Researchers at Stellenbosch University's (SU) Centre for Evidence-based Health Care (CEBHC) recently conducted a Cochrane systematic review to assess the effects and safety of replacing salt with low-sodium salt substitutes (LSSS).
The team, led by senior researcher and registered dietician Prof Celeste Naudé, was commissioned by the World Health Organisation (WHO) as part of their efforts to reduce global population salt intake. The reduction of population salt intake is key to controlling non-communicable disease worldwide – too much salt (sodium) contributes to high blood pressure, which can lead to heart attacks and strokes.
“Our systematic review is informing the development of a WHO guideline, which will contain a recommendation on the use of LSSS to reduce dietary sodium intake," explains Naudé. “The guideline will also provide key contextual information to facilitate the interpretation and implementation of the recommendation for clinical practice or public health policy."
Although many countries have initiated salt-reduction programmes, little progress has been made towards the WHO's target of reducing global population salt intake by 30% by 2025.
“The guideline and recommendation can be used by the 194 WHO member states to help them decide on whether they should implement strategies or policies that include using LSSS to reduce dietary sodium intake to help address cardiovascular health problems and burdens in their countries," Naudé says.
A systematic review aims to identify, appraise and synthesise all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. For this specific review, the CEBHC research team searched five electronic databases and trial registries for studies that compared the use of LSSS to regular salt, screening more than 6 000 titles and abstracts in this process.
“We compared and summarised the results of the studies and rated our confidence in the combined evidence, based on factors such as study methods and sizes. Pooling the results of 26 trials, we found that when compared to regular salt, LSSS probably reduce blood pressure, non-fatal cardiovascular events and cardiovascular deaths slightly, but also probably increase blood potassium slightly in adults," explains Naudé.
Potassium intake is pertinent as most LSSS replace some of the sodium with potassium-containing salts.
“Importantly, we could not make firm conclusions about the effects and safety of LSSS in the general population because evidence is limited for children, pregnant women, people known to have a risk of high blood potassium, and those who do not have high blood pressure," she says. “We are also unsure about the effects of LSSS when used in foods not prepared at home (ex. manufactured foods) because most of the evidence came from studies where LSSS was used on the table or added during cooking."
Naudé facilitated the commissioning of the review by WHO and was the senior author, supported by the CEBHC's Amanda Brand as first author, and Marianne Visser and Anel Schoonees as co-authors.
“The WHO has adopted internationally recognised methods and standards for guideline development, she explains. “These methods require that recommendations in WHO guidelines are based on a systematic, transparent, and comprehensive assessment of the balance of the potential benefits and harms of a specific policy or intervention, and explicit consideration of other relevant factors, such as feasibility and resource implications.
“I presented the findings of our systematic review to the WHO guideline development group responsible for this guideline (WHO Nutrition Guidance Expert Advisory Group (NUGAG) Subgroup on Diet and Health), and we participated in the various meetings where they considered our findings along with other relevant evidence to inform their comprehensive assessment, in order to formulate a recommendation on the use of LSSS to reduce sodium intake."