Postural Orthostatic Tachycardia Syndrome (POTS) is a complex disorder of the autonomic nervous system, primarily causing orthostatic intolerance. This condition is defined by an abnormally large increase in heart rate upon standing, accompanied by symptoms like lightheadedness, fatigue, and brain fog. Since there is no single cure, management focuses on reducing symptoms. One widely recommended non-pharmacological strategy involves a significantly increased intake of sodium (salt). This intentional dietary change addresses a core physiological problem contributing to the daily struggle of living with POTS.
The Core Problem in POTS: Chronic Hypovolemia
Many individuals diagnosed with POTS experience chronic hypovolemia, meaning they have a lower-than-normal total blood volume circulating in their system. Patients with POTS often have a moderate to severe deficit in their plasma and total blood volume compared to healthy individuals. This reduced circulating volume is a major physiological challenge the body must constantly manage.
When a person with POTS stands up, gravity pulls a significant portion of the already low blood volume downward into the lower body, including the legs and the splanchnic (abdominal) circulation. This phenomenon, known as venous pooling, results in an insufficient return of blood to the heart and the brain. In response to this sudden drop in central blood volume, the heart attempts to compensate by drastically increasing its beat rate, leading to the characteristic excessive tachycardia observed in the syndrome.
The underlying hypovolemia is often compounded by a failure in the body’s ability to properly conserve volume. Studies suggest an anomalous response in the renin-angiotensin-aldosterone system (RAAS), the hormone cascade that regulates blood pressure and fluid balance. This failure means the kidneys may not retain sodium and water efficiently, perpetuating the low-volume state.
Sodium’s Physiological Role in Fluid Retention
Increased sodium intake is based on a fundamental principle of human physiology concerning fluid balance. Sodium is the primary ion responsible for maintaining the volume of extracellular fluid, which includes the plasma component of blood. This function is governed by osmosis, where water naturally moves toward an area of higher solute concentration.
When sodium chloride is consumed and absorbed, it increases the concentration of solutes in the bloodstream. Homeostatic mechanisms detect this rise and respond by retaining more water to dilute the sodium and restore osmotic balance. The kidneys play a direct role by reducing the excretion of water into the urine.
This fluid retention directly expands the plasma volume, increasing the total amount of blood circulating in the body. For an individual with POTS, this intentional volume expansion helps overcome chronic hypovolemia.
Stabilizing Circulation and Reducing Orthostatic Stress
Increasing blood volume through higher sodium intake directly mitigates the severe circulatory challenges faced by those with POTS. Expanding the total circulating volume ensures more blood is available to return to the heart and brain, even when gravity causes pooling in the lower extremities. This volume expansion provides a buffer against the gravitational effects of standing.
With a higher baseline blood volume, the amount of blood that pools upon standing represents a smaller proportion of the total. This improved venous return helps stabilize cardiac output and blood pressure more effectively. A more stable circulation reduces the need for the autonomic nervous system to overcompensate.
The reduction in compensatory effort translates into a reduced severity of tachycardia. When the heart receives adequate blood volume, it no longer needs to race excessively to maintain perfusion to the brain. This improves orthostatic tolerance, leading to fewer symptoms like lightheadedness, fatigue, and palpitations. Volume expansion also reduces levels of standing plasma norepinephrine, a marker of sympathetic nervous system tone.
Practical Considerations for Increasing Sodium Intake
Implementing a high-sodium regimen requires careful attention and professional medical guidance. The sodium requirement for managing POTS is substantially higher than general recommendations, often needing 5 to 10 grams of sodium per day (the equivalent of 12.5 to 25 grams of table salt).
To achieve this target, patients supplement their diet using a variety of sources:
- Increasing dietary salt on meals.
- Consuming salty snacks like broths and pickles.
- Utilizing sodium chloride tablets or capsules.
- Using specialized electrolyte drink mixes.
Increased sodium intake must be paired with a significantly higher fluid intake, typically 2 to 3 liters of water or electrolyte-containing fluids daily. Medical supervision is necessary to monitor for potential side effects, such as edema or hypertension, ensuring the regimen is safe and correctly individualized.