Salt restriction and increased insulin production in hypertensive patients

The present study was performed to evaluate glucose metabolism, serum lipids and sympathetic activity during 12 weeks of a moderate salt restricted diet in hypertensive patients. The study was designed as a pre-test-post-test study. All patients from a controlled trial evaluating self-monitoring of urine chloride concentration as a remedy for enhancing diet compliance and blood pressure effect were included. Twenty male patients and 14 female patients with essential hypertension (mean age 53 years) were randomized to a self monitoring diet group and a diet only group. They were exposed to a moderately salt restricted diet during 12 weeks. Fasting serum insulin C-peptide, glucose, HbA1c, total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides were measured along with 24 h urine excretion of adrenaline, noradrenaline and vanillylmandelic acid (VMA). As a result, insulin C-peptide increased by 40% (p = 0.0001) whereas glucose rose by 6% (p = 0.02). Total cholesterol, LDL-cholesterol and HDL-cholesterol concentration were reduced by 6% (p = 0.001), 12% (p = 0.008) and 11% (p = 0.004) respectively. HbA1c, serum triglycerides, total/HDL-cholesterol ratio, urine catecholamines and VMA were unchanged during the trial. It is concluded that salt restriction may increase insulin resistance in hypertensive patients.