The findings were published in The New England Journal of Medicine, after researchers collected and analysed existing population level data on diet and cardiovascular mortality from 187 countries.
The team reported that the average level of sodium consumption globally in 2010 was 3.95g per day - nearly double the 2.0g recommended by the World Health Organization (WHO), adding that thier analysis of cardiovascular disease incidence and mortality showed that 1.65 million deaths from cardiovascular causes were attributed to sodium consumption above this reference level of 2.0 g per day.
"High sodium intake is known to increase blood pressure, a major risk factor for cardiovascular diseases including heart disease and stroke," said lead author Dr Dariush Mozaffarian of Tufts University, who led the research while at the Harvard School of Public Health. "However, the effects of excess sodium intake on cardiovascular diseases globally by age, sex, and nation had not been well established."
"These 1.65 million deaths represent nearly one in 10 of all deaths from cardiovascular causes worldwide. No world region and few countries were spared," added Mozaffarian. "These new findings inform the need for strong policies to reduce dietary sodium.”
The research was supported by a grant from the Bill and Melinda Gates Foundation
The US-based team collected and analysed existing data from 205 surveys of sodium intake in countries representing nearly three-quarters of the world's adult population, in combination with other global nutrition data, to calculate sodium intakes worldwide by country, age, and sex.
The effects of sodium on blood pressure and of blood pressure on cardiovascular diseases were determined separately in new pooled meta-analyses, including differences by age and race. These findings were then combined with current rates of cardiovascular diseases around the world to estimate the numbers of cardiovascular deaths attributable to sodium consumption above 2.0g per day.
Mozaffarian and his colleagues found that all regions of the world were above recommended levels, with regional averages ranging from 2.18g per day in sub-Saharan Africa to 5.51g per day in Central Asia.
In the United States, average daily sodium intake was 3.6g, 80% higher than the amount recommended by the World Health Organization.
“Whereas estimated sodium-associated cardiovascular mortality was highest in Central Asia, it was high ... in all regions,” wrote the research team – noting that rate of death from cardiovascular causes associated with sodium intake above the reference level was highest in the country of Georgia and lowest in Kenya, said the team.
"We found that four out of five global deaths attributable to higher than recommended sodium intakes occurred in middle- and low-income countries," explained last author John Powles from the University of Cambridge, UK.
The data also showed that 2 out of every 5 deaths were premature (before 70 years of age).
In their meta-analysis of controlled intervention studies, the researchers also reported that reduced sodium intake lowered blood pressure in all adults, with the largest effects identified among older individuals, black people, and those with pre-existing high blood pressure.
"Programs to reduce sodium intake could provide a practical and cost effective means for reducing premature deaths in adults around the world,” said Powles.
Source: The New England Journal of Medicine
Volume 371, pages 624-634, doi: 10.1056/NEJMoa1304127
“Global Sodium Consumption and Death from Cardiovascular Causes”
Authors: Dariush Mozaffarian, Saman Fahimi, et al