Seasonal Variation In Vitamin Research Articles

Seasonal Variation in Vitamin D Status Does Not Interfere with Improvements in Aerobic and Muscular Endurance in Conscripts during Basic Military Training.

Considering a lack of respective data, the primary objective of this study was to assess whether seasonal variation in vitamin D status (D-status) affects the extent of improvement in physical performance (PP) in conscripts during basic military training (BMT). D-status, PP and several blood parameters were measured repeatedly in conscripts whose 10-week BMT started in July (cohort S-C; n = 96) or in October (cohort A-C; n = 107). D-status during BMT was higher in S-C compared to A-C (overall serum 25(OH)D 61.4 ± 16.1 and 48.5 ± 20.7 nmol/L, respectively; p < 0.0001). Significant (p < 0.05) improvements in both aerobic and muscular endurance occurred in both cohorts during BMT. Pooled data of the two cohorts revealed a highly reliable (p = 0.000) but weak (R2 = 0.038-0.162) positive association between D-status and PP measures both at the beginning and end of BMT. However, further analysis showed that such a relationship occurred only in conscripts with insufficient or deficient D-status, but not in their vitamin D-sufficient companions. Significant (p < 0.05) increases in serum testosterone-to-cortisol ratio and decreases in ferritin levels occurred during BMT. In conclusion, a positive association exists between D-status and PP measures, but seasonal variation in D-status does not influence the extent of improvement in PP in conscripts during BMT.

Seasonal Variations in Vitamin D Levels and the Incident Dementia Among Older Adults Aged ≥60 Years in the UK Biobank.

Limited knowledge exists regarding the association between dementia incidence and vitamin D insufficiency/deficiency across seasons. This study aimed to evaluate the impact of seasonal serum vitamin D (25(OH)D) levels on dementia and its subtypes, considering potential modifiers. We analyzed 193,003 individuals aged 60-73 at baseline (2006-2010) from the UK Biobank cohort, with follow-up until 2018. 25(OH)D were measured at baseline, and incident dementia cases were identified through hospital records, death certificates, and self-reports. Out of 1,874 documented all-cause dementia cases, the median follow-up duration was 8.9 years. Linear and nonlinear associations between 25(OH)D and dementia incidence across seasons were observed. In multivariable-adjusted analysis, 25(OH)D deficiency was associated with a 1.5-fold (95% CIs: 1.2-2.0), 2.2-fold (1.5-3.0), 2.0-fold (1.5-2.7), and 1.7-fold (1.3-2.3) increased incidence of all-cause dementia in spring, summer, autumn, and winter, respectively. Adjusting for seasonal variations, 25(OH)D insufficiency and deficiency were associated with a 1.3-fold (1.1-1.4) and 1.8-fold (1.6-2.2) increased dementia incidence, respectively. This association remained significant across subgroups, including baseline age, gender, and education levels. Furthermore, 25(OH)D deficiency was associated with a 1.4-fold (1.1-1.8) and 1.5-fold (1.1-2.0) higher incidence of Alzheimer's disease and vascular dementia, respectively. These associations remained significant across all subgroups. 25(OH)D deficiency is associated with an increased incidence of dementia and its subtypes throughout the year.

Vitamin K variations in conger eel (Conger myriaster) influenced by harvest time and size

This study analyzed the variation in vitamin K content in conger eel (Conger myriaster) caught off Tongyeong, Gyeongsangnam-do, Korea, focusing on the influence of size (large and small) and harvest period (monthly throughout 2021). We applied enzymatic extraction and HPLC-fluorescence methods for the analysis of vitamin K1 (phylloquinone) and K2 (menaquinone). The vitamin K content in conger eel varied significantly with size and harvest season (p&lt;0.05). In large-sized samples, the phylloquinone content peaked in July (0.80±0.09 μg/100 g), while the highest menaquinone content was in May (0.79±0.11 μg/100 g). Conversely, in small-sized conger eels, the highest phylloquinone was found in December (1.94±0.15 μg/100 g), and the peak menaquinone level was in January (0.66±0.02 μg/100 g). The fat content was highest in July for large samples and in January for smaller ones. There was a positive correlation between fat and total vitamin K contents in conger eel (r=0.631, 0.667). Method validation and quality control measures ensured data reliability for vitamin K1 and K2 analyses. This study provides reliable information on the size and seasonal variations of vitamin K in conger eels, a staple in the Korean diet. This information is valuable for inclusion in Korea’s national food nutrition database and for formulating future national health and nutrition policies.

Serum 25-Hydroxyvitamin D Levels in Type 2 Diabetes Patients in North China: Seasonality and the Association between Vitamin D Status and Glycosylated Hemoglobin Levels.

Previous studies have reported a correlation between vitamin D levels and seasonality in healthy populations. However, there are few studies on the seasonal variation in vitamin D levels and its relationship with glycosylated hemoglobin (HbA1c) in patients with type 2 diabetes mellitus (T2DM). The objective of this study was to investigate seasonal changes in serum 25-hydroxyvitamin D [25(OH)D] levels and the associations between these vitamin D concentrations and HbA1c levels in T2DM patients in Hebei, China. A cross-sectional study of 1,074 individuals with T2DM was conducted from May 2018 to September 2021. Levels of 25(OH)D in these patients were assessed based on both sex and season, and relevant clinical or laboratory variables that could impact vitamin D status were also considered. In the T2DM patient cohort, the mean blood 25(OH)D levels were 17.05 ng/mL. A total of 698 patients (65.0%) had insufficient serum 25(OH)D levels. The vitamin D deficiency rates were significantly higher in the winter and spring compared to the autumn (P < 0.05), indicating that seasonal fluctuations can have a significant impact on 25(OH)D levels. The levels of vitamin D inadequacy were highest in the winter (74%), and females were more likely than males to be deficient (73.4% vs. 59.5%, P < 0.001). In comparison to the winter and spring, both males and females showed higher 25(OH)D levels in the summer (P < 0.001). HbA1c levels were 8.9% higher in those with vitamin D deficiencies than in nondeficient patients (P < 0.001). HbA1c and vitamin D levels were negatively correlated (r = -0.119, P < 0.001). Vitamin D deficiencies are particularly prevalent among T2DM patients in Hebei, China, with exceptionally high rates in the winter and spring. Female T2DM patients were at an elevated risk of vitamin D deficiency, and vitamin D levels were negatively correlated with HbA1c.

Seasonal variations of vitamin A, D and E levels in serum of female camels (Camelus dromedarius) and their calves raised in five geographic regions of Saudi Arabia

The aim of this study was to investigate the serum level of fat-soluble vitamins A, D and E in clinically healthy lactating female camel (Camelus dromedarius) and suckling calf > one-year-old during winter and summer seasons in five main regions of Saudi Arabia. 60 sera samples were collected and tested for vitamins A, D and E levels and the results were statistically analyzed. The statistical mean value of vitamin A was within the reported range but for D and E, there were minor variations. The effect of season was insignificant (p > 0.05) for vitamins A and E in the combined results of the dam and newborn together. This seasonal effect was highly significant in dam serum (p < 0.05). Region effect was significant for vitamin A in the northern area (p < 0.05) and for vitamin E in the southern region (p < 0.05). Correlations analysis revealed significant results in the season vs vitamin A and E p < 0.05. Mean values of vitamins A, D and E in dam and newborn did not observe significant variations however, in the season and regions there were significant variations which can be attributed to the climate difference, availability of balanced rations and camel management in each location of the five main regions of Saudi Arabia. There is a great need for further studies and the consequent development of supplementation programs and camel feed manufacturers awareness of such results is highly recommended.

Vitamin D Levels in the Pre- and Post-COVID-19 Pandemic Periods and Related Confinement at Pediatric Age

Coronavirus disease 2019 (COVID-19) restrictions have been correlated with vitamin D deficiency in children, but some uncertainties remain. We retrospectively studied vitamin 25-(OH) D blood levels in 2182 Italian children/adolescents hospitalized for various chronic diseases in the year before (n = 1052) and after (n = 1130) the nationwide lockdown. The type of underlying disease, gender, and mean age (91 ± 55 and 91 ± 61 months, respectively) of patients included in the two periods were comparable. Although mean levels were the same (p = 0.24), deficiency status affected a significantly higher number of subjects during the lockdown period than in the pre-COVID period (p = 0.03), particularly in summer (p = 0.02), and there was also a smoothing of seasonal variations in vitamin D levels. Particularly at risk were males (OR = 1.22; p = 0.03), the 1–5 year age group (OR = 1.57; p &lt; 0.01) and the 6–12 year age group (OR = 1.30; p = 0.04). Infants appeared not to be affected (p = 1.00). In the post-COVID period, the risk of vitamin D deficiency was unchanged in disease-specific groups. However, the proportion of deficiency or severe deficiency differed significantly in the subgroup with endocrinopathy (higher; Chi-square p = 0.04), and with respiratory problems and obesity (lower; Chi-square p = 0.01 and p &lt; 0.01, respectively). Conflicting/opposite literature results advocate for further studies to clearly indicate the need for supplementation during possible future periods of confinement.

Vitamin D deficiency in adolescents with obesity - Altered metabolism or environmental factors?

obesity childhood is related to vitamin D deficiency. The aim of this study was to compare vitamin D status between adolescents with obesity living in an urban area and in a rural area. We hypothesized that environmental factors would be decisive in reducing the body content of vitamin D in patients with obesity. a cross-sectional clinical and analytical study (calcium, phosphorus, calcidiol and parathyroid hormone) was carried out in a group of 259 adolescents with obesity (BMI-SDS > 2.0), 249 adolescents with severe obesity (BMI-SDS > 3.0) and 251 healthy adolescents. The place of residence was categorized as urban or rural. Vitamin D status was defined according to the US Endocrine Society criteria. vitamin D deficiency was significantly higher (p < 0.001) in severe obesity (55 %) and obesity groups (37.1 %) than in the control group (14 %). Vitamin D deficiency was more frequent in severe obesity (67.2 %) and obesity groups (51.2 %) living in urban areas than in those living in rural areas (41.5 % and 23.9 %, respectively). The patients with obesity living in urban residence did not present significant seasonal variations in vitamin D deficiency in contrast to those patients with obesity living in rural residence. the most probable mechanism for vitamin D deficiency in adolescents with obesity, rather than altered metabolic is the environmental factors (sedentary lifestyle and lack of adequate sunlight exposure).

Seasonal variations in vitamin D do not change the musculoskeletal health of physically active ambulatory men with cerebral palsy: a longitudinal cross-sectional comparison study

Increased levels of vitamin D in the summer months from natural seasonal variations in sun exposure have been linked to improvements in musculoskeletal health and function in UK populations; however, studies have shown that differences in lifestyles because of disability can inhibit the natural vitamin D increase in these populations. We hypothesized that men with cerebral palsy (CP) will experience smaller increases in 25-hydroxyvitamin D (25(OH)D) from winter to summer and men with CP will not experience any improvements in musculoskeletal health and function during the summer. A longitudinal observational study in 16 ambulant men with CP aged 21.0 ± 1.3 years and 16 healthy, physical activity matched, typically developed controls aged 25.4 ± 2.6 years, completed assessments of serum 25(OH)D and parathyroid hormone during winter and summer. Neuromuscular outcomes included vastus lateralis size, knee extensor strength, 10-m sprint, vertical jumps, and grip strength. Bone ultrasounds were performed to obtain radius and tibia T and Z scores. Men with CP and typically developed controls showed a 70.5% and 85.7% increase in serum 25(OH)D from winter to summer months, respectively. Neither group showed seasonal effect on neuromuscular outcomes muscle strength, size, vertical jump, or tibia and radius T and Z scores. A seasonal interaction effect was seen in the tibia T and Z scores (P < .05). In conclusion, there were similar seasonal increases in 25(OH)D observed in men with CP and typically developed controls, but serum 25(OH)D levels were still considered insufficient to improve bone or neuromuscular outcomes.

Simultaneous determination of six vitamin A substances by multi-wavelength HPLC and application to different marine shellfishes

An HPLC-DAD method was developed for the simultaneous analytical determination of six vitamin A substances (retinol, retinyl acetate, retinyl palmitate, retinoic acid, retinal and β-carotene) and applied to the analysis of vitamin A substances in five marine shellfishes. The chromatographic column was a YMC-β carotene C30 column (250 × 4.6 mm, 3 µm), and the mobile phases were selected as A (methanol), B (ultrapure water) and C (methyl tert-butyl ether). The initial ratio of the mobile phase was A:B:C= 90:1:9, which was maintained for 8 min, while the ratio of the three was changed to A:B:C= 35:0:65 and continued for 8 min, and finally returned to the initial ratio within 0.1 min. Ultrasound-assisted direct extraction was investigated, and the optimal extraction conditions were determined by exploring different sample-to-liquid ratios, extractants, extraction times and extraction temperatures. The method was validated and the established assay showed good linearity in the range of 0.5–50 μg/mL with good precision and accuracy. The experimental results showed that retinol, retinyl palmitate and β-carotene were present in the shellfish and there were seasonal variations of vitamin A substances in different marine economic shellfish.

The relationship between vitamin D levels in seasonal variations and Chinese patients with first-episode drug-naive depression

BackgroundVitamin D deficiency is highly prevalent worldwide and is associated with various diseases, including depression. Previous studies on vitamin D and depression have different conclusions. ObjectivesOur study aimed to examine the association between vitamin D levels in seasonal variation and depression. MethodsA total of 324 patients with first-episode depression aged 18–50 years were recruited for our study. Vitamin D levels were recorded, and PHQ-9 scale evaluation was performed in different seasons. Seasonal variations in vitamin D levels and depressive symptoms were examined. ResultsThe cohort comprised 77 males and 247 females. 98.1% of patients had insufficient or deficient vitamin D levels. The median vitamin D level was 12 ng/mL; 14.5 ng/mL in summer and 13 ng/mL in autumn, which was significantly higher than 9 ng/mL in spring, and the correlation between vitamin D level and PHQ-9 score was more significant in spring but not in summer and autumn. LimitationsOur study used cross-sectional data and could not examine the causal relationship of the vitamin D level and depressive symptoms. There are also some possible influencing factors, such as the dietary habits, outdoor sports, and the use of sunscreen were not investigated. ConclusionObservational data showed that the vitamin D level of depression is lower than the normal (30 ng/mL), and it is closely related to depressive symptoms in spring. The seasonal variations in vitamin D levels might play a critical role in Chinese patients with first-episode depression.

72 SEASONAL VARIATION IN HYPERPARATHYROIDISM IN OLDER IRISH ADULTS

Abstract Background Vitamin D deficiency is common in Ireland, varies by season and can result in secondary hyperparathyroidism. High Parathyroid Hormone (PTH) levels due to low vitamin D status are associated with increased bone turnover and lower bone mineral density, especially at cortical sites such as the hip. Given the variation in vitamin D status by time of year, our study aimed to examine for seasonal differences in hyperparthyroidism in older adults. Methods Study participants were from a large cross-sectional study of older Irish adults recruited from hospital outpatient services and GP practices. Exclusion criteria were: eGFR&amp;lt; 30ml/min and elevated serum calcium (&amp;gt;2.5 mmol/l) in order to avoid primary hyperparathyroidism or elevated serum PTH due to advanced renal impairment. Hyperparathyroidism was defined as a PTH level &amp;gt; 65 ng/ml. The relationship between hyperparathyroidism and season was examined in regression models adjusting for potential factors affecting PTH. Results There were 4324 participants, mean age 73.8 +/- 7.9 years, 65.4% were female. Hyperparathyroidism was more prevalent in Spring versus Autumn (17.4 vs 11.4 %, P = 0.0002). The increased prevalence remained after adjusting for age, gender, body mass index, timed up and go, dairy intake, eGFR, and smoking (OR 1.6, 1.2- 2.0, P=0.0003). This also corresponded to the seasonal variation in vitamin D status with deficiency (25(OH)D &amp;lt; 30 nmol/l) highest in Spring (23.3%) and lowest in Autumn (16.8%). Conclusion We found that hyperparathyroidism fluctuates with season in an inverse relationship with vitamin D. Overall, high PTH levels were 60% more likely in Spring versus Autumn. This emphasises the importance of maintaining adequate vitamin D status all year round. While we adjusted for dairy intake, we did not have accurate measures of total dietary calcium intake which could also vary seasonally and be a contributory factor.

Seasonal variation in vitamin D status of Japanese infants starts to emerge at 2 months of age: a retrospective cohort study.

Vitamin D seasonality has been reported in adults and children, suggesting that sunlight exposure has effects on 25(OH)D production. While vitamin D deficiency among infants has received significant attention, little is known about the extent to which vitamin D status during early infancy is affected by sunlight exposure. Here, we retrospectively analysed serum 25(OH)D levels of 692 samples obtained from healthy infants aged 1-2 months born at Saitama City Hospital, Japan (latitude 35·9° North) between August 2017 and September 2021. Data regarding the frequency of outdoor activities, formula intake and BMI were also collected and analysed. Month-to-month comparisons of vitamin D levels revealed significant variation in 25(OH)D levels in breastfed infants starting at 2 months, with maximal and minimal levels in September and January, respectively. An outdoor activity score of 0 was most common at 1 month (83·9 %) and a score of 3 was most common at 2 months (81·2 %), suggesting an increased amount of sunlight exposure at 2 months. Multiple linear regression analysis revealed the amount of formula intake to be significantly associated with vitamin D status at both 1 (t = 17·96) and 2 months (t = 16·30). Our results comprise the first evidence that seasonal variation of vitamin D begins at 2 months among breastfed infants from East Asia, though dietary intake appears to be the major determinant of vitamin D status. These findings provide new insights into the influence of dietary and non-dietary factors on vitamin D status during early infancy.

Vitamin D and Depressive Symptoms in Adults with Multiple Sclerosis: A Scoping Review

Background. Vitamin D deficiency has been correlated with Multiple Sclerosis (MS) risk and disease activity. There is some controversy as to whether vitamin D could have an impact on depressive symptoms in people with MS (pwMS). The aim of this scoping review was to evaluate the association between vitamin D status and depressive symptoms in pwMS. Methods. We searched databases to include studies published up to March 2021 to provide an overview of the available evidence on the correlation between vitamin D status and depressive symptoms in pwMS. The eligibility criteria were as follows: studies evaluating the use of vitamin D measurement on depressive symptoms in patients suffering from MS, including randomized and non-randomized studies; studies written in English; and studies exploring an adult population over the age of 18. Results. Eleven studies met our inclusion criteria: two of them were abstracts only; the majority were cross-sectional studies; two were prospective longitudinal studies; one was a retrospective cohort study; and one was a randomized placebo-controlled trial (RCT). Of the eleven studies selected, seven showed a potential correlation between low vitamin D levels and depressive symptoms. Conclusion. Future RCT studies should include patients with greater severity of depressive symptoms and should consider confounding factors such as sun exposure and seasonal variation of vitamin D.

Vitamin D Status and Seasonal Variation: A Retrospective Single Institution Database Study of Patients Pursuing Metabolic/Bariatric Surgery

•Marked seasonal variation was present in persons presenting for bariatric surgery.•Tailored supplementation in spring/winter should be considered to prevent vitamin D deficiency.•Pre and post-operative supplementation may be dependent on surgical type. BackgroundObesity is associated with suboptimal levels in vitamin D, a nutrient important for bone health and immune function. Seasonal variation in vitamin D may exacerbate this deficiency in persons with obesity, as exposure to ultraviolet B rays in sunlight is necessary for the conversion of vitamin D to its active form in the body. The aim of this study was to determine the relationship between season and vitamin D levels in persons with obesity pursuing bariatric surgery.Materials and MethodsThis retrospective cohort study from a single academic medical center investigated adult patients undergoing either primary sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) over a 20-year period. Demographics and serum 25-hydroxyvitamin D3 levels were collected from the first presenting visit to the bariatrics center. Continuous vitamin D3 levels were compared across seasons using a one-way Analysis of Variance (ANOVA). Vitamin D3 categories were examined across seasons using a Chi square test of independence.Results1,256 persons pursuing bariatric surgery (SG: N=697, RYGB: N=559) met the inclusion criteria. Baseline vitamin D values were available in 1,071 of the eligible patients. Overall, serum 25-hydroxyvitamin D3 levels showed a significant variation across the seasons of the year (P<0.001), with highest levels during summer (33.52±12.70 ng/mL) and lowest levels during spring (29.72±12.34 ng/mL) and winter (29.90±14.80 ng/mL).ConclusionsThis study demonstrates marked seasonal variation in serum 25-hydroxyvitamin D3 in patients with obesity presenting for bariatric surgery. These results emphasize the importance of utilizing tailored supplementation during the spring and winter months to prevent potential deficiency. Obesity is associated with suboptimal levels in vitamin D, a nutrient important for bone health and immune function. Seasonal variation in vitamin D may exacerbate this deficiency in persons with obesity, as exposure to ultraviolet B rays in sunlight is necessary for the conversion of vitamin D to its active form in the body. The aim of this study was to determine the relationship between season and vitamin D levels in persons with obesity pursuing bariatric surgery. This retrospective cohort study from a single academic medical center investigated adult patients undergoing either primary sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) over a 20-year period. Demographics and serum 25-hydroxyvitamin D3 levels were collected from the first presenting visit to the bariatrics center. Continuous vitamin D3 levels were compared across seasons using a one-way Analysis of Variance (ANOVA). Vitamin D3 categories were examined across seasons using a Chi square test of independence. 1,256 persons pursuing bariatric surgery (SG: N=697, RYGB: N=559) met the inclusion criteria. Baseline vitamin D values were available in 1,071 of the eligible patients. Overall, serum 25-hydroxyvitamin D3 levels showed a significant variation across the seasons of the year (P<0.001), with highest levels during summer (33.52±12.70 ng/mL) and lowest levels during spring (29.72±12.34 ng/mL) and winter (29.90±14.80 ng/mL). This study demonstrates marked seasonal variation in serum 25-hydroxyvitamin D3 in patients with obesity presenting for bariatric surgery. These results emphasize the importance of utilizing tailored supplementation during the spring and winter months to prevent potential deficiency.

Evaluating the association between maternal vitamin D deficiency and preeclampsia among Indian gravidas

ObjectiveThe association between vitamin D deficiency and devastating preeclampsia is still debated. In this present study, our aim is to evaluate whether a statistically significant association exists between vitamin D deficiency and preeclampsia in Indian gravidas. As to the best of our knowledge, no study of this context with such a large sample size is done in the Indian population till now. MethodA case-control study was performed in the year 2015–2019 where we enrolled 1000 pregnant women with preeclampsia admitted either in labor or for induction of labor in the study group and 1000 pregnant women without preeclampsia either in labor or admitted for induction of labor at term gestation in the control group. Serum 25-hydroxyvitamin D [25 (OH)] D levels of both the groups were measured through the radioimmunoassay method and analyzed. In both the groups, samples were collected equally across all the seasons of the year to avoid confounding by seasonal variation of vitamin D. Primary outcome measures the association of vitamin D deficiency and preeclampsia. While secondary outcome measures the correlation between levels of vitamin D deficiency with the severity of preeclampsia. ResultA significantly low mean vitamin D level was seen in preeclamptic women (11.0 ± 7.1 ng /ml) compared to normotensive (31.4 ± 1.7 ng/ml) with p < .001. We observed approximately 11 fold increased odds of having preeclampsia in vitamin D deficient women (OR: 11.308; 95 % CI 7.5982–14.0097). Moreover, we observed that as vitamin D level decreases, the severity of preeclampsia increases (p < .001). ConclusionCompared with normotensive women, preeclamptic women had a significantly low level of vitamin D, suggesting a significant association between vitamin D deficiency and preeclampsia.

Effect of latitude on seasonal variations of vitamin D and some cardiometabolic risk factors: national food and nutrition surveillance.

Despite a remarkable reduction in the occurrence of many micronutrient deficiencies in most countries, vitamin D deficiency has remained a global problem. Age-adjusted disability-adjusted life years lost due to cardiovascular disease in the Eastern Mediterranean Region, including in the Islamic Republic of Iran, are higher than the global average. To assess the effects of latitude and season on vitamin D status in the Iranian population and the association between vitamin D status and certain cardiometabolic risk factors. A sample of 1111 participants aged 19-65 years was randomly selected from 6 regions with latitudes ranging from 29º.0 N to 37.5º N. All anthropometric and biochemical assessments were performed twice a year, summer and winter during 2013 to 2014. Overall mean 25(OH)D concentration was 26.9 [standard deviation (SD) 17.8] nmol/L in winter and 43.4 (SD 32.9 nmol/L in summer (P < 0.001). Poor vitamin D status was noticeable in both seasons (90.1% and 69.2%, respectively). Being male (B, 7.6; 95% CI: 4.3 to 10.8; P < 0.001) and living at a latitude higher than 33 ° were positive predictors, and serum 25(OH)D concentration in winter (B, -0.2; 95% CI: -2.9 to -0.11; P < 0.001) was a negative predictor of changes of 25(OH)D concentrations. We found a high prevalence of suboptimal vitamin D status in Iranian adults throughout the year, irrespective of latitude and season. Improvement of mean circulating 25(OH)D concentrations in the community to 50+ nmol/L through a fortification programme is likely to engender healthy cardiometabolic changes.

Serum Levels of 25-Hydroxyvitamin D in Patients with Seborrheic Dermatitis: A Case-Control Study.

Several autoimmune papulosquamous skin conditions such as psoriasis, systemic lupus erythematous, and lichen planus have been associated with vitamin D deficiency or correlated with serum vitamin D level. This study was aimed at comparing the 25-hydroxyvitamin D (25(OH)D) status in patients with facial or scalp seborrheic dermatitis with healthy subjects. This case-control study included 289 patients (118 with psoriasis and 171 sex- and age-matched control subjects) from the outpatient clinic of two hospital dermatology departments in the west of Mazandaran province, Iran. All patients and control subjects were studied during one season to avoid seasonal variations in vitamin D levels. Serum mean ± standard deviation of 25(OH)D levels were significantly lower in seborrheic dermatitis patients than in control subjects (20.71 ± 8.16 vs. 23.91 ± 7.78, P = 0.007). Serum 25(OH)D levels were negatively associated with the risk of developing seborrheic dermatitis (odds ratio (OR): 0.898, 95% confidence interval (Cl): 0.840–0.960, P = 0.002). Also, vitamin D under 30 ng/ml was associated with OR: 4.22 (95% Cl: 1.077–16.534, P = 0.039) for seborrheic dermatitis. The severity of scalp disease was significantly associated with serum 25(OH)D level (P = 0.003). Cases with severe scalp scores had significantly lower serum 25(OH)D level compared to moderate OR score (P = 0.036). A similar trend was not seen in the facial disease. The 25(OH)D values are significantly lower in seborrheic dermatitis patients than in healthy subjects. Furthermore, the scalp disease severity was associated with lower serum 25(OH)D level. Our results may suggest that vitamin D may play a role in the pathogenesis of seborrheic dermatitis.

Vitamin D Status in Children in Greece and Its Relationship with Sunscreen Application.

The aim of this study was to characterize the prevalence and seasonal variation of vitamin D (vit D) deficiency/insufficiency in healthy children and adolescents in Greece, and to explore its relationship with the use of sunscreens. The serum level of 25-hydroxy-vitamin D (25(OH)D) was measured in 376 children and adolescents (184 males and 192 females) with a mean age of 7.6 ± 4.9 years, at different time points over a period of 13 months. The prevalence of low serum 25(OH)D level, including deficiency and insufficiency, was 66.2%. The lowest mean 25(OH)D was observed in the month of January (17.9 ± 6.8 ng/mL) and the highest in September, July, August, and October (34.6 ± 8.7, 33.0 ± 9.4, 30.1 ± 8.2, and 30.1 ± 10.6 ng/mL, respectively). Higher levels of serum 25(OH)D were detected in the children to whom sunscreens had been applied on the beach (p = 0.001) or off the beach (p < 0.001). The subjects with deficiency and insufficiency were significantly older than those with normal levels of 25(OH)D, but no significant differences were demonstrated according to gender. This study emphasizes the high prevalence of low serum levels of 25(OH)D and their seasonal variation in children living in a region characterized by many hours of sunshine. Our data suggest that the real-life use of sunscreens during the summer months allows sufficient sunlight to be received to enable production of vit D at a level adequate to maintain normal serum levels. Vit D supplements should be given to children during the months of lower sun exposure.

Lack of Seasonal Variations in Vitamin D Concentrations among Hospitalized Elderly Patients.

Background. Generally, most vitamin D in the human body (90–95%) is produced in the skin during exposure to sunlight. The effectiveness of this process depends on several biological and physical factors, e.g., age or latitude. Skin synthesis of vitamin D among elderly people is reduced. The aim of the study was to assess serum 25-hydroxyvitamin D [25(OH)D] seasonal variations in elderly patients hospitalized at the geriatric department. Methods. The study was carried out on 242 patients aged 60 years or older hospitalized at the geriatric department. The study group was categorized by four seasons as well as month. Results. The median (interquartile range) 25(OH)D concentration among all patients (n = 242) was 33.95 (26.96–45.18) nmol/L. There was no statistical significance in the median serum 25(OH)D concentration with regard to each of the four seasons: in the spring 32.95 (25.96–43.68) nmol/L, in the summer 38.69 (27.46–50.67) nmol/L, in the autumn 33.45 (27.08–44.18) nmol/L, in the winter 34.57 (23.46–43.93) nmol/L, (p = 0.48). Conclusions. Vitamin D deficiency was observed in all geriatric patients, irrespective of the season. The results of the study indicate no significant differences in median vitamin D concentration among the hospitalized patients across all four seasons. Even in the summer months, in our climate, it is fairly difficult for an elderly person to produce an adequate amount of vitamin D through the skin. Therefore, proper vitamin D supplementation is recommended and should be implemented in the elderly irrespective of the season.

Seasonal variation of vitamin D among healthy adult men in a subtropical region.

To evaluate seasonal variation of 25(OH)vitamin D [25(OH)D3] levels, and factors associated with it, in healthy adult men, who exercised outdoors for 50 min., at least twice a week, from 10AM to 4PM, in a Brazilian semitropical region. Blood samples were collected at the end of each season for 25(OH)D3, measured by liquid chromatography with tandem mass spectrometry. Ultraviolet irradiation was estimated by radiometer, calculating the daily photobiological response to vitamin D synthesis in human skin (D-VitD). The prevalence of 25(OH)D3 <20ng/mL changed with the seasons (p=0.000): 8.7% (n=6/69), 1.5% (n=1/66), 0 (n=0/64), and 21.7% (n=13/60), respectively, at the end of winter, spring, summer, and autumn. The prevalence, adjusted for multiple comparisons, was higher in winter than summer (p=0.026), and in autumn than spring (p=0.001) and summer (p=0.000). There were no associations of 25(OH) D3 levels with BMI (p=0.207), body fat (p=0.064), and phototype (p=0.485), in univariate analysis. It was associated with D-VitD in the 30 days before blood sampling (p=0.000), after adjustment to body fat. The prevalence of 25(OH)D3 <30ng/mL varied seasonally (p=0.000): 69.6% (n=48/69), 68.2% (n=45/66), 43.8% (n=28/64), and 88.4% (n=53/60), respectively, in winter, spring, summer, and autumn. In a Brazilian subtropical region, a seasonal variation in 25(OH)D3 was observed in healthy adult males, although they spent at least 50 min outdoors twice a week, wearing shorts and T-shirts. 25(OH)D3 <20ng/mL was 21.7% in autumn; D-vitD 30 days prior to blood sampling was the only factor independently associated with 25(OH)D3 levels.