FOR YEARS DOCTORS have warned that too much salt is bad for us and we should reduce our consumption of salty foods.

It now looks like that advice may be about to change slightly as a new study has found that although high levels of salt still puts people at risk of major heart problems, so does a low level of sodium intake.

The research, published in the Journal of the American Medical Association, found a link between a low intake of salt and an increased risk of dying from a cardiovascular event or being hospitalised with congestive heart failure.

Moderate intake is associated with the lowest risk of heart problems. So, the lesson is to get it just right.

Using 25-hour urinary data from almost 30,000 people at risk of heart disease, the researchers – led by an Irish doctor – found that moderate excretion is between 4 to 5.99 grams per day.

Compared to that happy-medium, sodium excretion of greater than 6-7 grams per day is associated with an increased risk of all heart problems. Excretion of less than 3 grams per day could lead to death from heart problems or congestive heart failure.

Calls for new guidelines

Professor Martin O’Donnell from NUI Galway, the paper’s lead researcher, said the important health issue had become topical again because of the recent publication of another study reporting an association between low-sodium intake and cardiac death.

“In general, previous observational studies have either reported a positive association, no association or an inverse association between sodium intake and heart disease and stroke. This has resulted in a lot of controversy. Our study is the first to report a J-shaped association between sodium intake and cardiovascular disease, which may explain why previous studies have found different results,” he said.

Current guidelines for salt intake that recommend less than 2.3 grams per day should now be questioned, said the report.

This will be particularly important for patients already suffering with heart diseases as they are vulnerable to the cardiovascular effects of very high or low-salt intake and are most likely to receive advice about restricting salt in their diets.

Professor O’Donnell said that his study confirms that high sodium intake is associated with increased risk of heart disease but also raises uncertainty about whether those with average salt intake should reduce it even further.

The authors have called for a large trial to determine whether reducing sodium intakes from moderate to low can result in lower rates of heart disease and stroke.

“While we accept there are challenges to conducting such trials, they are required urgently given their public health implications,” concluded Professor O’Donnell.