PUBLIC HEALTH NUTRITION AND EPIDEMIOLOGY

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1 PUBLIC HEALTH NUTRITION AND EPIDEMIOLOGY Body composition and vitamin D status: the Korea National Health And Nutrition Examination Survey IV (KNHANES IV) Department of Family Medicine, Busan Paik Hospital, Inje University College of Medicine, Busan, South Korea Journal of Human Nutrition and Dietetics Keywords body composition, dual energy X-ray absorptiometry, sex, vitamin D deficiency. Correspondence, Department of Family Medicine, Busan Paik Hospital, Kaegum-dong, Busan Jin-Gu, Busan , South Korea. Tel.: Fax: kayoung.fmlky@gmail.com How to cite this article. (2013) Body composition and vitamin D status: the Korea National Health And Nutrition Examination Survey IV (KNHANES IV). J Hum Nutr Diet. 26 (Suppl. 1), doi: /jhn Abstract Background: The present study aimed to assess the association of total and regional body fat percentage (FP) and lean mass (LM) with vitamin D deficiency {serum 25-hydroxyvitamin D [25(OH)D] <20 ng ml 1 } using the data of the Fourth Korea National Health And Nutrition Examination Survey (KNHANES IV). Methods: Subjects were participants of the KNHANES IV conducted in 2009 and were aged 19 years. In 6791 participants, serum 25(OH)D, body composition [body mass index, waist circumference, and total and regional (trunk and legs) FP and LM by dual energy X-ray absorptiometry] were measured. Confounders (age, residential place, housing status, occupation, smoking, alcohol use, physical activity, medical history and calcium intake per day) were assessed. Results: After adjusting for confounders, vitamin D deficiency was significantly associated with FP with the odds ratios (ORs) from 1.09 to 1.20, and LM with the ORs from 0.81 to 0.87 in men. In men, serum 25(OH)D remained inversely associated with FP tertiles after adjustment for LM, and positively with LM tertiles after adjustment for FP. When FM tertiles and LM tertiles were combined in men, the OR for vitamin D deficiency was 2.2 (P < 0.05) in the combined subgroup of highest total FM tertile and lowest total LM tertile compared to the subgroup of lowest total FM tertile and highest total LM tertile. However, these associations were nonsignificant or inconsistent in women. Conclusions: The associations of vitamin D deficiency with body fat and lean mass were significant in Korean men but were inconsistent in Korean women. Introduction Vitamin D deficiency has become a worldwide medical condition (Ginde et al., 2009; Kuchuk et al., 2009) and this trend has also been found in a Korean population (Choi et al., 2011). Besides the role of vitamin D in the proper mineralisation of bone, recent evidence suggests that individuals deficient in vitamin D are at increased risk of cardiovascular disease and mortality (Judd & Tangpricha, 2009; Barnard & Colon-Emeric, 2010). Body composition such as body fat and lean mass, which may be hazardous or protective for cardiovascular disease, has been associated with vitamin D deficiency (Parikh et al., 2004; Looker, 2005; Snijder et al., 2005; Hypponen & Power, 2006; Konradsen et al., 2008; Foo et al., 2009; Lenders et al., 2009; Stewart et al., 2009; Young et al., 2009; Beydoun et al., 2010; Cheng et al., 2010; Ceglia et al., 2011). Although a number of studies have shown that low vitamin D status was associated with higher body fat, these relationships have mostly been limited to non-asian populations (Parikh et al., 2004; Looker, 2005; Snijder et al., 2005; Hypponen & Power, 2006; Konradsen et al., 2008; Lenders et al., 2009; Young et al., 2009; Beydoun et al., 2010; Cheng et al., 2010). The strengths of associations between body fat and vitamin D in circulation has been different according to measures reflecting body fat (Snijder et al., Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd. 105

2 Body composition and vitamin D 2005), ethnicity (Looker, 2005; Young et al., 2009), age (i.e. stronger in younger than in older women) (Looker, 2005), sex (i.e. stronger in women than in men) (Snijder et al., 2005), regional adiposity (i.e. associated with subcutaneous and particularly visceral fat) (Cheng et al., 2010) and status of central obesity (i.e. stronger in a group of central obesity) (Beydoun et al., 2010). Compared to the relationships between body fat and vitamin D status, a handful number of studies have shown the relationships between lean mass and vitamin D status. Low vitamin D was associated with lower lean mass in adolescents (Foo et al., 2009; Lenders et al., 2009) and postmenopausal women (Stewart et al., 2009), whereas the relationship in adult men was nonsignificant after adjusting for covariates (Ceglia et al., 2011). Therefore, the relationship between lean mass and vitamin D status is inconsistent and studies on regional lean mass appear to be scarce. In this regard, it is expected that the relationships of vitamin D deficiency with body fat and lean mass may be different according to the measurement methods of body fat, distribution of body fat and lean mass, sex or age in women. In addition, there is a lack of understanding of the role played by combination of body fat and lean mass in these associations. Thus, the present study aimed to examine whether the relationships between vitamin D deficiency and measures of total and regional body fat and lean mass are different in three groups of subjects (men, pre- and postmenopausal women) using the data of the Fourth Korea National Health And Nutrition Examination Survey (KNHANES IV) conducted in Materials and methods Subjects The KNHANES IV Survey is a community-based, crosssectional survey conducted from 2007 to 2009 by the Division of Chronic Disease Surveillance, Korea Centers for Disease Control and Prevention. The KNHANES has been conducted periodically since 1998 to assess the health and nutritional status of the non-institutionalised Korean population. The sampling and data collection procedures have been described in detail previously (Choi et al., 2011). The present study included 6791 individuals (3065 males and 3726 females) aged 19 years with complete data available for menopausal status in women. All the participants in this survey previded their written informed consent. Measurement of serum 25-hydroxyvitamin D To measure serum serum 25-hydroxyvitamin D [25(OH) D] levels, blood samples of individual subjects were collected during the survey. Blood samples were properly processed, immediately refrigerated, and transported in cold storage to the Central Testing Institute in Seoul, Korea. Blood samples were analysed within 24 h after transportation. Serum 25(OH)D levels were measured using a counter (1470 Wizard; Perkin-Elmer, Turku, Finland) with a radioimmunoassay method (Dia-Sorin; Still Water, MN, USA). The interassay coefficients of variation were 11.7%, 10.5%, 8.6% and 12.5% at 8.6, 22.7, 33.0 and 49.0 ng ml 1 (Choi et al., 2011). Serum vitamin D level was classified as vitamin D deficiency, vitamin D insufficiency and vitamin D sufficiency, which was defined as a serum 25(OH)D level of <20 ng ml 1, ng ml 1 and 30 ng ml 1, respectively (Holick, 2009). Body composition Subjects had their weight and height measured in accordance to standard procedures. Body mass index (BMI) was calculated as kg m 2. Waist circumference (WC) was measured midway between the lowest lateral border of the ribs and the uppermost lateral iliac crest when the participants were standing. Total and regional (trunk and legs) body fat mass and lean mass were measured using whole body dual energy X-ray absorptiometry (DXA) (Discovery-W fan-beam densitometer; Hologic Inc., Bedford, MA, USA). Total fat percentage (TFP) was calculated as: [total fat mass/total mass (fat mass + lean mass + total body mineral content)] 9 100; trunk body fat percentage (TrFP) as: trunk fat mass/trunk mass; and leg fat percentage (LFP) as: leg fat mass/leg mass. Measures of lean mass were total lean mass (TLM), trunk lean mass and leg lean mass (LLM). Assessment of sociodemographic factors, life style, medical history and calcium intake Self-reported questionnaires were used to assess lifestyle (i.e. smoking status: current smoker versus nonsmoker); the Alcohol Use Disorders Identification Test (AUDIT) score (Barbor et al., 2001); regular walking of at least 30 min per time for five times a week (yes versus no); regular high-intensity exercise of at least 20 min per time for three times a week (yes versus no); and regular moderate-intensity exercise of at least 30 min per time for five times a week (yes versus no). A face-to-face interview was used to obtain data about a participant s sociodemographic factors [i.e. residential place (urban versus rural), housing status (apartment complex versus house) and occupation] and medical history of chronic diseases, as well as menopausal status for women. Occupation was categorised as: office work (including administration, 106 Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd.

3 Body composition and vitamin D clerical work, specialists, sales, service and students) and housewife versus manual work (agriculture, forestry and fishery, manual labour, engineering, assembling, and technical work). According to the medical history of chronic diseases, participants were categorised into those ever diagnosed as having cardiovascular diseases, hypertension, diabetes, arthritis, depression or cancer versus those not ever diagnosed as having these conditions. Daily calcium intake was evaluated using a structured food frequency questionnaire. Statistical analysis Linear regression analyses or a chi-squared test (linear-bylinear association) were applied to evaluate a linear trend in the relationships of the three categories of serum 25 (OH)D level (deficiency, insufficiency and sufficiency) with body composition and potential confounders (age, sociodemographic factors, lifestyle, medical history and calcium intake) in each of the three groups (men, and pre- and postmenopausal women). Multiple linear and logistic regression analyses were used to find associations between serum 25(OH)D level [logarithmically transformed continuous or categorical variables (<20 ng ml 1 versus 20 ng ml 1 )] and each measure of the body composition (per 1 SD change) after adjusting for confounders among overall subjects and each of the three groups. The analysis among overall subjects included an interaction test between the subjects group and each body composition measure. A general linear model was applied to assess an association between sexand menopause status-specific tertiles of TFP and serum 25(OH)D level after adjusting for confounders and TLM in each group of subjects. A similar analysis was applied for the relationship with sex- and menopause status-specific tertile of TLM. Multiple logistic regression analysis was also used to find an association between vitamin D deficiency and combinations of sex- and menopause status-specific tertiles of TFP and TLM after adjusting for confounders in each group of subjects. These analyses were performed using PASW STATISTICS, version 18 (SPSS Inc., Chicago, IL, USA) and MEDCALC, version (MedCalc Software, Mariakerke, Belgium). Results Of the 6791 participants, 4468 (63.3%) had vitamin D deficiency, and 62.6% of the 1596 postmenopausal women, 80.0% of 2130 premenopausal women and 57.6% of 3065 men were vitamin D deficient. Only 8.7% of men, 2.2% of premenopausal women and 6.3% of postmenopausal women had sufficient circulating vitamin D levels. Table 1 shows the relationships of serum 25(OH)D status with body composition and confounders. When the association between vitamin D status and body composition was evaluated, measures of body composition except for BMI increased linearly with decreased vitamin D status in men. By comparison, none of the body composition in premenopausal women and some of body composition (WC and body fat measures) in postmenopausal women were significantly associated with vitamin D status. Both men and women (regardless of menopause) with a lower vitamin D status were less likely to walk regularly, to live in rural areas and to be manual workers, whereas they were more likely to dwell in an apartment complex. In addition, men with a lower vitamin D status were more likely to be current smokers and to have a lower AUDIT score. Younger men and premenopausal women were more likely to have a lower vitamin D status and men and premenopausal women with medical history were more likely to have a higher vitamin D status (Table 1). Tables 2 and 3 summarise the associations between serum 25(OH)D level or vitamin D deficiency and the body composition with adjustment for confounders. When any interaction between overall subjects and each body composition measure was tested, it was significant except for LFP and LLM with respect to an association with serum 25(OH)D level, and significant for three measures of lean mass with respect to an association with vitamin D deficiency. However, substantial differences were found when comparing associations between the three groups, Serum 25(OH)D level was negatively associated with body fat percentage but positively associated with lean mass after adjustment. The relationships were significant for the measures of body fat percentage and lean mass in men, whereas relationships were significant only for measures of body fat percentage in postmenopausal women, and for LFP and TLM in premenopausal women (Table 2). The adjusted association between vitamin D deficiency and body composition was also significant for men: the adjusted odds of vitamin D deficiency was 9 20% higher with a l SD increase in body fat percentage, whereas it was 13 19% lower with a 1 SD increase in lean mass and 10% lower with a 1 SD increase in BMI. By comparison, there was no significant association between vitamin D deficiency and body composition in women regardless of menopausal status (Table 3). The group-difference in serum 25(OH)D level against tertiles of TFP and TLM is shown in Fig. 1. The serum 25(OH) D level was linearly decreased with group-specific tertiles of TFP after adjusting for covariates and even TLM and linearly increased with sex- and menopause status-specific tertiles of TLM after adjusting for covariates and TFP in men (P for trend <0.001), whereas no linear trends were Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd. 107

4 Body composition and vitamin D Table 1 Characteristics of the participants according to serum 25-hydroxyvitamin D [25(OH)D] levels for men and pre/post-menopausal women separately Men (n = 3065) Premenopausal women (n = 2130) Post-menopausal women (n = 1596) <20 ng ml ng ml 1 30 ng ml 1 <20 ng ml ng ml 1 30 ng ml 1 <20 ng ml ng ml 1 30 ng ml 1 n (%) 1765 (57.6) 1033 (33.7) 267 (8.7) 1704 (80.0) 380 (17.8) 46 (2.2) 999 (62.6) 496 (31.1) 101 (6.3) Body composition variables BMI (kg m 2 ) 23.9 (3.3) 24.1 (3.0) 23.7 (3.2) 22.6 (3.5) 22.9 (3.6) 23.3 (4.1) 24.3 (3.3) 24.2 (3.1) 23.6 (3.1) WC (cm) 83.9 (9.2) 84.8 (8.7) 84.0 (8.9)* 75.2 (9.4) 76.1 (9.4) 76.5 (9.6) 82.8 (9.5) 82.2 (8.8) 80.4 (9.3)* Total fat (%) 21.8 (5.3) 21.3 (5.2) 20.3 (4.8)* 31.5 (5.2) 31.4 (5.2) 32.2 (4.7) 34.0 (5.4) 33.2 (5.1) 32.6 (5.3)* Trunk fat (%) 24.0 (6.7) 23.7 (6.7) 22.8 (6.3)* 30.5 (7.1) 30.7 (6.9) 31.7 (6.7) 35.6 (6.6) 34.6 (6.5) 34.2 (7.0)* Leg fat (%) 19.7 (5.0) 18.8 (4.7) 18.0 (4.3)* 34.1 (5.1) 33.6 (5.1) 33.9 (4.8) 33.2 (5.7) 32.5 (5.4) 31.7 (5.1)* Total lean mass (kg) 53.4 (70.0) 53.6 (7.2) 52.1 (7.2)* 38.6 (4.8) 39.0 (4.9) 39.2 (5.5) 36.9 (4.6) 37.0 (4.4) 36.3 (4.5) Trunk lean mass (kg) 25.2 (3.3) 25.3 (3.4) 24.6 (3.5)* 18.8 (2.4) 19.0 (2.5) 19.2 (2.9) 18.3 (2.5) 18.3 (2.4) 17.8 (2.5) Leg lean mass (kg) 8.8 (1.4) 8.8 (1.4) 8.4 (1.4)* 6.2 (0.9) 6.2 (0.9) 6.2 (1.0) 5.7 (0.9) 5.7 (0.8) 5.6 (0.8) Confounders Age (years) 45.7 (16.3) 51.7 (16.1) 55.7 (14.3)* 36.3 (8.9) 37.6 (8.5) 37.8 (8.6)* 64.2 (9.5) 64.7 (9.2) 66.2 (8.9) AUDIT score 9.6 (7.4) 10.0 (7.8) 10.8 (8.1)* 4.5 (5.2) 4.3 (4.7) 4.8 (5.3) 2.5 (4.1) 2.4 (4.2) 2.5 (4.4) Calcium intake (mg day 1 ) 542 (350) 569 (351) 540 (361) 449 (280) 429 (238) 432 (195) 393 (499) 403 (291) 362 (235) Current smoking 810 (46.1) 405 (39.4) 103 (38.7)* 122 (7.2) 31 (8.3) 2 (4.3) 54 (5.5) 13 (2.6) 5 (5.0) Physical activity High intensity 325 (18.5) 209 (20.3) 51 (19.2) 260 (15.3) 77 (20.5) 6 (13.0) 118 (11.9) 57 (11.5) 13 (13.0) Moderate intensity 237 (13.5) 165 (16.0) 43 (16.2) 208 (12.2) 64 (17.0) 10 (21.7)* 149 (15.1) 68 (13.7) 17 (17.0) Walking 814 (46.4) 507 (43.2) 141 (53.0)* 707 (41.6) 177 (47.1) 23 (50.0)* 421 (42.4) 232 (46.8) 50 (50.0)* Rural residents 346 (19.6) 328 (31.8) 130 (48.7)* 261 (15.3) 82 (21.6) 12 (26.1)* 313 (31.3) 224 (45.2) 44 (43.6)* Dwell in apartment 802 (45.4) 376 (36.4) 61 (22.8)* 920 (54.0) 169 (44.5) 10 (21.7)* 329 (32.9) 115 (23.2) 22(21.8)* Manual worker 548 (31.3) 438 (43.0) 155 (59.8)* 176 (10.4) 54 (14.4) 7 (15.2)* 263 (26.5) 155 (31.3) 37 (37.8)* History of chronic diseases 371 (21.1) 250 (24.2) 68 (25.5)* 367 (21.6) 94 (24.8) 17 (37.0)* 623 (62.6) 316 (63.7) 268 (67.3) Data are the mean (SD) or n (%). *P < 0.05 using linear regression analyses or the chi-squares test (linear-by-linear association). Multiply by to convert to the International System of Units. The levels were defined as vitamin D deficiency [25(OH)D < 20 ng ml 1 ], vitamin D insufficiency [20 25(OH)D 29] and vitamin D sufficiency [25(OH)D 30 ng ml 1 ]. AUDIT, Alcohol Use Disorder Identification Test; BMI, body mass index; WC, waist circumference. 108 Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd.

5 Body composition and vitamin D Table 2 The associations between serum 25-hydroxyvitamin D [25(OH)D] levels and body composition variables (Z-score change) for men and pre/post-menopausal women separately Men (n = 3065) Premenopausal women (n = 2130) Post-menopausal women (n = 1596) Overall b (95% CI) Z-score b (95% CI) Z-score b (95% CI) Z-score b (95% CI) BMI (kg m 2 ) (0.006, 0.031)* (0.009, 0.033)* ( 0.008, 0.023) ( 0.045, 0.003) WC (cm) ( 0.004, 0.021) ( 0.002, 0.023) ( 0.006, 0.026) ( 0.051, 0.002)* Total fat (%) ( 0.037, 0.012)* ( 0.035, 0.010)* ( 0.016, 0.014) ( 0.062, 0.013)* Trunk fat (%) ( 0.031, 0.006)* ( 0.028, 0.003)* ( 0.011, 0.020) ( 0.055, 0.006)* Leg fat (%) ( 0.044, 0.019)* ( 0.044, 0.019)* ( 0.031, 0.001)* ( 0.067, 0.019)* Total lean mass (kg) (0.024, 0.050)* (0.029, 0.057)* (0.000, 0.030)* ( 0.019, 0.031) Trunk lean mass (kg) (0.014, 0.040)* (0.018, 0.044)* ( 0.007, 0.023) ( 0.032, 0.017) Leg lean mass (kg) (0.018, 0.045)* (0.024, 0.053)* ( 0.001, 0.029) ( 0.013, 0.037) *P < Multiply by to convert to the International System of Units. Multiple logistic regression model after adjusting for group divided by sex and menopausal status, interaction between each body composition measure and the group divided by sex and menopausal status, age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation and medical history; age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation and medical history. Significant interaction between each body composition measure and the group divided by sex and menopausal status. BMI, body mass index; CI, confidence interval; WC, waist circumference. significant in premenopausal women (Fig. 1). Similarly, in men, the serum 25(OH) D level was linearly decreased with tertiles of TrFP or LFP, and increased with tertiles of TLM or LLM after adjusting for confounders and other corresponding regional body composition measures (P for trend <0.001). When the associations between vitamin D deficiency and combination of tertiles of TLM and TFP were evaluated, men who were in the higher third of TFP and in the lower third of TLM were more likely to have vitamin D deficiency (P for trend <0.001). The multivariable adjusted odds ratio of vitamin D deficiency was 2.2 (95% confidence interval = ) for men who were in the lowest third for TLM and in the highest third for TFP compared to those in the highest third for TLM and in the lowest third for TFP (Fig. 2). However, for pre- and postmenopausal women, these associations were not significant. Discussion In this nationally representative Korean samples, vitamin D deficiency was associated with body composition after adjusting for confounders but the association was sexand menopause status-specific. Men with higher total or regional body fat percentage or those with lower total or regional lean mass were more likely to be vitamin D deficient regardless of their age, socio-demographic factors, lifestyle, medical history and calcium intake. By contrast, in women, vitamin D deficiency was not independently associated with body composition in multivariable adjusted models. Two anthropometric measures, BMI and WC, appear to be less likely to be associated with vitamin D status and also to be sex-specific. Therefore, the associations would be underestimated when the anthropometric measures are used in these associations instead of total or regional body fat, which could probably explain the inconsistent results among previous studies. These findings extend our knowledge of the association of vitamin D deficiency with either body fat or lean mass to an association with combined measures of body fat and lean mass, to sex-specific associations, and to associations with regional body composition. Previous observational studies could only evaluate the inverse association between body fat and serum 25(OH)D level (Parikh et al., 2004; Looker, 2005; Snijder et al., 2005; Hypponen & Power, 2006; Konradsen et al., 2008; Lenders et al., 2009; Young et al., 2009; Beydoun et al., 2010; Cheng et al., 2010) and the positive association between lean mass and serum 25(OH)D level (Foo et al., 2009; Lenders et al., 2009; Stewart et al., 2009). However, these studies did not indicate any association with a combination of body fat and lean body mass. Previous studies have Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd. 109

6 Body composition and vitamin D Table 3 The associations between vitamin D deficiency { serum 25-hydroxyvitamin D [25(OH)D] <20 ng ml 1 } and body composition variables (Z-score change) for men and pre/post-menopausal women separately Men (n = 3065) Premenopausal women (n = 2130) Post-menopausal women (n = 1596) Overall OR (95% CI) Z-score OR (95% CI) Z-score OR (95% CI) Z-score OR (95% CI) BMI (kg m 2 ) 0.91 (0.84, 0.98)* (0.83, 0.97)* (0.89, 1.14) (0.87, 1.16) WC (cm) 0.95 (0.88,1.03) (0.87, 1.02) (0.87, 1.12) (0.91, 1.21) Total fat (%) 1.15 (1.06, 1.25)* (1.05, 1.24)* (0.93, 1.17) (0.95, 1.27) Trunk fat (%) 1.10 (1.02, 1.20)* (1.01, 1.19)* (0.90, 1.14) (0.92, 1.23) Leg fat (%) 1.22 (1.12, 1.32)* (1.11, 1.31)* (0.98, 1.23) (0.98, 1.31) Total lean mass (kg) 0.83 (0.76, 0.90)* (0.74, 0.89)* (0.89, 1.12) (0.84, 1.12) Trunk lean mass (kg) 0.88 (0.81, 0.95)* (0.79, 0.94)* (0.90, 1.14) (0.88, 1.18) Leg lean mass (kg) 0.86 (0.78, 0.94)* (0.76, 0.91)* (0.92, 1.15) (0.83, 1.11) *P < Multiply by to convert to the International System of Units. Multiple logistic regression model after adjusting for group divided by sex and menopausal status, interaction between each body composition measure and the group divided by sex and menopausal status, age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation and medical history; age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation and medical history. Significant interaction between each body composition measure and the group divided by sex and menopausal status. BMI, body mass index; CI, confidence interval; OR, odds ratio; WC, waist circumference. largely provided a sex-adjusted link between body fat or BMI and serum 25(OH) D level (Harris & Dawson- Hughes, 2007; Konradsen et al., 2008; Young et al., 2009; Beydoun et al., 2010; Cheng et al., 2010), whereas many uncertainties remain for sex difference in these relationships (Snijder et al., 2005; Stewart et al., 2009; Ceglia et al., 2011). For example, Snijder et al. (2005) found a substantial difference in these associations between men and women in 453 participants of the Longitudinal Aging Study Amsterdam study who were aged 65 years, and the associations were stronger for women than for men (Snijder et al., 2005). In other studies, the association between lean mass and serum 25(OH)D level was not significant in men (Ceglia et al., 2011) but significant in postmenopausal women (Stewart et al., 2009). These findings are in striking contrast with the results of the present study. Probably, the discrepancy may be attributed to differences in ethnicity, serum 25(OH)D level, adjustment level of confounders, and variable characteristics of body composition and serum vitamin D (i.e. discrete or continuous variable). For example, in the Longitudinal Aging Study Amsterdam study, the subjects were predominantly Caucasian (99%) aged 65 years, and approximately 45% of the men (n = 237) and 56% of the women (n = 162) were vitamin D deficient. The adjusted confounders in the association between body fat and serum 25(OH)D, which were used as continuous variables, were season, age and smoking (Snijder et al., 2005). In the study by Ceglia et al. (2011), the subjects were 1115 non-hispanic black and Hispanic and non- Hispanic white men aged years. The association between quartile of 25(OH)D and lean mass (continuous variable) was adjusted for calcium intake, BMI, education, income, self-reported health, alcohol intake, arthritis and physical activity scale (Ceglia et al., 2011). Finally, in the study of Stewart et al. (2009), approximately 92% of the women (n = 240) were white and aged years, and 19% of them were vitamin D deficient. In that study, weight, age or years since menopause, serum C-reactive protein concentration, white blood cell count, energy expenditure and various dietary intake factors were adjusted in the regression analysis for the association between lean mass and serum 25(OH)D level (Stewart et al., 2009). The mechanisms linking a low vitamin D status and obesity are unclear. These inverse associations may be explained by a decreased bioavailability of circulating vitamin D, endogenously synthesised as a result of its increased deposition of vitamin D in adipose tissue or decreased sunlight exposure in obese individuals (Wortsman et al., 2000; Hypponen & Power, 2006). Conversely, obesity can also be the consequence of a low vitamin D status. A low serum 25 (OH)D level induces an increased parathyroid hormone level, which promotes calcium influx into the adipocytes. Subsequently, calcium influx into adipocytes enhances lipogenesis (Mccarty & Thomas, 2003). The finding of a positive association between lean body mass and vitamin D in the present study is important because vitamin D supplementation may be beneficial for increasing lean body mass in Korean men and there is evidence for a more rapid loss of skeletal muscle mass in men aged 40 years than in women (Flynn et al., 1992). 110 Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd.

7 Body composition and vitamin D 25(OH)D (ng ml 1 ) 25(OH)D (ng ml 1 ) Low Middle High Tertiles of total fat percentage Men Post-menopausal women Low Middle High Tertiles of total lean mass Men Post-menopausal women However, at present, there is no clear potential explanation for the association between lean body mass and vitamin D status and a temporal relationship between the two measures. Studies have reported that vitamin D had beneficial effects on muscle growth, development and contraction (Ceglia, 2008) and vitamin D receptor was found in muscle cells and neuronal cells (Bischoff et al., 2001). * Premenopausal women * * Premenopausal women Figure 1 Serum mean 25-hydroxyvitamin D [25(OH)D] levels plotted against the sex- and menopausal status-specific tertiles of total fat percentage (upper panel) and the sex- and menopausal status-specific tertiles of total lean mass (lower panel) after adjusting for age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation, medical history and total lean mass (upper panel) or total body fat percentage (lower panel). *P < Multiply by to convert to the International System of Units. Odds ratio * Low 1.9* 2.2* 2.2* 1.5* Middle 1.8* High Low High Middle The main strength of the present study lies in the nationally representative sample of Koreans with sufficient power for the investigation of these relationships. An additional strength is the availability of relevant confounding factors. However, there are limitations that also should be considered. Above all, the season of measurement affecting cutaneous ultraviolet-b exposure and dietary sources or vitamin D supplements that could influence serum 25(OH)D levels were not taken into account. Moreover, the present study had a cross-sectional design, which does not allow the evaluation of temporal relationships. Finally, despite adjustment for confounders, residual and unmeasured confounders may affect the results. In the KNHANES IV survey, 17% of Korean men and 27% of Korean women consumed vitamin and mineral supplements (Park, 2011). Although there are no representative data on the use of sunscreen in Korean adults, a clinical based study reported that 18% of men and 51% of women routinely used sunscreen (Bae et al., 2003). Given that people consuming supplements or using sunscreen have a healthier lifestyle, which may benefit body composition, the unmeasured lifestyle may explain the apparent association between body composition and vitamin D status. Additionally, data on the use of glucocorticoids and anticonvulsants, which may influence vitamin D status and body composition, were not available. In conclusion, in a population-based study using a national representative sample, total and regional body fat percentage and lean mass measured by DXA are associated with vitamin D deficiency or a low serum 25(OH)D level in men, independently of age, residential place, housing status, occupation, smoking, alcohol use, physical 1.2* 1.6* Men Figure 2 Odds ratio of vitamin D deficiency {serum 25- hydroxyvitamin D [25(OH)D] <20 ng ml 1 } in the subgroup of combined tertiles of total fat percentage and total lean mass compared to the reference group (highest tertiles of total lean mass and lowest tertiles of total fat percentage) after adjusting for age, smoking, Alcohol Use Disorder Identification Test score, physical activity, residential place, housing status, occupation and medical history in men. *P < Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd. 111

8 Body composition and vitamin D activity, medical history and calcium intake. There were found no or inconsistent associations in pre- and postmenopausal women, indicating a specific role of sex in these associations. Therefore, body composition may be a relevant indicator when assessing the risk of low vitamin D status in men. Further studies should be performed aiming to achieve a better understanding of these findings and to provide insights into whether the findings of the present study can be replicated in other populations. Conflict of interests, source of funding and authorship The author declares that there are no conflicts of interest. There is no funding to be declared. The author critically reviewed the manuscript and approved the final version submitted for publication. References Bae, J., Kim, S., Jang, S., Choi, J., Sung, K., Moon, K. & Koh, J. (2003) Awareness of harmful effects of sun exposure and sunscreen use in Korean. Korean J. Dermatol. 41, Barbor, T.F., Higgins-Biddle, J.C., Saunders, J.B. & Monteiro, M.G. (2001) The Alcohol Use Disorders Identification Test: Guidelines for Use in Primary Care. Geneva: World Health Organization, Department of Mental Health and Substance Dependence. Barnard, K. & Colon-Emeric, C. (2010) Extraskeletal effects of vitamin D in older adults: cardiovascular disease, mortality, mood, and cognition. Am. J. Geriatr. Pharmacother. 8, Beydoun, M.A., Boueiz, A., Shroff, M.R., Beydoun, H.A., Wang, Y. & Zonderman, A.B. (2010) Associations among 25-Hydroxyvitamin D, diet quality, and metabolic disturbance differ by adiposity in adults in the United States. J. Clin. Endocrinol. Metab. 95, Bischoff, H.A., Borchers, M., Gudat, F., Duermueller, U., Theiler, R., Stahelin, H.B. & Dick, W. (2001) In situ detection of 1,25-dihydroxyvitamin D3 receptor in human skeletal muscle tissue. Histochem. J. 33, Ceglia, L. (2008) Vitamin D and skeletal muscle tissue and function. Mol. Aspects Med. 29, Ceglia, L., Chiu, G.R., Harris, S.S. & Araujo, A.B. (2011) Serum 25-hydroxyvitamin D concentration and physical function in adult men. Clin. Endocrinol. 74, Cheng, S., Massaro, J.M., Fox, C.S., Larson, M.G., Keyes, M.J., McCabe, E.L., Robins, S.J., O donnell, C.J., Hoffmann, U., Jacques, P.F., Booth, S.L., Vasan, R.S., Wolf, M. & Wang, T.J. (2010) Adiposity, cardiometabolic risk, and vitamin D status: the framingham heart study. Diabetes 59, Choi, H.S., Oh, H.J., Choi, H., Choi, W.H., Kim, J.G., Kim, K.M., Kim, K.J., Rhee, Y. & Lim, S.K. (2011) Vitamin D insufficiency in Korea a greater threat to younger generation: the Korea National Health and Nutrition Examination Survey (KNHANES) J. Clin. Endocrinol. Metab. 96, Flynn, M.A., Nolph, G.B., Baker, A.S. & Krause, G. (1992) Aging in humans: a continuous 20-year study of physiologic and dietary parameters. J. Am. Coll. Nutr. 11, Foo, L.H., Zhang, Q., Zhu, K., Ma, G., Trube, A., Greenfield, H. & Fraser, D.R. (2009) Relationship between vitamin D status, body composition and physical exercise of adolescent girls in Beijing. Osteoporos. Int. 20, Ginde, A.A., Liu, M.C. & Camargo, C.A. Jr (2009) Demographic differences and trends of vitamin D insufficiency in the US population, Arch. Intern. Med. 169, Harris, S.S. & Dawson-Hughes, B. (2007) Reduced sun exposure does not explain the inverse association of 25- Hydroxyvitamin D with percent body fat in older adults. J. Clin. Endocrinol. Metab. 92, Holick, M.F. (2009) Vitamin D status: measurement, interpretation, and clinical application. Ann. Epidemiol. 19, Hypponen, E. & Power, C. (2006) Vitamin D status and glucose homeostasis in the 1958 British birth cohort: the role of obesity. Diabetes Care 29, Judd, S.E. & Tangpricha, V. (2009) Vitamin D deficiency and risk for cardiovascular disease. Am. J. Med. Sci. 338, Konradsen, S., Ag, H., Lindberg, F., Hexeberg, S. & Jorde, R. (2008) Serum 1,25-dihydroxy vitamin D is inversely associated with body mass index. Eur. J. Nutr. 47, Kuchuk, N.O., Van Schoor, N.M., Pluijm, S.M., Chines, A. & Lips, P. (2009) Vitamin D status, parathyroid function, bone turnover, and BMD in postmenopausal women with osteoporosis: global perspective. J. Bone Miner. Res. 24, Lenders, C.M., Feldman, H.A., Von Scheven, E., Merewood, A., Sweeney, C., Wilson, D.M., Lee, P.D., Abrams, S.H., Gitelman, S.E., Wertz, M.S., Klish, W.J., Taylor, G.A., Chen, T.C. & Holick, M.F. (2009) Relation of body fat indexes to vitamin D status and deficiency among obese adolescents. Am. J. Clin. Nutr. 90, Looker, A.C. (2005) Body fat and Vitamin D status in black versus white women. J. Clin. Endocrinol. Metab. 90, Mccarty, M.F. & Thomas, C.A. (2003) PTH excess may promote weight gain by impeding catecholamine-induced lipolysis-implications for the impact of calcium, vitamin D, and alcohol on body weight. Med. Hypotheses 61, Parikh, S.J., Edelman, M., Uwaifo, G.I., Freedman, R.J., Semega-Janneh, M., Reynolds, J. & Yanovski, J.A. (2004) The relationship between obesity and serum 1,25-dihydroxy vitamin D concentrations in healthy adults. J. Clin. Endocrinol. Metab. 89, Park, H. (2011) Top 10 dietary supplements of Korean adults from the 4th Korea National Healthy and Nutrition Examination Survey. Korean J. Fam. Med. 32, Snijder, M.B., Van Dam, R.M., Visser, M., Deeg, D.J.H., Dekker, J.M., Bouter, L.M., Seidell, J.C. & Lips, P. (2005) 112 Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd.

9 Body composition and vitamin D Adiposity in relation to Vitamin D status and parathyroid hormone levels: a population-based study in older men and women. J. Clin. Endocrinol. Metab. 90, Stewart, J.W., Alekel, D.L., Ritland, L.M., Van Loan, M., Gertz, E. & Genschel, U. (2009) Serum 25- hydroxyvitamin D is related to indicators of overall physical fitness in healthy postmenopausal women. Menopause 16, Wortsman, J., Matsuoka, L.Y., Chen, T.C., Lu, Z. & Holick, M.F. (2000) Decreased bioavailability of vitamin D in obesity. Am. J. Clin. Nutr. 72, Young, K.A., Engelman, C.D., Langefeld, C.D., Hairston, K.G., Haffner, S.M., Bryer-Ash, M. & Norris, J.M. (2009) Association of plasma vitamin D levels with adiposity in Hispanic and African Americans. J. Clin. Endocrinol. Metab. 94, Journal of Human Nutrition and Dietetics ª 2013 The British Dietetic Association Ltd. 113