Levels of 25-OH Vitamin D in Healthy Asymptomatic Adults: Pilot Study

Transcription

1 Pak J Med Res Vol. 51, No. 3, 2012 Original Article Levels of 25-OH Vitamin D in Healthy Asymptomatic Adults: Pilot Study Rabail Javed, Sidra Yasmin Malik, Saima Yaqub, Farkhanda Ghafoor, Muhammad Asim National Health Research Complex, Pakistan Medical Research Council, Sheikh Zayed Medical Complex Lahore. Abstract Background: The deficiency of Vitamin-D has been reported in all age groups in developing countries; in spite of adequate sun light required for the production of 25-hydroxyvitamin D. Objectives: To determine the levels of vitamin D among healthy asymptomatic adults. Study type & settings: Hospital based analytical study, conducted at Sheikh Zayed Medical Complex, Lahore. Subjects and Methods: Healthy subjects between years, who were either the staff of the hospital or attendants of the patients were included. Those who were taking vitamin supplement, using sun screen and lactating mothers were excluded. A proforma including the demographic information, exposure to sun, diet intake and BMI was recorded for all subjects. 5cc of blood was taken from all, serum separated, stored at -20ºC. 25-hydroxyvitamin D levels were done within 48 hours using ELISA method. A value between nmol/l was taken as normal using international standards. Results: Eighty healthy adults were enrolled whose mean age was 47.2±6.3 years. The levels of vitamin D ranged between nmol/l. Levels were deficient in 25% subjects and insufficient in 73.7% giving an overall low level in 98.7% of the respondents. Only 1.3% had sufficient 25-hydroxyvitamin D levels. The levels did not show any significant difference between genders, skin pigment or dietary intake. The levels for the yrs age group were significantly higher when compared with those in the age groups of yrs and yrs (p<0.041 and respectively). The association of 25-hydroxyvitamin D with exposure to sunlight was significant (p<0.001). Respondents with BMI >30 had significantly lower 25-hydroxyvitamin D levels than those who had BMI between (p<0.036). Conclusions: Low levels of vitamin D were found in 98% of the apparently healthy population. Key words: Vitamin D, healthy adults, sun exposure, diet. Pakistan Journal of Medical Research, 2012 (July - September) 82

2 Levels of 25-OH Vitamin D in Healthy Asymptomatic Adults: Pilot Study V Introduction itamin D has two major physiologically relevant forms i.e. vitamin D 2 (ergocalciferol) and vitamin D 3 (cholecalciferol). Vitamin D without a subscript refers to either D 2 or D 3 or both. Vitamin D 2 is obtained from yeast and plant material 1 while, Vitamin D 3 is produced in the skin after exposure to ultraviolet light from the sun or artificial sources, and it also occurs naturally in some foods. It is stored in liver as 25(OH) Vit D 3. Fish, mushrooms, eggs, and meat are rich in vitamin D 3 and are recommended to those suffering vitamin D 3 deficiency. Vit D 3 deficiency has become current health issue worldwide 2 because it plays a vital role in bone metabolism and many cellular, immunological processes 3-6. Low levels of vitamin D 3 have been related to various chronic and infectious diseases including cancer, multiple sclerosis, diabetes, rheumatoid arthritis, osteoporosis, cardiovascular disease and microbial infections At latitudes away from the equator, the amount of ultraviolet light from sun during winter months becomes inadequate to allow cutaneous vitamin D 3 synthesis 6,17. The amount of vitamin D 3 in blood varies with the countries where people live, their skin color, age, race, adiposity 18 and other factors People with darker skin are at greater risk of vitamin D 3 deficiency because increased pigment reduces their capacity to manufacture vitamin-d 3 from sunlight 20. In western countries, high levels of vitamin D3 have been reported in July Sept and low in January March, due to shorter day lengths of winter, therefore, people rely on stored and dietary 25(OH) vitamin D 3 to maintain normal vitamin-d3 status 22. In Pakistan different studies from different sites have reported a deficiency of 25(OH) vitamin D 3 in 97% healthy population 16,23-25 and similar results were reported from India, where 50 to 90% population had insufficient 25 (OH) vitamin D 3 levels Pakistan is a tropical country, with adequate exposure of sunlight all the year round, to produce vitamin-d 3 but in spite this, there is a gross deficiency of vitamin D. This study was planned to measure the levels of serum 25(OH) vitamin-d 3 in healthy adults. Corresponding Author: Rabail Javed PMRC National Health Research Complex Sheikh Zayed Medical Complex Lahore. rabailjaveed@hotmail.com Subjects and Methods It was a hospital based analytical study conducted on healthy asymptomatic males and females who were aged between years. They were either staff of Sheikh Zayed Medical Complex, Lahore or attendants of patients attending the out door department of the same hospital. Those taking vitamins supplements, using sun blocks and pregnant and lactating women were excluded from the study. Since this was a pilot study the sample size of 80 was taken on the basis of tests which can be applied in a single kit along with standards and quality control materials. Out of 80 subjects equal distribution was made between 2 genders. After the clearance of Institutional Review Board (IRB) Sheikh Zayed Medical Complex Lahore. (IRB Number: 1112), objectives of the study were explained to participants who were fulfilling the inclusion criteria. A written informed consent was taken from each. A semi structured questionnaire was filled for each participant which, included variables like height (cm), weight (kg), BMI (kg/m 2 ) and age (years), sun exposure (hours/day), and dietary habits. Measuring cups, plates, models of one ounce piece of meat, specified amount of grains were used as a tool to estimate the exact amount of diet consumed (food frequency charts/usual intake) by each participant. Blood (5cc) was drawn from each subject; serum was separated and stored at -20 C. Samples were analyzed within 48 hours of collection using ELISA kit from IDS (USA) for D 3 International standard value for serum 25(OH) vitamin D levels was taken which ranged between nmol/l As per protocol of the manufacturer the vitamin D levels were classified into deficient (less than 25nmol/L), insufficient (25-75 nmol/l) and sufficient ( nmol/l). The calibration range of assay was upto 380nmol/L with analytical sensitivity of 5nmol/L. Sample handling and temperature conditions were strictly observed for all procedures according to manufacturer s instructions. For precision of assay, calibrated micro/multichannel pipettes from Gilson were used throughout the assay procedures and washing was performed with automatic plate washer. Analysis for reporting the vitamin D levels was carried out using softmax statistical package. For diagnostic assurance of results, all investigation was carried out with 6-7 standards points and 3 quality control pools in assay batch. All records were entered into Statistical Package for Social Sciences (SPSS version 15.0 for Windows; SPSS Inc., Chicago, IL, USA) for analysis. The quantitative variables like age, weight, height and BMI were presented as mean and standard deviation. The qualitative variables like gender, profession, diet, sunlight exposure, skin color, type of clothing and history of any related disease were presented as frequency and percentages. Value of p 0.05 was considered significant. Anova was used for comparison of vitamin D levels with variables like BMI, diet intake and sun exposure. Results A total of 80 healthy adults (40 males & 40 females) between years were enrolled. Their mean age was 47.2±6.3 years. Pakistan Journal of Medical Research, 2012 (July - September) 83

3 Rabail Javed, Sidra Yasmin Malik, Saima Yaqub, Farkhanda Ghafoor, Muhammad Asim Mean serum 25(OH) vitamin D levels did not differ in subjects aged between years (p>0.05) but for age group, it was significantly higher when compared with age group years and years (Table-1). The mean vitamin D levels were almost similar in males (41.88±12.4 nmol/l) and females (37.02±18.42 nmol/l). Table 1: Serum 25(OH) vitamin D levels by age. Age Serum 25(OH)Vitamin D (nmol/l) (years) N (%) Mean (%) ±SD Min. Max (48.8) (22.5) (18.8) (10) Total 80(100) Vitamin D levels were insufficient in 59(73.8%) participants, they were deficient in 20(25%) thus making an aggregate of 98.7% to be either deficient or insufficient. Only 1(1.3%) person had sufficient levels (Table-2). Table 2: Sufficiency of 25(OH) vitamin D levels among study participants. Serum 25 (OH) Vitamin D (nmol/l) N % Deficient (<25) Insufficient (25-74) Sufficient (75-250) Total The criterion of serum 25(OH) Vitamin D levels is based on National Osteoporosis Foundation Prevention-Vitamin D. Skin complexion was wheatish in (55%) participants, fair in 19(23.8%) and dark in 17(21.3%). The vitamin D levels were significantly lower [35.94±18.38 nmol/l, p-value 0.60] in those having fair complexion than those with wheatish and dark complexion (40.1±15.11 nmol/l and 43.04±13 nmol/l respectively). The duration of sun exposure showed a positive correlation with higher levels of vitamin D 3 (Figure-1). Taking obesity as a factor affecting the absorbance of sunlight; it was observed that with the increase in BMI the levels of 25(OH) vitamin D decreased (Table-3). The highest vitamin D levels [45.35±17.69] were seen in participants having normal BMI ( kg/m 2 ) while obese participants with BMI >30 kg/m 2 had significantly lower levels (38.83±15.14). Dietary factor on the basis of recommended daily allowance (RDA) for the age group years is 600 IU/day. It was seen that the daily intake of vitamin D of the study participants ranged between 6 IU/day-160 IU/day. A significant association was seen between serum vitamin D and dietary intake of vitamin D (Figure-2). Figure 1: 25(OH) vitamin D levels verses sun exposure. Table 3: Body Mass Index (BMI) & serum 25(OH) vitamin D levels. BMI(kg/m 2 ) 25 (OH) Vitamin D (nmol/l) Mean ±SD Min Max and Above Total Figure 2: Dietary vitamin D verses 25(OH) vitamin D levels among study participants. Discussion Deficient or insufficient vitamin D levels were found in 98.7% healthy adults, which showed no association with the dietary intake. Vitamin D plays an important role in bone, mineral metabolism and also provides immunity 35. Its deficiency leads to different diseases such as autoimmune disorders, cardiovascular disorders, various cancers, diabetes, hypertension, osteoporosis, fractures in bones, osteomalacia and rickets 36. Pakistan Journal of Medical Research, 2012 (July - September) 84

4 Levels of 25-OH Vitamin D in Healthy Asymptomatic Adults: Pilot Study In the present study the age group years was selected since most of the diseases like diabetes, hypertension, and cardiovascular etc. start in this age group. Several other studies have also selected this age group with the mean age of 47.2±6.3 years. In this study 25(OH) vitamin D levels were measured by using ELISA kit IDS (USA), based on the performance of this kit in vitamin D External Quality Assessment scheme (DEQAS) UK. In the current study, 25% had deficient and 73.8% insufficient levels while only 1.3% had sufficient vitamin D levels. In other studies on healthy adults the deficiency of 25(OH) Vitamin D ranged between 41.6 to 92%, and insufficient levels were present in 72% 35,41. Sunlight is a major provider of vitamin D to humans. Radiation in the Ultra Violet B ( nm) portion of the solar spectrum, photolyzes 7- dehydrocholesterol in the skin to previtamin D 3, which is later converted to vitamin D 3. Seasonal effect on vitamin D levels has been reported 35,39, The current study was conducted in summer and a strong relation was seen between 25(OH) vitamin D levels and sun exposure. Effect of pigmentation on production of Vitamin D is reported by other workers 47,48 also, while, a study from Denmark reported that vitamin D levels are not dependent on skin pigmentation 45. Absorption of sunlight is also affected by BMI. Adipose tissue in obese people is a barrier for UV radiations to produce 25 (OH) Vitamin D 14,50. In this study it was seen that with an increase in BMI the levels of vitamin D decreased. This was also reported by others 35, Diet is also a source to provide vitamin D. The daily recommended dietary intake of vitamin D is 600 IU/day for the adults of age years 55. None of the participants were taking the recommended daily intake of vitamin D in their food (Figure-2). This could be a reason for the insufficient levels seen in 73% subjects in the present study. 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