Public health strategies to reduce salt intake for heart health benefits may not be needed, according to a large study which compared data from numerous countries.

Researchers from Canada believe consuming low levels of sodium may be as unhealthy as excessive consumption. But the controversial findings have also received criticism from health experts. 

The study titled "Urinary sodium excretion, blood pressure, cardiovascular disease, and mortality: a community-level prospective epidemiological cohort study" was recently published in the Lancet medical journal.

The research team followed 94,000 people, aged 35 to 70, for an average of eight years. They analyzed data on more than 300 communities from 18 countries around the world to look for any associated risk of heart health problems.

According to the World Health Organization (WHO), it is recommended adults consume less than 5 grams of salt per day, which is approximately one teaspoon. This is equivalent to less than 2 grams of sodium per day.

Experts have stated high sodium consumption can raise blood pressure and increase the risk of cardiovascular disease, stroke, and heart attack.

But the new findings suggested low levels of salt consumption might be just as dangerous, being linked to more heart attacks and deaths. Rather than to reduce salt intake, we should aim for moderate consumption, said first author Andrew Mente from McMaster University in Canada.

Referring to the recommended WHO salt intake, there was "little evidence in terms of improved health outcomes that individuals ever achieve at such a low level," he said. "Our bodies need essential nutrients like sodium, but the question is how much." 

It was only in places like China where the authors found a link to cardiovascular events. The reason was attributed to the relatively high sodium intake in these communities, sometimes exceeding five grams per day.

Other countries, which do not show these trends, may not require campaigns to cut down on salt according to the researchers. The study has stirred some debate, especially among experts who support reducing salt intake to the lowest levels possible.

This is not the first time as the same team published a similar study in 2016 which received criticism from many.

"The authors have not addressed any of the serious criticisms from the wider scientific community of their 2016 study," said Graham MacGregor, professor of cardiovascular medicine at the Queen Mary University of London.

MacGregor, who is the founder of the salt-reduction campaign CASH, listed criticisms such as the use of spot urine measurements and including ill participants.

This can lead to the problem of reverse causality — those suffering from heart disease may eat less food in general (and therefore, eat lesser salt). But it is likely their disease is what leads to death rather than their lowered salt intake.