Sodium is an essential mineral found inside all of your cells and in the fluids bathing your cells and tissues. While a little sodium is necessary for good health, excessive dietary intake of sodium, mainly as salt, is associated with high blood pressure and other health problems. Your body possesses mechanisms for maintaining optimal sodium levels in your bloodstream. Aldosterone, a hormone released by your adrenal glands in response to blood sodium concentrations, can be affected by sodium consumption.
Sodium’s primary function in your body is to regulate fluid balance. In his book, “Staying Healthy with Nutrition -- The Complete Guide to Diet and Nutritional Medicine,” Dr. Elson Haas concisely summarizes sodium’s role in fluid management when he says, “Where sodium goes, water goes.” In general, the more sodium you have in your tissues, the more water you must retain to maintain proper sodium concentrations. In addition to its importance in fluid balance, sodium helps modulate the acid-base balance in your tissues, and the shifting of sodium ions across cell membranes helps generate the impulses that allow your nerves and muscles to function.
Sodium concentrations in your tissues are regulated by a variety of mechanisms. By releasing hormones in response to variations in blood pressure, your kidneys tightly control sodium levels in your bloodstream. In addition, specialized stretch receptors in the walls of your blood vessels send signals to your brain regarding your serum sodium concentration, blood volume and blood pressure. Your brain interprets these signals and sends messages to your adrenal glands, which then alter their release of hormones – epinephrine, norepinephrine and aldosterone – that control your heart rate, blood vessel diameter and kidney function. If you consume more sodium, these mechanisms work to return your body to a normal balance.
Aldosterone, a hormone secreted by the outer layer of your adrenal glands, stimulates your kidneys to absorb more sodium and water while simultaneously releasing more potassium. Aldosterone secretion is increased by several mechanisms, including decreased blood flow to your kidneys, high serum potassium concentrations, increased acidity of your blood and falling blood pressure. In contrast, aldosterone secretion decreases as kidney blood flow increases, serum potassium levels fall, and blood volume increases. Serum sodium concentrations also affect aldosterone production. A study published in the April 1985 issue of “Endocrinology” demonstrated that increased serum sodium concentrations – a direct result of increased sodium consumption – decrease aldosterone secretion.
Aldosterone secretion is influenced by a complex interplay of several factors. Falling blood pressure, increasing potassium levels, higher blood acidity and decreased serum sodium concentrations trigger the release of aldosterone from your adrenals. Conversely, increased blood pressure, low potassium levels and high sodium levels inhibit aldosterone secretion. If you consume excess salt, your adrenals reduce their production of aldosterone, thereby allowing your kidneys to excrete more sodium. There are no recommended dietary allowances for sodium as it is widely available in foods. In fact, dietary sodium excess is more problematic than too little sodium. The American Heart Association recommends that you consume less than 1,500 mg of sodium daily, just a little over a half teaspoon of table salt.