Sodium is a mineral vital to proper functioning of your cells. Sodium in your body exists primarily as a positively-charged atom, or cation, and its charge is critical to its function. Sodium works in concert with chloride, a negatively charged ion, and with potassium, another cation. For optimal health, you require between 1.2 and 1.5 g of this mineral in your daily diet, according to the Linus Pauling Institute at Oregon State University. However, too much sodium can cause health problems, and therefore you should not consume more than 2.3 g in a day. Consult a dietitian with concerns about your sodium intake.
Fluid Balance
Sodium is the predominant cation in the fluid surrounding your cells, and it helps determine the volume of this extracellular fluid. Because balancing this fluid to meet your body's needs includes regulating blood volume, and blood volume helps determine blood pressure, sodium plays a role in maintaining blood pressure. For example, if you experience a loss in blood volume because of dehydration, your blood pressure goes down, and your kidneys begin to retain sodium. Increased sodium in your extracellular fluid attracts water, which increases your blood volume and therefore your blood pressure.
Membrane Potential
The cationic property of sodium allows it to function in the electrochemical gradient process called the membrane potential. The membrane potential describes the difference in concentration between positively-charged sodium ions outside the cell and positively-charged potassium ions inside the cell. This concentration difference results in an electrical charge across the cell membrane that helps contract your muscles, transmit nerve signals and maintain your heartbeat. Between 20 and 40 percent of your resting energy goes toward membrane potential function throughout your body, advises the Linus Pauling Institute.
Absorption of Nutrients
The cells of your small intestine absorb nutrients following digestion. The membranes of these cells contain a protein called a sodium-dependent transporter. The function of this transporter is to bind a specific sugar from carbohydrate digestion or amino acid from protein digestion and ferry it from your gut, across the cell membrane and into the intestinal cell. The transporter proteins can bind the sugar or amino acid only after they have first bound a sodium ion. This process depends on the electrochemical gradient produced by the presence of sodium ions on either side of the cell membrane.
Considerations
Sodium, often in the form of sodium chloride, is widely available in processed or preserved foods, and you can add it to foods as table salt. Many Western diets contain more sodium than is healthy. However, low serum sodium may result in a rare but potentially fatal condition known as hyponatremia, with symptoms of headache, muscle cramps, disorientation, fainting, seizures and coma.
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