The importance of potassium in heart health (Pt. 1)
When it comes to the health of the cell, we have seen that the right balance of electrolytes inside and outside of the cell is key to allow energy into the cell. For heart health this is important because the proper flow of electrolytes into and out of the heart cells is required to keep the heart from filling up with water (cardiac edema) and to keep the electrolytes present that allow the heart to beat properly. This is made possible by the presence of pumps on the cell membrane, called ‘sodium-potassium pumps’, that turn each of our cells into a little battery capable of releasing and storing energy and maintaining an electrical charge.
We also saw how the ‘Heart and Body Extract’, and an alkaline diet are the best sources of these electrolytes, namely, sodium, potassium, calcium and magnesium. In today’s blog, we will focus on the role of potassium in heart health, as observed by the ‘National Council on Potassium in Clinical Practice’. According to this council, low potassium is the most common electrolyte abnormality encountered in clinical practice, a condition known as ‘hypokalemia’ (1).
The ‘National Council on Potassium in Clinical Practice’ 1998 meeting
The critical role potassium has for heart health was studied in depth at a 1998 meeting of the ‘National Council on Potassium in Clinical Practice’. The Council was a multidisciplinary group comprising specialists in cardiology, hypertension, epidemiology, pharmacy, and compliance.
The main focus of this meeting was to study how maintaining normal levels of potassium in the body could help reverse challenging heart conditions. The evidence accumulated confirmed the crucial role potassium has for reducing the risk of life-threatening cardiac arrhythmias, high blood pressure and stroke. As a result of this meeting and its findings, new guidelines for potassium replacement therapy in clinical practice were established.
This initiative represented a new approach to the field of cardiology as, so far, potassium had not been the focus of treatment in any cardiological conditions. Quite the contrary, the many health challenges caused by hypertension and heart failure, had mandated the introduction of drugs that, according to the authors, disrupt electrolyte homeostasis, a fact that emphasizes the serious role of potassium.
The sodium-potassium pump
In their research, the authors were able to prove that, in healthy circumstances, potassium is one of the most abundant electrolytes in the body. Of the total body potassium content (about 3500 mmol), 90% is sequestered within cells, where it does all its work. This compartmentalization depends on its active transport through the cell membrane by the sodium-potassium pump, which maintains an intracellular positively charged ion ratio of 1:10. The smallest percentage of potassium can be found in the blood, as the blood is the main carrier for potassium to the cells. The loss of just 1% (35 mmol) of total body potassium content would seriously disturb the delicate balance between intracellular and extracellular potassium and would result in profound physiologic changes.
Clinical implications of potassium depletion
Potassium depletion, hypokalemia, is one of the most common electrolyte abnormalities encountered in clinical practice. More than 20% of hospitalized patients have this deficiency, and up to 40% of patients treated with thiazide diuretics.
The kidneys, being the major regulators of potassium levels, account for approximately 80% of potassium transit from the body; this is reason why kidney dysfunction can result in low levels of potassium.
But potassium homeostasis also depends to a large extent on the acid-alkaline balance in the body. Acidosis causes the cells to lose potassium. What is more, increases in insulin or glucose, and type 2 diabetes can affect potassium homeostasis as well.
Drugs like decongestants and bronchodilators can temporarily reduce potassium and increase sodium. Other potential causes include diuretic therapy, inadequate dietary potassium intake, high dietary sodium intake, and low magnesium. In most cases, hypokalemia is secondary to drug treatment, particularly diuretic therapy. Diuretics inhibit sodium reabsorption in the kidneys, creating a favorable electrochemical change toward potassium loss.
Hypokalemia occurs less frequently in patients with uncomplicated hypertension who take a diuretic but is more common in patients with congestive heart failure (CHF), nephrotic syndrome, or cirrhosis of the liver, who take an equivalent dose of a diuretic and consume approximately the same amount of potassium from food.
Aside from potassium-wasting drugs, hypokalemia is most commonly caused either by abnormal loss through the kidney due to metabolic alkalosis or by loss in the stool secondary to diarrhea.
According to other healthcare professionals, potassium deficiency is caused by the ‘improper processing of food over the last 100 years, complicated by the fact that the food industry has used super phosphate fertilizers’ (2).
Because potassium is a major intracellular positively charged ion, the tissues most severely affected by potassium imbalance are muscle and kidney cells. Manifestations of hypokalemia include generalized muscle weakness, paralytic ileus, and cardiac arrhythmias. Severe untreated hypokalemia, may progress to acute renal failure.
Protective effect of potassium
Data gathered from animal experiments and epidemiologic studies suggest that high potassium may reduce the risk of stroke. Part of the protective effect of potassium may be due to the fact that potassium lowers blood pressure. Other protective mechanisms include:
- Reduction of free radical formation, and oxidative stress
- May reduce macrophage adherence to the vascular wall, an important factor in the development of arterial lesions
In 1987, the results of a 12-year prospective population study showed that the relative risk of stroke-associated mortality was significantly lower with higher potassium intake. In fact, the study demonstrated that just a 10-mmol higher level of daily potassium intake was associated with a 40% reduction in the relative risk of stroke mortality. This apparent protective effect of potassium was independent of other nutritional variables, including caloric intake, dietary levels of fat, protein, and fiber, intake of calcium, magnesium, and alcohol. The authors also noted that the effect of potassium was greater than that which would have been predicted from its ability to lower blood pressure.
Similarly, an 8-year investigation of the association between dietary potassium intake and subsequent risk of stroke in 43,738 US men, aged 40 to 75 years, without previously diagnosed cardiovascular disease or diabetes was conducted. During the study follow-up, only 328 strokes were documented. The association between low potassium intake and subsequent stroke was more marked in hypertensive men.
Other investigators also found that the use of potassium supplements was inversely related to the risk of stroke, particularly among hypertensive men. They speculated that this relationship might be due, at least in part, to a reduction in the risk for hypokalemia.
Clinical implications in hypertension
Studies have shown a strong relation between potassium depletion and essential hypertension. Increasing the intake of potassium appears to have an antihypertensive effect that is evident in effects like vasodilation, and lower cardiovascular reactivity to norepinephrine or angiotensin II.
Similarly, correction of diuretic or laxative abuse can also raise potassium level and lower blood pressure.
The large-scale Nurses’ Health Study found that dietary potassium intake was inversely associated with blood pressure. Specifically, intake of potassium-rich fruits and vegetables was inversely related to systolic and diastolic pressure.
Similarly, 24-hour urinary potassium excretion, and the ratio of urinary sodium to potassium were found to be independently related to blood pressure in the ‘Intersalt’ study, a 52-center international study of electrolytes and blood pressure.
Additional information was provided by the ‘Rotterdam Study’, which evaluated the relationship between dietary electrolyte intake and blood pressure in 3,239 older people (age ≥55 years).
Another recent meta-analysis evaluating the effects of oral potassium supplementation on blood pressure, included 33 clinical trials involving 2,609 participants. The results demonstrated that potassium supplementation was associated with a significant reduction in systolic and diastolic blood pressure. The greatest effects were observed in participants who had a high sodium intake. This analysis suggests that low potassium intake may play an important role in the genesis of high blood pressure.
Clinical Implications in ‘Congestive Heart Failure’ (CHF)
Potassium depletion is commonly seen in patients with CHF, a condition that is characterized by electrolyte disturbances. CHF is linked to renal dysfunction and neurohormonal activation, both of which stimulate aldosterone, sympathetic nervous tone, and hypersecretion of adrenaline.
The researchers have observed a common misperception regarding angiotensin-converting enzyme (ACE) inhibitor therapy is that these drugs enhance potassium retention, thereby eliminating the need to add potassium or potassium-sparing diuretics to ACE inhibitor therapy. What they observed is that, in many cases, the prescribed dosages of ACE inhibitors in patients with CHF are insufficient to protect against potassium loss. Their recommendation is that potassium levels must be closely monitored in all patients with CHF, even those taking ACE inhibitors, to minimize the life-threatening risk of hypokalemia.
Clinical implications in patients with arrhythmias
Mild-to-moderate hypokalemia can increase the likelihood of cardiac arrhythmias in patients who have cardiac ischemia, heart failure, or left ventricular hypertrophy. This is not surprising taking into account the important role that potassium plays in the electrophysiologic properties of the heart. The resting membrane potential (RMP) (the difference in electrical charge inside and outside the cell) is determined by the ratio of intracellular to extracellular potassium. Changes in potassium levels modifies the amount of electricity able to pass the cell membrane and can have profound effects on impulse generation and conduction throughout the heart. Changes in this ratio, such as those induced by diuretic therapy, can alter cardiac conduction greatly.
Something significant observed during this research is that patients with hypertension who were prescribed non–potassium-sparing diuretics had approximately twice the risk of sudden cardiac death compared with users of potassium-sparing therapy.
To prove the link between hypokalemia and clinical heart arrhythmia and to determine the relationship of diuretic-induced hypokalemia, 17 hypertensive men receiving diuretics were studied. These patients had increased frequency and complexity of ventricular ectopic activity during diuretic therapy. However, oral potassium supplements or potassium-sparing agents reduced the complexity and frequency of arrhythmias by 85%, even after discontinuation of diuretic therapy.
There is also evidence that hypokalemia can trigger sustained ventricular tachycardia or ventricular fibrillation, particularly in the case of acute myocardial infarction.
Potassium supplementation strategies
All this evidence has led the authors to suggest that increasing potassium is necessary in the case of cardiac arrhythmias, such as heart failure, myocardial infarction or ischemic heart disease.
Repletion strategies should include eating foods high in potassium, potassium salts substitutes, and supplements. Potassium salts include potassium chloride, potassium phosphate, and potassium bicarbonate. Potassium phosphate is found primarily in food, and potassium bicarbonate is typically recommended in the case of metabolic acidosis (pH <7.4).
In our blog covering the alkaline diet we saw how fresh fruits and vegetables are a great source of alkalizing minerals, especially potassium. This includes kelp and garlic (3) found in the ‘Heart and Body Extract’; but also food sources like avocados, peas, beans, nuts, cocoa, seafood, and dark green vegetables.
According to Dr. David Jockers, “Kelp is extraordinarily rich in alkaline buffering nutrients such as sodium, potassium, magnesium and calcium. It is also a phenomenal source of chlorophyll to boost blood cell formation and purify the blood” (4).
The role of magnesium in potassium repletion
Magnesium is an important cofactor in potassium absorption and necessary for the maintenance of intracellular potassium levels. Research has demonstrated that long term magnesium deficiency could lead to the inability to replete potassium. It has been observed that many patients with potassium depletion most frequently also have magnesium deficiency. This is especially the case of patients on diuretics, which cause a substantial loss of intracellular potassium and magnesium. Some diuretics accelerate the excretion of magnesium by reducing its reabsorption in the kidneys.
It is thereby recommended considering the repletion of both magnesium and potassium for patients with hypokalemia.