Association of blood pressure, serum vitamin D, calcium and PTH in individuals over 40 in East Tehran

Introduction: Mean systolic and diastolic blood pressures and prevalence of hypertension vary throughout the world. These differences have mostly been explained by changes in diet and racial differences. However, it is believed that other factors such as calcium, vitamin D and PTH status may contribute to its pathogenesis. This study was conducted to assess the association between the serum 25-hydroxyvitamin D level and blood pressure and also between Ca, PTH and blood pressure among a group of individuals residing in Tehran. Materials and Methods: In this cross-sectional study, 251 subjects aged ≥ 40 years, 123 subjects with low vitamin D (≤ 20 ng/ml) and 128 with normal vitamin D levels(>20 ng/ml), were randomly selected from the population of the Tehran Lipid & Glucose Study (TLGS). Subject data included clinical, diet and biochemical information. Systolic blood pressure ≥ 140mm/Hg or diastolic blood pressure ≥90mm/Hg were considered as hypertension. Blood samples were taken and serum calcium, phosphorus, PTH and 25,OH vitamin D were measured. Nutritional assessment was done according to 72-hour recall and Ca and fiber intake were calculated. For each subject the energy intake to basal metabolism rate (EI:BMR) was calculated. Individuals having EI:BMR <1.35 and ≥2.4 were considered to be under-reporters and over-reporters, respectively. While comparing normotensive and hypertensive subjects for calcium intake and the correlation between blood pressure and Ca intake, under- and over-reporters were excluded. For data analysis, Student’s t test and Pearson correlation coefficient were used. Results: In this study 136 men and 115 women aged 40-72 years (mean±SD: 50±8) were studied. Mean age, BMI, waist, FBS, TG, CHOL, LDL, Ca, P, PTH and Albumin measurements, and also fiber and calcium intake were not significantly different between the two groups with normal and low serum vitamin D levels. 57 subjects (%22.7) were hypertensive. Comparing hypertensive and normotensive subjects, no significant difference between serum Ca, PTH and vitamin D status was seen in these subjects. After excluding under- and over-reporters and adjusting for fiber, calcium intake was also not significantly different between the two groups. In this study, correlations between serum calcium and PTH with blood pressure were not significant. No significance association was found between vitamin D and systolic blood pressure, diastolic blood pressure and mean arterial blood pressure. Conclusion: The results of this study suggest that no significant association exists between blood pressure and the serum 25-hydroxy vitamin D, calcium, PTH and calcium intake status of subjects aged≥ 40 years.