Blood pressure response to acute changes in dietary sodium in young Zimbabwean men

The primary objective of this study was to determine the effect of acute alterations in sodium intake upon the blood pressure and hormone levels of young Zimbabwean men.

Blood pressure, 24-h urinary electrolyte excretion and plasma concentrations of angiotensin II, aldosterone, and atrial natriuretic peptide were measured in normotensive black medical students. Three sets of measurements were taken: (1) during free access to sodium (baseline); (2) after 4 days on a low-sodium diet (10 mmol/day); and (3) after 4 days on a high-sodium diet (800 mmol/day).

Blood pressure was measured by random zero sphygmomanometry, hormone levels by radioimmunoassay, and urinary electrolytes by flame photometry.

The low-sodium diet caused the range of pulse pressure to narrow, with a decrease in systolic blood pressure (SBP) and an increase in diastolic blood pressure (DBP). With the introduction of the high-sodium diet, SBP increased and DBP decreased. Mean arterial pressure did not change. At the same time, angiotensin II and aldosterone decreased. Plasma atrial natriuretic peptide did not change. A subgroup of the men on the high-sodium diet also received 100 mmol potassium/day. The increase in SBP associated with high sodium was significantly attenuated by the presence of added potassium.

SBP of young black Zimbabwean men is lowered by dietary sodium restriction and rises with a large increase in dietary sodium for a short duration, but mean arterial pressure does not change due to the opposing decreases in DBP.