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Published in final edited form as: Am J Hum Biol. 2015 Sep 8;28(2):181–185. doi: 10.1002/ajhb.22766

Validity of Self-Reported Vitamin D Deficiency among Midlife Arab Women Living in Qatar

Linda M Gerber 1, Ashley E Giambrone 1, Hala M Al-Ali 2, Mohamud A Verjee 2
PMCID: PMC4783299  NIHMSID: NIHMS757774  PMID: 26345363

Abstract

Objectives

This study evaluates the level of agreement between self-reported vitamin D deficiency and serum vitamin D measured within the previous calendar year.

Methods

In a study in which serum 25(OH)D levels were retrieved from electronic health records, 523 women were asked whether they considered themselves to have vitamin D deficiency. Serum vitamin D levels were categorized as vitamin D deficiency if serum 25(OH)D was less than 20 ng/ml and as insufficiency if less than 30 ng/ml. The kappa statistic was computed to assess the level of agreement between serum 25(OH)D level and self-report responses.

Results

Agreement between self-reported and measured 25(OH)D levels was poor. The kappa statistic was −0.041 when using a cutpoint of <20 ng/ml and −0.008 using the cutpoint of < 30 ng/ml. Among women with levels ≥ 20 ng/ml, 82.4% believed that they were vitamin D deficient, while 13.3% who were below <20 ng/ml did not self-report deficiency. Among women who did not report vitamin D deficiency, 46.3% (37/80) had levels <20 ng/ml while 82.5% (66/80) had levels < 30 ng/ml.

Conclusions

These findings suggest that, although the prevalence of 25(OH)D < 20 ng/ml and < 30 ng/ml was quite high (53.2% and 84.7%, respectively), there was little agreement between measured levels and self-report of vitamin D deficiency. This may be due to belief in this region that low levels of serum vitamin D is widespread. Better communication is needed between healthcare providers and patients regarding transmission of laboratory results.

Keywords: Vitamin D deficiency, serum 25(OH)D concentration, midlife, menopause, Qatar

Vitamin D is important for skeletal health and may also play a role in many other aspects of human health, including cardiovascular disease, diabetes, neuromuscular disease and cancer (IOM, 2011; LeBlanc et al, 2014; Pittas et al, 2010; Theodoratou et al 2014). Vitamin D levels are determined by measuring total serum concentration of 25-hydroxyvitamin D (25(OH)D). Different organizations have suggested various guidelines for defining vitamin D deficiency and insufficiency, with most agreeing that levels lower than 20 ng/ml are associated with bone health (IOM, 2011; LeBlanc, 2014). Guidelines recommended by The Endocrine Society also defined vitamin D levels below 20 ng/ml as deficient but added vitamin D insufficiency as vitamin D of 21–29 ng/ml (Holick et al, 2011).

Low levels of 25(OH)D are common globally and many review articles have documented the variation in suboptimal levels by country and by risk groups (Wahl et al, 2012; Mithal et al, 2009; Palacios and Gonzalez, 2014; Lips, 2010, van Schoor and Lips, 2011, Prentice, 2008, Hagenau et al, 2009, Holick, 2007). Writing on behalf of the International Osteoporosis Foundation, Mithal et al (2009) described 25(OH)D levels in 46 different countries for children and adults, by gender. In countries where data were available, the vast majority of countries had mean or median levels of 25(OH)D less than 30 ng/ml with many having levels less than 20 ng/ml. A systematic review of 103 articles published between 2003 and 2013 concluded that low vitamin D status was a global problem (Palacios and Gonzalez, 2014).

Vitamin D deficiency is especially prevalent in the Middle East and has been associated with cultural and religious factors, female gender, and dietary practices (Lips, 2010; Mithal et al, 2009). Limited sun exposure due to a style of dress that covers most of the body has been noted to relate to high rates of hypovitaminosis D (El-Hajj Fuleihan and Deeb, 1999; El-Sonbaty and Abdul-Ghaffer, 1996; Gannage-Yared et al, 2000, Lips, 2010).

Low levels of 25(OH)D have been reported to be especially low among women in the Middle East (Elshafie et al, 2012; Al-Mohaimeed et al, 2012; Palacios and Gonzalez, 2014). Low consumption of milk (Elshafie et al, 2012) as well as low dietary intake from all food sources have been reported in the Middle East (Bener et al, 2009; Lips 2007). The lack of vitamin D fortified food has also been suggested to contribute to widespread low 25(OH)D levels (Gannage-Yared et al, 2000; Badawi et al, 2012; Musaiger et al, 2011).

Women at midlife are at increased risk for low vitamin D levels (Malabanan and Holick, 2003). In Qatar, as in much of the Middle East, women are at increased risk for vitamin D deficiency due to lifestyle, genetics, obesity, and diet. Among health care professionals in Qatar, although the mean level of 25(OH)D was low in both males and females, females were found to have lower levels (Mahdy et al, 2010). However, another study conducted in Qatar among males and females aged 30 through 60 years found mean 25(OH)D levels to be uniformly low (El-Menyar et al., 2012).

The possible role of alleles associated with vitamin D level in Arabs has also been reported (Elkum et al, 2014). Obesity presents another risk factor since the body fat sequesters vitamin D. Qatar has a very high prevalence of overweight and obesity, estimated to be between two-thirds and three-quarters of all adults (Ng et al, 2010).

As a result of this increased risk and due to media and public health initiatives, many women may believe they are vitamin D deficient. The aim of this study is to evaluate, for a large cross-section of midlife women living in Qatar, the level of agreement between self-reported vitamin D deficiency and serum vitamin D levels measured within the previous calendar year.

METHODS

Study Population

The Study of Women’s Health in Qatar (SWIQ) is a two-phase, mixed methods study conducted in Doha, in the State of Qatar. Data for this study were derived from a cross-sectional study conducted from July 2011 through May 2012. Women were recruited from nine primary health centers. Participants were eligible for inclusion if they were between 40 and 60 years of age, were either of Qatari nationality or other Arab National, and were either Arabic or English speaking. Participants were excluded if they had a history of bilateral oophorectomy. Additional information has been provided in an earlier report (Gerber et al., 2014). The protocol and consent form were approved by the institutional review committees at Weill Cornell Medical College-Qatar and at Hamad Medical Corporation, Qatar.

Survey Instrument

The survey instrument was developed using the Study of Women’s Health Across the Nation (SWAN) survey as a foundation, was piloted by a trained moderator and assistant moderator, who were both culturally and linguistically matched to the focus group participants. The survey instrument was first developed in English, translated into Arabic and then back-translated into English to confirm the quality of the translation. Face-to-face interviews were conducted and consisted of demographic, reproductive, and medical history questions.

Measures

Medical History

Participants were asked whether or not they suffer from any of 13 illnesses including vitamin D deficiency. Responses were coded as yes or no.

Serum vitamin D levels

Serum 25(OH)D levels, measured by immunoassay, were retrieved from electronic health records. Documented levels measured within one calendar year of the interview were recorded and the level closest to the interview was used. Vitamin D levels were categorized for the purpose of this report as vitamin D deficiency if serum 25(OH)D was less than 20 ng/ml and as insufficiency if less than 30ng/ml.

Anthropometric measurements

Height and weight were assessed twice by physical examination by a technician. The average of each pair of assessments was used. Body mass index (BMI) was calculated as weight (in kilograms) divided by the square of height (in meters).

Menstrual status

Questions about menopausal status included: asking about the last menstrual cycle, whether menstruation had occurred in the previous 12 months, regularity of menstruation and whether cycles had changed in length. Menopausal status was categorized into premenopausal, perimenopausal, and postmenopausal. Women having a hysterectomy but at least one ovary were categorized separately.

Statistical Analysis

For each participant, accuracy of self-reported vitamin D deficiency was categorized into 4 groups, self-reported vitamin D deficiency “yes” and 25(OH)D < 20ng/ml, self-reported vitamin D deficiency “yes” and 25(OH)D ≥20ng/ml, self-reported vitamin D deficiency “no” and 25(OH)D as <20ng/ml, and self-reported vitamin D deficiency “no” and 25(OH)D as ≥20ng/ml. Accurate responses included both categories where the self-reported response and the measured 25(OH) agreed. Inaccurate responses included both categories where the self-reported response and the measured 25(OH) levels did not agree.

Characteristics of the study participants were described as standard summary statistics. Student’s t-test was used to assess differences in mean vitamin D level by reported vitamin D deficiency and reported vitamin D supplementation. The unweighted kappa statistic and 95% confidence limits were computed to assess the level of agreement between the dichotomized 25(OH)D levels and self-report values. Multivariable logistic regression analysis was performed to examine factors associated with accuracy of reporting vitamin D deficiency. Age, BMI, education, and menopause status were included in the model. BMI was categorized as <25, 25-<30, 30-<35, and ≥35. Given the small number of people with a normal BMI (<25), those that were overweight (25-<30) were used as the referent group. Women who had a hysterectomy were removed from the model due to a small sample size. The odds ratios, 95% confidence intervals, and p values of the covariates were reported. All p-values are two sided and evaluated at the 0.05 alpha level. All analyses were performed using SAS v9.3 (SAS Institute, Cary, NC).

RESULTS

The mean age of the 523 participants was 49.7 ± 5.5 years with approximately half between 40–49 years of age and half between 50–60 years (Table 1). The majority of women were pre- or peri-menopausal (63.9%, 334/523) with a mean BMI of 34.5 kg/m2 (± 6.0). The mean vitamin D level was 19.8 ng/ml (± 9.3).

Table 1.

Selected Characteristics of the Study Participants

Characteristics N %
Age group, yrs
 40–49 256 49.0
 50–60 267 51.1
Menopause status
 Premenopausal 123 23.5
 Perimenopausal 211 40.3
 Postmenopausal 175 33.5
 Hysterectomy 14 2.7
BMI 34.5 6.0
 <25 21 4.0
 20-<30 96 18.4
 30-<35 178 34.0
 ≥35 228 43.6
Education
 Less than university 280 53.5
 University graduate & above 243 46.5
Mean SD
Serum 25(OH)D, ng/ml 19.8 9.3
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Table 2 compares the mean serum 25(OH) D levels by the participants’ self report of vitamin D deficiency and whether or not they reported taking vitamin D supplements. The means are the same for those who reported vitamin D deficiency and for those who did not (p=0.52). Similarly, those who reported taking vitamin D supplements had levels not significantly higher from those who did not report taking supplements (p=0.37).

Table 2.

Mean levels of 25(OH)D by self report of vitamin D deficiency and vitamin D supplementation

Total Sample (n=523) 25(OH) D level (ng/ml) (mean +/− SD) P-value
Reported vitamin D deficiency 0.516
 Yes (N=443) 19.7 +/− 9.1
 No (N=80) 20.4 +/− 10.6
Reported taking vitamin D supplement 0.367
 Yes (N=146) 20.4 +/− 9.1
 No (N=377) 19.6 +/− 9.4
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The agreement between self-reported vitamin D deficiency and measured serum levels of 25(OH) D is reported in Table 3. The prevalence of 25(OH)D < 20 ng/ml was 53.2% (278/523) while the prevalence of self-reported deficiency was 84.7% (443/523). Agreement between self-reported vitamin D deficiency with measured levels < 20 ng/ml was very poor (kappa = −0.041, 95% CI=−0.100–0.019). Agreement was also poor when comparing self-reported vitamin D deficiency using the cutpoint of < 30 ng/ml (kappa = −0.008, 95% CI=−0.040, 0.023). Agreement between self-reported vitamin D deficiency and measured 25(OH)D levels <20 was also evaluated stratified by categories of age, BMI, education, and menopause status. Agreement within each stratum was close to zero (range of kappa coefficient from −0.07 to 0.06) with no statistically significant differences within strata. Even among women having levels ≥ 20 ng/ml, 82.4% (202/245) believed they were vitamin D deficient, while 13.3% who were below <20 ng/ml did not report deficiency. Among women who did not report vitamin D deficiency, 46.3% (37/80) had levels <20 ng/ml while and 82.5% (66/80) had levels < 30 ng/ml.

Table 3.

Self-reported vitamin D deficiency: accuracy in reporting vitamin D deficiency using measured 25(OH)D cutpoints < 20 ng/ml and < 30 ng/ml

Self-reported Vitamin D Deficiency
25(OH)D level Yes (N=443) No (N=80) P-value Kappa 95% CI
<20 ng/ml 241 (86.7) 37 (13.3) 0.179 −0.041 (−0.100, 0.019)
≥20 ng/ml 202 (82.4) 43 (17.6)
<30 ng/ml 376 (85.1) 66 (14.9) 0.589 −0.008 (−0.040, 0.023)
≥30 ng/ml 67 (82.7) 14 (17.3)
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Table 4 presents selected characteristics of the study participants, stratified by whether or not their response to self report of vitamin D deficiency was categorized as accurate or inaccurate. Accurate reports did not differ from inaccurate reports by age, BMI, or menopausal status. Among women with more education, inaccurate reports occurred more often than among women with less education (50.6% vs 41.4%, respectively) and mean levels of 25(OH)D were significantly greater for women who gave inaccurate reports when compared to women who gave accurate reports (25.0 ng/ml vs 15.3 ng/ml, respectively).

Table 4.

Selected characteristics of study participants by accuracy of self-reported vitamin D deficiency

Accurate (N=284) Inaccurate (N=239) P-value
Age 49.6 +/− 5.7 49.8 +/− 5.3 0.593
BMI 35.0 +/− 6.5 34.1 +/− 5.6 0.067
25(OH)D (ng/ml) 15.3 +/− 7.4 25.0 +/− 8.7 <.0001
Education 0.035
 Less than university 164 (58.6) 116 (41.4)
 University graduate & above 120 (49.4) 123 (50.6)
Menopause status 0.082
 Premenopausal 76 (61.8) 47 (38.2)
 Perimenopausal 104 (49.3) 107 (50.7)
 Postmenopausal 97 (55.4) 78 (44.6)
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The distributions of 25(OH)D among women reporting vitamin D deficiency are illustrated by accuracy status in Figure 1. There is a wide range of measured 25(OH)D levels among women reporting vitamin D deficiency. Women who reported they were vitamin D deficient but, in fact, had 25(OH)D levels ≥ 20 ng/ml had a mean 25(OH)D level of 27.6 ng/ml compared to 13.0 ng/ml among women who accurately reported vitamin D deficiency.

Figure 1.

Figure 1

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Distribution of serum 25-hydroxyvitamin D in women reporting vitamin D deficiency (n=443)

Among women who responded inaccurately, the majority (84.5%, 202/239) reported vitamin D deficiency but had measured 25(OH)D levels ≥ 20 ng/ml. Women who did not report vitamin D deficiency but had 25(OH)D levels <20 ng/ml did not differ by age, BMI, education and menopause status from women who reported vitamin D deficiency but had measured 25(OH)D levels ≥20 ng/ml (data not shown).

A multivariable logistic regression model predicting inaccuracy of reporting vitamin D deficiency is presented in Table 5. Level of education was a significant predictor of inaccuracy of reporting vitamin D deficiency (adjusted OR = 1.46; 95% CI = 1.02–2.10), after controlling for age, BMI, and menopause status. Menopause status was an additional independent predictor of reporting inaccuracy; perimenopausal women had significantly greater odds of reporting inaccurately than premenopausal women (adjusted OR = 1.65; 95% CI = 1.02–2.64).

Table 5.

Multivariable Logistic Regression Analyses Predicting Inaccuracy of Reporting Vitamin D Deficiency

Predictor Variable Adjusted Odds Ratio (95% CI) P
Age
 40–49 Reference
 50–60 1.13 (0.74–1.73) 0.573
BMI
 <25 Reference
 25-<30 0.96 (0.37–2.51) 0.934
 30-<35 0.97 (0.39–2.42) 0.941
 ≥35 0.73 (0.30–1.83) 0.506
Education
 Less than university Reference
 University graduate & above 1.46 (1.02–2.10) 0.038
Menopause status
 Premenopausal Reference
 Perimenopausal 1.65 (1.02–2.64) 0.040
 Postmenopausal 1.26 (0.72–2.22) 0.423
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DISCUSSION

This study confirms that low levels of serum 25(OH) D are quite prevalent in the Gulf region. This is one of the few reports among women in Qatar and the first to highlight these high prevalence rates in women aged 40–60 years.

Although the prevalence of low levels of 25(OH) D was found to be very high (53% using <20 ng/ml and 80% using <30 ng/ml) and self-report of vitamin D deficiency was also very high (85%), individuals did not accurately report their measured vitamin D status. Mean levels of 25(OH) D were similar among women reporting vitamin D deficiency and those not reporting vitamin D deficiency.

The majority of the women who responded inaccurately, reported having vitamin D deficiency when their measured OH(25)D levels were ≥ 20 ng/ml. These women were more often university graduates or above when compared with women who responded accurately. Higher education and perimenopausal status were both independent predictors of responding inaccurately, after controlling for age and BMI. Research to date has been limited relating objective to self-reported measures and the current findings support the need for further investigation in this area.

A limitation of this study was that only a single measure of serum 25(OH) D was obtained from the electronic record, although this reflects common clinical practice. These measures were obtained, however, within one year prior to the interviews with the participants, where in all likelihood, recommendations for supplementation were given.

There are many reports in the literature, both scientific and lay press, to heighten awareness to the low levels of vitamin D found in Arab women generally (Ardawi et al, Lips, 2007; Kazmi, gulfnews.com) and in Qatar in particular (Badawi et al, 2012; Alhamad et al, 2014). The results suggest that many women assume their level to be low, either because they do not know their vitamin D had been measured or they were not informed of their results. Better communication is needed between healthcare providers and patients regarding transmission of laboratory results.

Acknowledgments

Study funding was provided by the Qatar National Research Fund, National Priorities Research Program. Support was also provided by the Clinical Translational Science Center (CTSC), National Center for Advancing Translational Sciences (NCATS) grant #UL1-TR000457-06.

The authors express their gratitude to all the women who generously gave their time to participate in the Study of Women’s Health in Qatar and to Darine Dimassi and Nadia Omar for their assistance with this project.

Footnotes

The authors report no conflicts of interest.

LITERATURE CITED

  1. Alhamad HK, Nadukkandiyil N, El-Menyar A, Abdel Wahab L, Sankaranarayanan A, Al Sulaiti EM. Vitamin D deficiency among the elderly: insights from Qatar. Curr Med Res Opin. 2014 Jun;30(6):1189–96. doi: 10.1185/03007995.2014.900003. [DOI] [PubMed] [Google Scholar]
  2. Al-Mohaimeed A, Khan NZ, Naeem A, Al-Mogbel E. Vitamin D status among women in Middle East. Journal of Health Science. 2012;2(6):49–56. [Google Scholar]
  3. Ardawi MS, Qari MH, Rouzi AA, Maimani AA, Raddadi RM. Vitamin D status in relation to obesity, bone mineral density, bone turnover markers and vitamin D receptor genotypes in healthy Saudi pre- and postmenopausal women. Osteoporos Int. 2011 Feb;22(2):463–75. doi: 10.1007/s00198-010-1249-7. [DOI] [PubMed] [Google Scholar]
  4. Badawi A, Arora P, Sadoun E, Al-Thani AA, Al Thani MH. Prevalence of vitamin D insufficiency in Qatar: a systematic review. J Public Health Res. 2012;1(3):229–235. doi: 10.4081/jphr.2012.e36. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bener A, Al-Ali M, Hoffmann GF. High prevalence of vitamin D deficiency in young children in a highly sunny humid country: a global health problem. Minerva Pediatr. 2009;61(1):15–22. [PubMed] [Google Scholar]
  6. El-Hajj Fuleihan G, Deeb M. Hypovitaminosis D in a sunny country. N Engl J Med. 1999;340:1840–1841. doi: 10.1056/NEJM199906103402316. [DOI] [PubMed] [Google Scholar]
  7. El-Menyar A, Rahil A, Dousa K, Ibrahim W, Ibrahim T, Khalifa R, Abdel Rahman MO. Low vitamin D and cardiovascular risk factors in males and females from a sunny, rich country. Open Cardiovasc Med J. 2012;6:76–80. doi: 10.2174/1874192401206010076. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. El-Sonbaty MR, Abdul-Ghaffar NU. Vitamin D deficiency in veiled Kuwaiti women. Eur J Clin Nutr. 1996;50:315–318. [PubMed] [Google Scholar]
  9. Elkun N, Alkayal F, Noronha F, Ali MM, Melhem M, Al-Arouj M, et al. Vitamin D insufficiency in Arabs and South Asians positively associates with polymorphisms in GC and CYP2R1 genes. PLoS ONE. 2014;9(11):e113102. doi: 10.1371/journal.pone.0113102. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Elshafie DE, Al-Khashan HI, Mishriky AM. Comparison of vitamin D deficiency in Saudi married couples. European Journal of Clinical Nutrition. 2012;66:742–745. doi: 10.1038/ejcn.2012.29. [DOI] [PubMed] [Google Scholar]
  11. Fields J, Trivedi NJ, Horton E, Mechanick JI. Vitamin D in the Persian Gulf: integrative physiology and socioeconomic factors. Curr Osteoporos Rep. 2011;9(4):243–250. doi: 10.1007/s11914-011-0071-2. [DOI] [PubMed] [Google Scholar]
  12. Gannage-Yared MH, Chemali R, Yaacoub N, et al. Hypovitaminosis D in a sunny country: relation to lifestyle and bone markers. J Bone Miner Res. 2000;15:1856–1862. doi: 10.1359/jbmr.2000.15.9.1856. [DOI] [PubMed] [Google Scholar]
  13. Gerber LM, Mamtani R, Chiu Y, Bener A, Murphy M, Cheema S, Verjee M. Use of complementary and alternative medicine among midlife Arab women living in Qatar. Eastern Mediterranean Health Journal. 2014;20(9):554–560. [PMC free article] [PubMed] [Google Scholar]
  14. Hagenau T, Vest R, Gissel TN, Poulsen CS, Erlandsen M, Mosekilde L, Vestergaard P. Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: an ecologic meta-regression analysis. Osteoporosis International. 2009;20:133–140. doi: 10.1007/s00198-008-0626-y. [DOI] [PubMed] [Google Scholar]
  15. Holick MF. Vitamin D deficiency. The New England Journal of Medicine. 2007;357:266–281. doi: 10.1056/NEJMra070553. [DOI] [PubMed] [Google Scholar]
  16. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM. Evaluation, treatment, prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96:1911–1930. doi: 10.1210/jc.2011-0385. [DOI] [PubMed] [Google Scholar]
  17. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM. Guidelines for preventing and treating vitamin D deficiency and insufficiency revisited. J Clin Endocrinol Metab. 2012;97(4):1153–8. doi: 10.1210/jc.2011-2601. [DOI] [PubMed] [Google Scholar]
  18. IOM (Institute of Medicine) Committee to Review Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press, Institute of Medicine; 2011. Dietary reference intakes for calcium and vitamin D. [Google Scholar]
  19. Kazmi A. Vitamin D deficiency hits Arab women and children. Gulf News; May 17, 2005. http://gulfnews.com/news/gulf/uae.health/vitaminD-deficiency-hits-arab-women-and-children-1.287946) Retrieved 30 November 2014. [Google Scholar]
  20. LeBlanc ES, Zakher B, Daeges M, Pappas M, Chou R. Screening for Vitamin D Deficiency: A Systematic Review for the U.S. Preventive Services Task Force. Ann Intern Med. doi: 10.7326/M14-1659. Epub ahead of print 25 November 2014. [DOI] [PubMed] [Google Scholar]
  21. Lips P. Vitamin D status and nutrition in Europe and Asia. J Steroid Biochem Mol Biol. 2007;103(3–5):620–625. doi: 10.1016/j.jsbmb.2006.12.076. [DOI] [PubMed] [Google Scholar]
  22. Lips P. Worldwide status of vitamin D nutrition. J Steroid Biochem Mol Biol. 2010;121:297–300. doi: 10.1016/j.jsbmb.2010.02.021. [DOI] [PubMed] [Google Scholar]
  23. Malabanan AO, Holick MF. Vitamin D and bone health in postmenopausal women. J Wom Health. 2003;12(2):151–156. doi: 10.1089/154099903321576547. [DOI] [PubMed] [Google Scholar]
  24. Mahdy S, Al-Emadi SA, Khanjar IA, Hammoudeh MM, Sarakbi HA, Siam AM, Abdelrahman MO. Vitamin D status in health care professionals in Qatar. Saudi Med J. 2010;31(1):74–77. [PubMed] [Google Scholar]
  25. Mithal A, Wahl DA, Bonjour J-P, Burckhardt P, Dawson-Hughes B, Eisman JA, El-Hajj Fuleihan G, Josse RG, Lips P, Morales-Torres J on behalf of the IOF Committee of Scientific Advisors (CSA) Nutrition Working Group. Global vitamin D status and determinants of hypovitaminosis D. Osteoporos Int. 2009;20:1807–1820. doi: 10.1007/s00198-009-0954-6. [DOI] [PubMed] [Google Scholar]
  26. Musaiger AO, Hassan AS, Obeid O. The paradox of nutrition-related diseases in the Arab countries: the need for action. Int J Environ Res Public Health. 2011;8(9):3637–3671. doi: 10.3390/ijerph8093637. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Ng SW, Zaghloul S, Ali HI, Harrison G, Popkin BM. The prevalence and trends of overweight, obesity and nutrition-related non-communicable diseases in the Arabian Gulf States. Obes Rev. 2011;12(1):1–13. doi: 10.1111/j.1467-789X.2010.00750.x. [DOI] [PubMed] [Google Scholar]
  28. Palacios C, Gonzalez L. Is vitamin D deficiency a major global public health problem? J Steroid Biochem Mol Biol. 2014;144:138–145. doi: 10.1016/j.jsbmb.2013.11.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Pittas AG, Chung M, Trikalinos T, Mitri J, Brendel M, Patel K, et al. Systematic review: vitamin D and cardiometabolic outcomes. Ann Intern Med. 2010;152:307–314. doi: 10.1059/0003-4819-152-5-201003020-00009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Prentice A. Vitamin D deficiency: a global perspective. Nutrition Review. 2008;66:S153–S164. doi: 10.1111/j.1753-4887.2008.00100.x. [DOI] [PubMed] [Google Scholar]
  31. Theodoratou E, Tzoulaki I, Zgaga L, Ioannidis JP. Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials. BMJ. 2014;348:g2035. doi: 10.1136/bmj.g2035. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. van Schoor NM, Lips P. Worldwide vitamin D status. Best Pract Res Clin Endocrinol Metab. 2011;25(4):671–80. doi: 10.1016/j.beem.2011.06.007. Review. [DOI] [PubMed] [Google Scholar]
  33. Wahl DA, Cooper C, Ebeling PR, Eggersdorfer M, Hilger J, Hoffmann K, Josse R, Kanis JA, Mithal A, Pierroz DD, Stenmark J, Stöcklin E, Dawson-Hughes B. A global representation of vitamin D status in healthy populations. Arch Osteoporos. 2012;7:155–172. doi: 10.1007/s11657-012-0093-0. [DOI] [PubMed] [Google Scholar]

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