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Story at-a-glance

• Sodium is an essential electrolyte that supports fluid balance, nerve signaling, muscle contraction, and heartbeat coordination; even small drops in blood sodium disrupt these essential functions
• A Virginia Tech study found that low blood sodium amplifies the effects of flecainide, a common rhythm-control drug, by disrupting key electrical support systems between heart cells
• Restoring sodium to the normal range reversed conduction delays. This confirms that the effects were due to a temporary sodium imbalance
• People on sodium channel blockers need to monitor sodium levels closely, as common triggers like diuretics or illness cause dangerous delays in heart signal conduction
• Most adults do well with around 3,500 milligrams of sodium daily, especially when it comes from unprocessed, mineral-rich sources balanced by adequate potassium intake

For decades, public health guidelines have emphasized lowering sodium intake to protect cardiovascular health. The goal is to limit the amount of sodium circulating in the bloodstream, which in turn lowers fluid retention and decreases the workload on the heart.1 However, this approach carries risk because sodium isn't just about blood pressure — it's also central to the electrical signals that keep your heartbeat steady.

When sodium levels drop too low, those signals slow down or misfire, disrupting heart rhythm and timing. This becomes especially important for the millions of people taking sodium channel blockers, which are drugs that slow the movement of sodium into heart cells to control abnormal rhythms.

Recent research shows that when sodium levels fall, the effects of these drugs on the heart's electrical conduction become far more pronounced.2 These findings challenge blanket salt restriction and underscore the importance of maintaining healthy sodium balance in those whose heart rhythms depend on it.

The Importance of Sodium (and Why Going Too Low Is Risky)

Sodium is far more than a seasoning on your plate. It is a vital electrolyte that supports nearly every major function in your body. The concentration of sodium in your blood and tissues is tightly regulated because even small changes have broad, sometimes dangerous, effects on your health. Some of its roles include:3,4

• Maintaining fluid balance and circulation — Sodium helps regulate the amount of water inside and around your cells, keeping tissues hydrated and maintaining the right blood volume for effective circulation. This balance is essential for stabilizing blood pressure and ensuring that oxygen and nutrients reach every organ.

• Supporting nerve signal transmission — Every thought, movement, and sensation depends on electrical impulses carried by nerve cells. These impulses are triggered by shifts in sodium and potassium across nerve cell membranes. Without enough sodium to generate and propagate these signals, communication between the brain, spinal cord, and the rest of the body slows or fails.

• Enabling muscle contraction — In skeletal, smooth, and cardiac muscle, sodium entry starts the electrical sequence that leads to contraction. In skeletal muscle, it coordinates movement and stability; in smooth muscle, it helps regulate processes like digestion and blood flow; and in the heart, it triggers the pumping action that circulates blood.

• Facilitating nutrient absorption and kidney function — In the small intestine, sodium drives the uptake of glucose and amino acids, supporting energy production and tissue repair. In the kidneys, sodium works with other electrolytes to regulate water retention or excretion, helping maintain overall fluid balance and acid-base stability.

• Risks of low sodium (hyponatremia) — When sodium levels fall below normal, symptoms range from headache, confusion, muscle cramps, and weakness to seizures, coma, and death in severe cases. The heart's electrical system is especially sensitive, and even mild changes disrupt rhythm and pumping efficiency.

• Why sodium is a drug target — Because sodium's movement into cells is so vital for electrical signaling, it is a target of sodium channel blockers. These drugs reduce the flow of sodium into cells, slowing conduction in order to control abnormal heart rhythms. While their goal is to stabilize rhythm, their effects become more pronounced and risky when sodium levels are already low.

How Hyponatremia Amplifies Flecainide's Effect on Cardiac Conduction

Researchers at the Fralin Biomedical Research Institute at Virginia Tech examined how hyponatremia interacts with sodium channel-blocking drugs to alter the heart's electrical activity. They focused on flecainide, a class Ic antiarrhythmic that binds to cardiac sodium channels and slows the flow of sodium into heart cells, reducing the speed of electrical impulse conduction.5

• How hyponatremia changes conduction — The heart's electrical signal begins when sodium rushes into cardiac cells, driven by the difference in sodium concentration inside and outside the cell (the sodium gradient). When blood sodium falls, this gradient weakens, making it harder for the signal to start and spread.

Mild changes are sometimes tolerated, but when the sodium channel-blocking effect of flecainide is added to a weakened gradient, conduction slows far more than either factor alone would cause.

• Investigating an ephaptic mechanism — The team explored whether this amplified slowing involved ephaptic coupling, a process where heart cells pass electrical signals through very narrow gaps between them. One of these spaces, the perinexus, contains a high concentration of sodium channels and is especially sensitive to both channel function and the balance of ions, including sodium, in the surrounding fluid.

• Effect of low sodium on ephaptic coupling — When sodium is low in the perinexus, the local electrical field that supports ephaptic coupling weakens. Combining this reduced electrical support with the loss of sodium channel activity from flecainide sharply decreases conduction efficiency, making the heart's signaling system more sluggish.

• Role of potassium currents — The study also found that outward potassium currents help reset the heart's electrical state between beats. When these currents were blocked, the heart's sensitivity to low sodium during flecainide use was reduced. This points to both ephaptic coupling and potassium-related mechanisms as factors in how hyponatremia slows conduction under sodium channel blockade.

• What controlled experiments showed — When flecainide was used at typical clinical levels alongside mild hyponatremia, conduction speed dropped significantly, and the QRS duration on the electrocardiogram became longer.

The QRS segment measures how quickly the ventricles activate; a longer duration means the electrical signal is taking more time to move through them. These results supported the theory that both sodium channel availability and the amount of sodium in the surrounding fluid determine how efficiently impulses travel.

• Reversibility of conduction impairment — Bringing sodium levels back into the normal range restored conduction speed and QRS duration. This confirms the slowdown was due to a temporary loss of optimal sodium balance and channel function, not permanent heart damage.

• Why this matters for maintaining sodium balance — The findings show that people taking flecainide, especially older adults or those with heart failure, face a greater risk of dangerous conduction delays when their sodium levels fall. Common triggers include diuretics, excessive water intake, and acute illness. According to Steven Poelszing, the study's senior author:

"Doctors have long known that sodium channel blockers can slow cardiac conduction, and that low sodium levels are risky. But what wasn't clear is why the combination of the two is so problematic. This study helps explain the mechanism."6

Preventing sodium from falling below its optimal range is essential for anyone taking sodium channel-blocking medication to maintain a stable heart rhythm. Yet the very people prescribed these drugs are often the ones advised to restrict their salt intake.

Why Blanket Salt Restrictions Don't Work for Everyone

Growing evidence continues to challenge the long-standing practice of lowering salt intake as a default strategy in heart disease management. In heart failure specifically, multiple reviews of past guidelines have found no consistent improvement in outcomes, and in some cases, strict limits appear to reduce quality of life without delivering measurable benefits.

• European guidelines drop blanket sodium restriction — In 2024, the European Journal of Heart Failure published a position paper noting that "recent data challenge the beneficial role of dietary sodium and fluid restriction in HF [heart failure]."7 This marked a shift from earlier recommendations, moving toward a more personalized approach to diet in heart failure care.

• Earlier evidence has not stood up to closer examination — A JAMA Internal Medicine systematic review assessed nine clinical trials involving people with heart failure and found no consistent proof that sodium restriction reduced hospital stays or eased symptoms.

While a handful of studies noted small improvements in fatigue or shortness of breath, these findings were inconsistent and had no effect on key outcomes such as mortality or hospitalization rates.8

• Going below 5 grams shows no extra advantage — Research in Progress in Cardiovascular Diseases found that reducing sodium intake to less than 5 grams per day — the World Health Organization's (WHO) advised limit — did not produce meaningful protection against heart failure-related complications. The authors concluded that pushing intake well below this threshold offers no added benefit for most patients.9,10

• A major trial found no benefit from aggressive sodium cuts — An international Lancet trial tracked 806 individuals with chronic heart failure, assigning them to either a sodium-restricted diet (under 1,500 mg daily) or standard dietary guidance.

After 12 months, there were no significant differences between the groups in mortality, cardiovascular hospital visits, or emergency care use. Notably, deaths from all causes were slightly higher in the low-sodium group (6%) compared to the standard diet group (4%).11

In addition, excessive sodium restriction triggers a rise in hormones like renin, aldosterone, and cortisol, which elevate blood pressure, cause fluid retention, and fuel inflammation. Elevated cortisol also promotes insulin resistance, impairs immune function, and accelerates tissue breakdown, all of which worsen cardiovascular health.

Sodium-to-Potassium Balance Matters More for Heart Health

While the conversation around heart health often centers on cutting sodium, the bigger picture is the balance between sodium and potassium. These two electrolytes work together to control electrical signaling in the heart, with sodium driving the depolarization that starts each beat and potassium restoring the electrical baseline so the next beat can occur. If either mineral is out of proportion to the other, the heart's rhythm and conduction efficiency will suffer.12

• Modern diets push this balance in the wrong direction — Ideally, you should consume about five times more potassium than sodium, yet the typical American gets nearly twice as much sodium instead. Over 70% of the sodium in the modern diet comes from refined sodium chloride found in packaged and restaurant foods.13

This industrial salt is 97.5% sodium chloride and contains roughly 39% sodium by weight. It is stripped of natural trace minerals like potassium and magnesium, making it nutritionally inferior to unrefined salts. A diet heavy in processed and takeout meals almost guarantees a skewed sodium-to-potassium ratio.

• This inverted ratio contributes to a wide range of chronic health problems — This includes high blood pressure, kidney stones, osteoporosis, cognitive decline, cataracts, erectile dysfunction, stomach ulcers, rheumatoid arthritis, and even certain cancers.

• Correcting the ratio — The most effective way to boost your potassium intake is through whole foods, such as spinach, beet greens, broccoli, winter squash, tomatoes, carrots, oranges, cantaloupe, coconut water, grass fed yogurt, kefir, and Swiss chard.14,15

Moreover, replace refined table salt with natural salts like pink Himalayan or sea salt, which contain more potassium and trace minerals than processed sodium chloride. Compared to iodized white table salt, which contains 151.68 milligrams per kilogram (mg/kg) of potassium, pink Himalayan salt contains 2,085.71 mg/kg.16

• How much is enough? — Many people do best with around 3,500 milligrams (mg) of sodium daily, which is higher than the American Heart Association's (AHA) 2,300 mg limit and far beyond their "ideal" 1,500 mg.17

However, if your salt comes from natural, unprocessed sources and is balanced by a high potassium intake, this level supports healthy physiology. For potassium, aim for at least 3,400 mg daily for men and 2,600 mg for women, with 3,500 to 5,000 mg ideal for improving cardiovascular health.18

Frequently Asked Questions (FAQs) About Sodium and Heart Health

Q: Can having low sodium levels really cause problems?

A: Sodium is essential for various physiological functions, including helping generate and conduct the electrical signals that control your heartbeat. If levels drop too low (hyponatremia), these signals slow or misfire. This causes fatigue, confusion, muscle weakness, or, in severe cases, seizures, coma, or heart rhythm problems.

Q: How does low sodium affect people on sodium channel blockers like flecainide?

A: Sodium channel blockers already slow the movement of sodium into heart cells. If blood sodium is also low, the slowing effect becomes much stronger, which dangerously delays the heart's electrical conduction and increases the risk of arrhythmia.

Q: How much sodium should I really be eating each day?

A: Most people do well with around 3,500 milligrams of sodium daily. This is higher than the AHA's 2,300 mg limit. If your sodium comes from natural, unprocessed sources and your potassium intake is high, this amount supports healthy fluid balance, nerve function, and heart rhythm.

Q: Is all salt the same?

A: No. Processed table salt is nearly pure sodium chloride and stripped of trace minerals. Natural salts, like pink Himalayan or quality sea salt, contain more potassium and magnesium, which support overall electrolyte balance.

Q: What role does potassium play in all of this?

A: Potassium works in opposition to sodium, resetting the heart's electrical state after each beat. It also supports normal blood pressure and fluid balance. The recommended potassium intake is 3,400 mg per day for men and 2,600 mg for women, with 3,500 to 5,000 mg often considered ideal for cardiovascular health. This is best achieved through potassium-rich foods like leafy greens, squash, tomatoes, citrus, and yogurt.

Sources and References

• 1 Nutrients. 2022 Mar 26;14(7):1386
• 2, 5 Heart Rhythm April 26, 2025
• 3 MSD Manual, Overview of Sodium's Role in the Body
• 4 Nutrients. 2023 Jan 12;15(2):395
• 6 News Medical Life Sciences, July 15, 2025
• 7 European Journal of Heart Failure (2024) 26, 730–741
• 8 JAMA Intern Med. 2018;178(12):1693-1700
• 9 Progress in Cardiovascular Diseases January-February 2024, Volume 82, Pages 43-54
• 10 WHO, Sodium Reduction, February 7, 2025
• 11 The Lancet, Volume 399, Issue 10333, 1391–1400
• 12 AHA, Hyperkalemia (High Potassium)
• 13 FDA, Sodium Reduction in the Food Supply, November 1, 2024
• 14 Harvard T.H. Chan School of Public Health, Potassium
• 15, 18 AHA, How Potassium Can Help Control High Blood Pressure
• 16 Foods. 2020 Oct; 9(10): 1490, Table 2
• 17 AHA, How much sodium should I eat per day?