Legislation reducing salt content in processed foods linked with drop in blood pressure among South Africans
Almost a decade after South Africa began regulating sodium content in processed foods, a study has found that salt consumption and blood pressure levels among South Africans significantly decreased.
And if those drops persist, deaths related to high blood pressure and cardiovascular disease (CVD)—conditions linked with overconsumption of sodium—might drop too, according to the study’s corresponding author Thomas Gaziano, associate professor in Harvard T.H. Chan School of Public Health’s Department of Health Policy and Management and core faculty in the Center for Health Decision Science.
“High blood pressure is a lead risk factor for mortality in Africa and the rest of the world,” Gaziano said. “Our study suggests other countries could adopt similar regulations and look for similar improvements.”
Regulations to limit sodium consumption
CVD is one of the leading causes of death worldwide. Each year, it’s responsible for nearly 20 million deaths, and about half of those dying had high blood pressure. In 2013, South Africa became one of the first countries in the world—and the first country in Africa—to pass regulations on sodium content in processed foods, in an effort to lower rates of high blood pressure and, in turn, mortality. The legislation, the most extensive that any country has passed, called for sodium reductions in 13 categories of food, including bread, breakfast cereals, butter and fat spreads, chips and savory snacks, processed meats, soups, sauces, and stock concentrates. By 2016, manufacturers were required to reduce sodium content in these foods between 20% and 70%, then lower them further, between 5% and 46%, by 2019.
The study by Gaziano and colleagues was published Feb. 5 in JAMA Cardiology, and was part of the Health and Aging in Africa: Longitudinal Studies in South Africa (HAALSA) program, a partnership between Harvard Chan School; University of Witwatersrand, Johannesburg; University of Cape Town; and the Columbia University Department of Neurology. HAALSA evaluates how policy and other drivers of health influence chronic and infectious diseases, including dementia, cardiometabolic disorders, and HIV, among South Africans ages 40 and above, in order to better understand health outcomes within an increasingly aging society. The program is funded by the National Institutes of Aging, part of the National Institutes of Health.
To assess the effectiveness of sodium regulation, the study looked at salt consumption and blood pressure among the HAALSA cohort, composed of more than 5,000 adults ages 40 and above in rural South Africa. The researchers measured sodium levels in participants’ urine and took their blood pressure at three different times: in 2014, before the regulations were implemented, and again in 2018 and 2021.
Blood pressure reductions
Participants’ sodium consumption fell by about 10% over the seven-year study period, the researchers found. In addition, the proportion of the study population that achieved ideal sodium consumption—less than two grams of salt per day, according to the World Health Organization—increased from 7% to 17%. Every gram of sodium reduction was associated with a 1.3 millimeters of mercury (mmHg) reduction in blood pressure.
“If this reduced sodium consumption remains constant over time, it could be associated with lower rates of cardiovascular disease mortality as well as of stroke, heart failure, end-stage renal disease, and vascular dementia, all of which are also associated with high blood pressure,” Gaziano said. “Reductions of even one mmHg annually could lead to tens of thousands of deaths averted each year.”
While the researchers noted that this observational study can’t prove causation—it isn’t definite that South Africa’s regulations on sodium directly led to the decreases in salt consumption and blood pressure—Gaziano said the legislation can still serve as a model for other countries, including the U.S.
“Our country has an aging population with increasing health burdens, and despite spending more on health care, in the last few years we’ve seen a first-ever reversal of a trend of reductions in CVD mortality,” he said. “We expect our medications and medical devices to be safe. We should be willing to see a similar reasonable evaluation of processed foods.”
