Sodium

Sodium is an essential nutrient, vital for the human body's optimal function. Its influence extends beyond mere taste enhancement, playing a pivotal role in various physiological processes. 

Sodium, an electrolyte, is a mineral found abundantly in nature and is a fundamental component of table salt (sodium chloride).

Sodium regulates fluid balance, aids in nerve signaling, muscle contraction, and contributes to maintaining blood pressure.

Understanding its significance, dietary sources, recommended intake, and implications of its levels is crucial for maintaining overall health.

Definition and Function of Sodium

Definition of Sodium: What is Sodium?  [1., 8., 9.]

Sodium, an essential electrolyte found predominantly in extracellular fluid, is an osmotically active cation responsible for maintaining fluid balance and regulating cell membrane potential through active transport with potassium. While potassium is the primary intracellular cation, sodium is the primary extracellular cation.

Sodium's total body content, around 4000 mmol in an average adult, is primarily extracellular, with the remainder found in bones and intracellularly, where its concentration is much lower. 

Its regulation primarily occurs in the kidneys, with reabsorption mainly happening in the proximal tubule and distal convoluted tubule, facilitated by sodium-chloride symporters and regulated by aldosterone. 

Sodium plays a pivotal role in the renin-angiotensin-aldosterone system (RAAS), where its regulation influences blood pressure and fluid balance. When blood sodium levels are low, renin is released by the kidneys, initiating a cascade leading to the production of aldosterone, which promotes sodium reabsorption in the kidneys, conserving water and increasing blood volume to maintain homeostasis.

When sodium levels are high, the renin-angiotensin-aldosterone system (RAAS) is suppressed. This leads to decreased renin release, which subsequently reduces the production of angiotensin II and aldosterone. 

As a result, less sodium is reabsorbed in the kidneys, promoting its excretion along with water, which helps to lower blood volume and regulate blood pressure.

Sodium imbalance can lead to electrolyte disorders like hyponatremia, characterized by low serum sodium levels, and hypernatremia, marked by high serum sodium levels, each presenting with distinct neurological manifestations. 

Sodium is important for maintaining osmolality, fluid distribution, and cellular function.  Its balance is intricately controlled by various mechanisms including hormonal control, renal adaptation to dietary intake variations, and physical factors influencing tubular reabsorption. 

However, the exact mechanisms underlying sodium balance regulation remain partially understood as they involve complex interactions between factors like glomerular filtration rate, tubular fluid flow, hormonal influences, and serum sodium concentration.

Functions of Sodium: What Does Sodium Do in the Body?

Sodium’s functions as an extracellular cation responsible for maintaining the electrolyte gradient between intercellular and extracellular compartments makes it responsible for many of its functions in human health and associated conditions, which include:

Blood pressure regulation: sodium plays a crucial role in regulating blood pressure levels within the body by influencing fluid balance and vascular tone.

Cardiovascular health: excess sodium intake has been linked to increased risk of cardiovascular diseases such as hypertension, stroke, and heart disease.

Endothelial function: high dietary sodium levels can impair endothelial function, contributing to vascular dysfunction and cardiovascular complications.

Arterial stiffness: elevated sodium intake is associated with increased arterial stiffness, which is a risk factor for cardiovascular events like heart attacks and strokes.

Left ventricular hypertrophy: sodium intake affects left ventricular mass and thickness, contributing to the development of left ventricular hypertrophy, a marker of cardiovascular risk.

Renal function: sodium levels influence renal function, and excessive sodium intake can lead to impaired kidney function and increased risk of kidney disease.

Neurological function: sodium plays a role in neurological function, and dysregulation of sodium levels can impact nerve signaling and function.

Autonomic nervous system regulation: sodium levels can influence the autonomic nervous system, which regulates involuntary bodily functions such as heart rate, digestion, and respiratory rate.  [7.]

Sodium influences the autonomic nervous system function by modulating the excitability of neurons and regulating neurotransmitter release. High sodium levels can lead to increased sympathetic nervous system activity, which can elevate heart rate, constrict blood vessels, and raise blood pressure. 

Conversely, low sodium levels can stimulate the release of hormones like aldosterone and angiotensin II, which can affect autonomic function by regulating fluid balance and electrolyte levels.

Sympathetic outflow: high sodium intake can lead to increased sympathetic outflow, which may contribute to hypertension and cardiovascular complications.

Fluid balance: sodium is essential for maintaining fluid balance within the body, influencing hydration levels and cellular function.

Cellular homeostasis: sodium plays a critical role in maintaining cellular homeostasis by regulating cell volume and intracellular signaling pathways.

Dietary Sources of Sodium  [3.]

Sodium is readily available in the average diet, and is commonly added to foods, especially to processed foods.  

Processed Foods/Salt Added Foods:

• Table salt, baking soda, baking powder
• Bouillon cubes, powdered broths, soups, gravies
• Soy sauce
• Snack foods (e.g. pretzels, cheese puffs, popcorn)
• Bacon
• Sauces and spreads
• Processed vegetables
• Butter/margarine
• Processed fish and meats
• Cereals and cereal products (e.g. bread, breakfast cereals, biscuits, cakes, pastries)

Foods Naturally Containing Sodium:

• Cheese, hard
• Cheese, soft
• Fish, raw or frozen
• Eggs
• Milk and cream
• Vegetables, fresh or frozen
• Fruits, fresh or frozen

Recommended Intake of Sodium: How Much Should I Get?

The Dietary Guidelines for Americans recommends adults limit sodium intake to less than 2,300 mg per day—that’s equal to about 1 teaspoon of table salt.  Most Americans consume more than this.  Many health benefits are associated with decreased salt intake, so supplementation is typically not required.  [10.]

Testing Options for Sodium

General Lab Testing Information and Sample Type

Sodium levels are typically assessed via a blood test in serum.  A venipuncture is typically required.  Sodium is a standard component of the basic and comprehensive metabolic panels, which provide an overview of some critical electrolytes and minerals in the blood.  

Preparation for Lab

Fasting is often required, but it is important to check with your ordering provider.

Interpreting Test Results

Reference Range for Serum Sodium Levels

It is important to consult with the laboratory company used for their reference ranges.  However, a typical reference range for serum sodium is:  [6.]

‍

Adults: 136-145 mEq/L (136-145 mmol/L)

Clinical Significance of High Levels of Sodium  [2., 4.]

Hypernatremia is the condition of excessive sodium levels in the blood.  

The most common symptom of hypernatremia is thirst.  In the most severe cases, symptoms of profound hypernatremia include confusion (delirium), muscle spasms (myoclonus), seizures, unconsciousness, and potentially death, due to impairments in brain function.  [MERCK>>>>

Possible causes of hypernatremia include:

• Dehydration is the most common cause of hypernatremia.  This is usually due to excessive vomiting, diarrhea, sweating, or the excessive use of diuretics, often in the setting of insignificant water intake.  [4.]

• Ascites in the setting of liver cirrhosis, particularly in patients treated with lactulose leading to profound diarrhea and free water loss.

• Fluid resuscitation in burn patients, often due to failure to replace evaporative water loss.

• Dehydration in pediatric patients, especially following ingestion of hypertonic liquids or loss of hypotonic fluids in stool or urine.  Dehydrated pediatric patients often present with normal sodium levels, so electrolyte panels should be used as part of a comprehensive assessment of dehydration in children.  

• Initial evaluation and monitoring of hyperosmolar hyperglycemic state, where hyperglycemia causes water to be drawn from intracellular to extracellular space, leading to hypernatremia.

• Suspected child abuse, with hypernatremia indicative of water deprivation related to punishment or toilet training.

• Suspected heat illness, where hypernatremia may occur due to overhydration.

• Suspected hypernatremia, defined as serum sodium level higher than 145 mEq/L, often associated with intense thirst.

• Suspected or known acute subarachnoid hemorrhage, where hypernatremia can occur due to treatment for neurologic complications.

• Suspected or known heart failure, with mild reduction in serum sodium levels associated with increased hospitalization and mortality.

• Suspected or known hemolytic uremic syndrome, where hypernatremia may result from rehydration with hypotonic saline.

• Suspected or known seizures, including status epilepticus, where hypernatremia may occur when a seizure-provoking serum sodium threshold is reached.

• Suspected porphyria, with sodium decrease as a classic feature, possibly due to syndrome of inappropriate antidiuretic hormone secretion.

• Adrenal disease, including Cushing’s Disease and hyperaldosteronism, is a less common cause of hypernatremia.  [4.]

Clinical Significance of Low Levels of Sodium  [2., 5.]

Hyponatremia is the condition of lower than normal levels of sodium in the blood.  

Symptoms of hyponatremia primarily involve central nervous system dysfunction and are more pronounced in cases of rapid onset or in older and chronically ill patients.  

As serum sodium levels drop below 115 mEq/L, symptoms can escalate to stupor, neuromuscular hyperexcitability, hyperreflexia, seizures, coma, and even death. Severe cerebral edema, particularly notable in premenopausal women, may lead to complications like hypothalamic and posterior pituitary infarction, osmotic demyelination syndrome, or brain stem herniation.

Causes of hyponatremia can include:

Hypovolemic Hyponatremia (Fluid loss):

• Extrarenal fluid losses: vomiting, severe diarrhea, third-space fluid sequestration

• Renal fluid losses: mineralocorticoid deficiency, thiazide diuretic therapy, osmotic diuresis, salt-losing nephropathy

• Diuretics: thiazide diuretics, loop diuretics

Euvolemic Hyponatremia (Sodium levels are normal in the setting of increased total body water):

• Primary polydipsia (increased thirst)
• Excessive water intake in:some text
  • Addison disease
  • Hypothyroidism
  • Nonosmotic vasopressin release (e.g., stress, postoperative states, medications)
• Syndrome of inappropriate ADH secretion (SIADH)
• Transurethral resection of the prostate, cystoscopic, or hysteroscopic procedures using hypotonic fluid as irrigant

Hypervolemic Hyponatremia (Low sodium in the blood (hyponatremia) accompanied by an increase in total body sodium content and extracellular fluid volume. Although the sodium concentration in the blood is low, there is an excess of sodium and fluid in the body):

• Edematous disorders: heart failure, cirrhosis, nephrotic syndrome (pseudohyponatremia due to interference with sodium measurement by elevated lipids)

Syndrome of Inappropriate ADH Secretion (SIADH)

Cerebral Salt Wasting (CSW)

Hyponatremia in AIDS patients: occurs in >50% of hospitalized AIDS patients  [5.]

Natural Ways to Optimize Sodium Levels for Overall Wellness

• Embrace a Mediterranean-style diet rich in fresh fruits, vegetables, whole grains, nuts, seeds, and healthy fats as a foundational part of cardiovascular and kidney wellness.

• Choose whole, unprocessed foods that naturally contain sodium, such as vegetables, fruits, dairy, and seafood.

• Use herbs, spices, and citrus juices to flavor meals instead of relying heavily on salt.

• Moderate your sodium intake by limiting processed and packaged foods, which often contain high levels of added sodium.

• Stay adequately hydrated by drinking water throughout the day and consuming hydrating foods like watermelon, cucumber, and oranges.

• Replenish electrolytes after intense exercise or sweating with natural sources like coconut water or bananas.

• Seek guidance from a healthcare provider or registered dietitian to tailor your diet and sodium intake to your individual needs and health conditions, particularly before deciding to use electrolyte replacement as part of a daily plan.

Order Sodium Testing

Click here to compare testing options and order testing for sodium levels.