The Relationship Between Vitamin D and Body Mass Index ... - IDOSI

Middle-East Journal of Scientific Research 24 (5): 1628-1637, 2016 ISSN 1990-9233 © IDOSI Publications, 2016 DOI: 10.5829/idosi.mejsr.2016.24.05.23500

The Relationship Between Vitamin D and Body Mass Index among Faculty Members of King Abdulaziz University 1

Fatimah M. Yousef, 1Ola A. Alsayed and 2Elham A. Al Nagshabandi 1

Department of Food and Nutrition, Faculty of Home Economics, King Abdulaziz University, Jeddah, Saudi Arabia 2 Department of Medical Surgical Nursing, Faculty of Nursing, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract: Vitamin D deficiency is a global health problem worldwide and is considered to be a pandemic with implications for compromised bone health and other chronic diseases. Few studies have examined the association between vitamin D status and body mass index (BMI) related to parathyroid hormone (PTH). However, prospective data using the biomarker serum 25-hydroxyvitamin D 25(OH) D3 are limited and therefore examined in the present study. This study aims to evaluate the level of vitamin D status among healthy women and examine the relation between BMI and 25(OH)D3 and PTH levels in a cross-sectional sample of 100 women ranging in age from (25-45) years. Participants were selected from the faculty members of King Abdulaziz University, Jeddah, Saudi Arabia between October 2014 to May 2015. Anthropometric measurements, personal, medical history questionnaire, food frequency questionnaire (FFQ) for vitamin D and sun exposure questionnaire were collected from all the participants in the present study, blood samples for serum 25(OH)D3 and PTH were collected from all subjects. The obtained results showed that the majority of healthy women case of the study by 83.0% has deficiency in vitamin D status, while 14.0% have insufficiency in vitamin D, whereas only 3.0% have sufficiency in 25 (OH) D3 concentrations with a mean level of 34.71±15.6 SD. Moreover, the study showed negative association between level of circulating 25(OH) D3 and PTH (P=0.01) and there is a statistically significant and inverse correlation between level of circulating 25(OH) D3 and BMI (P=0.04). It can be concluded that 83% of participants consisted of healthy women is in deficient status of vitamin D, while 3% showed sufficient status with higher levels of PTH and most of these have high BMI. Key words: Body mass index

Vitamin D status

Parathyroid hormone

INTRODUCTION Vitamin D is a fat soluble vitamin that functions as pre-hormone and it is naturally present via a few food or supplements. It has the ability to target many specific tissues in the body [1]. Also, it promotes absorption of calcium from the small intestine and the major biological function is to maintain normal blood levels of calcium and phosphate [1]. Vitamin D can be synthesized endogenously by direct sun exposure strike the skin and trigger vitamin D synthesis [2]. Vitamin D obtained from sun exposure, food and supplements is biologically interactions and must undergo two hydroxylations in the body. The first activation occurs in the liver which Corresponding Author:

converts vitamin D to 25-hydroxyvitamin D (25(OH) 2D3), also known as calcidiol is the best measure for vitamin D level [3]. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D (1,25(OH) 2D3), also known as calcitriol [3]. Numerous characteristics such as body fat darker skin tone and physical activity also contribute to vitamin D status [2, 3]. The prevalence of vitamin D deficiency has become a major public health problem [4]. Even though, Ultraviolet (UV) sunlight in Saudi Arabia is high throughout the year, Saudi Arabian people have severe vitamin D deficiency especially women [5]. In 2015, female Saudis aged 15 and older examine for vitamin D deficiency, 54.4% in women under age of 50 and more than 50- 60% in postmenopausal

Fatimah M. Yousef, Department of Food and Nutrition, Faculty of Home Economics, King Abdulaziz University, Jeddah, Saudi Arabia.

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women reported to have vitamin D deficiency [6]. The role of vitamin D in many biological systems has been actively researched in recent years [1]. Vitamin D insufficiency also increases the risk of bone loss and osteoporotic fractures in older people. Previous studies have reported an association between vitamin D insufficiency and increased risk of chronic diseases such as colorectal cancer, hypertension, cardiovascular disease, diabetes mellitus and obesity [7, 8]. Obesity is an excessive accumulation of body fat and in its gross manifestation poses a real threat to health. It is the most prevalent, chronic medical condition in the developed as well as in the developing countries. The World Health Organization (WHO) defined obesity as a body mass index (BMI) of 30 kg/m2 or more, is pandemic. In Saudi Arabia, WHO showed that the prevalence of obesity in males is 28.6% and in females is 39.1% [9]. In a Saudi study it was found that the prevalence of obesity was 49.15% in women and 29.94% in men [10]. In another study the prevalence of overweight and obesity was higher amongst a group of married women than among a group of single women [11]. The potential link between vitamin D and obesity was observed from ancient time. They demonstrated that there is a consistent association between increased body fat or BMI and lower serum 25(OH)2D3 concentrations which could be attributed to the sequestration of the fat-soluble vitamin D in the adipose tissue [8] . In 2013 there is a large study that found a correlation between the lower concentration of 25(OH)2D3 with higher level of parathyroid hormone (PTH) and low 1,25(OH)2D3 concentrations [12]. In another study the percentage of body fat content is inversely related to the level of serum 25(OH)2D3 in healthy women [13]. Therefore, the present study aims to evaluate the level of vitamin D status among healthy women and to examine the relations between BMI and 25(OH)D3 and PTH levels. Statement of Purpose: This is the first study was carried out at Department of Food and Nutrition, King Abdulaziz University of Saudi Arabia to investigate the level of vitamin D status and the relations between BMI and 25(OH)D3 and PTH levels among healthy women of the faculty members of King Abdulaziz University. This study can help to evaluate the vitamin D status in healthy women and know the reason to vitamin D deficiency and the reason to BMI increase in women. Hopefully the result of the research will fill the gap between utilizing scientific knowledge and applying them in clinical practices as well

as preventing common diseases in Saudi women population. Hypothesis: Vitamin D status in Saudi women will be below the standard level (20 ng/ml). Low level of circulating 25(OH) D3 will be associated with increased body mass index and higher PTH. Low level of circulating 25(OH) D3 will be associated with increasing waist circumference. Subjects and Methods Study Design: Cross-sectional study to investigate the association of serum 25(OH)D concentrations with BMI and PTH [14]. Subjects: In this study we recruited 100 women (25-45) years [15], from King Abdulaziz University, Jeddah Saudi Arabia between October 2014 to May 2015 as faculty members of different colleges. All participants completed consent form before entering this study and the collected blood samples for serum 25(OH)D3 and PTH for all subjects were routinely analyzed at KAU Hospital Biochemistry Lab. Exclusion criteria consisted of any subjects not resident of Saudi Arabia for at least 5 years, the presence of metabolic bone diseases, diabetes mellitus, cardiovascular disease, renal or hepatic endocrine, autoimmune disease and the participants not willing to provide blood samples [16, 17]. We collected measurements in accordance with generally accepted rules (weight, high, BMI and waist to hip ratio) [18] personal, medical history questionnaire, food frequency questionnaire (FFQ) for vitamin D (vitamin D research group iom, 2007/2008) and sun exposure questionnaire [19] from all the participants in the study. The intervieweradministered FFQ contained 20 food items that are found to contain, =10 IU of vitamin D3 and analyses item by nutrient values for each food item were derived from the 2008 United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference 28 [20]. Blood samples were routinely analyzed at King Abdulaziz University Hospital Biochemistry Lab. Both 25(OH)D and PTH were measured by immunochemiluminescent assay (Siemens Advia Centaur XP, Siemens Health care Diagnostics Inc., Tarrytown, NY, USA) [21-23]. The 25(OH)D concentration (expressed as nmol/l) given at baseline and in-study [24].

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Statistical Analyses: Stratified sample and descriptive tools (Frequency distribution and graphs) used. Furthermore, examine the normality of data by ShapiroWilk tests and examine the relationship of 25(OH) D with other variable done by Pearson correlation analysis. Chi-square was used to test variables on vitamin D. All statistical analyses were performed by using SPSS (version 20) (p 3% of body fat in women. Adiposity (percentage body fat) and BMI in non-morbidly obese persons are also inversely correlated with vitamin D status [27]. However, the association of adiposity with serum 25(OH)D is stronger than that with body weight and BMI [27]. The reason for this phenomenon may be that BMI and body weight do not necessarily reflect the percentage of body fat. Athletes and well-trained persons may have relatively high BMI and may be considered overweight or even obese, while they have quite low total fat mass [42]. A cohort studied done in Riyadh showed the prevalence of vitamin D deficiency in the cohort studied was 78.1% in females [43]. In the current study, about 83.0% of healthy women studied exhibited vitamin D deficiency and only 3% of all women were considered in sufficient state with a mean level of (34.71±15.6). This finding was consistent with the study done by Tuffaha et al.[6] which showed that 62.65% of Saudis women have vitamin D deficiency. Lack of sunlight exposure, lack of availability of vitamin D-fortified foods and lack of or insufficient vitamin supplementations were the most likely factors explaining the high prevalence of vitamin D deficiency. Saudi women wear the abaya, the headscarf and necab, minimizing any sun exposure outdoors which can be of protective clothing from the main source of vitamin D. Limited sun exposure due to intense heat, cultural reasons for covering the body and an infrastructure that makes sun exposure difficult [44]. Covering skin with clothing prevents skin from contacting with UV-B rays essential for production of vitamin D [44-46]. In the current study it was found that only 16% of the participants were exposed to the sun for more than 30 minute at last week and 50% of them exposed to the sun around 5-30 minute every week, where 34% of women exposed to the sun less than 5 minute. In 2009, study recorded that a white woman exposed to the sun for only

12 min of summer midday sun with bare arms and legs would produce approximately 3000 IU of vitamin D. In contrast, a similarly dressed woman with black skin would need 2 hours of sun exposure to produce the same [46]. Vitamin D deficiency is very common in the Middle-East and there is a relationship with skin covering clothes and staying outside of the sun [47]. In addition, our participants had slightly darker skin complexion, as most of Saudi Arabian women. It should also be noted that few foods naturally contain vitamin D2 or D3. In the United States, milk, yogurt, cereal and some bread products are fortified with vitamin D. Saadat-Ali et al. [48] showed that food items consumed in the Eastern Province of KSA were not fortified. In addition to that the study found that there is no significant association between total 25(OH) D3 concentration and vitamin D intake and types of dietary supplements due to the small sample size. In contrast, Mithal et al. [49] found that serum 25(OH)D3 levels below 75 nmol/L are prevalent in every region studied whilst levels below 25 nmol/L are most common in regions such as South Asia and the Middle East. Older age, female sex, higher latitude, winter season, darker skin pigmentation, less sunlight exposure, dietary habits and absence of vitamin D fortification are the main factors that are significantly associated with lower 25(OH)D3 levels. It was found a negative association between level of circulating 25(OH) 2D3 and PTH. This means that as PTH increases, the level of circulating 25(OH)D3 for healthy women case of the study decreases. Other study, Olmos et al. [50] showed the same finding in multivariate analysis, 25(OH) D3 levels were negatively correlated with serum PTH and body mass index. Serum PTH concentrations rise steeply when circulating 25(OH)D levels fall below the threshold of 8 ng/ml and the increase in PTH is significantly attenuated when 25(OH)D values exceed 20 ng/ml. The present study found that, there is a significant and inverse association between total 25(OH)D3 serum concentration and waist circumference at the significant level (0.05), while the results did not find any statistically significant association between total 25(OH)D3 concentration and (age, weight at 18 years, hip and WHR). In a study at 2005 it showed the same finding of higher body mass index and waist circumference that were statistically significantly associated with lower 25(OH)D3 and with higher PTH [51]. Also, Diaz et al. [52] found serum 25(OH)D levels were inversely correlated to waist circumference. They explored that there are only two factors that contributed positively or negatively on the level of 25(OH)D3 concentration at a significant level that include: how long exposed to sun light in the last week,

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which has a positive effect on the level of 25(OH)D3 concentration, which means as women are exposed more to sun light during the last week, this would contributed in increasing the level of 25(OH)D3 concentration. The second factor that has a significant effect on the level of 25(OH) D3 concentration is the total PTH concentration, which has a negative association with 25(OH)D3 concentration, that means total PTH concentration affect negatively on the level of 25(OH)D3 concentration, so as total PTH increases, that would lead to decrease in the level of 25(OH)D3 concentration. Limitations of this study are the possibility that the study was cross-sectional design and therefore, no inference on causality can be made. In addition the serum was drawn at only one time (in month October 2014 to May 2015) rather than multiple times. However, the strengths of our study was first study done in faculty members of King Abdulaziz University in female only to investigate vitamin D status in relation to BMI and PTH.

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CONCLUSION

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A significant inverse association between BMI and the serum levels 25(OH) D3 was found. Therefore, decreasing level of circulating 25(OH) D3 may highly contribute to increasing BMI. Further studies are needed to address the effect of VDR gene expression in adipose tissue with obesity and type II-diabetes. REFERENCES 1.

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