Widely Used, Unlikely Stress Reducer: Salt

Sunset at Sea, 1882There may be a very good reason for the impulse to reach for salt-laden foods and snacks. New research from the University of Cincinnati, reported in the April 6, 2011, issue of The Journal of Neuroscience, shows that elevated consumption of salt can reduce the body’s natural stress reaction. Sodium, the main ingredient of salt, inhibits the release of hormones along the hypothalamic-pituitary-adrenal (HPA) axis, which are released into circulation in reactions to stressors. More specifically, an elevated sodium intake limits the stress reaction by suppressing the release of the octapeptide angiotensin II (Ang II), which provides the major hormonal support of the growth and function of the zona glomerulosa of the adrenal cortex and the secretion of the excitatory hormone aldosterone. Conversely, higher sodium intake increases the activity of oxytocin, an anti-stress hormone.

Life stressors cause an immediate challenge to the body’s homeostatic balance, and cause physiological and psychological reactions that affect hormonal, cardiovascular, and behavioral responses. This new research examined the neural mechanisms underlying the stress reaction within the context of such a homeostatic challenge. The focus was on the impact of an elevated intake of sodium on the hypothalamic-pituitary-adrenal (HPA) axis, the cardiovascular system, and behavior in response to an acute psychological stressor.

Relative to controls whose sodium levels were normal, subjects with elevated salt intake showed a decrease in HPA activation in response to a psychological stressor. In addition, the increase in sodium also reduced the cardiovascular response and promoted faster recovery to pre-stress levels. Even more remarkable, subjects with increased sodium intake had significantly more oxytocin- and vasopressin-containing neurons within the supraoptic and paraventricular nuclei of the hypothalamus and greatly elevated circulating levels of oxytocin. The endocrine and cardiovascular profile of subjects with elevated sodium also produced a decrease in anxiety-like behaviors when they were put through a social interaction test.

The researchers concluded that the results single out sodium as a potent inhibitor of the HPA, cardiovascular, and behavioral aspects of the stress reaction.

Eat More Salt, Feel Less Stress?

Apparently, we are already doing so, by the millions of pounds. Americans have consistently consumed approximately 3,700 mg of sodium daily throughout the last three decades, or nearly 65% more than the recommended daily salt intake of 2,300 mg. Most restaurant food, prepackaged and processed food, deli food, table and bar snacks, and fast food are loaded with salt, sugars and fats. Sodium is added primarily as a flavor enhancer, but also to satisfy our hidden and very powerful salt appetite.

The downside of elevated salt consumption: too much sodium is a precipitating factor in heart failure, an increased risk for gastric cancer, a contributor to hypertension. In fact, the ill-effects of too much sodium consumption are so widespread throughout the body that salt-intake reduction is often one of the first approaches to the treatment of a variety of metabolic conditions. Could it be that this widely used (and tasty) stress reducer is not what it appears to be? Perhaps its “calming” and anxiety reduction effects—much like those of alcohol—come at a price that, if properly understood, we may not be willing to pay.