title: 25-Hydoxyvitamin D levels among healthy Saudi Arabian women. Calcium Absorption Varies within the Reference Range for Serum 25-Hydroxyvitamin D Vitamin D status in healthy Moroccan men and women aged 50 years and older: a cross-sectional study Associations of vitamin D status with bone mineral density, bone turnover, bone loss and fracture risk in healthy postmenopausal women. The OFELY study. The levels of bone turnover markers in Chinese postmenopausal women: Peking Vertebral Fracture study The effects of calcitriol on falls and fractures and physical performance tests Vitamin D and skin physiology: a D-lightful story. EMAS position statement: Vitamin D and postmenopausal health. Vitamin D Insufficiency Among Postmenopausal Women in Urban and Rural Areas in Guilan, Northern Iran Vitamin D supplementation increases calcium absorption without a threshold effect.
abstract: OBJECTIVE To assess the serum level of 25 hydroxyvitamin D 25OHD  among healthy Saudi Arabian women living in the eastern province . METHODS A cross-sectional r and omized study was conducted between February 1st 2008 and May 31st 2008 at the King Fahd University Hospital , Al-Khobar , Kingdom of Saudi Arabia in 200 Saudi women between 25 - 35 years group 1 and women of > or = 50 years group 2 .  Clinical examination , laboratory tests , a complete blood picture , serum calcium , phosphorous , alkaline phosphatase , parathormone , and the serum levels of 25OHD levels were carried out . Data on lifestyle , dietary , and demographic question naires were collected . Vitamin D was defined as deficient with serum level < 50 nmol/L , insufficient between 52 - 72 nmol/L , and normal as 75nmol/L. RESULTS In group 1 , 70 % of women had normal 25OHD , and in women of group 2 , 45 % had normal levels of 25OHD . Alkaline phosphatase and parathormone levels were significantly higher in women with low vitamin D levels . Sun exposure and consumption of dairy products were minimal . CONCLUSION Vitamin D deficiency among healthy young Saudi women of 25 - 35 years was 30 % and 55 % in women of > or = 50 years . This study indicates that hypovitaminosis D is common in young and postmenopausal women . Efforts are require to augment and encouraged women for adequate exposure to sunlight and increased intake of fortified vitamin D products to maintain skeletal health Background : Calcium absorption is generally considered to be impaired under conditions of vitamin D deficiency , but the vitamin D status that fully normalizes absorption is not known for humans . Objective : To quantify calcium absorption at two levels of vitamin D repletion , using pharmacokinetic methods and commercially marketed calcium supplements . Design : Two experiments performed in the spring of the year , one year apart . In the first , in which participants were pretreated with 25-hydroxyvitamin D ( 25OHD )  , mean serum 25OHD concentration was 86.5 nmol/L ; and in the other , with no pretreatment , mean serum concentration was 50.2 nmol/L. Participants received 500 mg oral calcium loads as a part of a st and ard low calcium breakfast . A low calcium lunch was provided at mid-day . Blood was obtained fasting and at frequent intervals for 10 to 12 hours thereafter . Methods : Relative calcium absorption at the two 25OHD concentrations was estimated from the area under the curve ( AUC ) for the load-induced increment in serum total calcium . Results : AUC9 ( ± SEM ) , was 3.63 mg hr/dL ± 0.234 in participants pretreated with 25OHD  and 2.20 ± 0.240 in those not pretreated ( P < 0.001 ) . In brief , absorption was 65 % higher at serum 25OHD levels averaging 86.5 nmol/L than at levels averaging 50 nmol/L ( both values within the nominal reference range for this analyte ) . Conclusions : Despite the fact that the mean serum 25OHD level in the experiment without supplementation was within the current reference ranges , calcium absorptive performance at 50 nmol/L was significantly reduced relative to that at a mean 25OHD level of 86 nmol/L. Thus , individuals with serum 25-hydroxyvitamin D levels at the low end of the current reference ranges may not be getting the full benefit from their calcium intake . We conclude that the lower end of the current reference range is set too low Summary This study aim ed to compare the  vitamin D status  in healthy Moroccan men and women aged 50 years and older . A total of 186 Moroccan women and 68 men , who had no previous diagnosis of osteoporosis , were recruited prospect ively . We found in this study a high prevalence of hypovitaminosis D with no difference between men and women . Purpose The main purpose of this study was to describe and compare the  vitamin D status , parathormone , calcium , and phosphate  of healthy Moroccan men and women aged 50 years and older . Methods We conducted two cross-sectional studies , in postmenopausal women from October 2008 to November 2009 and in men over 50 years old , from December 2009 to August 2010 . A total of 186 Moroccan women and 68 men , who had no previous diagnosis of osteoporosis , were recruited prospect ively . For the definition of hypovitaminosis D , the preferred level for 25-hydroxyvitamin D ( 25(OH)D ) insufficiency , which is now recommended by many experts , is 30 ng/mL ( 75 nmol/L ) , and the levels below 10 ng/ml ( 25 nmol/L ) indicate deficiency . Results The prevalence of vitamin D deficiency in men and women was 4.4 and 8.6 % , respectively , and the prevalence of vitamin D(25(OH ) D ) insufficiency in men and women were 85.2 and 77.4 % , respectively . In men and women , no correlations were found between intact parathormone ( PTHi ) and 25(OH ) D ( r = 0.056 ) . Conclusions Despite a sunny environment , we found in this study a high prevalence of hypovitaminosis D ( insufficiency + deficiency ) in Moroccan men over 50 years old and postmenopausal women INTRODUCTION Vitamin D status is considered as an important determinant of bone health but supplementation trials with vitamin D(3 ) have yielded conflicting results . The aim of this study was to investigate the associations between serum 25-hydroxyvitamin D ( 25-OH D ) , bone turnover markers , bone mineral density ( BMD ) , radius bone loss and incidence of fracture in postmenopausal women . METHODS 669 postmenopausal women ( mean age : 62.2 years ) belonging to a population -based cohort were followed prospect ively for a median of 11.2 years . At baseline , 25-OH D levels , BMD , bone turnover markers and clinical risk factors of osteoporosis were assessed . BMD loss at the radius was estimated by annual measurements of BMD and all incident fractures which occurred in 134 women were confirmed by radiographs . RESULTS 73 % and 35 % of women had serum 25-OH D levels below 75 and 50 nmol/l which correspond respectively to the median and lowest optimal values recently proposed for fracture prevention . 11 % of women had levels below 30 nmol/l . Serum 25-OH D correlated modestly with intact PTH ( r(2)=0.023 , p<0.0001 ) , but not with bone turnover markers or BMD at the hip and radius after adjustment for age . When levels of 25-OH D were considered as a continuous variable , there was no significant association between 25-OH D levels and radius BMD loss or fracture risk . After adjustment for age , there was no significant difference in incidence of fracture , BMD , radius BMD loss , bone turnover markers , grip strength and the percentage of fallers in the previous year between women with 25-OH D levels below or above 75 , 50 or 30 nmol/l . CONCLUSIONS In a population of home-dwelling healthy postmenopausal women with few of them with severe vitamin D deficiency , vitamin D status may not be an important determinant of bone health Objective : The aim of this study was to evaluate serum N-aminoterminal propeptide of type I collagen ( P1NP ) , C-terminal telopeptide of type I collagen ( & bgr;-CTX ) , and vitamin D status in healthy Chinese postmenopausal women . The study was also design ed to investigate their possible relationships with osteoporosis phenotypes . Methods : A community-based population of 1,724 postmenopausal women in Beijing was r and omly selected .  Serum bone turnover markers and 25-hydroxyvitamin D [ 25(OH)D ]  were tested by an automated Roche electrochemiluminescence system . Dual-energy x-ray absorptiometry was used to measure bone mineral density ( BMD ) . Results : The mean ( SD ) values of serum & bgr;-CTX and P1NP were 0.439 ( 0.210 ) and 56.7 ( 27.9 ) ng/mL , respectively . The 25(OH)D level of postmenopausal women in Beijing was remarkably low ( 13.2 ± 5.4 ng/mL ) . Serum & bgr;-CTX and P1NP levels were negatively correlated with BMDs of lumbar spine , femoral neck , and total hip ( all P < 0.01 ) . The cubic regression model better fitted the relationships of BMD and bone turnover markers . Serum & bgr;-CTX levels were significantly higher in women with sustained osteoporotic fracture or vertebral fracture ( P = 0.006 and 0.012 , respectively ) . No association between P1NP and fracture or vertebral fracture was detected . The same situation applied to 25(OH)D. 25(OH)D was negatively correlated with & bgr;-CTX and P1NP ( r = −0.073 and −0.088 , P = 0.002 and < 0.001 , respectively ) . Conclusions : Serum & bgr;-CTX and P1NP levels were negatively correlated with BMD . & bgr;-CTX was significantly higher in postmenopausal women with sustained fracture or vertebral fracture . Vitamin D deficiency was highly prevalent in postmenopausal women in Beijing There is an increase in the incidence of falls with aging and about 10 % of falls lead to fractures . Nearly all hip fractures are due to falls and hip fractures are the most severe of the osteoporotic fractures because they lead to a 20 % mortality rate and a loss of independent living in 50 % of cases . Although there are multiple factors associated with falls , our interest is the role that vitamin D metabolism plays in the pathogenesis of falls . Recent clinical trials show that both vitamin D and the metabolite calcitriol reduce the number of falls by 30 - 40 % in elderly subjects . This should also reduce the number of fractures . In European studies , the decrease in falls could be attributed to an improvement in the muscle weakness that often accompanies vitamin D deficiency . However , in the studies using calcitriol there was no vitamin D deficiency , so the mechanism of its efficacy is less clear . It could be due to increased muscle strength , an improvement in the neurological control of balance or both . Underst and ing these mechanisms would allow us to search for analogs of vitamin D that act more selectively on muscle and on the central nervous system Throughout evolution , exposure to sunlight and the photo synthesis of vitamin D(3 ) in the skin has been critically important for the evolution of l and vertebrates . During exposure to sunlight , the solar UVB photons with energies 290 - 315 nm are absorbed by 7-dehydrocholesterol in the skin and converted to previtamin D(3 ) . Previtamin D(3 ) undergoes a rapid transformation within the plasma membrane to vitamin D(3 ) . Excessive exposure to sunlight will not result in vitamin D intoxication because both previtamin D(3 ) and vitamin D(3 ) are photolyzed to several noncalcemic photoproducts . During the winter at latitudes above approximately 35 degrees , there is minimal , if any , previtamin D(3 ) production in the skin . Altitude also has a significant effect on vitamin D(3 ) production . At 27 degrees N in November , very little ( approximately 0.5 % ) previtamin D(3 ) synthesis was detected in Agra ( 169 m ) and Katm and u ( 1400 m ) . There was an approximately 2- and 4-fold increase in previtamin D(3 ) production at approximately 3400 m and at Everest base camp ( 5300 m ) , respectively . Increased skin pigmentation , application of a sunscreen , aging , and clothing have a dramatic effect on previtamin D(3 ) production in the skin . It is estimated that exposure in a bathing suit to 1 minimal erythemal dose ( MED ) is equivalent to ingesting between 10,000 and 25,000 IU of vitamin D(2 ) . The importance of sunlight for providing most humans with their vitamin D requirement is well documented by the seasonal variation in circulating levels of 25-hydroxyvitamin D [ 25(OH)D ] . Vitamin D deficiency [ i.e. , 25(OH)D < 20 ng/ml ] is common in both children and adults worldwide . Exposure to lamps that produce UVB radiation is an excellent source for producing vitamin D(3 ) in the skin and is especially efficacious in patients with fat malabsorption syndromes . The major cause of vitamin D deficiency globally is an underappreciation of sunlight 's role in providing humans with their vitamin D(3 ) requirement . Very few foods naturally contain vitamin D , and those that do have a very variable vitamin D content . Recently it was observed that wild caught salmon had between 75 % and 90 % more vitamin D(3 ) compared with farmed salmon . The associations regarding increased risk of common deadly cancers , autoimmune diseases , infectious diseases , and cardiovascular disease with living at higher latitudes and being prone to vitamin D deficiency should alert all health care professionals about the importance of vitamin D for overall health and well being INTRODUCTION There is emerging evidence on the widespread tissue effects of vitamin D. AIMS To formulate a position statement on the role of vitamin D in postmenopausal women . MATERIAL S AND METHODS Literature review and consensus of expert opinion . RESULTS AND CONCLUSIONS Epidemiological and prospect i ve studies have related vitamin D deficiency with not only osteoporosis but also cardiovascular disease , diabetes , cancer , infections and neurodegenerative disease . However the evidence is robust for skeletal but not nonskeletal outcomes where data from large prospect i ve studies are lacking . The major natural source of vitamin D is cutaneous synthesis through exposure to sunlight with a small amount from the diet in animal-based foods such as fatty fish , eggs and milk . Vitamin D status is determined by measuring serum 25-hydroxyvitamin D [ 25(OH)D ] levels . Optimal serum 25(OH)D levels are in the region of 30 - 90 ng/mL ( 75 - 225 nmol/L ) though there is no international consensus . Levels vary according to time of the year ( lower in the winter ) , latitude , altitude , air pollution , skin pigmentation , use of sunscreens and clothing coverage . Risk factors for low serum 25(OH)D levels include : obesity , malabsorption syndromes , medication use ( e.g. anticonvulsants , antiretrovirals ) , skin aging , low sun exposure and those in residential care . Fortified foods do not necessarily provide sufficient amounts of vitamin D. Regular sunlight exposure ( without sunscreens ) for 15 min , 3 - 4 times a week , in the middle of the day in summer generate healthy levels . The recommended daily allowance is 600 IU/day increasing to 800 IU/day in those aged 71 years and older . Supplementation can be undertaken with either vitamin D2 ( ergocalciferol ) or vitamin D3 ( cholecalciferol ) with monitoring depending on the dose used and the presence of concomitant medical conditions such as renal disease This study aim ed to describe vitamin D status in postmenopausal women in urban and rural areas in Guilan , northern Iran . Between October 2004 and February 2005 a group of 750 women older than 50 years was r and omly selected from urban and rural areas in Guilan . The participants were interviewed to collect data on age , educational level , body weight , height , employment status , reproductive history , medications , history of illness , and supplement use . Serum 25(OH ) D was measured in 646 women ( 427 in urban areas and 219 women in rural areas ) . Serum 25(OH ) D levels in urban and rural postmenopausal women were 18.5 ± 13.5 ng/ml and 22.9 ± 13.8 ng/ml ( P < 0.0001 ) , respectively . In urban and rural areas , 84.7 % and 79.5 % of the women had serum 25(OH ) D levels less than 30 ng/ml , respectively . In this study , serum vitamin D levels and prevalence of vitamin D insufficiency was related to educational level in urban women . The urban women in the lowest educational level ( < 5 years schooling ) had a better vitamin D status than other educational groups . This study showed that a high proportion of postmenopausal women living in Guilan province  had vitamin D insufficiency . Vitamin D inadequacy was more common in urban areas and especially in the upper social class . Supplement use and national strategies to prevent vitamin D insufficiency are strongly needed in this community BACKGROUND The maximal calcium absorption in response to vitamin D has been proposed as a biomarker for vitamin D sufficiency . OBJECTIVE The objective was to determine whether there is a threshold beyond which increasing doses of vitamin D , or concentrations of serum 25-hydroxyvitamin D [ 25(OH)D ] , no longer increase calcium absorption . DESIGN This was a placebo-controlled , dose-response , r and omized , double-blind study of the effect of vitamin D on calcium absorption in healthy postmenopausal women . Seventy-six healthy postmenopausal women were r and omly assigned to placebo or 800 IU ( 20 μg ) , 2000 IU ( 50 μg ) , or 4000 IU ( 100 μg ) vitamin D₃ for 8 wk . The technique of dual isotopes of stable calcium was used with a calcium carrier to measure calcium absorption at baseline and after 8 wk . RESULTS Seventy-one women with a mean ± SD age of 58.8 ± 4.9 y completed the study . The mean calcium intake was 1142 ± 509 mg/d and serum 25(OH)D was 63 ± 14 nmol/L at baseline . A statistically significant linear trend of an increase in calcium absorption adjusted for age and body mass index with increasing vitamin D₃ dose or serum 25(OH)D concentration was observed . A 6.7 % absolute increase in calcium absorption was found in the highest vitamin D₃ group ( 100 μg ) . No evidence of nonlinearity was observed in the dose-response curve . CONCLUSIONS No evidence of a threshold of calcium absorption was found with a serum 25(OH)D range from 40 to 130 nmol/L. Calcium absorption in this range is not a useful biomarker to determine nutritional recommendations for vitamin
target: Neither latitude , region of the world , nor laboratory methodology were found to be associated with the prevalence of hypovitaminosis
background: BACKGROUND Hypovitaminosis D is considered a global public health issue .
  Knowledge of its true dimensions will allow us to design interventions and plan preventive measures that can have a significant impact on human health .
  OBJECTIVES The aim of this study was to evaluate the prevalence of hypovitaminosis D , defined as a serum 25-hydroxyvitamin D concentration < 30 ng/ml , in postmenopausal women around the world , as well as to identify the potential associated factors .