• 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)

• Nutrition Research and Practice
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• v.9 no.2
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• pp.158-164
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• 2015

BACKGROUND/OBJECTIVES: Vitamin D deficiency is common in hemodialysis patients. The aim of this study was to identify whether or not sun exposure and dietary vitamin D intake have effects on serum 25-hydroxyvitamin D (25(OH)D) status in hemodialysis (HD) patients. The objective was to identify the main determinants of serum vitamin D status in the study subjects. SUBJECTS/METHODS: A cross-sectional study of 47 HD patients (19 males and 28 females) was performed. We assessed serum 25(OH)D and $1,25(OH)_2D$ levels between August and September 2012 and analyzed the prevalence of vitamin D deficiency in HD patients. To evaluate the determinants of serum 25(OH)D levels, we surveyed dietary vitamin D intake, degree of sun exposure, and outdoor activities. To compare biological variables, serum 25(OH)D was stratified as below 15 ng/ml or above 15 ng/ml. RESULTS: Mean 25(OH)D and $1,25(OH)_2D$ levels were $13.5{\pm}5.8ng/ml$ and $20.6{\pm}11.8pg/ml$, respectively. The proportions of serum 25(OH)D deficiency (< 15 ng/ml), insufficiency (15-< 30 ng/ml), and sufficiency (${\geq}30ng/ml$) in subjects were 72.4%, 23.4%, and 4.3%, respectively. Prevalence of vitamin D deficiency in female patients was 78.6%, whereas that in males was 63.2% (P = 0.046). Vitamin D intake and sun exposure time were not significantly different between the two stratified serum 25(OH)D levels. Dietary intake of vitamin D did not contribute to increased serum 25(OH)D levels in HD patients. The main effective factors affecting serum 25(OH)D status were found to be the sun exposure and active outdoor exercise. CONCLUSIONS: Hypovitaminosis D is common in HD patients and is higher in females than in males. Sun exposure is the most important determinant of serum 25(OH)D status in HD patients.

• 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.

• Clinical and Experimental Reproductive Medicine
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• v.46 no.3
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• pp.132-139
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• 2019

Objective: Vitamin D-binding protein (VDBP) mediates various biological processes in humans. The goal of this study was to investigate whether VDBP gene polymorphisms could predispose Korean women to endometriosis. Methods: We prospectively enrolled women with endometriosis (n = 16) and healthy controls (n = 16). Total serum 25-hydroxyl vitamin D (25(OH)D) concentrations were measured using an Elecsys vitamin D total kit. Levels of bioavailable and free 25(OH)D were calculated. Concentrations of VDBP were measured using a vitamin D BP Quantikine ELISA kit. DNA was extracted using a DNeasy blood & tissue kit. Two single-nucleotide polymorphisms (SNPs; rs4588 and rs7041) in GC, the gene that codes for VDBP, were analyzed using a TaqMan SNP genotyping assay kit. The functional variant of VDBP was determined based on the results of the two SNPs. Results: Gravidity and parity were significantly lower in the endometriosis patients than in the control group, but serum CA-125 levels and the erythrocyte sedimentation rate were significantly higher. Total serum 25(OH)D levels in the endometriosis patients were significantly lower than in the control group. However, serum bioavailable 25(OH)D, free 25(OH)D, and VDBP levels did not differ significantly between the endometriosis and control groups. The genotypes and allele frequencies of GC were similar in both groups. Conclusion: Korean women with endometriosis had lower total serum 25(OH)D concentrations than controls. Neither serum VDBP concentrations nor polymorphisms in the gene coding for VDBP were associated with endometriosis. Further studies are needed to investigate the pathophysiology and clinical implications of 25(OH)D and VDBP in endometriosis.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.6
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• pp.2227-2230
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• 2015

Background: Prostate cancer (PCa) is one of the most commonly diagnosed neoplasms and the second leading cause of cancer death in men in the Western world. Vitamin D (1,25dihydroxy vitamin D) is linked to many biological processes that influence oncogenesis but data on relations between its genetic variants and cancer risk have been inconsistent. The aim of this study was to determine associations between a vitamin D genetic polymorphism and 25-hydroxyvitamin D [25(OH)D] levels and prostate cancer. Materials and Methods: Genomic DNA was extracted from 124 Jordanian prostate cancer patients and 100 healthy volunteers. Ethical approval was granted from the ethical committee at Hashemite University and written consent was given by all patients. PCR was used to amplify the vitamin D receptor Fok1 polymorphism fragment. 25(OH)D serum levels were measured by competitive immunoassay. Results: All genotypes were in Hardy-Weinberg equilibrium. Genotype frequency for Fok1 genotypes FF, Ff and ff was 30.7%, 61.3% and 8.06%, for prostate cancer patients, while frequencies for the control group was 28.0%, 66.0% and 6.0%, respectively, with no significant differences. Vitamin D serum level was significantly lower in prostate cancer patients (mean 7.7 ng/ml) compared to the control group (21.8 ng/ml). No significant association was noted between 25(OH)D and VDR Fok1 gene polymorphism among Jordanians overall, but significant associations were evident among prostate cancer patients (FF, Ff and ff : 25(OH)D levels of 6.2, 8.2 and 9.9) and controls (19.0, 22.5 and 26.3, respectively). An inverse association was noted between 25(OH)D serum level less than 10ng/ml and prostate cancer risk (OR 35.5 and 95% CI 14.3- 88.0). Conclusions: There is strong inverse association between 25(OH)D serum level less than 10ng/ml level and prostate cancer risk.

• Korean Journal of Community Nutrition
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• v.19 no.3
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• pp.231-240
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• 2014

Objectives: This study was intended to examine the seasonal differences in outdoor activity times and dietary vitamin D intakes, and explicates their relative impact on improving serum 25-(OH) vitamin D status among Korean young women. Methods: A cross-sectional study was conducted with 135 free-living women aged 19-39 years in Daegu-Kyungbook, Korea. We compared the results from 52 women for the summer and 83 women for the winter. Dietary intake of vitamin D was assessed by 24 hour recall method for non-consecutive three days as well as by food frequency method. Daily outdoor activity times were derived from 24 hour physical activity diary. Results: The average dietary intake of vitamin D of the participants by 24 hour recall method was 3.1 ${\mu}g$ during the summer, 3.3 ${\mu}g$ during the winter, showing no significant difference between the two seasons. Times spent on outdoor activities (p < 0.01) in the summer (= $23.8{\pm}23.6$ min) were much longer than that in the winter (= $10.8{\pm}13.4$ min). The serum 25-(OH) vitamin D levels of participants were $17.5{\pm}7.5$ ng/mL in the summer and $13.4{\pm}4.3$ ng/mL in the winter, showing that the latter was significantly lower than that of the former (p<0.001). The serum 25-(OH) vitamin D levels of subjects were positively related to outdoor activities (r=0.315, p<0.05) during the summer, while related to dietary intake (r=0.252, p<0.05) during the winter. Conclusions: In order to improve the current vitamin D status of Korean young women, nutrition education programs should focus on increasing more dietary intake especially during the winter, and performing more outdoor activities in other seasons.

• Korean Journal of Community Nutrition
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• v.20 no.2
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• pp.120-128
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• 2015

Objectives: The purpose of this study was to examine the relative impact of seasonal differences and age on dietary vitamin D intakes, outdoor activity time and serum vitamin D status among Korean postmenopausal women. Methods: A cross-sectional study was conducted with 164 free-living postmenopausal women (mean age=55.4 years) in Daegu, Korea. Dietary intake, daily physical activity patterns and fasting blood samples were collected during summer and winter. We compared the results from 75 women during summer and 89 women during winter. Dietary intake of vitamin D was assessed by 24-hour recall method. Daily outdoor activity time was derived from physical activity diary. Results: The average dietary intake of vitamin D of the participants was $3.7{\mu}g$ during summer, $3.3{\mu}g$ during winter, showing no significant difference between the two seasons. The average time spent on outdoor activities was not significantly different between summer ($=35.1{\pm}75.0min/d$) and winter ($=48.5{\pm}76.8min/d$). The average serum 25-(OH) vitamin D concentrations of participants was $17.5{\pm}7.5ng/mL$ in the summer and $13.4{\pm}4.3ng/mL$ in the winter, showing no significant differences by season. Dietary intake of vitamin D was not related to age. When total subjects were divided into two groups by age, the average serum 25-(OH) vitamin D concentration was significantly higher in older group (p=0.047) and time spent on outdoor activities was also (p=0.018) significantly higher in the older group. Conclusions: In order to improve the current vitamin D status of Korean postmenopausal women, nutrition education programs should focus more on adequate intake of vitamin D, while maintaining enough outdoor activities over the season.

• Journal of Nutrition and Health
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• v.49 no.1
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• pp.28-35
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• 2016

Purpose: Vitamin D status is associated with several chronic diseases related to obesity. In this study, we evaluate the nutritional status of vitamin D and its relation to obesity indices in Korean women. Methods: A total of 156 healthy women participated. Vitamin D status (serum $25-OH-vitamin\;D_3$ level) and obesity indices (body mass index, body fat mass, waisthip ratio, and body fat percentage etc.) and serum lipid profiles and serum adipokine (leptin and adiponectin) levels were analyzed. Results: The $25(OH)D_3$ level showed an extremely skewed distribution from 4.1 ng/ml to 24.4 ng/ml and mean $25(OH)D_3$ level was $9.0{\pm}4.0ng/ml$. With cut-off level for vitamin D deficiency (< 12.0 ng/ml), insufficiency (12-19.9 ng/ml) and sufficiency (${\geq}20ng/ml$), 77.6%, 19.2%, and 3.2% of subjects showed vitamin D deficiency, insufficiency, and sufficiency status, respectively. The $25(OH)D_3$ level showed positive correlation with weight (r = 0.2461, p < 0.01), body mass index (r = 0.2913, p < 0.001), body fat contents (r = 0.1691, p < 0.05), fat free mass (r = 0.2330, p < 0.01), and waist hip ratio (r = 0.1749, p < 0.05) after adjusted by age. The $25(OH)D_3$ level showed no significant correlation with serum lipid profiles and adipokine levels. Conclusion: Most subjects (76.6%) in this study, who had a vitamin D deficient status and serum $25(OH)D_3$ level, showed positive correlation with several obesity indices, however further research based on a large Korean population is needed to confirm the relationship.

• Korean Journal of Community Nutrition
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• v.19 no.2
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• pp.122-132
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• 2014

Objectives: This study was conducted to investigate the vitamin D status and to determine the association between serum 25-hydroxyvitamin D [25(OH)D] concentrations and consumption frequencies of vitamin D rich foods in Korean adults and older adults. Methods: Subjects were 10,374 adults and 2,792 older adults participating in the 2008-2009 Korea National Health and Nutrition Examination Survey (KNHANES). Consumption frequencies of vitamin D rich foods were estimated by using a qualitative food frequency questionnaire (FFQ). Eleven food items such as beef, egg, mackerel, tuna, yellow corvina, pollack, anchovy, mushroom, milk, yogurt, and ice cream were selected as vitamin D rich foods based on previous research. Results: The proportions of deficiency (< 12 ng/mL), inadequacy (12-20 ng/mL) and sufficiency (${\geq}20ng/mL$) of serum 25(OH)D concentrations from June to November and December to May in adults were 8.8%, 42.3%, 48.8%, and 28.2%, 52.8%, 19.1%, respectively. The proportions of deficiency, inadequacy and sufficiency of serum 25(OH)D concentrations from June to November and December to May in older adults were 10.1%, 32.4%, 57.5%, and 24.1%, 45.4%, 30.5%, respectively. The mean serum 25(OH)D concentrations in adults were positively related to the consumption frequencies of mackerel, anchovy, all fish, milk and milk dairy products. The mean serum 25(OH)D concentrations in older adults were positively related to the consumption frequencies of yellow corvina and negatively related to the consumption frequencies of ice cream. Conclusions: Our results suggest that Korean adults were more deficient in serum 25(OH)D concentrations than older adults. The consumption of vitamin D rich foods may affect vitamin D status in Korean adults. Further studies are required to confirm these findings.

• 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.