiposity and family history of T2DM on that association is warranted.