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Health News Archive 703 - Cardiovascular Health
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Potassium Protects the Heart

Genetically salt-sensitive rats were fed a normal diet (0.3% sodium chloride) or a high-salt diet (8% sodium chloride), with or without high potassium intake (8% potassium chloride) for eight weeks. High salt intake significantly increased blood pressure, impaired left ventricular relaxation, and increased the activity of IVADPH oxidase in cardiac tissue. High potassium intake improved left ventricular relaxation and reversed the elevation of NADPH oxidase activity, even though blood pressure remained high.

In other studies, dogs made potassium-deficient by means of a low-potassium diet and administration thiazide diuretics showed impairments of both systolic and diastolic heart function, with the most striking effect being a 49% reduction in the peak rate of ventricular filling. In a study of healthy human volunteers, potassium depletion resulted in a 14% reduction in the peak rate of ventricular filling. In a randomized trial, elderly men who switched from regular salt to potassium-enriched salt (49% potassium chloride, 49% sodium chloride, 2% other additives) for 31 months had a 41% decrease in cardiovascular mortality.

Comment by Alan Gaby, M.D.

Diastolic dysfunction (impaired left ventricular filling) is a common and important, though under-appreciated, cause of heart failure. In one recent study, of 556 unselected patients with heart failure, 55% had a normal left ventricular ejection fraction, indicating that heart failure was almost certainly due to diastolic dysfunction. Patients with diastolic heart failure have mortality rates similar to those with systolic heart failure.

The studies reviewed above suggest that potassium deficiency can contribute to diastolic dysfunction and possibly to systolic dysfunction as well. One mechanism by which potassium might help prevent heart failure is by inhibiting cardiac NADPH oxidase activity, thereby decreasing oxidative stress.

Most people do not consume enough fruits and vegetables (the main dietary sources of potassium). Some diuretics used to treat heart failure may also promote or exacerbate potassium deficiency. In addition, some of the pathophysiological mechanisms underlying heart failure may lead to a loss of both potassium and magnesium from myocardial cells. Magnesium is required for the intracellular uptake of potassium, so potassium supplementation alone will not correct intracellular potassium deficiency unless magnesium deficiency is also corrected. In patients with renal failure (which is sometimes associated with heart failure), potassium and magnesium should be administered with caution and monitored with appropriate lab tests.

Source

Matsui H, et at. Protective effect of potassium against the hypertensive cardiac dysfunction: association with reactive oxygen species reduction. Hypertension. 2006;48:225-231.

Young DB. Potassium depletion and diastolic dysfunction. Hypertension. 2006;48:201-202.

Chang HY, et al. Effect of potassium-enriched salt on cardiovascular mortality and medical expenses of elderly men. Am J Clin Nutr. 2006;83:1289-1296.

Reprinted with exclusive permission from The Townsend Letter. Aug 2007

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