The emphasis on dietary control of high blood pressure has been on reducing sodium intake. However, new findings suggest that increasing potassium intake is important too. For it is the ratio between sodium and potassium which influences the risk of stroke and heart attack.

Summary

Reduction of sodium intake has long been advised to reduce high blood pressure and its associated health risks. But a new study shows this is not the full story. Measurement of sodium and potassium levels in urine shows that it is the sodium to potassium ratio that determines stroke and heart attack risk - the higher the potassium intake, the lower the ratio and the lower the risk. Therefore, equal weight should be given to increasing potassium intake through fruit and vegetable consumption.

Introduction

Hypertension is a well known risk factor for heart disease and stroke. It can be controlled by medication but also by several lifestyle measures such as weight loss, reducing alcohol consumption and cutting salt intake. Many Americans eat far more salt than they should (one teaspoon a day equivalent is what the experts advise as a maximum) and thereby put their health at risk. But previous studies on salt intake and blood pressure have relied on asking people about their dietary intake, which is not very accurate. The current study relies on measurement of urine samples, which is objective, and it also includes the potassium factor.

What was done

This work, carried out by researchers at Loyola University, is part of the Trials of Hypertension Prevention project. Nearly 3,000 subjects with slightly raised blood pressure had urine levels of both sodium and potassium levels measured over an 18 month period and then, in another part of the study, over a 36 month period. They were followed up for 10-15 years to record the number of strokes, heart attacks and related conditions.

What was found

Neither sodium nor potassium alone was predictive of cardiovascular disease. It was the ratio of sodium to potassium that mattered. Those with the highest ratio (sodium high, potassium low) were 50 percent more likely to have a cardiovascular event than those with the lowest level.

What this study means

Cutting salt consumption is still important. But so too is boosting potassium levels and this has probably been given less attention in hypertension prevention and management. You can get more potassium (as you might have guessed) through eating more fruit and vegetables. Potatoes, sweet potatoes, bananas, tuna, tomato sauce and orange juice are foods that are especially rich in potassium.

Source

Joint effects of sodium and potassium intake on subsequent cardiovascular disease: The Trials of Hypertension Prevention follow-up study NR. Cook, E. Obarzenek,  et al, Archives of Internal Medicine, January 2009, vol. 169, pp. 32--40