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. 2022 Aug 10;2022(8):CD015207. doi: 10.1002/14651858.CD015207

Sarkkinen 2011.

Study characteristics
Methods Study design: Randomised controlled trial
Study grouping: Parallel group
Country: Finland
Setting: Intervention conducted in households in Kuopio; outcomes measured at Food and Health Research Centre, University of Eastern Finland
Aim of study: To determine the feasibility of replacing sodium chloride with a novel mineral salt (50% sodium chloride, 25% potassium chloride and 25% magnesium ammonium potassium chloride hydrate); and the effect of replacement on blood pressure
Unit of allocation: adults (aged 18 years or older)
Start date: NR
End date: NR
Relevant study limitations as reported by study authors: Small sample size
Sample size calculation: NR
Participants Baseline Characteristics
LSSS intervention

  • Age: in years, mean (SD): 57 (12)

  • Gender: Female, % (n/N): 59 (13/22)

  • Ethnicity/race: European

  • Smoking: Smokers, % (n/N): 14 (3/22)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 28 (3)

  • Blood pressure status: Mildly hypertensive (SBP 130 to 159; DBP 85 to 99), %: 100 (25/25)

  • Antihypertensive medication used: Use of antihypertensive medication, % (n/N): 0 (0/22)

  • Cardiovascular disease or stroke: Active heart disease, % (n/N): 0 (0/22)

  • Diabetes mellitus: Type 1 and type 2 DM, % (n/N): 0 (0/22)

  • Renal impairment: Abnormal kidney function, % (n/N): 0 (0/22)

  • Dietary potassium intake: NR

  • Dietary sodium intake: in points according to Finnish Heart association, mean (SD): 11.7 (2.5)

  • Urinary potassium excretion: mmol/24 h, mean (SD): 79 (31)

  • Urinary sodium excretion: mmol/24 h, mean (SD): 130 (47)


Control

  • Age: in years, mean (SD): 54 (11)

  • Gender: Female, % (n/N): 39 (9/23)

  • Ethnicity/race: European

  • Smoking: Smokers, % (n/N): 13 (3/23)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 28 (3)

  • Blood pressure status: Mildly hypertensive (SBP 130 to 159; DBP 85 to 99), %: 100 (25/25)

  • Antihypertensive medication used: Use of antihypertensive medication, % (n/N): 0 (0/25)

  • Cardiovascular disease or stroke: Active heart disease, % (n/N): 0 (0/23)

  • Diabetes mellitus: Type 1 and type 2 DM, % (n/N): 0 (0/23)

  • Renal impairment: Abnormal kidney function, % (n/N): 0 (0/23)

  • Dietary potassium intake: NR

  • Dietary sodium intake: in points according to Finnish Heart association, mean (SD): 11.9 (1.4)

  • Urinary potassium excretion: mmol/24 h, mean (SD): 82 (22)

  • Urinary sodium excretion: mmol/24 h, mean (SD): 151 (44)


Inclusion criteria: Subjects aged between 25 and 75 years; with systolic blood pressure between 130 and 159 mmHg and/or diastolic blood pressure between 85 and 99 mmHg; with BMI between 23 and 40 kg/m2, and stable body weight
Exclusion criteria: Subjects on antihypertensive medication, nonsteroidal anti‐inflammatory drugs, cyclosporine or tacrolimus; with secondary hypertension, type 1 or 2 diabetes, history of active heart disease or cancer, abnormal electrolyte concentrations, proteinuria; with abnormal liver, kidney or thyroid function; currently following a low salt diet (six points or fewer on the salt intake test of the Finnish Heart Association); abusing drugs or alcohol; who are pregnant, or lactating
Pretreatment: None
Method of recruitment of participants: Recruitment of subjects was done through announcements in local newspapers and from the volunteer register of Oy Foodfiles (affiliation of the first author), after which potential participants were screened by telephone.
Informed consent obtained: Yes, written
Clusters: n/a
Subgroups planned/measured: NR
Subgroups reported: NR
Participant flow
Assessed for eligibility: n = 168
Excluded (number with reasons): n = 118 (reasons NR)
Randomised: n = 50
Allocated to LSSS intervention(s): n = 25
Allocated to control: n = 25
Received allocated LSSS intervention(s): NR
Did not receive allocated LSSS intervention(s): NR
Lost to follow‐up (LSSS intervention group): n = 3 (reasons NR)
Discontinued intervention (LSSS intervention group): NR
Analysed (LSSS intervention group): n = 22
Excluded from analysis (LSSS intervention group): NR
Received allocated control: NR
Did not receive allocated control: NR
Lost to follow‐up (control group): n = 2 (reasons NR) 
Discontinued intervention (control group): NR
Analysed (control group): n = 23
Excluded from analysis (control group): NR
Interventions Intervention Characteristics
LSSS intervention

  • Theoretical basis: Restriction in dietary salt lowers blood pressure. Substituting potassium and/or magnesium salts may increase the feasibility of salt restriction and reduce blood pressure more than restriction of sodium alone.

  • Description: "Smart Salt" SMS50 (50% NaCl; 25% KCl; 25% Mg salt)

  • LSSS category: < 30% KCl

  • Contains fortificant: NR

  • Delivery: Non‐discretionary and discretionary use

  • Duration of run‐in period: 4 weeks on habitual diet

  • Duration of active intervention: 8 weeks

  • Duration of follow‐up (as reported): none

  • Total duration of study (as reported): 8 weeks

  • Timing: The daily amount of test foods in the diet was based on national dietary data in Finland (FinDiet 2007), and LSSS was used throughout the study for cooking, baking and at the table.

  • Implementation: Test foods provided were industrially processed main dishes (casseroles, soups, pastas, pizza and minced meat dishes), bread (70% rye bread and 30% multigrain), frankfurters sausage/cold cuts and Edam cheese which replace 60% of sodium. The analysed concentration of sodium (expressed as NaCl) in the test foods varied between 0.38‐1.41% in SmartSalt foods.

  • Providers: Manufactured by SmartSalt, Inc., California, USA

  • Co‐interventions: Participants instructed to avoid salt‐rich products (e.g. salty snacks, soy sauce, olives, salt‐rich cheeses, stock cubes, salty and smoked fish), products containing bioactive peptides (Evolus), liquorice, ammonium chloride products and any food supplements that may affect BP.

  • Resource requirements: NR

  • Integrity of delivery: The sodium chloride reduction was intended to be reduced by 3.1 to 5.6 grams (approximately 1.2 to 2.2 grams of sodium), depending on energy intake and dietary habits. Individual diaries with use of test products were kept by participants. Good compliance was reported by study authors.


Control

  • Theoretical basis: To enable comparison of LSSS intervention with standard practice

  • Description: Regular salt (100% NaCl)

  • Contains fortificant: NR

  • Delivery: Non‐discretionary and discretionary use

  • Duration of run‐in period: 4 weeks on habitual diet

  • Duration of active intervention: 8 weeks

  • Duration of follow‐up (as reported): none

  • Total duration of study (as reported): 8 weeks

  • Timing: The daily amount of test foods in the diet was based on national dietary data in Finland (FinDiet 2007), and regular salt was used throughout the study for cooking, baking and at the table.

  • Implementation: Test foods provided were industrially processed main dishes (casseroles, soups, pastas, pizza and minced meat dishes), bread (70% rye bread and 30% multigrain), frankfurters sausage/cold cuts and Edam cheese. The analysed concentration of sodium (expressed as NaCl) in the test foods varied between 0.64‐2.03% in regular salt foods.

  • Providers: Manufactured by Akzo Nobel Salt, The Netherlands

  • Co‐interventions: Participants instructed to avoid salt‐rich products (e.g. salty snacks, soy sauce, olives, salt‐rich cheeses, stock cubes, salty and smoked fish), products containing bioactive peptides (Evolus), liquorice, ammonium chloride products and any food supplements that may affect BP.

  • Resource requirements: NR

  • Integrity of delivery: Individual diaries with use of test products were kept by participants. Good compliance was reported by study authors.
Outcomes Primary outcomes: 

  • Diastolic Blood Pressure (DBP): Outcome measurement: Measurements taken with an automatic sphygmomanometer (after 10 mins rest) in sitting position. Three measurements with 2 minutes in between taken during the morning. The last 2 measurements were averaged. Time points: 3, 6, 8 weeks

  • Systolic Blood Pressure (SBP): Outcome measurement: Measurements taken with an automatic sphygmomanometer (after 10 mins rest) in sitting position. Three measurements with 2 minutes in between taken during the morning. The last 2 measurements were averaged. Time points: 3, 6, 8 weeks

  • Hypertension (as reported, or SBP > 140 mmHg or DBP > 85 mmHg): NR

  • Blood pressure control (achieving blood pressure threshold or 'control' as prespecified): NR

  • Cardiovascular events‐stroke: NR

  • Cardiovascular events‐myocardial infarction: NR

  • Cardiovascular events‐other: Cardiovascular symptoms; outcome measurement: Subjects recorded any adverse events in their daily diary. Time points: duration of the study

  • Cardiovascular mortality: NR

  • Blood potassium: Outcome measurement: Blood samples were taken following 10 to 12 hours of overnight fasting, and were analysed using standard methods, ion‐specific electrode analysis for serum potassium, at ISLAB laboratories. Time points: 8 weeks

  • Hyperkalaemia: NR

  • Hypokalaemia: NR


Secondary outcomes: 

  • All‐cause mortality: NR

  • Adverse events: Respiratory, abdominal/intestinal symptoms; outcome measurement: Subjects recorded any adverse events in their daily diary. Time points: duration of the study

  • Antihypertensive medication use: NR

  • Body Mass index (BMI): Outcome measurement: Calculated from standard equation using weight determined by calibrated digital scale and height measured by telescoping measuring rod, to the nearest crossed half a centimetre. Time points: 8 weeks

  • Serum creatinine: NR

  • Albuminuria: NR

  • Urinary albumin‐to‐creatinine ratio (uACR): NR

  • Fasting blood glucose: NR

  • Blood triglycerides: NR

  • Total blood cholesterol: NR

  • 24‐h urinary sodium excretion: 24‐hour urine sample. Time points: 8 weeks

  • 24‐h urinary potassium excretion: 24‐hour urine sample. Time points: 8 weeks
Notes Funding source: The study was supported by SmartSalt® Inc, California, USA.
Authors name: Essi S. Sarkkinen
Institution: Oy Foodfiles Ltd, CRO in the field of nutrition
Email: essi.sarkkinen@foodfiles.com
Possible conflicts of interest (for study authors): "The authors declare that they have no competing interests."
Sources used for data extraction: Journal article with results of the trial; non‐commercial trial registry record
Trial registration details: ISRCTN01739816
 
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Unclear risk Insufficient information on how the randomisation sequence was generated
Allocation concealment (selection bias) Unclear risk Insufficient information on how the randomisation sequence was protected
Blinding of participants and personnel (performance bias)
All outcomes Low risk The study was reported as 'double‐blind', but it was not clear whether participants and personnel were blinded (outcome assessors were reported as blinded). Given that the intervention involved test foods in addition to salt intervention, leading to minimal potential lifestyle modification, it was unlikely that outcomes of interest would be affected by a lack of blinding.
Blinding of outcome assessment (detection bias)
All outcomes Low risk It was reported that the study nurse was unaware of treatment allocation.
 
Incomplete outcome data (attrition bias)
All outcomes Low risk Overall attrition was 3/25 (12%) in the intervention and 2/25 (8%) in the control group, with no reasons provided.
Selective reporting (reporting bias) Unclear risk No study protocol or prospective trial registry entry available
Other bias Low risk None identified
Overall risk of bias Unclear risk Unclear risk of bias for allocation concealment; low risk of bias for incomplete outcome data