QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hatun, S. Articles by Gökalp, A. S. Search for Related Content PubMed PubMed Citation Articles by Hatun, S. Articles by Gökalp, A. S.

---

Community and International Nutrition

Subclinical Vitamin D Deficiency Is Increased in Adolescent Girls Who Wear Concealing Clothing¹

Department of Pediatrics and ^* Nuclear Medicine, Kocaeli University, School of Medicine, Kocaeli, Turkey

²To whom correspondence and reprint requests should be addressed. E-mail: shatun{at}isbank.net.tr.

	ABSTRACT

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Vitamin D deficiency continues to be a worldwide problem, especially in developing countries. The aim of this study was to investigate potential risk factors for vitamin D deficiency. Girls (n = 89) aged 13 to 17 y were enrolled in the study. Study subjects were stratified into 3 groups: Group I included girls living in a suburban area; Group II girls lived in an urban area, and Group III girls lived in an urban area and wore concealing clothes for religious reasons. At the end of winter (in April) serum 25-hydroxyvitamin D [25(OH)D] levels were measured and dietary data were collected using questionnaires. Vitamin D deficiency was defined as a serum 25(OH)D concentration < 25 nmol/L, and insufficiency as a 25(OH)D concentration between 25 and 50 nmol/L. The lumbar and femur neck bone mineral densities (BMD) were measured using dual X-ray absorptiometry (DEXA). Overall, 39 girls (43.8%) had vitamin D insufficiency and 19 (21.3%) had vitamin D deficiency. In group III (wearing covered dress) the serum 25(OH)D concentrations (28.13 ± 12.53 nmol/L) were significantly lower than in the other 2 groups, and within this group, 50% of girls were vitamin D deficient. The lumbar and femur neck BMD of girls with lower 25(OH)D levels did not differ from those with adequate vitamin D levels. We conclude that vitamin D deficiency is an important problem in Turkish adolescent girls, especially in those who follow a religious dress code; therefore, vitamin D supplementation appears to be necessary for adolescent girls.

KEY WORDS: • vitamin D deficiency • adolescent girls • bone density

The prevalence of rickets in the world is on the rise not only in developing but in developed countries as well (1). Over the past decade, the majority of cases with rickets in developed countries occurred in breast-fed infants, children with dark skin, or those who remain fully clothed for religious or social reasons, i.e., those at greatest risk for inadequate vitamin D production from sun exposure (2,3). Additionally, it was noted that deficiency of vitamin D in infants increasingly depends on their mother’s vitamin D status in some ethnic groups of developed countries (4). Recent reports on vitamin D deficiency and/or rickets in adolescence pointed out a high prevalence in the Middle East (5–9). Vitamin D deficiency during adolescence may lead to carpopedal spasms, diffuse limb pains, deformities of the lower limbs, and generalized weakness (5).

25-Hydroxyvitamin D [25(OH)D]³ is the precursor of the active metabolite calcitriol, and serum 25(OH)D concentrations reflect body stores of vitamin D. Serum 25(OH)D levels are dependent on vitamin D intake, and cutaneous synthesis in the skin upon exposure to solar UV-B radiation (UVB). The vitamin D content of most conventional food is not adequate for maintaince of normal plasma levels; therefore, cutaneous production is the most important source (10). Seasonal variations in sunlight exposure and the screening effect of air pollution for UVB are the main factors suggested to be responsible for inadequate skin production of vitamin D, and the ensuing deficiency (11). Recent reports from Middle Eastern countries have also emphasized the relation between deficiency of vitamin D and life style, i.e., concealing clothing (5–7).

The vital role of vitamin D in bone mineralization depends on its critical role in the absorption of calcium and phosphorus in the intestine as well as the differentiation of cells in the osteoblastic lineage (10). When intestinal absorption of calcium is impaired due to vitamin D deficiency, the calcium requirement is met by an increase in serum parathyroid hormone (PTH) and 1,25 dihydroxyvitamin D, through their resorptive effects on the skeleton. As a result, bone mineralization is impaired, and rickets or osteomalacia develops (3). In healthy normal subjects, bone mineralization continues throughout childhood and young adulthood until peak bone mass is reached. During this process, total body calcium increases from 25 g in newborns to 900 g in women, and 1200 g in men (12). "Peak bone mass," defined as the maximum amount of bone mass accrued at the end of skeletal growth and consolidation, is an important factor that determines an individual’s risk of developing osteoporotic fractures in later life, and 40–60% of the "peak bone mass" is accrued during puberty concomitant with the pubertal growth spurt (13). For this reason, vitamin D deficiency, which has a deleterious effect on skeletal health in adults and the elderly, may have its roots in adolescence. However, there is insufficient information in the literature on adolescent bone health and its relation with vitamin D status (14–17).

In Turkey, almost half of the adolescent girls prefer to wear clothes that cover them completely, and their outdoor activity is limited. There are reports of adolescent girls and women with osteomalacia resulting from limited sunlight exposure and wearing concealing clothing, suggesting that vitamin D insufficiency may be a problem among Turkish adolescent girls and young women (18,19).

The primary objective of this study was to determine the prevalence of vitamin D deficiency among healthy adolescent girls, especially among those who follow the Islamic dress code of wearing concealing clothing. The secondary objective was to determine the association of vitamin D levels on bone mineral density (BMD) during a critical period for bone mass accretion (20).

	SUBJECTS AND METHODS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Participants and protocol. The study was conducted in Kocaeli, a relatively developed region of Turkey, located at 30°E and 40°N. The subjects were from 3 different high schools. Group I comprised students from a school located in a suburban region of the city, Group II included those from a school located in an urban region, and Group III was composed of students from a religious school in an urban region who wore concealing clothes for religious reasons. First, girls with systemic disease or using any medications or supplements known to affect skeletal metabolism were excluded from the study. A total of 89 healthy girls were selected by a systematic sampling method from among eligible students, and all agreed to take part in the study. They were between the ages of 13 and 17 y.

The study was performed in 2 phases. At the end of winter (April 2001), subjects kept a nutritional diary for a week. They wrote down all foods, beverages, and vitamins consumed. Daily vitamin D intake was estimated from self-reports of the subjects, using national dietary references⁴ on the vitamin D content of food. A questionnaire was used to determine the style of dress, time spent outdoors during the school day and on the weekend, daily diet, and socioeconomic status (SES). The SES level was evaluated according to the level of education and income of the parents. The number of rooms in the house was assessed, and the SES level was classified as high (H), middle (M), or low (L). Parents with university, high school, and primary school education were considered to be H, M, and L, respectively. This questionnaire was tested in 5 students previously.

At study entry, anthropometric measurements were made and pubertal stage was determined using Tanner’s classification by the same pediatric endocrinologist; blood samples were withdrawn from fasting subjects for serum 25(OH)D, calcium (Ca), phosphorous (P), and alkaline phosphates (ALP) measurements. Bone mineral density (BMD) was measured using dual X-ray absorptiometry (DEXA). Vitamin D deficiency was defined as serum 25(OH)D < 25 nmol/L and insufficiency as 25(OH)D from 25 to 50 nmol/L (21,22).

In phase 2, girls with serum 25(OH)D levels < 50 nmol/L (n = 58) were recalled at the end of summer (in October) for a second measurement of Ca, P, ALP, 25(OH)D, as well as intact PTH (iPTH). However, 3 girls did not participate in phase 2 because they had moved to another city.

The study was reviewed and approved by the institutional review board, and informed consent was obtained from the subjects.

    Biochemical analysis, and BMD measurements. Serum 25(OH)D was measured using RIA according to the manufacturer’s protocol (Biosource 25OH-Vit.D3-Ria-CT Kit). The detection limit (sensitivity) of the assay was 1.5 nmol/L and cross-reactivity for 25OH ergocalciferol (specifity) was 0.6%. The normal range for 25(OH)D was stated as 28–175 nmol/L and the intra- and interassay CVs were 7 and 7.7%, respectively. Our laboratory range for 25(OH)D was 25–212 nmol/L and intra- and interassay CV were 7.1%, and 7.9% respectively. Serum levels of Ca, P, and ALP were measured using a Beckman CX-9 autoanalyzer. Serum iPTH was measured using an original assay using Roche Diagnostics E-170 Modular Analytics immunoanalyzer equipment. The manufacturer’s normal range for iPTH was 15–65 ng/L and intra- and interassay CVs were 2.8, and 3.4%, respectively.

Bone mineral content (BMC; g) was determined at L2–L4 vertebrae, and femoral neck by DEXA (Norland XR-26) with a CV of 0.42% for repeated short-term phantom measurements. BMD was expressed in units of g/cm². The in vivo precision was 1.37% for measurements of the lumbar spine, and 0.86% for the femoral neck. Normative data of the manufacturer were used as a reference. The areal BMD (aBMD) is influenced by the true volumetric BMD (g/cm³) and bone size. Thus, a tall child will have a higher aBMD than a short child of the same age and with identical true volumetric BMD. Therefore, differences in height, weight, and DXA measured bone area (BA) of the girls in the 3 groups might influence the results. We compared femur neck and spinal BMC in the 3 groups after adjustment for BA, body height, weight, and Tanner stages of sexual development.

    Statistical analysis. Results are given as means ± SD or numbers and percentages. The distribution of continuous variables was analyzed via the Shapiro-Wilk test of normality. The comparison of continuous variables was done using the Kruskal Wallis and Man-Whitney U test if the distribution was skewed. In the remaining normally distributed variables, ANOVA and Tukey tests were used for comparison. End of winter and end of summer levels of 25(OH)D (in students with vitamin D insufficiency and deficiency at the end of winter) were compared using paired samples t test. The ratio of vitamin D deficiency at the end of winter was compared between groups using ² test. Any relation between the end of winter levels of 25(OH)D, Ca, P, ALP, and BMD for all girls were analyzed using Pearson’s correlation analysis. Differences were considered significant at P < 0.05. The spinal and femur neck BMC obtained via DEXA were adjusted by analysis of covariance for BA, body height, weight and Tanner stages of sexual development (dependent factor: BMC; fixed factor: Group; covariates: height, weight, BA, Tanner score).

	RESULTS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The general characteristics of the subjects are shown in Table 1. The girls were 14.8 ± 0.6 y old and all were pubertal. The 3 groups did not differ in SES, daily vitamin D intake, or outdoor activity. Girls in group III were shorter than those in the other groups (P < 0.001). Daily vitamin D intake was not correlated with serum 25(OH)D level (r = 0.1, P = 0.1).

View larger version (17K): [in this window] [in a new window]   FIGURE 1 The end of summer mean serum levels of 25(OH)D of adolescent Turkish girls with previously low vitamin D levels (nmol/L). Serum 25(OH)D concentration in suburban girls (Group I, n = 29), urban girls (Group II, n = 30) and urban girls wearing concealing clothing (Group III, n = 30) at the end of summer who were vitamin D insufficient and deficient at the end of winter. Values are means ± SD. *Different from the end of winter (paired-sample t test), P < 0.05.

    Bone mineral density measurements. The lumbar and femur neck BMD measurements of girls with lower vitamin D levels did not differ from those with an adequate level (Table 2).

	DISCUSSION

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
This cross-sectional study demonstrated that vitamin D insufficiency (43.8%) and deficiency (21%) are common among Turkish adolescent girls at the end of the winter. This finding is more striking in girls who wear concealing clothing such that half had 25(OH)D levels < 25 nmol/L at the end of the winter. In addition, they did not improve significantly during the summer, whereas the vitamin D status of girls in the other groups did. In Turkey, the main source of vitamin D is cutaneous synthesis because there is no food fortification with vitamin D, and supplementation of vitamin D is not a routine practice in adolescents. It was established previously that upon exposure of 6% of the body to a "minimal erythemal dose" of UV energy 2–3 times a week for 5 min, 25 µg/d vitamin D is synthesized (23). Vitamin D insufficiency was reported in up to 80% of pregnant women as well as women of reproductive age in Turkey. Also, a relation between SES, wearing concealing clothing, and maternal vitamin D insufficiency was shown (24–27). Similar observations were reported in Muslim and Orthodox Jewish communities in the Middle East and other countries (28–31). These observations indicate that style of dress is an important determinant of vitamin D status, and clothing that covers the body from head to toe presents a major problem in terms of vitamin D synthesis.

The negative correlation between vitamin D levels and PTH was expected, given the physiologic relation between vitamin D status and PTH (32,33). Despite these factors, it is surprising that no clinical or biochemical evidence of rickets was detected in study participants, and secondary hyperparathyroidism was observed in only 2 girls. Studies in adults showed that a reduction in 25(OH)D levels below 37.5 nmol/L induces an increase in serum PTH levels (34,35). Moreover, if these changes persist, they would induce physiologic, clinical, and pathologic effects (i.e., acceleration in bone formation—resorption velocity, osteoporosis, mild osteomalacia, increase in fracture risk) (15,17,36). Although a level of 27.5 nmol/L is suggested as a cutoff value for vitamin D insufficiency in adults (22), there are no data in children for a cutoff value in 25(OH)D that would induce an increase in PTH. The rarity of hyperparathyroidism in spite of considerable vitamin D deficiency in our study suggests that the lower limits of 25(OH)D levels for the definition of vitamin D deficiency and insufficiency in youth may be different from those in adults. Because the degree and course of secondary hyperparathyroidism are related to the duration of the deficiency as well as the serum level, subclinical vitamin D insufficiency should not be considered unimportant because of a normal PTH level.

Conflicting data exist in the literature concerning the relation between low serum 25(OH)D and BMD. In some studies, it was shown that vitamin D insufficiency may have a negative effect on peak bone mass (37) and reduce forearm (38) and lumbar bone density (31), whereas other studies did not support these findings (39). In our study, we did not observe a relation between serum 25(OH)D levels and BMD. In addition, girls with vitamin D deficiency had bone densities similar to those with normal vitamin D levels. This suggests that the negative effect of vitamin D insufficiency may not be reflected in BMD measurements in the short term. Further studies are required to examine these effects in the long term. On the basis of the the significantly lower height in group III compared with the other 2 groups, we speculate that a long-term effect of vitamin D deficiency may be short stature. It is possible that the BMC or BMD is maintained during vitamin D deficiency in these girls at the expense of height, and the main effect of poor vitamin D status is stunting in these girls. However, we did not investigate the etiology of decreased height because the heights of all subjects were within normal limits.

In conclusion, vitamin D insufficiency and deficiency are common among Turkish adolescent girls, particularly in those following the strict Islamic dress code. Even though our study failed to provide strong evidence for its clinical consequences, subclinical vitamin D insufficiency and deficiency are common problems in adolescent girls. Vitamin D supplementation is an efficient and feasible way to maintain serum 25(OH)D levels (40,41); therefore, we propose that vitamin D supplementation may be necessary during the adolescent years, especially in high-risk regions and groups.

	FOOTNOTES

 
¹ Presented as an oral presentation at the Turkish National Pediatric Meeting in Kapadokya, 2002 and as a poster presentation at the 42nd Annual Meeting of The European Society for Paediatric Endocrinology, 18–21 September 2003, Ljubljana, Slovenia (Islam, O., Hatun, S., Babaoglu, K., Cizmecoglu, F. & Gökalp, A. S. Vitamin D deficiency and risk factors in adolescent girls).

³ Abbreviations used: ALP, alkaline phosphatase; aBMD, areal bone mineral density; BA, bone area; BMC, bone mineral content; BMD, bone mineral density; DEXA, dual X-ray absorptiometry; i PTH, intact parathyroid hormone; SES, socioeconomic status; 25(OH)D, 25-hydroxyvitamin D.

⁴ National dietary references. Unpublished document, 2002. Hacettepe University Nutrition and Diet Department, Ankara, Turkey.

Manuscript received 15 June 2004. Initial review completed 29 August 2004. Revision accepted 27 October 2004.

	LITERATURE CITED

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Hochberg, Z., Bereket, A., Davenport, M., Delemarre-Van de Waal, H. A., De Schepper, J., Levine, M. A., Shaw, N., Schoenau, E., van Coeverden, S. C., Weisman, Y. & Zadik, Z. (2002) Consensus development for the supplementation of vitamin D in childhood and adolescence. Horm. Res. 58:39-51.

2. Kreiter, S. R., Schwartz, R. P., Kirkman, H. N., Jr, Charlton, P. A., Calikoglu, A. S. & Davenport, M. L. (2000) Nutritional rickets in African American breast-fed infants. J. Pediatr. 137:153-157.[Medline]

3. Joiner, T. A., Foster, C. & Shope, T. (2000) The many faces of vitamin D deficiency rickets. Pediatr. Rev. 21:296-302.[Free Full Text]

4. Shaw, N. J. & Pal, B. R. (2002) Vitamin D deficiency in UK Asian families: activating a new concern. Arch. Dis. Child. 86:147-149.[Abstract/Free Full Text]

5. Narchi, H., El Jamil, M. & Kulaylat, N. (2001) Symptomatic rickets in adolescence. Arch. Dis. Child. 84:501-503.[Abstract/Free Full Text]

6. Al-Jurayyan, N. A., El-Desouki, M. E., Al-Herbish, A. S., Al-Mazyad, A. S. & Al-Qhtani, M. M. (2002) Nutritional rickets and osteomalacia in school children and adolescents. Saudi Med. J. 23:182-185.[Medline]

7. El-Hajj Fuleihan, G., Nabulsi, M., Choucair, M., Salamoun, M., Hajj Shahine, C., Kizirian, A. & Tannous, R. (2001) Hypovitaminosis D in healthy schoolchildren. Pediatrics 107:E53.

8. Lehtonen-Veromaa, M., Mottonen, T., Irjala, K., Karkkainen, M., Lamberg-Allardt, C., Hakola, P. & Viikari, J. (1999) Vitamin D intake is low and hypovitaminosis D common in healthy 9- to 15-year-old Finnish girls. Eur. J. Clin. Nutr. 53:746-751.[Medline]

9. Du, X., Greenfield, H., Fraser, D. R., Ge, K., Trube, A. & Wang, Y. (2001) Vitamin D deficiency and associated factors in adolescent girls in Beijing. Am. J. Clin. Nutr. 74:494-500.[Abstract/Free Full Text]

10. Holick, M. F. (2003) Vitamin D: a millenium perspective. J. Cell. Biochem. 88:296-307.[Medline]

11. Agarwal, K. S., Mughal, M. Z., Upadhyay, P., Berry, J. L., Mawer, E. B. & Puliyel, J. M. (2002) The impact of atmospheric pollution on vitamin D status of infants and toddlers in Delhi, India. Arch. Dis. Child. 87:111-113.[Abstract/Free Full Text]

12. Leonard, M. B. & Zemel, B. S. (2002) Current concepts in pediatric bone disease. Pediatr. Clin. N. Am. 49:143-173.[Medline]

13. Bachard, K. L. (2000) Making an impact on pediatric bone health. J. Pediatr. 136:137-139.[Medline]

14. Kinyamu, H. K., Gallagher, J. C., Rafferty, K. A. & Balhorn, K. E. (1998) Dietary calcium and vitamin D intake in elderly woman: effect on serum parathyroid hormone and vitamin D metabolites. Am. J. Clin. Nutr. 67:342-348.[Abstract]

15. Gloth, F. M., Gundberg, C. M., Hollis, B. W., Haddad, J. G. & Tobin, J. D. (1995) Vitamin D deficiency in homebound elderly persons. J. Am. Med. Assoc. 274:1683-1686.[Abstract]

16. LeBoff, M. S., Kohlmeier, L., Hurwitz, S., Franklin, J., Wright, J. & Glowacki, J.. (1999) Occult vitamin D deficiency in postmenopausal US women with acute hip fracture. J. Am. Med. Assoc. 281:1505-1511.[Abstract/Free Full Text]

17. Haden, S. T., El-Hajj Fuleihan, G., Angell, G. E., Cotran, N. M. & LeBoff, M. S. (1999) Calcidiol and PTH levels in women attending an osteoporosis program. Calcif. Tissue Int. 64:275-279.[Medline]

18. Demirçeken, F., Zorlu, P., Kutlu, A. O., Teziç, T. & Dar, S. (2001) Adolescent rickets due to lack of sunlight: a case report. Çocuk Sal Hastalklar Derg. 44:79-81.

19. Gullu, S., Erdogan, M. F., Uysal, A. R., Baskal, N., Kamel, A. N. & Erdogan, G. (1998) A potential risk for osteomalacia due to sociocultural lifestyle in Turkish women. Endocr. J. 45:675-681.[Medline]

20. Sabatier, J. P., Guaydier-Souquieres, G. & Laroche, D. (1996) Bone mineral acquisition during adolescence and early childhood: a study in 574 healthy females 10–24-years-old. Osteoporos. Int. 6:141-148.[Medline]

21. McKenna, M. J. & Freaney, R. (1999) Secondary hyperparathyroidism in the elderly: means to defining hypovitaminosis D. Osteoporos. Int. 8:S3-S6.

22. American Academy of Pediatrics (2003) Clinical report: prevention of rickets and vitamin D deficiency: new guidelines for vitamin D. Pediatrics 111:908-911.[Abstract/Free Full Text]

23. Holick, M. F. (1999) Vitamin D. Shills, M. E. Olson, J. A. Shike, M. Ross, C. A. eds. Modern Nutrition in Health and Disease 9th ed. 1999 Williams & Williams Baltimore, MD. .

24. Pehlivan, I., Hatun, ., Aydogan, M., Babaoglu, K., Türker, G. & Gökalp, A. S. (2002) Maternal serum vitamin D levels in the third trimester of pregnancy. Turk. J. Med. Sci. 32:237-241.

25. Alagol, F., Shihadeh, Y., Boztepe, H., Tanakol, R., Yarman, S., Azizlerli, H. & Sandalci, O. (2000) Sunlight exposure and vitamin D deficiency in Turkish women. J. Endocrinol. Investig. 23:173-177.[Medline]

26. Andïran, N., Yordam, N. & Ozön, A. (2002) The risk factors for vitamin D deficiency in breast-fed newborns and their mothers. Nutrition 18:47-50.[Medline]

27. Guzel, R., Kozanoglu, E., Guler-Uysal, F., Soyupak, S. & Sarpel, T. (2001) Vitamin D status and bone mineral density of veiled and unveiled Turkish women. J. Womens Health Gend. Based Med. 10:765-770.[Medline]

28. Mishal, A. A. (2001) Effects of different dress styles on vitamin D levels in healthy young Jordanian women. Osteoporos. Int. 12:931-935.[Medline]

29. Meulmeester, J. F., van den Berg, H., Wedel, M., Boshuis, P. G., Hulshof, K. F. & Luyken, R. (1990) Vitamin D status, parathyroid hormone and sunlight in Turkish, Moroccan and Caucasian children in The Netherlands. Eur. J. Clin. Nutr. Jun. 44:461-470.

30. Diamond, T. H., Levy, S., Smith, A. & Day, P. (2002) High bone turnover in Muslim women with vitamin D deficiency. Med. J. Aust. 177:139-141.[Medline]

31. Taha, W., Chin, D., Silverberg, A. I., Lashiker, L., Khateeb, N. & Anhalt, H. (2001) Reduced spinal bone mineral density in adolescents of ultra-orthodox Jewish community in Brooklyn. Pediatrics 107:1-6.[Abstract/Free Full Text]

32. Guillemant, J., Le Taupin, H. T., Taright, N., Alemandou, A., Peres, G. & Guillemant, S. (1999) Vitamin D status during puberty in French healthy male adolescents. Osteoporos. Int. 10:222-225.[Medline]

33. Guillemant, J., Cabrol, S., Allemandou, A., Peres, G. & Guillemant, S. (1995) Vitamin D dependent seasonal variation of PTH in growing male adolescents. Bone 17:513-516.[Medline]

34. Gloth, F. M., Gundberg, C. M., Hollis, B. W., Haddad, J. G. & Tobin, J. D. (1995) Vitamin D deficiency in homebound elderly persons. J. Am. Med. Assoc. 274:1683-1686.

35. Lips, P., Wiersinga, A., van Ginkel, F. C., Jongen, M. J., Netelenbos, J. C., Hackeng, W. H., Delmas, P. D. & van der Vijgh, W. J. (1988) The effect of vitamin D supplementation on vitamin D status and parathyroid function in elderly subjects. J. Clin. Endocrinol. Metab. 67:644-650.[Abstract]

36. Eriksen, E. F. & Glerup, H. (2002) Vitamin D deficiency and aging: implications for general health and osteoporosis. Biogerontology 3:73-77.[Medline]

37. Lehtonen-Veromaa, M. K., Mottonen, T. T., Nuotio, I. O., Irjala, K. M., Leino, A. E. & Viikari, J. S. (2002) Vitamin D and attainment of peak bone mass among peripubertal Finnish girls: a 3-y prospective study. Am. J. Clin. Nutr. 76:1446-1453.[Abstract/Free Full Text]

38. Outila, T. A., Karkkainen, M. U. & Lamberg-Allardt, C. J. (2001) Vitamin D status affects serum parathyroid hormone concentrations during winter in female adolescents: associations with forearm bone mineral density. Am. J. Clin. Nutr. 74:206-210.[Abstract/Free Full Text]

39. Kristinsson, J. O., Valdimarsson, O., Sigurdsson, G., Franzson, L., Olafsson, I. & Steingrimsdottir, L. (1998) Serum 25-hydroxyvitamin D levels and bone mineral density in 16–20 years-old girls: lack of association. J. Intern. Med. :243.

40. Lehtonen-Veromaa, M., Mottonen, T., Nuotio, I., Irjala, K. & Viikari, J. (2002) The effect of conventional vitamin D(2) supplementation on serum 25(OH)D concentration is weak among peripubertal Finnish girls: a 3-y prospective study. Eur. J. Clin. Nutr. 56:431-437.[Medline]

41. Calikoglu, A. S. & Davenport, M. L. (2003) Prophylactic vitamin D supplementation. Endocr. Dev. 6:233-258.[Medline]

This article has been cited by other articles:

				B. Hintzpeter, C. Scheidt-Nave, M. J. Muller, L. Schenk, and G. B. M. Mensink Higher Prevalence of Vitamin D Deficiency Is Associated with Immigrant Background among Children and Adolescents in Germany J. Nutr., August 1, 2008; 138(8): 1482 - 1490. [Abstract] [Full Text] [PDF]

				S. Hatun, A. Bereket, B. Ozkan, T. Cothkun, R. Kose, and A. Suha Calykothlu Free vitamin D supplementation for every infant in Turkey Arch. Dis. Child., April 1, 2007; 92(4): 373 - 374. [Full Text] [PDF]

				Minerva BMJ, April 16, 2005; 330(7496): E348 - E348. [Full Text] [PDF]

				Minerva BMJ, February 5, 2005; 330(7486): 316 - 316. [Full Text] [PDF]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hatun, S. Articles by Gökalp, A. S. Search for Related Content PubMed PubMed Citation Articles by Hatun, S. Articles by Gökalp, A. S.