Low-salt diets could be doing more harm than good

A worldwide study has found that low-salt diets may actually increase the risk of cardiovascular disease (CVD) and death compared to average salt consumption.

The study, published in The Lancet, of more than 130,000 people from 49 countries, examined whether the relationship between sodium (salt) intake and death, heart disease and stroke differs in people with high blood pressure compared to those with normal blood pressure.

The researchers showed that regardless of whether people have high blood pressure, low sodium intake is associated with more heart attacks, strokes and deaths compared to average intake.

“These are extremely important findings for those who are suffering from high blood pressure,” said Andrew Mente, lead author of the study, a principal investigator of Population Health Research Institute (PHRI) of McMaster University, in Canada, and an associate professor of clinical epidemiology and biostatistics at McMaster’s Michael G. DeGroote School of Medicine.

“While our data highlights the importance of reducing high salt intake in people with hypertension, it does not support reducing salt intake to low levels.

“Our findings are important because they show that lowering sodium is best targeted at those with hypertension who also consume high-sodium diets.”

Previous studies have shown that low sodium, compared to average sodium intake, is related to increased cardiovascular risk and mortality, even though low sodium intake is associated with lower blood pressure. This study shows that the risks associated with low sodium intake — less than 3 g/day — are consistent regardless of a patient’s hypertension status.

Further, the findings show that while there is a limit below which sodium intake may be unsafe, the harm associated with high sodium consumption appears to be confined to only those with hypertension.

Only about 10% of the population in the global study had both hypertension and high sodium consumption (greater than 6 g/day). Mente said that this suggests that the majority of individuals in most countries are consuming the right amount of salt.

He said that targeted salt reduction in those who are most susceptible because of hypertension and high salt consumption may be preferable to a population-wide approach to reducing sodium intake. He added that what is now generally recommended as a healthy daily ceiling for sodium consumption appears to be set too low, regardless of a person’s blood pressure level.

“Low sodium intake reduces blood pressure modestly, compared to average intake, but low sodium intake also has other effects, including adverse elevations of certain hormones, which may outweigh any benefits. The key question is not whether blood pressure is lower with very low salt intake, instead it is whether it improves health,” Mente said.