Dietary intake of calcium, magnesium and potassium in relation to blood pressure: Tehran Lipid and Glucose Study

In spite of many studies about the association of diet with blood pressure, yet the relationship between micronutrients and blood pressure remains obscure. This study aimed at evaluating the dietary intake of calcium, magnesium and potassium in relation to blood pressure. Trained interviewers collected dietary data on 1470 participants of Tehran Lipid and Glucose Study by means of two 24-hour dietary recalls. Energy intake (EI) to BMR ratio was calculated. Under- and over-reporters (EI: BMR<1.35 and >=2.4, respectively) were excluded from the study. Trained physicians according to standard protocols measured blood pressure. Hypertension was defined as SBP≥140 or DBP≥90 mmHg. After excluding subjects who used blood pressure-lowering drugs or vitamin-mineral supplements 94 hypertensives were included in the study. Normotensive persons, as control group, were selected randomly from subjects who were matched with hypertensives regarding age, sex, weight, BMI, energy and fiber intake. Mean ± SD of age was 42± 15 and 41± 15years for hypertensives and normotensives, respectively. Dietary intakes of calcium, magnesium and potassium were lower than RDA. Hypertensives had lower intake of calcium and potassium than normotensives (611±256 vs. 771±276 mg/d and 2461±808 vs. 2740±691 mg/d). Magnesium intake was not significantly different between the two groups. Blood pressure was decreased with calcium and potassium intake, but not with magnesium intake. The results showed an inverse correlation of calcium and potassium with blood pressure. There was no relationship between magnesium and blood pressure.