Determination of vitamin D serum levels in women receiving vitamin supplementation: The PERSIAN Guilan Cohort Study

Background: Vitamin D is a basic nutrient and plays a very crucial role in preventing various diseases, so it is known as an indicator of health and survival. Objective: This study was conducted to determine the serum level of vitamin D in women receiving vitamin supplementation in Persian Guilan cohort study (PGCS). Methods: In this analytic cross-sectional study that was conducted on PERSIAN Guilan cohort, 614 subjects from 5633 women aged 35 to 70 years old who were taking vitamin D supplements were selected through census method. Required data were collected in two sections of demographic and social characteristics and serum measurement 25-hydroxy vitamin D3 at three levels of deficient (<10), insufficient (10-20) and sufficient (>20 ng/ml). Data analysis was done using descriptive and inferential statistics. P <0.05 was considered statistically significant. Results: The mean age of people was 50.3±8.7 years, of which 5.2 % of the subjects had vitamin D deficiency, 29.5% had insufficient serum level and 65.4% subjects with sufficient serum levels. Based on the results, there was a significant relationship between employment status, place of residence and housing area with vitamin D level (P<0.05), and non-employed persons (P=0.044), living in the city (P=0.002) and a residential house with a higher area (P=0.014) had higher levels of vitamin D. There was no significant association between serum vitamin D levels with age, body mass index, marital status, alcohol consumption, level of education and how to take vitamin D supplementation. Conclusion: In the present study, about one third of vitamin consumers did not have a sufficient serum level despite taking the supplement, so it is expected that the country's health system, health officials, and policymakers pay attention to the education program of optimum consumption as well as appropriate prescription of vitamin D supplement.