Objectives: To investigate the relationship between salt sensitivity and hyperinsulinaemia in rural black African subjects.
Design: An intervention study where 27 subjects were divided into two groups; group 1 was initially salt loaded (300 mmol Na+/day), while group 2 was salt restricted (25 mmol Na+/day), each for 4 days, after which a cross-over study was done.
Setting: Chidamoyo, a rural area 383 km north of Harare, Zimbabwe.
Subjects: Twenty-seven rural volunteers (16 women, 11 men).
Outcome measures: Systolic and diastolic blood pressures, salt sensitivity, insulin and glucose levels, body mass index and mean arterial pressure.
Results: Mean arterial pressure, which was 91 +/- 2 mmHg on a low-salt diet, increased significantly (P < 0.01) to 105 +/- 3 mmHg on high-salt diet in the salt-sensitive subjects. In the same salt-sensitive subjects, the fasting insulin level was 8.4 +/- 0.8 microU/ml on a low-salt and 6.1 +/- 1.0 microU/ml on a high-salt diet. The difference was not statistically significant.
Conclusions: Although salt pressor sensitivity was demonstrated in the subjects, there was no accompanying increase but rather a decrease in fasting insulin levels, suggesting that in the short term, salt sensitivity and hyperinsulinaemia are not linked in raising blood pressure in this sample of rural Zimbabwean subjects.