A new study by US researchers found that a moderate reduction in daily salt intake could reduce deaths and rates of heart disease among Americans, and among African Americans in particular, because they are more likely to have high blood pressure and for it to be sensitive to salt.
The study was the work of lead author Dr Kirsten Bibbins-Domingo, an assistant professor of Medicine and of Epidemiology at the University of California, San Francisco, and colleagues. The findings are being presented at the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention which is taking place from Tuesday March 10th to Saturday March 14th at the Westin Innsbruck Resort in Palm Harbor, Florida.
Americans eat between 9 and 12 grams of salt per day. As each gram of salt contains 0.4 grams of sodium, this translates to between 3,600 and 4,800 mg of sodium. Most health organizations recommend a daily amount of between 2,000 and 2,400 mg of sodium. The American Heart Association recommends that healthy adults should limit their daily sodium intake to under 2,300 mg (about 1 teaspoon of salt) a day.
Lots of studies have shown for some time that the more salt we eat the more likely we are to have high blood pressure and heart disease, yet in the US salt consumption has gone up by 50 per cent, and blood pressure by nearly the same amount, since the 1970s, said the researchers.
Bibbins-Domingo and colleagues found that for every gram of salt reduced in the daily American diet there would most likely be a quarter of a million fewer new cases of heart disease and over 200,000 fewer deaths over ten years.
Bibbins-Domingo explained that such a hardly detectable reduction could have dramatic benefits for Americans.
To work out these figures, she and her colleagues used a validated computer simulation of heart disease in the US adult population.
“It was a surprise to see the magnitude of the impact on the population, given the very small reductions in salt that we were modeling,” said Bibbins-Domingo.
The researchers found that a reduction of 3 grams a day (about 1,200 mg of sodium) would lead to 6 per cent fewer new heart disease cases, 8 per cent fewer cases of heart attack, and 3 per cent fewer deaths.
They suggested these benefits would be even bigger for African Americans because they are more likely to have high blood pressure and for it to be sensitive to salt. Among this section of the population, a 3 gram a day reduction in salt intake would lead to 10 per cent fewer new cases of heart disease, 13 per cent fewer heart attacks, 6 per cent fewer deaths.
Bibbins-Domingo and colleagues used a simulation package called the Coronary Heart Disease Policy Model which estimates what might happen to heart disease in the US adult population as a result of particular changes in national policy or trends. For example the package has been used to project the impact on heart disease rates and deaths as a result of rising childhood obesity.
They used the model to predict what might happen to cardiovascular disease and death rates between 2010 and 2019 in response to immediate reductions in daily salt intake from 0 up to 6 grams.
The model estimated that more than 800,000 life years could be saved for each reduction of 1 gram of salt, while a 6 gram a day reduction would result in more than 4 million life-years saved, 1.4 million fewer cases of heart disease and 1.1 million fewer deaths.
Bibbins-Domingo explained the problem people have when they try to lower salt intake:
“It’s clear that we need to lower salt intake, but individuals find it hard to make substantial cuts because most salt comes from processed foods, not from the salt shaker.”
The study therefore suggests that a large part of the responsibilty lies with the the food industry and its regulators; together they could make a significant contribution to the heart-health of Americans by reducing salt in processed food, even if it is only by a small amount.
An intramural grant from the University of California, San Francisco Clinical and Translational Sciences Institute Strategic Opportunities for Support paid for the study.
Sources: American Heart Association.
Written by: Catharine Paddock, PhD