Dietary sodium and potassium intake and their association with blood pressure in a non-hypertensive Iranian adult population: Isfahan salt study

Aim: The association of sodium (Na) and potassium (K) intake with blood pressure (BP) is an ongoing debate, especially in central Iran. We aimed to examine the mean Na and K intake, major sources of Na and the relationship between BP and dietary and urinary Na and K.

Methods: This cross-sectional study was performed in central Iran in 2013-2014. A total of 796 non-hypertensive adults aged >18 years were randomly recruited. The semi-quantitative food frequency questionnaire was used to assess dietary Na and K intake. Moreover, 24-hour urine samples were collected to measure 24-hour urinary Na (UNa) and K (UK) as biomarkers. BP was measured twice on each arm using a standard protocol.

Results: The mean Na and K intake were 4309.6 ± 1344.4 and 2732.7 ± 1050.5 mg/day, respectively. Table and cooking salt were the main sources of Na. Odds ratio (OR) (95% confidence interval (CI)) of the crude model in the highest quartile of UNa indicated a significant association with the higher risk of prehypertension (OR (95% CI): 2.09 (1.09-4.05); P for trend = 0.007). After adjustment for potential confounders, prehypertension was significantly associated with increasing dietary Na/K ratio (OR (95% CI): 1.28 (1.01-1.57); P for trend = 0.046) and UNa/UK ratio (OR (95% CI): 2.15(1.08-4.55); P for trend = 0.029).

Conclusions: Increasing dietary and urinary Na/K ratios and UNa were associated with elevated BP and prehypertension occurrence. These findings support the necessity of developing a salt reduction programme in our country.