Dietary salt contributes to high blood pressure by increasing blood volume. The heart has to work harder to pump thicker blood which increases blood pressure.
Women are more prone towards high blood pressure at the onset of menopause and postmenopausally. As such, evidence is accumulating in regard to the role of estrogen and high blood pressure (hypertension). A recent study by The University of Texas Health Science Center concluded that estrogen protects against high salt hypertension by attenuating (lessening) the activation of the sympathetic nervous system.
Salt sensitive and salt resistant female rats were fed a 4% NaCl diet. Blood pressure was measured by radiotelemetry. Subjects were divided into three groups: those producing estrogen, not producing estrogen, and those not producing estrogen but supplemented with estrogen replacement. After eight weeks, sympathetic nervous system activation was assessed by urinary excretion of norepinephrine, and by the blood pressure response to ganglionic blockage. Norepinephrine is a biochemical marker of sympathetic nervous system activation.
Subjects not producing estrogen had a significantly higher blood pressure 175 ± 6 mm Hg compared to subjects producing estrogen 153 ± 5 mm Hg. Estrogen replacement in salt sensitive subjects not producing estrogen prevented the increase in blood presure 152 ± 6 mm Hg.
Urinary norepinephrine was significantly greater in subjects not producing estrogen 40 ± 8 ng/ml compared to subjects producing estrogen 21 ± 2 ng/ml. Estrogen replacement in subjects prevented the increase in norepinephrine excretion 20 ± 1 ng/ml.
In salt sensitive subjects, the fall in blood pressure with ganglionic blockage was increased in those not producing estrogen compared to those producing estrogen, which was prevented with estrogen replacement.
This study concluded that estrogen loss augments (increases), and estrogen replacement attenuates(lessens) the effect of the sympathetic nervous system to hypertension in salt sensitive subjects on a high salt diet.
Postmenopausal women naturally experience a loss of estrogen which may predispose some women to high blood pressure. A low sodium diet at midlife is beneficial to arterial health/function.
Source:
Effect of estrogen on sympathetic nervous system activation in high salt hypertension
Carmen Hinojosa-Laborde, Cindy Mehring and Teresa Craig Anesthesiology, University of Texas Health Science Center at San Antonio, San Antonio, TX
The FASEB Journal. 2008;22:941.7
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