Summary The impact of replacing salt with a low-sodium salt substitute (LSSS) was examined in adults and children in a review published online August 10 in the Cochrane Library. Amanda Brand, Ph.D., from Stellenbosch University in South Africa, and colleagues examined the effects and safety of replacing salt with LSSS to reduce sodium intake on cardiovascular health among adults, pregnant women, and children. We included data from 26 randomized controlled trials, with 34,961 adults and 92 children who were randomly assigned to LSSS or regular salt. No studies in pregnant women were identified. The researchers found that compared with regular salt, LSSS likely slightly reduced diastolic blood pressure (DBP) and systolic blood pressure (SBP) (mean difference, −2.43 and −4.76 mm Hg, respectively). ) among adults. Compared with regular salt, LSSS probably reduces nonfatal stroke, nonfatal acute coronary syndrome, and cardiovascular mortality (absolute effect, 20, 150, and 180 less/100,000 person-years, respectively) and probably slightly increases potassium in blood (average difference, 0.12 mmol/L). On average, compared with table salt, LSSS may make little or no difference in hypertension and hyperkalemia (absolute effect, 17 less and four more/100,000, respectively). We found very uncertain evidence for the effects of LSSS on blood pressure control, various cardiovascular events, stroke mortality, hypokalemia, and other adverse events. The evidence is very uncertain about the impact of LSSS on DBP and SBP in children. "These small effects may be important when LSSS interventions are implemented at the population level," the authors write. |
Background
High blood pressure, or hypertension, is the leading cause of preventable deaths worldwide. Diets high in sodium (mainly sodium chloride) and low in potassium contribute to raising blood pressure. The WHO recommends reducing the average sodium intake of the population through effective and safe strategies to reduce hypertension and its associated disease burden. Incorporating low sodium salt substitutes (LSSS) into population strategies is increasingly recognized as a potential sodium reduction strategy, particularly in populations where a substantial proportion of the Total sodium intake comes from discretionary salt. LSSS contain lower concentrations of sodium through its displacement with predominantly potassium or other minerals.
Potassium-containing LSSS can potentially simultaneously decrease sodium intake and increase potassium intake. The benefits of LSSS include its potential blood pressure-lowering effect and its relatively low cost. However, there are concerns about the potential adverse effects of LSSS, such as hyperkalemia, particularly in people at risk, for example, those with chronic kidney disease (CKD) or taking medications that affect potassium excretion.
Goals
To evaluate the effects and safety of salt substitution with LSSS to reduce sodium intake on cardiovascular health in adults, pregnant women and children.
Search methods
We searched MEDLINE (PubMed), Embase (Ovid), Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCOhost), ClinicalTrials. gov and WHO International Clinical Trials Registry Platform (ICTRP) until August 18, 2021, and selected reference lists of included trials and relevant systematic reviews. No language or publication restrictions were applied.
Main results
We included 26 RCTs, 16 randomized individual participants and 10 randomized groups (families, households or villages). A total of 34,961 adult participants and 92 children were randomized to LSSS or regular salt, with the smallest trial including 10 and the largest involving 20,995 participants. No studies in pregnant women were identified. The studies included only participants with hypertension (11/26), normal blood pressure (1/26), prehypertension (1/26), or participants with and without hypertension (11/26).
This was unknown in the remaining studies. The largest study included only participants with an elevated risk of stroke at baseline. Seven studies included adult participants possibly at risk for hyperkalaemia. The 26 trials specifically excluded participants for whom increased potassium intake is known to be potentially harmful.
The proportion of sodium chloride replacement in LSSS interventions ranged from approximately 3% to 77%. The majority of trials (23/26) investigated LSSS in which potassium-containing salts were used to replace sodium. In the majority of trials, implementation of the LSSS was discretionary (22/26). The duration of the trial ranged from two months to almost five years.
The overall risk of bias was assessed as high in six trials and unclear in 12 trials.
LSSS compared to regular salt in adults: LSSS compared to regular salt probably reduces DBP on average (mean difference (MD) -2.43 mmHg, 95% confidence interval (CI) -3.50 to -1.36; 20,830 participants, 19 RCTs, moderate certainty evidence) and SBP (MD -4.76 mmHg, 95% CI -6.01 to -3.50; 21,414 participants, 20 RCTs, evidence of moderate certainty) slightly.
On average, LSSS probably reduces non-fatal stroke (absolute effect (AE) 20 less/100,000 person-years, 95% CI -40 to 2; 21,250 participants, 3 RCTs, moderate-certainty evidence), non-fatal acute coronary syndrome (AE 150 less/100,000 person-years, 95% CI -250 to 30; 20,995 participants, 1 RCT, moderate-certainty evidence) and cardiovascular mortality (AE 180 less/100,000 person-years) person, 95% CI: -310 to 0; 23,200 participants, 3 RCTs, moderate-certainty evidence) slightly, and probably slightly increases blood potassium (MD 0.12 mmol/L, 95% CI: 0. 07 to 0.18; 784 participants, 6 RCTs, moderate-certainty evidence), compared with common salt.
LSSS may make little or no difference, on average, in hypertension (AE 17 less/1000, 95% CI -58 to 17; 2566 participants, 1 RCT, low-certainty evidence) and hyperkalaemia (AE 4 more /100,000, 95% CI -47 to 121, 22,849 participants, 5 RCTs, moderate-certainty evidence) compared with table salt. The evidence is very uncertain about the effects of LSSS on blood pressure control, various cardiovascular events, stroke mortality, hypokalaemia and other adverse events (very low-certainty evidence).
LSSS compared to regular salt in children: The evidence is very uncertain about the effects of LSSS on DBP and SBP in children. We found no evidence about the effects of LSSS on hypertension, blood pressure control, blood potassium, hyperkalaemia and hypokalaemia in children.
Authors’ conclusions
Compared with regular salt, LSSS probably slightly reduces blood pressure, nonfatal cardiovascular events, and cardiovascular mortality in adults. However, LSSS probably also slightly increases blood potassium in adults. These small effects may be important when LSSS interventions are implemented at the population level.
Evidence is limited for adults without elevated blood pressure, and there is a lack of evidence in pregnant women and people in whom increased potassium intake is known to be potentially harmful, limiting conclusions about the safety of LSSS in the population. general. We also cannot draw firm conclusions about the effects of non-discretionary LSSS implementations. The evidence is very uncertain about the effects of LSSS on blood pressure in children.
Key messages
• In adults, using LSSS instead of regular salt in food is likely to slightly reduce blood pressure. Adults who use LSSS instead of regular salt probably have a slightly lower risk of nonfatal heart disease, such as a stroke or a sudden reduction in blood flow to the heart, and death from heart disease.
• Using LSSS instead of table salt is also likely to slightly increase the level of potassium in the blood (a mineral that keeps the heart beating at the correct rate) in adults. This could be harmful for people who cannot effectively regulate potassium in their bodies. Other evidence on safety is very limited.
• We are not sure about the effects of using LSSS instead of regular salt on blood pressure in children, or if using LSSS is safe in children.
• This evidence may not directly apply to people who are known to be at risk for high blood potassium levels, such as people with kidney problems or who take certain medications.
What are low sodium salt substitutes (LSSS)?
LSSS are products with less sodium than normal salt. The amounts of sodium in LSSS are reduced by replacing some of the sodium with potassium or other minerals. LSSS can help reduce the risks of using regular salt, since eating too much sodium and too little potassium contributes to high blood pressure. Globally, high blood pressure is the leading cause of preventable deaths, mainly because it causes strokes, acute coronary syndrome (ACS, in which less blood flows to the heart) and kidney problems.
However, LSSS also has potential health risks. Using LSSS can lead to higher than normal blood potassium levels (hyperkalemia), which causes problems with the speed and rhythm of your heartbeat, or can cause your heart to stop. These risks are greater in certain people, for example, those whose kidneys do not work properly to remove potassium.
