Sodium and Your Heart

One of the earliest signs of impending heart disease is a decline in the ability of very small coronary arteries to relax (or not). The measurement of this ability to relax is known as Coronary Flow Reserve (CFR), and a low measurement is considered a poor score.

By now you probably know that a diet high in sodium can affect your overall blood pressure, which can lead to heart attack and stroke. Researchers at Emory University in Atlanta; University of Washington in Seattle, Washington; and the US Department of Veterans' Affairs collaborated to find out if sodium intake had an effect on CFR (Am J Clin Nutr 2012; 95(3):572-9).

They made use of data collected from the Emory Twins Heart Study, which was made up of members of the Vietnam Era Twin Registry. This is a group of male twins, raised in the same family, who served in the US military between 1964 and 1975. Research on twins is especially valuable because of their genetic similarity, which in this case allows researchers to better understand the impact of individual diet having to take into account variation between non-twin individuals. In short, the impact of diet is easier to see because the researchers can compare two different diets in what is genetically the same person.

As part of the Emory Twins Heart Study, researchers performed PET scans on the hearts of the participants and were able to compute their CFR. A detailed dietary questionnaire allowed them to assess the participants' sodium intake.

After also taking into account such variables as blood pressure, cholesterol scores, smoking status and physical activity, the researchers found that a poor CFR score was strongly related to higher sodium intake. In fact, for every additional 1000 milligrams of sodium consumed per day, a participant's CFR decreased by 10%. In fact, those in the two highest levels of sodium intake (out of 5 levels) all had CFR scores in the abnormal range - which is believed to be linked to a greater risk of heart attack and death from heart disease.

What this means for you

The take-home message here is that higher sodium intake affects your heart's function at a very basic level - much more basic than simple blood pressure. With just a little effort you can easily cut your sodium intake: measure how much salt you put in your food, avoid processed foods if you can (or read labels carefully), and don't add salt at the table before tasting your food. There are more tips on reducing sodium intake in our Low Sodium Diet section.

First posted: July 18, 2012