SMASH: Population-Based Sodium Reduction Sees Success in China

A population-based intervention that targeted schools, businesses, and individual households helped a province in China reduce its sodium intake and had a modest effect on blood pressure, researchers have found. Importantly, the program also helped improve awareness about salt consumption that could lead to long-term compliance.

At the time the study began, the mean sodium intake per person in China was 10.5 g per day, which is about twice the daily limit recommended by both Chinese Dietary Guidelines and the World Health Organization. Five years later, urinary sodium excretion levels were down, potassium levels were up, and mean systolic BP had declined by 1.8 mm Hg and diastolic BP by 3.1 mm Hg, according to results published April 27, 2020, ahead of print, in JAMA Internal Medicine.

As to whether the intensive program, conducted in a single Chinese province, is feasible in other parts of the world, Tracy Y. Wang, MD (Duke Clinical Research Institute, Durham, NC), who wrote an editor’s note for the paper, said there is no reason elements of it couldn’t be incorporated by the United States and other nations of the world.

“This was a highly impactful intervention that clearly works,” she told TCTMD. “Basically, what it's telling us is we need to commit to doing something like this—not [ask] whether or not we can do it. We need to commit to doing it.”

Concentrated Efforts to SMASH Salt Use and BP

Unlike citizens of many other countries, Chinese people eat the majority of their meals at home, with about 80% of their dietary sodium coming from home cooking. The Shandong Ministry of Health Action on Salt and Hypertension (SMASH) researchers, led by Aiqiang Xu, PhD (Shandong University, Jinan, China), focused on reducing the use of sodium-rich condiments among people living in Shandong Province. Their effort was massive and extensive: distributing 13 million salt measuring spoons; displaying millions of posters, pamphlets, and signs in schools, communities, restaurants, and cafeterias; putting up over 74,000 low-sodium diet billboards; conducting nearly 70,000 training sessions for community members; and running advertisements on local media. The investigators also collaborated with supermarkets, food processors, and restaurants to make salt labeling clear and provide sodium substitutes.

A further part of their effort to engage the community was the creation of a Family Salt Reduction Campaign in which model families were selected to be role models for the community. SMASH also aimed targeted educational outreach at women, who were likely to be the ones preparing meals, and at schools where children and their parents would see and hear the salt-reduction messages.

More than 15,000 adults aged 18 to 69 years were first surveyed in 2011 (preintervention group) and more than 16,000 were surveyed in 2016 (postintervention group). Additionally, subgroups of approximately 2,000 people were chosen from the pre- and postintervention groups to undergo 24-hour urine sample collection to test for sodium and potassium.

Messaging can only go so far, but if you start young and you’re consistent, there’s a good chance those messages will stay in place and have some impact. Tracy Wang

Sodium excretion decreased from a mean of 5,338 mg per day in 2011 to 4,013 mg per day in 2016, a reduction of approximately 25%. Mean potassium levels increased from 1,607 mg per day in 2011 to 1,850 mg per day in 2016, an increase of 15%. Additionally, the mean sodium-to-potassium ratio declined from 6.9 to 4.3, a decrease of more than 35% (P < 0.001 for all comparisons).

Mean systolic BP decreased from 131.8 mm Hg in 2011 to 130.0 mm Hg in 2016 (P = 0.04), while diastolic BP declined from a mean of 83.9 mm Hg to 80.8 mm Hg (P < 0.001). According to Xu and colleagues, the changes were consistent across subgroups but more pronounced in those who were older, had prehypertension and hypertension, and had less formal education.

Results from the pre- and postintervention surveys on knowledge, attitudes, and behaviors regarding sodium showed that overall knowledge in the community about dietary salt recommendations increased from 31.7% to 57.6%. Self-reported use of the scaled salt spoons more than doubled from 14.6% to 36.1%, reading processed food labeling increased from 18.4% to 32.1%, and actions taken to reduce dietary salt increased from 35.7% to 61.1% (P < 0.001 for all comparisons).

Hope for Public Health Initiatives

Xu and colleagues note that although the reductions in BP were modest, “even a slight population-wide reduction in BP might have a substantial association with CVD incidence.”

The study had no control group, however, so there is no way to know for certain that the changes in sodium excretion and BP were related entirely to the salt-reduction efforts, Xu and colleagues acknowledge. In her paper, Wang agrees, pointing out that large public health interventions like SMASH “can be messy to study” in the context of a before-and-after comparison.

“In addition, changes in blood pressure and salt sales compared favorably with concurrent trends in other regions of China,” Wang writes.

SMASH shares some similarities with a recent Peruvian study, in which investigators created a salt alternative known as Liz. Through promotion of the product in communities for use at home and in restaurants, systolic and diastolic BP levels decreased significantly, with larger reductions seen in certain high-risk groups. Importantly, the community-wide incidence of hypertension in that study (defined as a threshold of 140/90 mm Hg) declined by more than half.

Unlike the Chinese study with no control group, the Peruvian effort used a stepped-wedge, cluster-randomized design in which communities entered the study at different times. To TCTMD, Wang said that while the latter is preferable to having no control group, the long-term public health benefits of both studies could be significant and wide-ranging.

“Messaging can only go so far, but if you start young and you’re consistent, there’s a good chance those messages will stay in place and have some impact,” she concluded.