Seasonal Changes In Vitamin Research Articles

Seasonal changes in vitamin A metabolism-related factors in the oviduct of Chinese brown frog (Rana dybowskii)

The oviduct of the Chinese brown frog (Rana dybowskii) expands during pre-brumation rather than the breeding period, exhibiting a special physiological feature. Vitamin A is essential for the proper growth and development of many organisms, including the reproductive system such as ovary and oviduct. Vitamin A is metabolized into retinoic acid, which is crucial for oviduct formation. This study examined the relationship between oviducal expansion and vitamin A metabolism. We observed a significant increase in the weight and diameter of the oviduct in Rana dybowskii during pre-brumation. Vitamin A and its active metabolite, retinoic acid, notably increased during pre-brumation. The mRNA levels of retinol binding protein 4 (rbp4) and its receptor stra6 gene, involved in vitamin A transport, were elevated during pre-brumation compared to the breeding period. In the vitamin A metabolic pathway, the mRNA expression level of retinoic acid synthase aldh1a2 decreased significantly during pre-brumation, while the mRNA levels of retinoic acid α receptor (rarα) and the retinoic acid catabolic enzyme cyp26a1 increased significantly during pre-brumation, but not during the breeding period. Immunohistochemical results showed that Rbp4, Stra6, Aldh1a2, Rarα, and Cyp26a1 were expressed in ampulla region of the oviduct. Western blot results indicated that Aldh1a2 expression was lower, while Rbp4, Stra6, RARα, and Cyp26a1 were higher during pre-brumation compared to the breeding period. Transcriptome analyses further identified differential genes in the oviduct and found enrichment of differential genes in the vitamin A metabolism pathway, providing evidences for our study. These results suggest that the vitamin A metabolic pathway is more active during pre-brumation compared to the breeding period, and retinoic acid may regulate pre-brumation oviductal expansion through Rarα-mediated autocrine/paracrine modulation.

Seasonal Changes in Vitamin D Levels of Healthy Children in Mid-Latitude, Asian Urban Area.

PurposeThis study aimed to investigate the seasonal changes in vitamin D levels in a healthy pediatric population living in mid-latitude East Asian urban areas.MethodsA pediatric population was selected from single secondary hospital visitors. Clinical data and serum vitamin D levels were collected retrospectively. Statistical analyses were performed based on the month of the blood sampling date, subject age, and vitamin D supplementation history. The data were categorized into three subgroups based on serum vitamin D levels—adequate (≥30 ng/mL), insufficient (20–29 ng/mL), and deficient (<20 ng/mL).ResultsOf the 481 patients, 172 had vitamin D supplementation history. More than 70% of the total study population had inadequate vitamin D levels (<30 ng/mL). The non-supplemented group and the supplemented group showed significantly uneven monthly distribution of the adequate, insufficient, and deficient subgroups. Only the non-supplemented group showed significantly different average vitamin D levels in the summer months compared to the winter months. In the non-supplemented group, vitamin D levels were the lowest in March, the highest in August and September. Significant relevance was noted between vitamin D supplementation status and vitamin D serum level in February and March. There was no significant difference between different age groups in terms of the distribution of vitamin D levels.ConclusionCurrently-widespread vitamin D replacement methods seem to have some effect on increasing the overall serum vitamin D levels, specifically during late winter when natural serum vitamin D levels plunge. However, they are unable to fully compensate the seasonal fluctuation.

Seasonal variation in vitamin D status, bone health and athletic performance in competitive university student athletes: a longitudinal study.

Vitamin D deficiency has been commonly reported in elite athletes, but the vitamin D status of UK university athletes in different training environments remains unknown. The present study aimed to determine any seasonal changes in vitamin D status among indoor and outdoor athletes, and whether there was any relationship between vitamin D status and indices of physical performance and bone health. A group of forty-seven university athletes (indoor n 22, outdoor n 25) were tested during autumn and spring for serum vitamin D status, bone health and physical performance parameters. Blood samples were analysed for serum 25-hydroxyvitamin D (s-25(OH)D) status. Peak isometric knee extensor torque using an isokinetic dynamometer and jump height was assessed using an Optojump. Aerobic capacity was estimated using the Yo-Yo intermittent recovery test. Peripheral quantitative computed tomography scans measured radial bone mineral density. Statistical analyses were performed using appropriate parametric/non-parametric testing depending on the normality of the data. s-25(OH)D significantly fell between autumn (52·8 (sd 22·0) nmol/l) and spring (31·0 (sd 16·5) nmol/l; P < 0·001). In spring, 34% of participants were considered to be vitamin D deficient (<25 nmol/l) according to the revised 2016 UK guidelines. These data suggest that UK university athletes are at risk of vitamin D deficiency. Thus, further research is warranted to investigate the concomitant effects of low vitamin D status on health and performance outcomes in university athletes residing at northern latitudes.

Seasonal Variation in Serum 25-hydroxy Vitamin D and its Association with Clinical Morbidity in Healthy Infants from Northern India

To evaluate the seasonal change in serum 25-hydroxyvitamin D (25-OHD) level in healthy infants and to relate it to common childhood morbidities. 72 healthy breastfed infants residing in Delhi were enrolled at the end of summer and followed till the end of winter [mean (SD) duration 200 (10) d]. Serum 25-OHD was estimated at baseline and follow-up. Infants were monitored for common childhood diseases. Mean (SD) serum 25-OHD level was lower at the end of winter (20.7 (8.02) ng/mL) than summer (22.9 (8.70) ng/mL) [mean difference (95% CI) -2.14 ng/mL (-3.36, -1.06), P<0.001). The seasonal distribution of children according to vitamin D status in summer and winter - Deficient (15.3%, 12.5%), Insufficient (19.4%, 30.6%) and Sufficient (65.3%, 56.9%), respectively was comparable P=0.17). The morbidity profile remained unaffected by change in vitamin D status from summer to winter. Seasonal changes in vitamin D levels do not have significant clinical effect or effect on overall vitamin D status in apparently healthy infants from North India. This may have implications for results of population surveys for vitamin D status, irrespective of the season when they are conducted.

Vitamin D status is associated with muscle strength and quality of life in patients with COPD: a seasonal prospective observation study.

BackgroundOwing to hospitalization, reduced functional capacity and consequently, less sunlight exposure, suboptimal vitamin D status (25-hydroxyvitamin D [25(OH)D]⩽50 nmol/L) is prevalent among COPD patients.ObjectiveThis study aimed to investigate seasonal changes in vitamin D status and any associated changes in fat-free mass (FFM), muscle strength and quality of life (QoL) in COPD patients.Patients and methodsCOPD patients living in Northern Ireland (n=51) completed study visits at the end of winter (March/April) and at the end of summer (September/October), corresponding to the nadir and peak of vitamin D status, respectively. At both time points, serum concentration of 25(OH)D was quantified by liquid chromatography-tandem mass spectrometry, FFM (kg) was measured using bioelectrical impedance and muscle strength (kg) was measured using handgrip dynamometry. QoL was assessed using the validated St George’s Respiratory Questionnaire.ResultsMean±SD 25(OH)D concentration was significantly higher at the end of summer compared to the end of winter (52.5±30.5 nmol/L vs 33.7±28.4 nmol/L, P<0.001); and house- bound patients had significantly lower 25(OH)D concentration compared to nonhousebound patients at the end of summer (42.9±4.2 vs 57.2±9.9 nmol/L; P⩽0.001). Muscle strength (at both time points) and QoL (end of summer only) were positively predicted by 25(OH)D concentration, independent of age, sex and smoking status.ConclusionThis study highlights the need for health policies to include a recommendation for year-round vitamin D supplementation in housebound COPD patients, and wintertime supplementation in nonhousebound patients, to maintain optimal 25(OH)D concentrations to protect musculoskeletal health. Furthermore, an optimal vitamin D status may have potential benefits for QoL in these patients.

Summer and Winter Seasonal Changes in Vitamin D Status of Captive Rhinoceros Iguanas (Cyclura cornuta)

Abstract Four long-term captive adult rhinoceros iguanas (Cyclura cornuta) on display at the Dallas Zoo (Dallas, TX) were maintained for several years in an outdoor enclosure in the summer and in a smaller indoor enclosure in the winter. While fully exposed to sunlight and given the opportunity to supplement their diet with live vegetation each summer, they were deprived of the benefits of full sun exposure, including ultraviolet B (UVB) exposure, and they received no dietary vitamin D for several months each winter. Maintained with this protocol, the animals seemed healthy and they reproduced. However, increasing awareness of the important role of UVB in vitamin D–mediated calcium metabolism and the potential health risk of UVB and vitamin D deprivation stimulated us to focus more on seasonal changes in vitamin D status and possible subtle changes in health status throughout winter. From September 2008 to October 2010, an 85% decline in the serum 25-hydroxyvitamin D3 (calcidiol) concentrations was measur...

Wintertime surgery increases the risk of conversion to hip arthroplasty after internal fixation of femoral neck fracture.

The study demonstrates that wintertime surgeries are associated with impaired fracture healing and increases the risk of conversion to hip arthroplasty after osteosynthesis of femoral neck fracture. Furthermore, the results raise the possibility of association between seasonal changes in vitamin D levels and impaired fracture healing of femoral neck fracture. Although the changes of vitamin D level and calcitropic hormones influencing bone metabolism are seasonal, the effect of seasons on hip fracture healing is unknown. We assessed the effects of seasonal periodicity on conversion to hip arthroplasty after primary osteosynthesis of femoral neck fracture. This nationwide retrospective observational cohort study involved 2779 patients aged ≥ 60 years who underwent internal screw fixation for primary femoral neck fracture and were discharged in 2000. Cases requiring conversion to arthroplasty during the 8-year follow-up derived from the Hungarian health insurance database were registered. Risk factors assessed included sex, age, fracture type, season of primary surgery and surgical delay. Competing-risks regression analysis was used for data analyses. During the observation period, 190 conversions to hip arthroplasty (6.8%) were identified, yielding an overall incidence of 19.5 per 1000 person-years. The crude incidence rates of conversions after osteosynthesis in winter, spring, summer and fall were 28.6, 17.8, 16.9 and 14.7 per 1000 person-years, respectively. Besides younger age, female sex and intracapsular fracture displacement, wintertime primary osteosynthesis significantly increased the risk of conversion (fall vs. winter, hazard ratio (HR): 0.50, 95% confidence interval [95% CI 0.33-0.76]; spring vs. winter, HR: 0.63, [95% CI 0.44-0.92]; summer vs. winter, HR: 0.62, [95% CI 0.42-0.91]). Our study demonstrate that wintertime primary osteosynthesis increases the risk of conversion surgeries. The results may help improving the outcome of primary fixation of femoral neck fractures.

Vitamin E improves growth of collared flycatcherFicedula albicollisyoung: a supplementation experiment

In altricial birds, the quantity and quality of food provided by parents is a crucial determinant of nestling performance. Vitamin E is an important micronutrient with various physiological functions, including a positive role in the antioxidant system. Sufficient intake of vitamin E has been shown to condition normal avian development in poultry, yet, our knowledge of the role of vitamin E in free‐living birds is limited. Thus, we experimentally examined the effects of vitamin E on nestling development in the collared flycatcherFicedula albicollis. We supplemented nestlings with vitamin E and evaluated their growth and survival till fledging. Increased availability of vitamin E did not affect body mass, wing length or survival, but improved tarsus growth. The effect of supplementation on tarsus length changed over season and with initial body mass. Supplemented nestlings that were smaller at hatching and those that hatched later in the season grew longer tarsi compared to the control. Our results suggest that 1) vitamin E may be limiting for the development of collared flycatcher nestlings, 2) seasonal changes of vitamin E availability may affect breeding success of collared flycatchers, and 3) increased income of vitamin E may improve growth of nestlings with bad start in life.

Seasonal changes in vitamin D status among Danish adolescent girls and elderly women: the influence of sun exposure and vitamin D intake

To determine seasonal variation in vitamin D status in healthy Caucasian adolescent girls and elderly community-dwelling women living in Denmark, and to quantify the impact of sun exposure and intake on the seasonal changes in vitamin D status. A 1-year longitudinal observational study of 54 girls (11-13 years) and 52 women (70-75 years). The participants were examined three times (winter-summer-winter). Serum 25-hydroxyvitamin D (S-25OHD) concentration and vitamin D intake were measured at each visit. Sun exposure was measured during summer. S-25OHD concentrations (winter, summer, winter) were median (25, 75 percentiles) 23.4 (16.5, 36.4), 60.3 (42.7, 67.7), 29.5 (22.2, 40.4) and 47.2 (27.3, 61.1), 67.3 (35.1, 79.2), 50.5 (32.7, 65.5)nmol/l for girls and women, respectively. The usual sun habits were determinant (P=0.002) for change in vitamin D status from winter to summer. Vitamin D intake from supplements (P<0.0001) and diet (P=0.002) were determinants for change in vitamin D status from summer to winter. Winter vitamin D status of 50 nmol/l is achievable when vitamin D status the previous summer was ≈ 100 nmol/l. If summer vitamin D status is only ≈ 60 nmol/l, vitamin D status the following winter would be ≈ 28 nmol/l. Low vitamin D status among adolescent girls and elderly women during two consecutive winter seasons, improved vitamin D status during the summer and better vitamin D status in women than in girls was found. The estimations show that a summer S-25OHD concentration ≈ 100 nmol/l is needed to achieve a concentration of ≈ 50 nmol/l the following winter.

Study of vitamin D status of rheumatoid arthritis patients Rationale and design of a cross-sectional study by the osteoporosis and metabolic bone diseases study group of the Italian Society of Rheumatology (SIR)

The fundamental role of Vitamin D has been long known in regulating calcium homeostasis and bone metabolism. An increased contribution of Vitamin D was recently described in association with a lower incidence of Rheumatoid Arthritis (RA). This must not be surprising, as the immunomodulating effects of Vitamin D are clear, which have been attributed protective effects in autoimmune disorders such as some chronic inflammatory bowel diseases, multiple sclerosis and type I diabetes. An interaction was suggested between Vitamin D metabolism and inflammation indexes through mediation of TNF-alpha which is also especially involved in osteoclastic resorption and therefore in bone loss processes. Some preliminary data would indicate an association between seasonal changes of Vitamin D serum levels, latitude and disease activity (DAS28) in RA patients. Consequently, the Osteoporosis and Metabolic Bone Diseases Study Group of SIR believes that there are grounded reasons for assessing the Vitamin D status of RA patients in order to investigate whether this is to be related to physiopathological and clinical aspects of disease other than those of bone involvement. Primary end point of the study will be to assess the levels of 25 OH Vitamin D in RA patients. Secondary endpoints will include correlation with dis-ease activity, densitometry values and bone turnover. The cross-sectional study will enroll patients of both sex genders, age ranging between 30 and 75 years according to the 1988 ACR criteria, onset of symptoms at least 2 years prior to study enrollment. Patients will be excluded suffering from osteo-metabolic diseases, liver and kidney insufficiency and those administered Vitamin D boli in the previous 12 months. Disease activity will be evaluated with the HAQ. Hemato-chemical tests and femoral and lumbar bone densitometry will be performed, unless recently undergone by patients. Blood levels of 25 OH C Vitamin D and PHT and of the two bone remodelling markers (bone alkaline phosphatase and serum CTX) will be measured, as well. Patient enrollment will start on February 2007 and will last 4 months. By the end of 2007 the study will be concluded and results will be published.

Seasonal variation of vitamin D and HbA1c levels in patients with type 1 diabetes mellitus in the Middle East

IntroductionThe discovery that many tissues express the vitamin D receptor and are able to transform the 25-hydroxyvitamin D into 1,25-dihydroxyvitamin D (active metabolite) has led to the hypothesis that vitamin D could have a role in the pathogenesis and prevention of diabetes mellitus. Accumulating evidence has linked vitamin D deficiency with immunological disturbance in type 1 diabetes mellitus. Several epidemiological studies have shown lower serum 25-hydroxyvitamin D concentrations in diabetic individuals compared to nondiabetic individuals.Patients and methodsA total of 105 Lebanese patients with type 1 diabetes mellitus were recruited. Levels of HbA1c and vitamin D were recorded during two phases with phase 1 being the period from June–September 2009 and phase 2 from January–April 2009.ResultsVitamin D levels at the end of sunny season (phase 2), reflecting the previous sunny months, were found to be higher than in the early summer season (phase 1) reflecting the previous cloudy months season, with a mean change of 0.70 ± 6.87 ng/mL (P = 0.029). HbA1c levels were higher in phase 2 than in phase 1 with an increase of 0.175% ± 1.46% (P = 0.113).ConclusionVitamin D levels were higher at the end of the sunny season than at the end of cloudy season. HbA1c was also lower (but not significantly so) in the early summer season (cloudy months). There was a weak correlation between seasonal changes of vitamin D levels and the control of blood glucose as monitored by HbA1c in a cohort of Lebanese patients with type 1 diabetes mellitus.

Modelling the seasonal variation of vitamin D due to sun exposure

The current interest in vitamin D as a preventive agent in many chronic diseases has led to a reappraisal of adequate sun exposure. Yet just what constitutes adequacy remains to be clearly defined and validated. To do this requires an understanding of how behaviour outdoors during the year translates into seasonal changes in vitamin D status. To develop a model for estimating the changes in serum 25-hydroxyvitamin D [25(OH)D] levels as a consequence of sun exposure throughout the year. A novel mathematical model is described that incorporates the changes in serum 25(OH)D following a single, whole-body exposure to solar ultraviolet radiation with daily sun exposure in order to estimate the annual variation in serum 25(OH)D. The model yields results that agree closely with measured data from a large population-based study. Application of the model showed that current advice about 10-20 min of daily sun exposure during the summer months does little in the way of boosting overall 25(OH)D levels, while sufficient sun exposure that could achieve a worthwhile benefit would compromise skin health. There is little in the way of public health advice concerning the benefits of sun exposure that can be given as an effective means of maintaining adequate vitamin D levels throughout the year. Instead it would seem safer and more effective to fortify more foods with vitamin D and/or to consider the use of supplements during the winter months. Messages concerning sun exposure should remain focused on the detrimental effects of excessive sun exposure and should avoid giving specific advice on what might be 'optimal' sun exposure.

Simvastatin Does Not Affect Vitamin D Status, but Low Vitamin D Levels Are Associated with Dyslipidemia: Results from a Randomised, Controlled Trial

Objectives. Statin drugs act as inhibitors of the 3-hydroxy-3methylglutaryl coenzyme A (HMG-CoA) reductase enzyme early in the mevalonate pathway, thereby reducing the endogenous cholesterol synthesis. In recent studies, it has been suggested from epidemiological data that statins also may improve vitamin D status, as measured by increased plasma 25-hydroxyvitamin D (25OHD) levels. We now report the results from a randomised controlled trial on effects of simvastatin on plasma 25OHD levels. Design and Methods. We randomised 82 healthy postmenopausal women to one year of treatment with either simvastatin 40 mg/d or placebo and performed measurement at baseline and after 26 and 52 weeks of treatment. The study was completed by 77 subjects. Results. Compared with placebo, plasma levels of cholesterol and low-density lipoproteins decreased in response to treatment with simvastatin, but our study showed no effect of simvastatin on vitamin D status. However, plasma levels of triglycerides were inversely associated with tertiles of plasma 25OHD levels and changes in plasma triglycerides levels correlated inversely with seasonal changes in vitamin D status. Conclusion. Our data do not support a pharmacological effect of statins on vitamin D status, but do suggest that vitamin D may influence plasma lipid profile and thus be of importance to cardiovascular health.

Nutritional quality of organic, conventional, and seasonally grown broccoli using vitamin C as a marker

Organically labeled vegetables are considered by many consumers to be healthier than non-organic or ‘conventional’ varieties. However, whether the organic-labeled vegetables contain more nutrients is not clear. The purpose of this study is to examine the nutritional quality of broccoli using vitamin C, a fragile and abundant nutrient, in broccoli as a biomarker. The vitamin C content was assayed (2,6-dichlorophenolindophenol method) in broccoli samples obtained from supermarkets that are considered the point of consumer consumption. These samples were obtained during different seasons when the broccoli could be either harvested locally or shipped far distances. The findings indicate that vitamin C could be used as a marker under a controlled laboratory environment with some limitations and, although the vitamin C content of organically and conventionally labeled broccoli was not significantly different, significant seasonal changes have been observed. The fall values for vitamin C were almost twice as high as those for spring for both varieties (P=0.021 for organic and P=0.012 for conventional). The seasonal changes in vitamin C content are larger than the differences between organically labeled and conventionally grown broccoli.

Seasonal Changes in Vitamin D Status and Bone Turnover in Healthy Irish Postmenopausal Women

To examine the effect of season on biochemical markers of bone turnover in 51-to 75-year-old Irish women and to investigate whether such changes are related to vitamin D status. Longitudinal observational study. Cork, Ireland (52 degrees N). 76 apparently healthy, free-living postmenopausal women (aged 51-75 years), not taking any medication and free from any condition likely to affect vitamin D status or calcium/bone metabolism. Serum 25-hydroxyvitamin D [S-25(OH)D] showed a clear seasonal variation with significantly higher (p < 0.001) values during late summer than late winter. Both urinary pyridinoline (Ur-Pyr) (p < 0.01) and deoxypyridinoline (Ur-Dpyr) (p < 0.001), but not serum parathyroid hormone or osteocalcin, showed a marked seasonal variation with lowest values during late-summer. Stratifying women into those with S-25(OH)D levels > or = or <50 nmol/L (vitamin D adequate and inadequate, respectively) during late-winter, showed that Ur-Pyr and Ur-Dpyr in both groups were significantly (p < 0.05) lower during late summer, and the magnitude of the reduction from winter to summer was similar in both groups. Seasonal changes in bone resorption markers appeared to be linked to seasonal changes in vitamin D status. Further research is needed to investigate the impact of these changes on risk of bone loss and fracture.

Seasonal Changes of Vitamin A and Beta-Carotene Levels of Serum and Liver in Holstein Cows

In present study seasonal changes of serum vitamin A and beta-carotene levels in 342 cows and liver levels of vitamin A and beta-carotene in 371 cows was investigated in a slaughterhouse around Tehran (Iran) between November1996- October 1997. We also selected animals from two sexes and divided them to the 5 age groups ( less than 2, 2-3, 3-4, 4-5 years old and more than 5 years old) . A simple and cheep method (spectrophotometry) was used for measuring vitamin A and beta-carotene. The results were analyzed statistically by multifactorial repeated measures (ANOVA), multiple-regression and Pearson's correlation. Results showed that the values of mean of liver and serum vitamin A levels and liver levels of beta-carotene were within normal range (189.3 µg/gr, 67.2 µg/dl and 21.1 µg/gr respectively). These values in different seasons, age groups and two sexes were normal, too. While serum levels of beta-carotene concentration (85.5 µg/dl) was lower than normal range. Results also showed that liver vitamin A and liver and serum beta-carotene in female were significantly more than male's but there wasn't there wasn't significant difference between male and female serum vitamin A. In different age groups significant difference was seen only in liver vitamin A (maximum in cows more than 5 years old and minimum in cows less than two years old). These findings are just in accordance with results of previous studies. Serum vitamin A in winter and serum beta-carotene in autumn was significantly higher than other seasons. These finding are different with similar study that performed in Poland. There wasn't significant difference between seasons liver vitamin A and beta-carotene. Reference

Beta-Carotene and Vitamin A Content in Blood Plasma and the Liver of Slaughter Buffaloes in Different Seasons of the Year in Ahvaz (Iran)

Vitamin A is one of the most important fat-soluble vitamins. Because of its particular role in different tissues and organs, in deficiency conditions various clinical signs are seen. In addition sometimes the marginal deficiency is present and clinical signs are not visible but performance defects such as infertility is seen. In some regions of Iran, buffalo is breading for production of milk and meat. In large animal, much study about beta-carotene and vitamin A is done in cow and information about buffalo is little. In present study, seasonal changes of vitamin A and beta-carotene in serum and liver of 120 buffaloes was investigated in Ahvaz slaughterhouse (Iran), between May 1998-April 1999. We, also, selected animals from 2 sexes and divided them to the 5 age groups ( less than 2 , 2-3 , 3-4, 4-5 and more than 5 yrs old). Spectrophotometery was used for measuring vitamin A and beta-carotene. The results were analyzed statistically with multifactorial repeated measures ( ANOVA) and Pearson's correlations. Results showed that the values of mean of serum and liver vitamin A and serum and liver beta-carotene. (69.01 ± 2.23 µg/dl, 111.99 ± 6.42 µg/gr 21.43 ± 2.21 µg/dl, 23.19 ± 2.23 µg/gr respectively) are similar to normal ranges in cows. These values in different seasons, age groups and 2 sexes were normal, too. There wasn't significant difference between vitamin A and beta- carotene values of the serum and livers for both the 2 sexes and age groups. We couldn't find any similar study about the effect of sex and age groups on vitamin A and betacarotene content in Buffalo. Rather, these findings are not in accordance with the results of previous studies in cow. However, the was significant seasonal variations in serum vitamin A ( max in autumn and min in spring) and liver vitamin A ( max in spring and min in winter). The difference between seasons serum vitamin A is similar to those reported in similar studies performed in Yugoslavia. There wasn't significant difference between different seasons serum and liver beta carotene .

Seasonal changes in calciotropic hormones, bone markers, and bone mineral density in elderly women.

Seasonal variation of serum vitamin D metabolites, PTH, bone turnover markers, and bone mineral density (BMD), adjusted for confounding variables, was studied in a cross-sectional population of 251 ambulatory elderly women aged 65-77 yr. A significant (P < 0.05) seasonal change was observed in serum 25 hydroxyvitamin D (25OHD), bone resorption marker (urine N-telopeptide), and BMD of the spine, total body, and mid-radius. Serum 25OHD was significantly lower (P < 0.05) in winter (December, January, February, March) compared with summer (June, July, August, September), with the nadir in February (68.4 +/- 6.74 nmol/liter) and the zenith in August (85.6 +/- 5.12 nmol/liter). Mean serum PTH levels were higher in winter when serum 25OHD was low, and mean serum PTH was lower in summer when serum 25OHD was high, although the seasonal change in serum PTH was not significant. The change in serum 1,25-dihydroxy vitamin D(3) paralleled that of serum 25OHD levels, but the seasonal effect was not significant. Mean 24-h urine N-telopeptide showed a significant seasonal change (P < 0.05); it was about 24% higher in February (zenith) compared with that in August (nadir). The zenith month of urine N-telopeptide levels corresponded to the nadir month of serum 25OHD levels and vice versa. A significant (P < 0.05) inverse correlation was observed between 24-h urine N-telopeptides and serum 25OHD levels. There was a significant (P < 0.05) seasonal change in mean BMD of spine, total body, and mid-radius. These changes paralleled those in serum 25OHD levels. Spine BMD was 8.4% higher in August (zenith) compared with that in February (nadir), whereas total body BMD and mid-radius BMD were 6.1 and 7.6% higher, respectively, in July (zenith) compared with that in January (nadir). There was a nonsignificant increase of 3.6% in total hip BMD. In summary (see Fig. 5), the seasonal changes in vitamin D metabolism in elderly women are closely associated with small changes in serum PTH, changes in bone resorption, and BMD.

Seasonal variation in glycated haemoglobin in diabetics.

Good control of blood glucose concentration in insulin-dependent diabetics leads to fewer complications. Monitoring of glucose control is therefore central to the management of patients with diabetes. This is achieved both by the frequent measurement of blood glucose concentrations and by the measurement of blood glycated haemoglobin (sometimes referred to as haemoglobin A1c (HbA1c)). There have been a few isolated reports that glycated haemoglobin is subject to a seasonal variation in diabetics, both in children in Britain and in adults in Sweden. This is clearly important in interpreting changes in glycated haemoglobin in response to therapeutic interventions. Here we report that glycated haemoglobin in a British adult diabetic population is subject to seasonal variation. During a study investigating the effect of clinical glycated haemoglobin measurement on diabetic control (to be reported), it was noticed that there was an overall worsening of diabetic control (as assessed by glycated haemoglobin measurement) over the ®rst 6 months of the study (autumn 1995 to spring 1996), suggesting that there might be a systematic effect. Patients (both type 1 and type 2 diabetics) attending the diabetic clinic were therefore followed for a further 2 years. A total of 6721 results on 1295 mainly Caucasian patients [54% male, 51% type 1 diabetics aged 52+11 years, mean+standard deviation (SD)] were obtained using a dedicated cation exchange high-performance liquid chromatography (HPLC) system (the `Diamat’, Biorad Ltd, Hemel Hempstead, UK). Each patient provided an average of 5 2 samples (range 1±6, SD 2 3) at approximately 3-, 6or 12-month intervals over a 2-year period. The results (see Fig. 1) clearly show a seasonal variation, with a maximum in the spring (March, April, May) and a nadir in the autumn (September, October, November). The averages+SD for the autumn months of 1995, 1996 and 1997 during the study were 8 52+1 53 (n=783), 8 57+1 6 (n=695) and 8 51+1 6 (n=608). For the spring months of 1996 and 1997 they were 9 21+1 7 (n=623) and 9 04+1 7 (n=578). The differences between each autumn and each spring average glycated haemoglobin were all highly statistically signi®cant (P50 0001, Student’s unpaired two-tailed t-test). There is no reason to suppose that by chance more well controlled diabetics were seen in the spring than in the autumn, although if this were to be the case it would confound the results. The fact that two complete cycles of peaks and troughs were found also argues against this being a chance ®nding. During this period there was no change in the performance of the assay [the range of the monthly percentage coef®cients of variation (%CVs) for the low control at a glycated haemoglobin of 5 4% was 2 3±4 3, and for the high control at a glycated haemoglobin of 10 0% was 1 2±2 3]. These results are in broad agreement with previous studies in British children, which showed a peak in February and a trough in August, and in Swedish adults, which showed a peak in January and a trough in July, although the peaks and troughs observed in the present study occurred a little later. These results are most easily interpreted as there being a seasonal variation in blood glucose levels. It is interesting to note that the peak glycated haemoglobin found here was in the spring. Glycated haemoglobin is affected by the average of the blood glucose for about the previous 3 months. This would have extended into the previous winter months, the season of increased infections which would be expected to worsen diabetic control. Other seasonal factors, such as seasonal food availability, the amount of exercise undertaken or the seasonal changes in vitamin D levels, might also be important. These factors will necessarily vary from year to year, and so it is not surprising that the characteristics of the spring peaks are not identical. It has recently been shown in a cohort study of 21 healthy females that glycated Short Report Ann Clin Biochem 2001; 38: 59±60

Seasonal Changes of Vitamin C, Sugar and Organic Acid in "Konatsu Mikan", New Summer Orange (Citrus Tamurana)

Seasonal Changes of Vitamin C, Sugar and Organic Acid in "Konatsu Mikan", New Summer Orange (Citrus Tamurana)