Effects of dietary sodium substitution with potassium and magnesium in hypertensive type II diabetics: a randomised blind controlled parallel study

We have previously demonstrated that modest sodium restriction has a hypotensive effect in hypertensive diabetic subjects. A randomised blind controlled study has therefore been performed to study the effect of replacement of added salt intake using a salt substitute (50% NaCl, 40% KCL, 10% Mg2+, supplied by Cederroth, Sweden), compared to added whole salt intake over a 9 month period of 40 hypertensive Type II diabetic subjects (mean age 62.5 +/- 7.8 years; 24 males and 16 females). After 3 months, there was a significant reduction in systolic blood pressure (SBP) in the salt substitution group (163.2 +/- 24.2 to 153.6 +/- 20.8 mm Hg; P < 0.03) which was maintained at 9 months, when compared to the whole salt group (151.5 +/- 20.6 vs 173 +/- 18.9 mm Hg; P < 0.05). No significant changes were observed in mean weight, fasting lipid or insulin levels or diabetic control (measured by glycosylated haemoglobin). A greater number of patients were withdrawn during the study period owing to consistent BP > 160/95 in the whole salt group (n = 10) compared to salt substitute (n = 4). No significant changes were observed in diastolic pressure, 24-h urine sodium or magnesium excretion, but urine potassium was significantly increased in the salt substitute group (58.8 to 77.3: P < 0.05). The results of this study suggest that substitution of sodium, by potassium and magnesium, produces a clinically significant reduction in SBP in hypertensive Type II diabetic patients, and should be a useful antihypertensive therapy in this patient group.