|Year : 2020 | Volume
| Issue : 2 | Page : 67-73
Prevalence of vitamin D deficiency and associated risk factors among adults in Chandigarh
Divesh Dik, Maninder Kaur
Department of Anthropology, Panjab University, Chandigarh, India
|Date of Submission||07-Jul-2020|
|Date of Decision||12-Sep-2020|
|Date of Acceptance||28-Oct-2020|
|Date of Web Publication||30-Dec-2020|
Department of Anthropology, Panjab University, Sector-14, Chandigarh - 160 014
Source of Support: None, Conflict of Interest: None
Background: Vitamin D deficiency is a global health concern affecting individuals across all the age groups in both the genders. Aims and Objectives: The present study intends to assess the prevalence of Vitamin D deficiency and associated risk factors in adult males and females of Chandigarh. Materials and Methods: The sample included 332 males and 295 females of the age ranging between 30 and 70 years. Vitamin D level of all the participants was estimated by employing chemiluminescence immunoassay method. All the subjects were divided into three categories of Vitamin D level, i.e., normal range (>30–100 ng/ml), insufficiency (21–29 ng/ml), and deficiency (0–20 ng/ml) as per the Endocrine Society Guidelines (2011). Results: The overall prevalence of Vitamin D deficiency was found to be 28.5% in males and 63.4% in females of Chandigarh. The prevalence of Vitamin D deficiency exhibited an age-associated increment in both the males and females. Conclusion: Lesser physical activity and no intake of calcium, Vitamin D, and multivitamin supplements were possible determinants of Vitamin D deficiency.
Keywords: Prevalence, risk factors, sufficiency, Vitamin D deficiency
|How to cite this article:|
Dik D, Kaur M. Prevalence of vitamin D deficiency and associated risk factors among adults in Chandigarh. Int J Adv Med Health Res 2020;7:67-73
| Introduction|| |
Vitamin D is a unique nutrient, which can be synthesized endogenously (skin) as well as from exogenous source (diet) and also functions as a hormone. Vitamin D is actually a fat-soluble steroidal prohormone that has very prominent endocrine, paracrine, and autocrine functions. The two forms of Vitamin D, i.e., ergocalciferol and cholecalciferol, differ only in their side chain structure; however, these differences have no significant impact upon the metabolism. It has been noticed by earlier studies that both forms of Vitamin D (D2 and D3) exhibit identical responses in the body upon activation and the potency to cure Vitamin D-deficiency rickets.,,
The findings of Mithal identified genetic, lifestyle, and geographical factors as possible determinants of Vitamin D status of the individual. It is a key regulator of bone metabolism and plays a significant role in adipogenesis and the prevention of a range of diseases, including osteoporosis, cancer, diabetes, and immune disorders.,,, The recent data from European countries examined by Laird mentioned the possible correlation of Vitamin D levels with COVID-19 mortality on the basis of its impact on cytokine response to pathogens.
There are several anthropometric, physiological, and biochemical factors which impact the Vitamin D levels in the body. Obesity is related to changes in the Vitamin D levels in the endocrine system. Lower levels of serum 25-hydroxyvitamin D (25-OHD) in morbidly obese individuals may be secondary to an alteration in tissue distribution as a result of increase in adipose mass. Earlier work from Webb as well as from Holick had outlined the role of sunlight in regulating cutaneous synthesis of the Vitamin D and have implicated factors in Vitamin D3 synthesis in the skin to include aging, melanin pigmentation, season of the year, latitude, and use of sunscreen.,
Published literature in this domain suggests high prevalence of Vitamin D deficiency across various parts of the world. Even after the completion of several studies among various populations, there is a paucity of searchable data on Chandigarh population. Moreover, India is a tropical country with ample sunlight all through the year, but still previous studies recorded high percentage of deficiency.,,, Hence, to provide an overview about Vitamin D status, the present study is an attempt to assess the prevalence of the Vitamin D deficiency and associated risk factors among the adult males and females of Chandigarh.
| Materials and Methods|| |
The present study was conducted with the objective to assess the prevalence of the Vitamin D and their associated risk factors among the adult male and females of Chandigarh, India, which is the capital of states named Punjab and Haryana. In the present cross-sectional study, a random sampling procedure was adopted to select 332 males and 295 females, with age ranging between 30 and 70 years. Before initiating data collection, all the participants were informed about the nature as well as purpose of the study, and their verbal informed consent was also obtained. Union territory of Chandigarh comprised the city of Chandigarh and a number of adjoining villages, but the data were not collected from the rural areas. The data were collected from different sectors of Chandigarh city. Data collection was carried out from December 2017 to March 2019 from various parts of union territory of Chandigarh. The sample size was calculated applying the formula (n = Zα2 × p × q/d2) with 95% of confidence interval and 5% probability of type 1 error. If the prevalence of deficiency was assumed to be 40%, using the aforementioned formula, the estimated sample size would be 590. On the basis of inclusion and exclusion criteria, a sample of 627 participants was selected. Background information of all the subjects regarding their age, education, occupation, and diet was collected using a detailed questionnaire. Informed consent was taken from each participant, and ethical clearance for conducting the study was obtained from the institutional ethical committee.
Exclusion criteria: Subjects having any chronic liver disease, long illness, history of medication with corticosteroids, hormone replacement therapy, and any record/history of surgery were excluded from the study. Pregnant women were also excluded from the data collection.
Level of daily physical activity was determined using a questionnaire and stratified into four following categories: no activity (sedentary lifestyle), mild physical activity (0–20 min/day), moderate physical activity (21–40 min/day), and heavy physical activity (41–60 min/day). For the estimation of the Vitamin D of the participants, chemiluminescence immunoassay (CLIA) method was adopted. Blood samples were collected by a trained technician. The samples were transported to the laboratory in cool packs and were stored at -20°C. Serum 25 (OH) Vitamin D level was estimated by CLIA technique (Beckman dxi 600) in the laboratory. Vitamin D level was stratified into three categories, i.e., normal range (>30–100 ng/ml), Vitamin D insufficiency (21–29 ng/ml), and Vitamin D deficiency (0–20 ng/ml). Additional information about intake of Vitamin D supplements, calcium supplements, and multivitamin and awareness of hypovitaminosis D was also recorded. The details regarding the type of food intake (vegetarian, nonvegetarian, and ovo-vegetarian) were obtained from each participant.
The collected data were analyzed by employing Statistical Package for Social Sciences (SPSS) version 21.0 (SPSS Inc.). The qualitative data were expressed as percentage. Differences of categorical variables between normal and Vitamin D deficient participants were computed using Chi-square test. The level of significance for all analysis was set at P < 0 · 05 and a confidence interval of 95%.
| Results|| |
The prevalence of Vitamin D insufficiency and deficiency across various age groups in males and females of Chandigarh is presented in [Table 1]. It is evident from the Table 1 that the overall prevalence of Vitamin D deficiency was 28.52% in males and 63.38% in females of Chandigarh. In males, age group-wise distribution of Vitamin D insufficiency was maximum in the oldest age group of 51–70 years (21.32%), whereas the youngest age group of 30–40 years presented minimum insufficiency of Vitamin D (6%). It was noted that minimum percentage of the males with Vitamin D sufficiency was present in the age group of 51–70 years (4.5%), whereas the youngest age group exhibited highest percentage of the males with Vitamin D sufficiency (15.01%) category [Figure 1]. Vitamin D deficiency was found to be highly prevalent in the age group of 51–70 years (9.9%), whereas an equal percentage of the individuals with Vitamin D deficiency (9.39%) were noted in the age groups of 30–40 and 41–50 years.
|Table 1: Prevalence of Vitamin D insufficiency and deficiency across various age groups in males and females of Chandigarh|
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|Figure 1: Prevalence of Vitamin D insufficiency and deficiency across various age groups in males and females of Chandigarh|
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In females, the maximum Vitamin D deficiency was found in the age group of 51–70 (30.5%), whereas in the age groups of 30–40 and 41–50 years, it was found to be 10.5% and 22.37%, respectively [Table 1]. Only 9.83% of participants in the age group of 30–40 years had normal Vitamin D level and it further decreased with increasing age and finally reached to 6.1% from 51 to 70 years. The prevalence of Vitamin D deficiency was significantly higher in females than their male counterparts in each age group. The results of Chi-square test revealed that significant gender difference exists across all the three categories of Vitamin D levels, i.e., normal (6.043*), deficient (10.105**), and insufficient (10.134**) categories.
[Table 2] summarizes the prevalence of Vitamin D deficiency with respect to different sociodemographic variables among males and females of Chandigarh. A substantial proportion of the males (16.27%) and females (14.24%) employed in government services were Vitamin D deficient. A significant number of housewives (40.34%) were Vitamin D deficient. About 3.31% of males and 8.81% of females engaged in the private jobs were Vitamin D deficient. The subjects having mild physical activity (males 12.35% and females 29.49%) exhibited the highest percentage of Vitamin D deficiency, followed by moderate (males 5.42% and females 7.12%) and heavy physical activity (males 2.71% and females 1.02%) in both the genders. The subjects who were not having any intake of Vitamin D revealed considerable prevalence of Vitamin D deficiency in males (26.81%) as well as females (53.22%) as compared to their counterparts with regular intake of Vitamin D (males1.51% and females 7.46%). Similar findings were noticed for intake of calcium as well as intake of multivitamin supplements, where subjects with regular or irregular intake presented little prevalence of VDD as compared to their counterparts with no supplement intake, where Vitamin D deficiency was significantly higher.
|Table 2: Prevalence of Vitamin D deficiency with respect to different sociodemographic variables among males and females of Chandigarh|
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The prevalence of Vitamin D deficiency was lowest in the subjects having ovo-vegetarian diet in both the genders (males 2.11% and female 9.15%), whereas males having nonvegetarian diet showed higher prevalence of VDD (17.77%) than their vegetarian counterparts (8.73%). Interestingly, an opposite trend was witnessed for females where subjects with vegetarian diet (39.32%) had higher prevalence of VDD than subjects having nonvegetarian diet (14.92%). The prevalence of Vitamin D deficiency was found to be significantly more among males (21.69%) and females (44.41%) who were not aware about hypovitaminosis D than the subjects who were aware about this deficiency.
| Discussion|| |
Vitamin D deficiency is a silent epidemic throughout the world in all age groups in both the males and females. In the present study, the overall prevalence of Vitamin D deficiency was found to be 28·52 in males and 63·4% in females of Chandigarh, indicating that the prevalence of Vitamin D deficiency was significantly higher in females than their male counterparts. Similarly, the largest study carried out by Daly noticed that Vitamin D deficiency was 31% among Australian adults aged 25 years and over. They further recorded that females, obese, and older participants had increased risk of having deficiency. While studying gender-specific differences in the prevalence of Vitamin D deficiency among a cohort group of doctors, Multani found higher prevalence of deficiency in females than their age-matched male counterparts (males 85% vs. 97 · 5% females). Zargar also conducted a cross-sectional study on Kashmiri individuals and recorded prevalence of deficiency as 76 · 6% in males and 94 · 4% in females.
Likewise, Gill also observed significantly more 25(OH) D levels among males as compared to their female counterparts. In agreement with the findings of the present study, many researchers established that females had lower serum 25(OH) D levels than males. Higher prevalence of Vitamin D deficiency among females may be attributed to greater percentage of body fat among females.,, To study the worldwide variability in Vitamin D deficiency, the present study has been compared with preexisting studies on the topic from different countries. The overall Vitamin D deficiency in the present population of Chandigarh was found to be 44·97%, which was lower than the Vitamin D deficiency in various population-based studies in India as of Hyderabad, Odisha, and Jammu and Kashmir.,, The prevalence of Vitamin D deficiency was lower in the population of North-West Punjab as stated by Bachhel. The comparison from the global studies indicated higher prevalence of Vitamin D deficiency in Chandigarh than South Australian, Caucasian population, Jordan and Iraqi population, Southeastern U S. population, Brazilian population, Danish population, Portuguese population, and Tianjin population. [24,31-37] However, Saudi Arabian population was having higher prevalence of Vitamin D deficiency than the population of Chandigarh. The review of international and national data clearly exhibited that despite methodological differences, the prevalence of deficiency varies in almost every part of the world on the basis of the characteristics of the population studied.
The current cross-sectional study highlighted that the percentage of males and females in the normal Vitamin D category decreased with increasing age, whereas an inverse trend was documented in Vitamin D deficiency category for both the males and females. A population-based cohort study conducted by González-Molero in Spain illustrated with the multiple linear regression model that the level of 25-OHD had a significant correlation with age. Daly demonstrated that the mean value of serum 25(OH)D decreased with age for both males and females, thereby showing an increased prevalence of deficiency with advancing age. However, in the study of Gill, age was not significantly associated with Vitamin D deficiency, and surprisingly, the mean levels of 25(OH)D were higher in the older age groups. The findings of Al-Horani were also in consensus with the findings of our study, indicating a decrement in the levels of serum Vitamin D levels with increasing age among the healthy Iraqi population. Age-associated decline in the level of Vitamin D may be due to inhibitory effect of aging on the efficiency of cutaneous synthesis of Vitamin D. Moreover, the female participants of the present study had limited outdoor activities, little physical activity coupled with faulty dietary intake.
The present research studied the role of occupation in vitamin D deficiency and it was noticed that out of the total participants, 16·27% of males and 14·24% of females who were in government services found to be Vitamin D deficient. A substantial proportion of housewives (40·34%) were Vitamin D deficient. About 3·31% of males and 8·81% of females engaged in the private jobs were Vitamin D deficient. Occupation was found to have a significant association with the Vitamin D levels for males in our study, which is in agreement with the study of Jeong on Korean population, who stated a significant association of occupation with the Vitamin D levels both for males and females. They reported that 73·8% of male and 88·1% of female office workers were Vitamin D deficient. Bachhel conducted a cross-sectional study on the Punjab population and noticed a statistically significant association between Vitamin D levels and occupation. However, the study of Suryanarayana noticed no significant association between the occupation and Vitamin D deficiency in both the males and females from Hyderabad population.
Physical activity is a modifiable determinant of Vitamin D status; the participants of the present study with sufficient level of physical activity demonstrated better Vitamin D status than the subjects with insufficient physical activity. A report of Gill also identified that the subjects undertaking no or <150 min/week of physical activity exhibited lower levels of serum Vitamin D as compared to subjects having sufficient physical activity. Similarly, earlier studies had also reported a significant association between level of physical activity and serum 25(OH) D levels.,,, While conflicting evidence was noticed from the study of Lee et al., where no association was reported between serum Vitamin D levels and level of physical activity among males and females. Suryanarayana also observed no association of physical activity with deficiency. It has been observed by Al-Othman that physical activity is responsible for enhanced lipolysis as well as boosting mobilization of deposited Vitamin D from the body fat, thereby promoting the concentration of serum 25 (OH) D.
In the present findings, the participants who were not having any intake of supplemental Vitamin D revealed considerable prevalence of Vitamin D deficiency in males as well as females as compared to their counterparts with regular intake of Vitamin D supplements. Similar findings were noticed for intake of calcium as well as intake of multivitamin supplements, where subjects with regular or irregular intake presented low prevalence of deficiency as compared to their counterparts with no supplement intake, where Vitamin D deficiency was significantly higher. Contrasting evidence were noted from the previous studies presenting nonsignificant association between the Vitamin D supplementation and Vitamin D deficiency in males and females, which is in coherence with our study. There was a strong association between Vitamin D supplementation and serum Vitamin D levels reported in other studies.,, Similarly, Pfeifer reported that calcium supplementation up to 8 weeks increased the mean level of the serum 25(OH) D3 from 24 · 63 ± 12 · 14 (nmol/mL) to 44 · 36 ± 27 · 38 (nmol/mL) and of serum 1,25(OH) 2D3 (ng/L) from 36 · 78 ± 15 · 69 (ng/L) to 48 · 43 ± 25 · 67 (ng/L). A cross-sectional study of Gill documented that subjects without any supplementation of Vitamin D exhibited lower serum 25(OH) Vitamin D (19 · 9%) than the participants taking supplements (10 · 7%). As the diet imparts a significant role in maintaining the Vitamin D levels, we have included the diet pattern in our study. The prevalence of Vitamin D deficiency was lowest in the subjects having ovo-vegetarian diet in both the genders (males 2 · 11%, female 9 · 15%), whereas males having nonvegetarian diet showed higher prevalence of deficiency (17 · 77%) than their vegetarian counterparts (8 · 73%). Interestingly, an opposite trend was witnessed for females, where subjects with vegetarian diet (39 · 32%) had higher prevalence of deficiency than subjects having nonvegetarian diet (14 · 92%). Observations of Suryanarayana portrayed that the prevalence of deficiency was relatively higher (58%) among vegetarians as compared to their nonvegetarian counterparts (50 · 9%). This high prevalence of deficiency among vegetarians may be because vegetarian diet sources are rich in a biologically less active ergocalciferol, whereas the animal diet sources such as primarily in fish oil have abundance of cholecalciferol. It was noted by Khadilkar that the fiber and phytates present in the vegetarian diet are responsible to diminish the storage of Vitamin D.
In the current cross-sectional study, the prevalence of Vitamin D deficiency was found to be significantly more among males (21 · 69%) and females (44 · 41%) who were not aware about hypovitaminosis D than the subjects who were aware about this deficiency (males 6 · 93% and females 18 · 98%). Alemu and Varnam reported in their study on North-West England population that 72% of participants had prior knowledge about Vitamin D, whereas 28% of participants had no knowledge regarding the Vitamin D. Ignorance regarding the Vitamin D deficiency is also one of the major reasons of its high prevalence in India.
| Conclusion|| |
It can be concluded that although in India, there are longer hours of sunshine, still Vitamin D deficiency is quite prevalent. Even the published literature in this domain highlighted substantial prevalence of subclinical Vitamin D deficiency in all age levels. In our study, the overall as well as age group-wise prevalence of Vitamin D deficiency was significantly higher in females as compared to their age-matched male counterparts. An age-related fall in the concentration of serum 25(OH) D in both the genders was also documented. Regular physical activity, intake of calcium, Vitamin D, as well as multivitamin supplements is a potential modifiable determinant to improve the Vitamin D status. Hence, the findings of the present study indicated that diet and lifestyle modifications may be beneficial to control vitamin D deficiency. Therefore, the findings of our study can play a significant role in identifying the vulnerable groups as well as recognizing the determinants of this growing health burden.
We thank UGC-CAS II Department of Anthropology, Panjab University and New Delhi, for funding.
Financial support and sponsorship
The study was supported by the University Grants Commission, New Delhi, India, (research vide letter no. 854/[NET-DEC.2014]).
Conflicts of interest
There are no conflicts of interest.
| References|| |
Al-Othman A, Musharaf SA, Daghri NM, Krishnaswamy S, Yusuf DS, Alkharfy KM, et al
. Effect of physical activity and sun exposure on Vitamin D status of Saudi children and adolescents. BMC Pediatr 2012;12:92.
Vanchinathan V, Lim HW. A dermatologist's perspective on Vitamin D. Mayo Clin Proc 2012;87:372-80.
Fieser LF, Fieser M. Vitamin D in Steroids. New York: Reinhold; 1959. p. 90-168.
Jones G, Strugnell SA, DeLuca HF. Current understanding of the molecular actions of Vitamin D. Physiol Rev 1998;78:1193-231.
Jurutka PW, Whitfield GK, Hsieh JC, Thompson PD, Haussler CA, Haussler MR. Molecular nature of the Vitamin D receptor and its role in regulation of gene expression. Rev Endocr Metab Disord 2001;2:203-16.
Mithal A, Wahl DA, Bonjour JP, Burckhardt P, Hughes BD, Eisman A, et al
. Global Vitamin D status and determinants of hypovitaminosis D. Osteoporos Int 2009;20:1807-20.
Kremer R, Rabbani SA. Vitamin D and Vitamin D analogs in cancer progression and metastasis. In Singh G, Rabbani SA, editor. Bone Metastasis. Cancer Drug Discovery and Development. Totowa NJ: Humana Press; 2005. p. 29-57.
Mathieu C, Badenhoop K. Vitamin D and Type 1 diabetes mellitus: State of the art. Trends Endocrinol Metab 2005;16:261-6.
Davis CD, Dwyer JT. The sunshine vitamin: Benefits beyond bone? J Natl Cancer Inst 2007;99:1563-5.
Holick MF. The Vitamin D deficiency pandemic: A forgotten hormone important for health. Public Health Rev 2010;32:267-83.
Laird E, Rhodes J, Kenny RA. Vitamin D and inflammation: Potential implications for severity of COVID-19. Ir Med J 2020;113:81.
Arunabh S, Pollack S, Yeh J, Aloia JF. Body fat content and 25-hydroxyvitamin D levels in healthy women. J Clin Endocrinol Metab 2003;88:157-61.
Webb AR, Decosta BR, Holick MF. Sunlight regulates the cutaneous production of Vitamin D3 by causing its photodegradation. J Clin Endocrinol Metab 1989;68:882-7.
Holick MF, Matsuoka LY, Wortsman J. Age, Vitamin D, and solar ultraviolet. Lancet 1989;2:1104-5.
Ramakrishnan S, Bhansali A, Bhadada K, Sharma R, Walia R, Ravikiran M, et al
. Vitamin D status and its seasonal variability in healthy young adults in an Asian Indian urban population. Endocr Pract 2011;17:185-91.
Baidya A, Chowdhury S, Mukhopadhyay S, Ghosh S. Profile of Vitamin D in a cohort of physicians and diabetologists in Kolkata. Indian J Endocrinol Metab 2012;16 Suppl 2:S416-7.
Tandon VR, Sharma S, Mahajan S, Raina K, Mahajan A, Khajuria V, et al
. Prevalence of Vitamin D deficiency Among indian menopausal women and its correlation with diabetes: A first Indian cross sectional data. J Midlife Health 2014;5:121-5.
Suryanarayana P, Arlappa N, Geddam B, Rajkumar PL, Prasad U, Raju BB, et al
. Prevalence of Vitamin D deficiency and its associated factors among the urban elderly population in Hyderabad metropolitan city, South India. Ann Hum Biol 2018;45:136-9.
Charan J, Biswas T. How to calculate sample size for different study designs in medical research? Indian J Psychol Med 2013;35:121-6.
] [Full text]
Bischoff-Ferrari HA, Giovannucci E, Willett C, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr 2006;84:18-28.
Daly M, Gagnon C, Lu ZX, Magliano DJ, Dunstan DW, Sikaris KA, et al
. Prevalence of Vitamin D deficiency and its determinants in Australian adults aged 25 years and older: A national, population-based study. Clin Endocrinol (Oxf) 2012;77:26-35.
Multani SK, Sarathi V, Shivane V, Bandgar TR, Menon PS, Shah NS. Study of bone mineral density in resident doctors working at a teaching hospital. J Postgrad Med 2010;56:65-70.
] [Full text]
Zargar AH, Ahmad S, Masoodi SR, Wani AI, Bashir MI, Laway BA, et al
. Vitamin D status in apparently healthy adults in Kashmir valley of Indian subcontinent. Postgrad Med J 2007;83:713-6.
Gill K, Hill L, Shanahan E, Taylor W, Appleton L, Grant F, et al
. Vitamin D levels in an Australian population. BMC Public Health 2014;14:1001.
Alsuwadia AO, Farag YM, Sayyari AA, Mousa DH, Alhejaili F, Al-Harbi AS, et al
. Prevalence of Vitamin D deficiency in Saudi Adults. Saudi Med J 2013;34:814-8.
Hussain AN, Alkhenizan AH, El Shaker M, Raef H, Gabr A. Increasing trends and significance of hypovitaminosis D: A population-based study in the Kingdom of Saudi Arabia. Arch Osteoporos 2014;9:190.
Perna L, Haug U, Schöttker B, Müller H, Raum E, Jansen E, et al
. Public health implications of standardized 25-hydroxyvitamin D levels: A decrease in the prevalence of Vitamin D deficiency among older women in Germany. Prev Med 2012;55:228-32.
Rattan R, Sahoo D, Mahapatra S. Prevalence of Vitamin D deficiency in adults in the coastal regions of Odisha, India. IOSR J Pharm Biol Sci 2016;11:49-52.
Kapoor M, Charak G. Evaluation of prevalence pattern of Vitamin D deficiency in known population an observational study. J Adv Med Dent Sci Res 2018;6:52-4.
Bachhel R, Singh NR, Sidhu JS. Prevalence of Vitamin D deficiency in North-West Punjab population: A cross-sectional study. Int J Appl Basic Med Res 2015;5:7-11.
Snijder MB, van Dam RM, Visser M, Deeg JH, Dekker JM, Bouter LM, et al
. Adiposity in relation to Vitamin D status and parathyroid hormone levels: A population-based study in older men and women. J Clin Endocrinol Metab 2005;90:4119-23.
Al-Horani H, Dayyih WB, Mallah E, Hamad M, Mima M, Awad R, et al
. nationality, gender, age, and body mass index influences on Vitamin D concentration among elderly patients and young Iraqi and Jordanian in Jordan. Biochem Res Int 2016;2016:8920503.
McCullough L, Bostick M, Daniel CR, Flanders D, Shaukat A, Davison J, et al
. Vitamin D status and impact of Vitamin D3 and/or calcium supplementation in a randomized pilot study in the Southeastern United States. J Am Coll Nutr 2009;28:678-86.
Martins JS, Palhares MO, Teixeira OC, Ramos MG. Vitamin D status and its association with parathyroid hormone concentration in Brazilians. J Nutr Metab 2017;2017:9056470.
Brot C, Vestergaard P, Kolthoff N, Gram J, Hermann AP, Sørensen OH. Vitamin D status and its adequacy in healthy Danish perimenopausal women: Relationships to dietary intake, sun exposure and serum parathyroid hormone. Br J Nutr 2001;86 Suppl 1:S97-103.
Santos A, Amaral TF, Guerra RS, Sousa AS, Álvares L, Moreira P, et al
. Vitamin D status and associated factors among Portuguese older adults: Results from the nutrition UP 65 cross-sectional study. BMJ Open 2017;7:e016123.
Zhang M, Li P, Zhu Y, Chang H, Wang X, Liu W, et al
. Higher visceral fat area increases the risk of Vitamin D insufficiency and deficiency in Chinese adults. Nutr Metab (Lond) 2015;12:50.
Al-Mogbel ES. Vitamin D status among adult Saudi females visiting primary health care clinics. Int J Health Sci (Qassim) 2012;6:116-26.
González-Molero I, Morcillo S, Valdes S, Valero VP, Botas P, Delgado E, et al
. Vitamin D deficiency in Spain: A population-based cohort study. Eur J Clin Nutr 2010;65:321-8.
Lester E, Skinner RK, Wills MR. Seasonal variation in serum-25-hydroxyvitamin-D in the elderly in Britain. Lancet 1977;309:979-80.
Jeong H, Hong S, Heo Y, Chun H, Kim D, Park J, et al
. Vitamin D status and associated occupational factors in Korean wage workers: Data from the 5th
Korea national health and nutrition examination survey (KNHANES 2010-2012). Ann Occup Environ Med 2014;26:28.
van den Heuvel EG, van Schoor N, Jongh RT, Visser M, Lips P. Cross-sectional study on different characteristics of physical activity as determinants of Vitamin D status; inadequate in half of the population. Eur J Clin Nutr 2013;67:360-5.
Wanner M, Richard A, Martin B, Linseisen J, Rohrmann S. Associations between objective and self-reported physical activity and Vitamin D serum levels in the US population. Cancer Causes Control 2015;26:881-91.
Touvier M, Deschasaux M, Montourcy M, Sutton A, Charnaux N, Kesse-Guyot E, et al
. Determinants of Vitamin D status in Caucasian adults: Influence of sun exposure, dietary intake, sociodemographic, lifestyle, anthropometric, and genetic factors. J Invest Dermatol 2014;135:378-88.
Lee K. Sex-specific relationships between alcohol consumption and Vitamin D levels: The Korea national health and nutrition examination survey 2009. Nutr Res Pract 2012;6:86-90.
Kmiec P, Zmijewski M, Waszak P, Sworczak K, Lizakowska-Kmiec M. Vitamin D deficiency during winter months among an adult, predominantly urban, population in northern Poland. Endokrynol Pol 2014;65:105-13.
Pfeifer M, Begerow B, Minne HW, Nachtigall D, Hansen C. Effects of a short-term Vitamin D(3) and calcium supplementation on blood pressure and parathyroid hormone levels in elderly women. J Clin Endocrinol Metab 2001;86:1633-7.
van der Meer IM, Middelkoop BJ, Boeke AJ, Lips P. Prevalence of Vitamin D deficiency among Turkish, Moroccan, Indian and Sub-Sahara African populations in Europe and their countries of origin: An overview. Osteoporos Int 2011;22:1009-21.
de Rui M, Toffanello ED, Veronese N, Zambon S, Bolzetta F, Sartori L, et al
. Vitamin D deficiency and leisure time activities in the elderly: Are all pastimes the same PLoS One 2014;9:e94805.
Khadilkar AV. Vitamin D deficiency in Indian adolescents. Indian Pediatr 2010;47:755-6.
Alemu E, Varnam R. Awareness of Vitamin D deficiency among at-risk patients. BMC Res Notes 2012;5:17.
[Table 1], [Table 2]