The effect of potassium supplementation in persons with a high-normal blood pressure. Results from phase I of the Trials of Hypertension Prevention (TOHP). Trials of Hypertension Prevention (TOHP) Collaborative Research Group

Potassium - a scoping review for Nordic Nutrition Recommendations 2023

Potassium (K) is an essential mineral that is necessary for normal cell and membrane function and for maintaining both fluid balance and acid-base balance. Potassium is furthermore very important for normal excitation, for example in nerves and muscle. It is widely available in several food products, with the most important dietary sources being potatoes, fruits, vegetables, cereal and cereal products, milk and dairy products, and meat and meat products. Potassium deficiency and toxicity is rare in healthy people, but dietary potassium is associated with other health outcomes. Results from observational studies have shown that a potassium intake above 3500 mg/day (90 mmol/day) is associated with a reduced risk of stroke. Similarly, intervention studies provide evidence that this level of potassium intake has a beneficial effect on blood pressure, particularly among persons with hypertension and in persons with a high sodium intake (>4 g/day, equivalent to >10 g salt/day).

Vitamins and Minerals for Blood Pressure Reduction in the General, Normotensive Population: A Systematic Review and Meta-Analysis of Six Supplements

Hypertension is the leading preventable risk factor for cardiovascular disease and all-cause mortality worldwide. However, studies have shown increased risk of mortality from heart disease and stroke even within the normal blood pressure (BP) range, starting at BPs above 110-115/70-75 mm Hg. Nutraceuticals, such as vitamins and minerals, have been studied extensively for their efficacy in lowering BP and may be of benefit to the general, normotensive population in achieving optimal BP. Our study investigated the effects of six nutraceuticals (Vitamins: C, D, E; Minerals: Calcium, Magnesium, Potassium) on both systolic blood pressure (SBP) and diastolic blood pressure (DBP) in this population. We performed a systematic review and pairwise meta-analysis for all six supplements versus placebo. Calcium and magnesium achieved significant reductions in both SBP and DBP of -1.37/-1.63 mm Hg and -2.79/-1.56 mm Hg, respectively. Vitamin E and potassium only yielded significant reductions in SBP with values of -1.76 mm Hg and -2.10 mm Hg, respectively. Vitamins C and D were not found to significantly lower either SBP or DBP. Future studies should determine optimal dosage and treatment length for these supplements in the general, normotensive population.

Short-term efficacy of non-pharmacological interventions for global population with elevated blood pressure: A network meta-analysis

Background

This study aims to compare the potential short-term effects of non-pharmacological interventions (NPIs) on prehypertensive people, and provide evidence for intervention models with potential in future community-based management.

Methods

In this Bayesian network meta-analysis, Pubmed, Embase, and Web of science were screened up to 16 October 2021. Prehypertensive patients (systolic blood pressure, SBP 120-139 mmHg/diastolic blood pressure, DBP 80-89 mmHg) with a follow-up period longer than 4 weeks were targeted. Sixteen NPIs were identified during the scope review and categorized into five groups. Reduction in SBP and DBP was selected as outcome variables and the effect sizes were compared using consistency models among interventions and intervention groups. Grade approach was used to assess the certainty of evidence.

Results

Thirty-nine studies with 8,279 participants were included. For SBP, strengthen exercises were the most advantageous intervention group when compared with usual care (mean difference = -6.02 mmHg, 95% CI -8.16 to -3.87), and combination exercise, isometric exercise, and aerobic exercise were the three most effective specific interventions. For DBP, relaxation was the most advantageous intervention group when compared with usual care (mean difference = -4.99 mmHg, 95% CI -7.03 to -2.96), and acupuncture, meditation, and combination exercise were the three most effective specific interventions. No inconsistency was found between indirect and direct evidence. However, heterogeneity was detected in some studies.

Conclusion

NPIs can bring short-term BP reduction benefits for prehypertensive patients, especially exercise and relaxation. NPIs could potentially be included in community-based disease management for prehypertensive population once long-term real-world effectiveness and cost-effectiveness are proven.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=151518, identifier: CRD42020151518.

Clarifying Optimal Sodium InTake In Cardiovasular and Kidney (COSTICK) Diseases: a study protocol for two randomised controlled trials

Background: While low sodium intake (<2.3g/day) is recommended for all, there is uncertainty about feasibility and net cardiovascular effects. In COSTICK, we evaluated the effects of a dietary counselling intervention (reduced sodium intake) on intermediate cardiorenal outcomes in patients with (STICK) and without (COSIP) mild/moderate kidney disease. Methods: This is a protocol for two phase IIb randomised, two-group, parallel, open-label, controlled, single centre trials. Participants were aged >40 years with stable blood pressure, unchanged anti-hypertensive medications, willing to modify diet and provided written informed consent. Participants were excluded for abnormal sodium handling, heart failure, high dose diuretics, immunosuppression, pregnancy/lactation, postural hypotension, cognitive impairment, high or low body mass index (BMI) or inclusion in another trial. STICK participants had estimated glomerular filtration rate (eGFR) 30-60ml/min/1.73m2 and were excluded for acute kidney Injury, rapidly declining eGFR; known glomerular disease or current use of non-steroidal anti-inflammatory drugs. For COSIP, participants were excluded for known kidney or cardiovascular disease. Participants were randomized to usual care only (healthy eating) or an additional sodium lowering intervention (target <100mmol/day) through specific counseling (sodium use in foods, fresh over processed foods, sodium content of foods and eating outside of home). In STICK the primary outcome is change in 24-hour urinary creatinine clearance. In COSIP, the primary outcome is change in five biomarkers (renin, aldosterone, high sensitivity troponin T, pro-B-type natriuretic peptide and C-reactive protein). Our primary report (COSTICK), reports six biomarker outcome measures in the entire population at 2 years follow-up. Discussion: These Phase II trials will explore uncertainty about low sodium intake and cardiovascular and kidney biomarkers, and help determine the feasibility of low sodium intake. Trial results will also provide preliminary information to guide a future definitive clinical trial, if indicated. Trial registration: STICK: ClinicalTrials.gov NCT02738736 (04/04/2016); COSIP: ClinicalTrials.gov NCT02458248 (15/05/2016)

Clarifying Optimal Sodium InTake In Cardiovasular and Kidney (COSTICK) Diseases: a study protocol for two randomised controlled trials

Background: While low sodium intake (<2.3g/day) is recommended for all, there is uncertainty about feasibility and net cardiovascular effects. In COSTICK, we evaluated the effects of a dietary counselling intervention (reduced sodium intake) on intermediate cardiorenal outcomes in patients with (STICK) and without (COSIP) mild/moderate kidney disease. Methods: This is a protocol for two phase IIb randomised, two-group, parallel, open-label, controlled, single centre trials. Participants were aged >40 years with stable blood pressure, unchanged anti-hypertensive medications, willing to modify diet and provided written informed consent. Participants were excluded for abnormal sodium handling, heart failure, high dose diuretics, immunosuppression, pregnancy/lactation, postural hypotension, cognitive impairment, high or low body mass index (BMI) or inclusion in another trial. STICK participants had estimated glomerular filtration rate (eGFR) 30-60ml/min/1.73m2 and were excluded for acute kidney Injury, rapidly declining eGFR; known glomerular disease or current use of non-steroidal anti-inflammatory drugs. For COSIP, participants were excluded for known kidney or cardiovascular disease. Participants were randomized to usual care only (healthy eating) or an additional sodium lowering intervention (target <100mmol/day) through specific counseling (sodium use in foods, fresh over processed foods, sodium content of foods and eating outside of home). In STICK the primary outcome is change in 24-hour urinary creatinine clearance. In COSIP, the primary outcome is change in five biomarkers (renin, aldosterone, high sensitivity troponin T, pro-B-type natriuretic peptide and C-reactive protein). Our primary report (COSTICK), reports six biomarker outcome measures in the entire population at 2 years follow-up. Discussion: These Phase II trials will explore uncertainty about low sodium intake and cardiovascular and kidney biomarkers, and help determine the feasibility of low sodium intake. Trial results will also provide preliminary information to guide a future definitive clinical trial, if indicated. Trial registration: STICK: ClinicalTrials.gov NCT02738736 (04/04/2016); COSIP: ClinicalTrials.gov NCT02458248 (15/05/2016)

Potassium Intake and Blood Pressure: A Dose-Response Meta-Analysis of Randomized Controlled Trials

Background

Epidemiologic studies, including trials, suggest an association between potassium intake and blood pressure (BP). However, the strength and shape of this relationship is uncertain.

Methods and Results

We performed a meta‐analysis to explore the dose‐response relationship between potassium supplementation and BP in randomized‐controlled trials with a duration ≥4 weeks using the recently developed 1‐stage cubic spline regression model. This model allows use of trials with at least 2 exposure categories. We identified 32 eligible trials. Most were conducted in adults with hypertension using a crossover design and potassium supplementation doses that ranged from 30 to 140 mmol/d. We observed a U‐shaped relationship between 24‐hour active and control arm differences in potassium excretion and BP levels, with weakening of the BP reduction effect above differences of 30 mmol/d and a BP increase above differences ≈80 mmol/d. Achieved potassium excretion analysis also identified a U‐shaped relationship. The BP‐lowering effects of potassium supplementation were stronger in participants with hypertension and at higher levels of sodium intake. The BP increase with high potassium excretion was noted in participants with antihypertensive drug‐treated hypertension but not in their untreated counterparts.

Conclusions

We identified a nonlinear relationship between potassium intake and both systolic and diastolic BP, although estimates for BP effects of high potassium intakes should be interpreted with caution because of limited availability of trials. Our findings indicate an adequate intake of potassium is desirable to achieve a lower BP level but suggest excessive potassium supplementation should be avoided, particularly in specific subgroups.

Taste, Salt Consumption, and Local Explanations around Hypertension in a Rural Population in Northern Peru

Interventions to promote behaviors to reduce sodium intake require messages tailored to local understandings of the relationship between what we eat and our health. We studied local explanations about hypertension, the relationship between local diet, salt intake, and health status, and participants' opinions about changing food habits. This study provided inputs for a social marketing campaign in Peru promoting the use of a salt substitute containing less sodium than regular salt. Qualitative methods (focus groups and in-depth interviews) were utilized with local populations, people with hypertension, and health personnel in six rural villages. Participants were 18-65 years old, 41% men. Participants established a direct relationship between emotions and hypertension, regardless of age, gender, and hypertension status. Those without hypertension established a connection between eating too much/eating fried food and health status but not between salt consumption and hypertension. Participants rejected dietary changes. Economic barriers and high appreciation of local culinary traditions were the main reasons for this. It is the conclusion of this paper that introducing and promoting salt substitutes require creative strategies that need to acknowledge local explanatory disease models such as the strong association between emotional wellbeing and hypertension, give a positive spin to changing food habits, and resist the "common sense" strategy of information provision around the causal connection between salt consumption and hypertension.

Potassium supplementation and heart rate: A meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

Increasing the intake of potassium has been shown to lower blood pressure, but whether it also affects heart rate (HR) is largely unknown. We therefore assessed the effect of potassium supplementation on HR in a meta-analysis of randomized controlled trials.

METHODS AND RESULTS

We searched PubMed (1966-October 2014) for randomized, placebo-controlled trials in healthy adults with a minimum duration of two weeks in which the effect of increased potassium intake on HR was assessed. In addition, reference lists from meta-analysis papers on potassium and blood pressure were hand-searched for publications. Two investigators independently extracted the data. We performed random effects meta-analyses, subgroup and meta-regression analyses for characteristics of the study (e.g. design, intervention duration, potassium dose and salt type, change in potassium excretion, sodium excretion during intervention) and study population (e.g. gender, age, hypertensive status, pre-study HR, pre-study potassium excretion). A total of 22 trials (1086 subjects), with a median potassium dose of 2.5 g/day (range: 0.9-4.7 g/day), and median intervention duration of 4 weeks (range: 2-24 weeks) were included. The meta-analysis showed no overall effect of increased potassium intake on HR (0.19 bpm, 95% CI: -0.44, 0.82). Stratified analyses yielded no significant effects of potassium intake on HR in subgroups, and there was no evidence for a dose-response relationship in meta-regression analyses.

CONCLUSION

A chronic increase in potassium intake with supplemental doses of 2-3 g/day is unlikely to affect HR in apparently healthy adults.

Daily potassium intake and sodium-to-potassium ratio in the reduction of blood pressure: a meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the efficacy of daily potassium intake on decreasing blood pressure in non-medicated normotensive or hypertensive patients, and to determine the relationship between potassium intake, sodium-to-potassium ratio and reduction in blood pressure.

DESIGN

Mixed-effect meta-analyses and meta-regression models.

DATA SOURCES

Medline and the references of previous meta-analyses.

STUDIES ELIGIBILITY CRITERIA

Randomized controlled trials with potassium supplementation, with blood pressure as the primary outcome, in non-medicated patients.

RESULTS

Fifteen randomized controlled trials of potassium supplementation in patients without antihypertensive medication were selected for the meta-analyses (917 patients). Potassium supplementation resulted in reduction of SBP by 4.7 mmHg [95% confidence interval (CI) 2.4-7.0] and DBP by 3.5 mmHg (95% CI 1.3-5.7) in all patients. The effect was found to be greater in hypertensive patients, with a reduction of SBP by 6.8 mmHg (95% CI 4.3-9.3) and DBP by 4.6 mmHg (95% CI 1.8-7.5). Meta-regression analysis showed that both increased daily potassium excretion and decreased sodium-to-potassium ratio were associated with blood pressure reduction (P < 0.05). Increased total daily potassium urinary excretion from 60 to 100 mmol/day and decrease of sodium-to-potassium ratio were shown to be necessary to explain the estimated effect.

CONCLUSION

Potassium supplementation is associated with reduction of blood pressure in patients who are not on antihypertensive medication, and the effect is significant in hypertensive patients. The reduction in blood pressure significantly correlates with decreased daily urinary sodium-to-potassium ratio and increased urinary potassium. Patients with elevated blood pressure may benefit from increased potassium intake along with controlled or decreased sodium intake.

Intakes of magnesium, potassium, and calcium and the risk of stroke among men

BACKGROUND

Intakes of magnesium, potassium, and calcium have been inversely associated with the incidence of hypertension, a known risk factor for stroke. However, only a few studies have examined intakes of these cations in relation to risk of stroke.

AIM

The aim of this study was to investigate whether high intake of magnesium, potassium, and calcium is associated with reduced stroke risk among men.

METHODS

We prospectively examined the associations between intakes of magnesium, potassium, and calcium from diet and supplements, and the risk of incident stroke among 42 669 men in the Health Professionals Follow-up Study, aged 40 to 75 years and free of diagnosed cardiovascular disease and cancer at baseline in 1986. We calculated the hazard ratio of total, ischemic, and haemorrhagic strokes by quintiles of each cation intake, and of a combined dietary score of all three cations, using multivariate Cox proportional hazard models.

RESULTS

During 24 years of follow-up, 1547 total stroke events were documented. In multivariate analyses, the relative risks and 95% confidence intervals of total stroke for men in the highest vs. lowest quintile were 0·87 (95% confidence interval, 0·74-1·02; P, trend = 0·04) for dietary magnesium, 0·89 (95% confidence interval, 0·76-1·05; P, trend = 0·10) for dietary potassium, and 0·89 (95% confidence interval, 0·75-1·04; P, trend = 0·25) for dietary calcium intake. The relative risk of total stroke for men in the highest vs. lowest quintile was 0·74 (95% confidence interval, 0·59-0·93; P, trend = 0·003) for supplemental magnesium, 0·66 (95% confidence interval, 0·50-0·86; P, trend = 0·002) for supplemental potassium, and 1·01 (95% confidence interval, 0·84-1·20; P, trend = 0·83) for supplemental calcium intake. For total intake (dietary and supplemental), the relative risk of total stroke for men in the highest vs. lowest quintile was 0·83 (95% confidence interval, 0·70-0·99; P, trend = 0·04) for magnesium, 0·88 (95% confidence interval, 0·75-4; P, trend = 6) for potassium, and 3 (95% confidence interval, 79-09; P, trend = 84) for calcium. Men in the highest quintile for a combined dietary score of all three cations had a multivariate relative risk of 0·79 (95% confidence interval, 0·67-0·92; P, trend = 0·008) for total stroke, compared with those in the lowest.

CONCLUSIONS

A diet rich in magnesium, potassium, and calcium may contribute to reduced risk of stroke among men. Because of significant collinearity, the independent contribution of each cation is difficult to define.

Differences in weight loss and health outcomes among African Americans and whites in multicentre trials

The efficacy of behavioural lifestyle interventions (BLI) for weight loss and prevention and treatment of diabetes and hypertension is well established but may vary among racial/ethnic subgroups. This report reviews literature from 1990 to 2012 to determine if outcomes were similar among African Americans (AA) and whites participating in multicentre BLIs funded by the National Institutes of Health. We identified seven relevant trials that reported subgroup analyses for AA. On average, AA lost less weight at 6 months (AA: -1.6 to -7.5 kg; whites: -3.8 to -8.2 kg), but also had less or similar weight regain compared with whites. There were no reported differences between races in diabetes incidence. Three analyses reported no differences in blood pressure; however, a fourth reported that AA women were the only group that did not experience a significant change in blood pressure. Despite increased attention to cultural relevance, race-specific differences in weight loss persist in trials spanning 20 years; however, risk factor modification was similar across race/ethnic groups. Additional research is needed to understand the mechanisms of risk factor modification, and potential for weight change to promote even greater risk factor modification for AA than has been observed to date.

Urinary potassium excretion and risk of developing hypertension: the prevention of renal and vascular end-stage disease study

Previous prospective cohort studies on the association between potassium intake and risk of hypertension have almost exclusively relied on self-reported dietary data, whereas repeated 24-hour urine excretions, as estimate of dietary uptake, may provide a more objective and quantitative estimate of this association. Risk of hypertension (defined as blood pressure ≥140/90 mm Hg or initiation of blood pressure-lowering drugs) was prospectively studied in 5511 normotensive subjects aged 28 to 75 years not using blood pressure-lowering drugs at baseline of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study. Potassium excretion was measured in two 24-hour urine specimens at baseline (1997-1998) and midway during follow-up (2001-2003). Baseline median potassium excretion was 70 mmol/24 h (interquartile range, 57-85 mmol/24 h), which corresponds to a dietary potassium intake of ≈91 mmol/24 h. During a median follow-up of 7.6 years (interquartile range, 5.0-9.3 years), 1172 subjects developed hypertension. The lowest sex-specific tertile of potassium excretion (men: <68 mmol/24 h; women: <58 mmol/24 h) had an increased risk of hypertension after multivariable adjustment (hazard ratio, 1.20; 95% confidence interval, 1.05-1.37), compared with the upper 2 tertiles (Pnonlinearity=0.008). The proportion of hypertension attributable to low potassium excretion was 6.2% (95% confidence interval, 1.7%-10.9%). No association was found between the sodium to potassium excretion ratio and risk of hypertension after multivariable adjustment. Low urinary potassium excretion was associated with an increased risk of developing hypertension. Dietary strategies to increase potassium intake to the recommended level of 90 mmol/d may have the potential to reduce the incidence of hypertension.

The impact of sodium and potassium on hypertension risk

The pathogenic role of sodium surfeit in primary hypertension is widely recognized but that of potassium deficiency usually has been ignored or at best assigned subsidiary status. Weighing the available evidence, we recently proposed that the chief environmental factor in the pathogenesis of primary hypertension and the associated cardiovascular risk is the interaction of the sodium surfeit and potassium deficiency in the body. Here, we present the major evidence highlighting the relationship between high-sodium intake and hypertension. We then examine the blood pressure-lowering effects of potassium in conjunction with the pernicious impact of potassium deficiency on hypertension and cardiovascular risk. We conclude with summarizing recent human trials that have probed the joint effects of sodium and potassium intake on hypertension and its cardiovascular sequelae. The latter studies lend considerable fresh support to the thesis that the interaction of the sodium surfeit and potassium deficiency in the body, rather than either disturbance by itself, is the critical environmental factor in the pathogenesis of hypertension.

Launching a salt substitute to reduce blood pressure at the population level: a cluster randomized stepped wedge trial in Peru

BACKGROUND

Controlling hypertension rates and maintaining normal blood pressure, particularly in resource-constrained settings, represent ongoing challenges of effective and affordable implementation in health care. One of the strategies being largely advocated to improve high blood pressure calls for salt reduction strategies. This study aims to estimate the impact of a population-level intervention based on sodium reduction and potassium increase - in practice, introducing a low-sodium, high-potassium salt substitute - on adult blood pressure levels.

METHODS/DESIGN

The proposed implementation research study includes two components: Phase 1, an exploratory component, and Phase 2, an intervention component. The exploratory component involves a triangle taste test and a formative research study designed to gain an understanding of the best implementation methods. Phase 2 involves a pragmatic stepped wedge trial design where the intervention will be progressively implemented in several clusters starting the intervention randomly at different times. In addition, we will evaluate the implementation strategy using a cost-effectiveness analysis.

DISCUSSION

This is the first project in a Latin-American setting to implement a salt substitution intervention at the population level to tackle high blood pressure. Data generated and lessons learnt from this study will provide a strong platform to address potential interventions applicable to other similar low- and middle-income settings.

TRIAL REGISTRATION

This study is registered in ClinicalTrials.gov NCT01960972.

Role of dietary salt and potassium intake in cardiovascular health and disease: a review of the evidence

The objective of this review was to provide a synthesis of the evidence on the effect of dietary salt and potassium intake on population blood pressure, cardiovascular disease, and mortality. Dietary guidelines and recommendations are outlined, current controversies regarding the evidence are discussed, and recommendations are made on the basis of the evidence. Designed search strategies were used to search various databases for available studies. Randomized trials of the effect of dietary salt intake reduction or increased potassium intake on blood pressure, target organ damage, cardiovascular disease, and mortality were included. Fifty-two publications from January 1, 1990, to January 31, 2013, were identified for inclusion. Consideration was given to variations in the search terms used and the spelling of terms so that studies were not overlooked, and search terms took the following general form: (dietary salt or dietary sodium or [synonyms]) and (dietary potassium or [synonyms]) and (blood pressure or hypertension or vascular disease or heart disease or chronic kidney disease or stroke or mortality or [synonyms]). Evidence from these studies demonstrates that high salt intake not only increases blood pressure but also plays a role in endothelial dysfunction, cardiovascular structure and function, albuminuria and kidney disease progression, and cardiovascular morbidity and mortality in the general population. Conversely, dietary potassium intake attenuates these effects, showing a linkage to reduction in stroke rates and cardiovascular disease risk. Various subpopulations, such as overweight and obese individuals and aging adults, exhibit greater sensitivity to the effects of reduced salt intake and may gain the most benefits. A diet that includes modest salt restriction while increasing potassium intake serves as a strategy to prevent or control hypertension and decrease cardiovascular morbidity and mortality. Thus, the body of evidence supports population-wide sodium intake reduction and recommended increases in dietary potassium intake as outlined by current guidelines as an essential public health effort to prevent kidney disease, stroke, and cardiovascular disease.

Association of urinary sodium/potassium ratio with blood pressure: sex and racial differences

BACKGROUND AND OBJECTIVES

Previous studies reporting an association between high BP and high sodium and low potassium intake or urinary sodium/potassium ratio (U[Na(+)]/[K(+)]) primarily included white men and did not control for cardiovascular risk factors.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This cross-sectional study investigated the association of U[Na(+)]/[K(+)] with BP in 3303 participants using robust linear regression.

RESULTS

Mean age was 43±10 years, 56% of participants were women, and 52% were African American. BP was higher in African Americans than in non-African Americans, 131/81±20/11 versus 120/76±16/9 mmHg (P<0.001). Mean U[Na(+)]/[K(+)] was 4.4±3.0 in African Americans and 4.1±2.5 in non-African Americans (P=0.002), with medians (interquartile ranges) of 3.7 (3.2) and 3.6 (2.8). Systolic BP increased by 1.6 mmHg (95% confidence interval, 1.0, 2.2) and diastolic BP by 1.0 mmHg (95% confidence interval, 0.6, 1.4) for each 3-unit increase in U[Na(+)]/[K(+)] (P<0.001 for both). This association remained significant after adjusting for diabetes mellitus, smoking, body mass index, total cholesterol, GFR, and urine albumin/creatinine ratio. There was no interaction between African-American race and U[Na(+)]/[K(+)], but for any given value of U[Na(+)]/[K(+)], both systolic BP and diastolic BP were higher in African Americans than in non-African Americans. The diastolic BP increase was higher in men than in women per 3-unit increase in U[Na(+)]/[K(+)] (1.6 versus 0.9 mmHg, interaction P=0.03).

CONCLUSIONS

Dietary Na(+) excess and K(+) deficiency may play an important role in the pathogenesis of hypertension independent of cardiovascular risk factors. This association may be more pronounced in men than in women.

Reduced dietary salt for the prevention of cardiovascular disease: a meta-analysis of randomized controlled trials (Cochrane review)

BACKGROUND

Although meta-analyses of randomized controlled trials (RCTs) of salt reduction report a reduction in the level of blood pressure (BP), the effect of reduced dietary salt on cardiovascular disease (CVD) events remains unclear.

METHODS

We searched for RCTs with follow-up of at least 6 months that compared dietary salt reduction (restricted salt dietary intervention or advice to reduce salt intake) to control/no intervention in adults, and reported mortality or CVD morbidity data. Outcomes were pooled at end of trial or longest follow-up point.

RESULTS

Seven studies were identified: three in normotensives, two in hypertensives, one in a mixed population of normo- and hypertensives and one in heart failure. Salt reduction was associated with reductions in urinary salt excretion of between 27 and 39 mmol/24 h and reductions in systolic BP between 1 and 4 mm Hg. Relative risks (RRs) for all-cause mortality in normotensives (longest follow-up-RR: 0.90, 95% confidence interval (CI): 0.58-1.40, 79 deaths) and hypertensives (longest follow-up RR 0.96, 0.83-1.11, 565 deaths) showed no strong evidence of any effect of salt reduction CVD morbidity in people with normal BP (longest follow-up: RR 0.71, 0.42-1.20, 200 events) and raised BP at baseline (end of trial: RR 0.84, 0.57-1.23, 93 events) also showed no strong evidence of benefit. Salt restriction increased the risk of all-cause mortality in those with heart failure (end of trial RR 2.59, 1.04-6.44, 21 deaths).We found no information on participant's health-related quality of life.

CONCLUSIONS

Despite collating more event data than previous systematic reviews of RCTs (665 deaths in some 6,250 participants) there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or CVD morbidity. Our estimates of benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small BP reduction achieved.

Non-pharmacological aspects of blood pressure management: what are the data?

Hypertension affects 29% of US adults and is a significant risk factor for cardiovascular morbidity and mortality. Epidemiological data support contribution of several dietary and other lifestyle-related factors to the development of high blood pressure (BP). Several clinical trials investigated the efficacy of non-pharmacological interventions and lifestyle modifications to reduce BP. Best evidence from randomized controlled trials supports BP-lowering effects of weight loss, the Dietary Approaches to Stop Hypertension (DASH) diet, and dietary sodium (Na(+)) reduction in those with prehypertension, with more pronounced effects in those with hypertension. In hypertensive participants, the effects on BP of DASH combined with low Na(+) alone or with the addition of weight loss were greater than or equal to those of single-drug therapy. Trials where food was provided to participants were more successful in showing a BP-lowering effect. However, clinical studies with long-term follow-up revealed that lifestyle modifications were difficult to maintain. Findings from controlled trials of increased potassium, calcium, or magnesium intake, or reduction in alcohol intake revealed modest BP-lowering effects and are less conclusive. The reported effects of exercise independent of weight loss on BP are inconsistent.

Comparison of the Framingham Heart Study hypertension model with blood pressure alone in the prediction of risk of hypertension: the Multi-Ethnic Study of Atherosclerosis

A prediction model, developed in the Framingham Heart Study (FHS), has been proposed for use in estimating a given individual's risk of hypertension. We compared this model with systolic blood pressure (SBP) alone and age-specific diastolic blood pressure categories for the prediction of hypertension. Participants in the Multi-Ethnic Study of Atherosclerosis, without hypertension or diabetes mellitus (n=3013), were followed for the incidence of hypertension (SBP > or =140 mm Hg and/or diastolic blood pressure > or =90 mm Hg and/or the initiation of antihypertensive medication). The predicted probability of developing hypertension among 4 adjacent study examinations, with a median of 1.6 years between examinations, was determined. The mean (SD) age of participants was 58.5 (9.7) years, and 53% were women. During follow-up, 849 incident cases of hypertension occurred. The c statistic for the FHS model was 0.788 (95% CI: 0.773 to 0.804) compared with 0.768 (95% CI: 0.751 to 0.785; P=0.096 compared with the FHS model) for SBP alone and 0.699 (95% CI: 0.681 to 0.717; P<0.001 compared with the FHS model) for age-specific diastolic blood pressure categories. The relative integrated discrimination improvement index for the FHS model versus SBP alone was 10.0% (95% CI: -1.7% to 22.7%) and versus age-specific diastolic blood pressure categories was 146.0% (95% CI: 116.0% to 181.0%). Using the FHS model, there were significant differences between observed and predicted hypertension risks (Hosmer-Lemeshow goodness of fit: P<0.001); recalibrated and best-fit models produced a better model fit (P=0.064 and 0.245, respectively). In this multiethnic cohort of US adults, the FHS model was not substantially better than SBP alone for predicting hypertension.

Potassium supplementation for the management of primary hypertension in adults

BACKGROUND

Epidemiological evidence on the effects of potassium on blood pressure is inconsistent.

OBJECTIVES

To evaluate the effects of potassium supplementation on health outcomes and blood pressure in people with elevated blood pressure.

SEARCH STRATEGY

We searched the Cochrane Library, MEDLINE, EMBASE, Science Citation Index, ISI Proceedings, ClinicalTrials.gov, Current Controlled Trials, CAB abstracts, and reference lists of systematic reviews, meta-analyses and randomised controlled trials (RCTs) included in the review.

SELECTION CRITERIA

Inclusion criteria were: 1) RCTs of a parallel or crossover design comparing oral potassium supplements with placebo, no treatment, or usual care; 2) treatment and follow-up >=8 weeks; 3) participants over 18 years, with raised systolic blood pressure (SBP) >=140 mmHg or diastolic blood pressure (DBP) >=85 mmHg); 4) SBP and DBP reported at end of follow-up. We excluded trials where: participants were pregnant; received antihypertensive medication which changed during the study; or potassium supplementation was combined with other interventions.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. Disagreements were resolved by discussion or a third reviewer. Random effects meta-analyses and sensitivity analyses were conducted.

MAIN RESULTS

Six RCT's (n=483), with eight to 16 weeks follow-up, met our inclusion criteria. Meta-analysis of five trials (n=425) with adequate data indicated that potassium supplementation compared to control resulted in a large but statistically non-significant reductions in SBP (mean difference: -11.2, 95% CI: -25.2 to 2.7) and DBP (mean difference: -5.0, 95% CI: -12.5 to 2.4). The substantial heterogeneity between trials was not explained by potassium dose, quality of trials or baseline blood pressure. Excluding one trial in an African population with very high baseline blood pressure resulted in smaller overall reductions in blood pressure (SBP mean difference: -3.9, 95% CI: -8.6 to 0.8; DBP mean difference: -1.5, 95% CI: -6.2 to 3.1). Further sensitivity analysis restricted to two high quality trials (n=138) also found non-significant reductions in blood pressure (SBP mean difference: -7.1, 95% CI: -19.9 to 5.7; DBP mean difference: -5.5, 95% CI: -14.5 to 3.5).

AUTHORS' CONCLUSIONS

This systematic review found no statistically significant effect of potassium supplementation on blood pressure. Because of the small number of participants in the two high quality trials, the short duration of follow-up, and the unexplained heterogeneity between trials, the evidence about the effect of potassium supplementation on blood pressure is not conclusive. Further high quality RCTs of longer duration are required to clarify whether potassium supplementation can reduce blood pressure and improve health outcomes.

Advice to reduce dietary salt for prevention of cardiovascular disease

BACKGROUND

Restricting sodium intake in elevated blood pressure over short periods of time reduces blood pressure. Long term effects (on mortality, morbidity or blood pressure) of advice to reduce salt in patients with elevated or normal blood pressure are unclear.

OBJECTIVES

To assess in adults the long term effects (mortality, cardiovascular events, blood pressure, quality of life, weight, urinary sodium excretion, other nutrients and use of anti-hypertensive medications) of advice to restrict dietary sodium using all relevant randomised controlled trials.

SEARCH STRATEGY

The Cochrane Library, MEDLINE, EMBASE, bibliographies of included studies and related systematic reviews were searched for unconfounded randomised trials in healthy adults aiming to reduce sodium intake over at least 6 months. Attempts were made to trace unpublished or missed studies and authors of all included trials were contacted. There were no language restrictions.

SELECTION CRITERIA

Inclusion decisions were independently duplicated and based on the following criteria: 1) randomisation was adequate; 2) there was a usual or control diet group; 3) the intervention aimed to reduce sodium intake; 4) the intervention was not multifactorial; 5) the participants were not children, acutely ill, pregnant or institutionalised; 6) follow-up was at least 26 weeks; 7) data on any of the outcomes of interest were available.

DATA COLLECTION AND ANALYSIS

Decisions on validity and data extraction were made independently by two reviewers, disagreements were resolved by discussion or if necessary by a third reviewer. Random effects meta-analysis, sub-grouping, sensitivity analysis and meta-regression were performed.

MAIN RESULTS

Three trials in normotensives (n=2326), five in untreated hypertensives (n=387) and three in treated hypertensives (n=801) were included, with follow up from six months to seven years. The large, high quality (and therefore most informative) studies used intensive behavioural interventions. Deaths and cardiovascular events were inconsistently defined and reported; only 17 deaths equally distributed between intervention and control groups occurred. Systolic and diastolic blood pressures were reduced at 13 to 60 months in those given low sodium advice as compared with controls (systolic by 1.1 mm Hg, 95% CI 1.8 to 0.4, diastolic by 0.6 mm hg, 95% CI 1.5 to -0.3), as was urinary 24 hour sodium excretion (by 35.5 mmol/ 24 hours, 95% CI 47.2 to 23.9). Degree of reduction in sodium intake and change in blood pressure were not related. People on anti-hypertensive medications were able to stop their medication more often on a reduced sodium diet as compared with controls, while maintaining similar blood pressure control.

REVIEWER'S CONCLUSIONS

Intensive interventions, unsuited to primary care or population prevention programmes, provide only minimal reductions in blood pressure during long-term trials. Further evaluations to assess effects on morbidity and mortality outcomes are needed for populations as a whole and for patients with elevated blood pressure. Evidence from a large and small trial showed that a low sodium diet helps in maintenance of lower blood pressure following withdrawal of antihypertensives. If this is confirmed, with no increase in cardiovascular events, then targeting of comprehensive dietary and behavioural programmes in patients with elevated blood pressure requiring drug treatment would be justified.

Blood pressure response to changes in sodium and potassium intake: a metaregression analysis of randomised trials

The objective of the study was to assess the blood pressure response to changes in sodium and potassium intake and examine effect modification by age, gender, blood pressure, body weight and habitual sodium and potassium intake. Randomised trials of sodium reduction or potassium supplementation and blood pressure were identified through reference lists of systematic reviews and an additional MEDLINE search (January 1995-March 2001). A total of 40 sodium trials and 27 potassium trials in adults with a minimum duration of 2 weeks were selected for analysis. Data on changes in electrolyte intake and blood pressure during intervention were collected, as well as data on mean age, gender, body weight, initial electrolyte intake and initial blood pressure of the trial populations. Blood pressure effects of changes in electrolyte intake were assessed by weighted metaregression analysis, overall and in strata of trial population characteristics. Analyses were repeated with adjustment for potential confounders. Sodium reduction (median: -77 mmol/24 h) was associated with a change of -2.54 mmHg (95% CI: -3.16, -1.92) in systolic blood pressure and -1.96 mmHg (-2.41, -1.51) in diastolic blood pressure. Corresponding values for increased potassium intake (median: 44 mmol/24 h) were -2.42 mmHg (-3.75, -1.08) and -1.57 mmHg (-2.65, -0.50). Blood pressure response was larger in hypertensives than normotensives, both for sodium (systolic: -5.24 vs -1.26 mmHg, P < 0.001; diastolic: -3.69 vs -1.14 mmHg, P < 0.001) and potassium (systolic: -3.51 vs -0.97 mmHg, P=0.089; diastolic: -2.51 vs -0.34 mmHg, P=0.074). In conclusion, reduced intake of sodium and increased intake of potassium could make an important contribution to the prevention of hypertension, especially in populations with elevated blood pressure.

Reduced dietary salt for prevention of cardiovascular disease

BACKGROUND

Restricting sodium intake in elevated blood pressure over short periods of time reduces blood pressure. Long term effects (on mortality, morbidity or blood pressure) of advice to reduce salt in patients with elevated or normal blood pressure are unclear.

OBJECTIVES

To assess in adults the long term effects (mortality, cardiovascular events, blood pressure, quality of life, weight, urinary sodium excretion, other nutrients and use of anti-hypertensive medications) of advice to restrict dietary sodium using all relevant randomised controlled trials.

SEARCH STRATEGY

The Cochrane Library, MEDLINE, EMBASE, bibliographies of included studies and related systematic reviews were searched for unconfounded randomised trials in healthy adults aiming to reduce sodium intake over at least 6 months. Attempts were made to trace unpublished or missed studies and authors of all included trials were contacted. There were no language restrictions.

SELECTION CRITERIA

Inclusion decisions were independently duplicated and based on the following criteria: 1) randomisation was adequate; 2) there was a usual or control diet group; 3) the intervention aimed to reduce sodium intake; 4) the intervention was not multifactorial; 5) the participants were not children, acutely ill, pregnant or institutionalised; 6) follow-up was at least 26 weeks; 7) data on any of the outcomes of interest were available.

DATA COLLECTION AND ANALYSIS

Decisions on validity and data extraction were made independently by two reviewers, disagreements were resolved by discussion or if necessary by a third reviewer. Random effects meta-analysis, sub-grouping, sensitivity analysis and meta-regression were performed.

MAIN RESULTS

Three trials in normotensives (n=2326), five in untreated hypertensives (n=387) and three in treated hypertensives (n=801) were included, with follow up from six months to seven years. The large, high quality (and therefore most informative) studies used intensive behavioural interventions. Deaths and cardiovascular events were inconsistently defined and reported; only 17 deaths equally distributed between intervention and control groups occurred. Systolic and diastolic blood pressures were reduced at 13 to 60 months in those given low sodium advice as compared with controls (systolic by 1.1 mm Hg, 95% CI 1.8 to 0.4, diastolic by 0.6 mm hg, 95% CI 1.5 to -0.3), as was urinary 24 hour sodium excretion (by 35.5 mmol/ 24 hours, 95% CI 47.2 to 23.9). Degree of reduction in sodium intake and change in blood pressure were not related. People on anti-hypertensive medications were able to stop their medication more often on a reduced sodium diet as compared with controls, while maintaining similar blood pressure control.

REVIEWER'S CONCLUSIONS

Intensive interventions, unsuited to primary care or population prevention programmes, provide only minimal reductions in blood pressure during long-term trials. Further evaluations to assess effects on morbidity and mortality outcomes are needed for populations as a whole and for patients with elevated blood pressure. Evidence from a large and small trial showed that a low sodium diet helps in maintenance of lower blood pressure following withdrawal of antihypertensives. If this is confirmed, with no increase in cardiovascular events, then targeting of comprehensive dietary and behavioural programmes in patients with elevated blood pressure requiring drug treatment would be justified.

Dietary potassium intake and risk of stroke in US men and women: National Health and Nutrition Examination Survey I epidemiologic follow-up study

BACKGROUND AND PURPOSE

The few prospective studies that have explored the association between dietary intake of potassium and risk of stroke have reported inconsistent findings. This study examines the relationship between dietary potassium intake and the risk of stroke in a representative sample of the US general population.

METHODS

Study participants included 9805 US men and women who participated in the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-Up Study. Dietary potassium and total energy intake were estimated at baseline by using a 24-hour dietary recall. Incidence data for stroke and coronary heart disease were obtained from medical records and death certificates.

RESULTS

Over an average of 19 years of follow up, 927 stroke events and 1847 coronary heart disease events were documented. Overall, stroke hazard was significantly different among quartiles of potassium intake (likelihood ratio P=0.03); however, a test of linear trend across quartiles did not reach a customary level of statistical significance (P=0.14). Participants consuming a low potassium diet at baseline (<34.6 mmol potassium per day) experienced a 28% higher hazard of stroke (hazard ratio 1.28, 95% CI 1.11 to 1.47; P<0.001) than other participants, after adjustment for established cardiovascular disease risk factors.

CONCLUSIONS

These findings suggest that low dietary potassium intake is associated with an increased risk of stroke. However, the possibility that the association is due to residual confounding cannot be entirely ruled out in this observational study.

Effect of potassium supplementation on blood pressure in Chinese: a randomized, placebo-controlled trial

OBJECTIVE

To examine the effect of potassium supplementation on blood pressure (BP) in a Chinese population who consume a habitual high sodium and low potassium diet.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Community sample from Beijing, China.

PARTICIPANTS

A total of 150 men and women aged 35-64 years with an initial systolic BP 130-159 mmHg and/or diastolic BP 80-94 mmHg.

INTERVENTIONS

Participants were randomly assigned to take 60 mmol potassium chloride supplement or placebo for 12 weeks.

MAIN OUTCOME MEASURE(S)

BP measurements were obtained at baseline, and at 6 weeks and 12 weeks during the trial, using random-zero sphygmomanometers.

RESULTS

The average baseline urinary excretion of sodium and potassium was 182 mmol/24 h and 36 mmol/24 h. Baseline BP and other measured variables were similar between the potassium supplementation and placebo groups. In the active compared to the placebo treatment group, the urinary excretion of potassium was significantly increased by 20.6 mmol/24 h (P< 0.001) during 12 weeks of intervention. Compared to placebo, active treatment was associated with a significant reduction in systolic BP (-5.00 mmHg, 95% CI: -2.13 to -7.88 mmHg, P < 0.001) but not diastolic BP (-0.63 mmHg, 95% CI: -2.49 to1.23 mmHg, P = 0.51) during 12-week intervention.

CONCLUSION

These data indicate that moderate potassium supplementation resulted in a substantial reduction in systolic BP. Our findings suggest that increased potassium intake may play an important role in the prevention and treatment of hypertension in China.

Diet, blood pressure and hypertension

Prevention of hypertension, and control of blood pressure in patients with hypertension, are necessary for the reduction of cardiovascular morbidity and mortality. Lifestyle modifications are one of the most important tools for effective lowering of blood pressure. Most randomized controlled studies have shown that even a modest weight loss of 3-9% is associated with a significant reduction in systolic and diastolic blood pressure of roughly 3 mm Hg in overweight people. Limitation of sodium chloride in food has historically been considered the critical change for reducing blood pressure. Changes in sodium intake do affect blood pressure in older persons and in patients with hypertension and diabetes, whereas its role in population blood pressure has proven controversial. Recent meta-analyses indicate that adequate intake of minerals, e.g. potassium and probably calcium, rather than restriction of sodium, should be the focus of dietary recommendations. Although epidemiological data point to a direct relation between the intake of saturated fat, starch and alcohol, as well as an inverse relationship to the intake of omega-3 fatty acids and protein, our knowledge about macronutrients and blood pressure is scanty. It may well prove more productive to look at food instead of placing emphasis on single nutrients. Thus the Dietary Approaches to Stop Hypertension (DASH) demonstrates that a diet rich in fruits, vegetables, low-fat dairy products, fibre and minerals (calcium, potassium and magnesium) produces a potent antihypertensive effect. Such a diet is not very restrictive and should not produce compliance problems. Further high-quality research on the influence of macronutrients and food will yield data for updated recommendations, enabling better prevention and control of the blood pressure problem.

Effect on blood pressure of potassium, calcium, and magnesium in women with low habitual intake

In populations, dietary intakes of potassium, calcium, and magnesium each have been inversely associated with blood pressure. However, most clinical trials in normotensive populations have not found that dietary supplements of these minerals lowered blood pressure. We tested the hypothesis that normotensive persons who have low habitual intake of these minerals would be particularly responsive to supplementation. Three hundred normotensive women in the Nurses Health Study II (mean age, 39 years), whose reported intakes of potassium, calcium, and magnesium were between the 10th and 15th percentiles, received for 16 weeks' duration daily supplements of either potassium 40 mmol, calcium 30 mmol (1200 mg), magnesium 14 mmol (336 mg), all three minerals together or placebos. At baseline, mean (+/-SD) 24-hour ambulatory blood pressures were 116+/-8 and 73+/-6 mm Hg systolic and diastolic, respectively, and mean dietary intakes of potassium, calcium, and magnesium were 62+/-20 mmol/d, 638+/-265 mg/d, and 239+/-79 mg/d, respectively. The mean differences (with 95% confidence intervals) of the changes in systolic and diastolic blood pressures between the treatment and placebo groups were significant for potassium, -2.0 (-3.7 to -0.3) and -1.7 (-3.0 to -0.4), but not for calcium, -0.6 (-2.2 to 1.0) and -0.7 (-2.0 to 0.6), or for magnesium, -0.9 (-2.6 to 0.8) and -0.7 (-2.2 to 0.8). The administration of calcium and magnesium with potassium did not enhance the effect of potassium alone, and the changes in blood pressure were not significant -1.3 (-3.0 to 0.4) and -0.9 (-2.2 to 0.4). In conclusion, potassium, but not calcium or magnesium supplements, has a modest blood pressure-lowering effect in normotensive persons with low dietary intake. This study strengthens evidence for the importance of potassium for blood pressure regulation in the general population.

Nutrient intake and blood pressure in the Dietary Intervention Study in Children

Delineating the role that diet plays in blood pressure levels in children is important for guiding dietary recommendations for the prevention of hypertension. The purpose of this study was to investigate relationships between dietary nutrients and blood pressure in children. Data were analyzed from 662 participants in the Dietary Intervention Study in Children who had elevated low-density lipoprotein cholesterol and were aged 8 to 11 years at baseline. Three 24-hour dietary recalls, systolic pressure, diastolic pressure, height, and weight were obtained at baseline, 1 year, and 3 years. Nutrients analyzed were the micronutrients calcium, magnesium, and potassium; the macronutrients protein, carbohydrates, total fat, saturated fat, polyunsaturated fat, and monounsaturated fat; dietary cholesterol; and total dietary fiber. Baseline and 3-year longitudinal relationships were examined through multivariate models on diastolic and systolic pressures separately, controlling for height, weight, sex, and total caloric intake. The following associations were found in longitudinal analyses: analyzing each nutrient separately, for systolic pressure, inverse associations with calcium (P < .05); magnesium, potassium, and protein (all P < .01); and fiber (P < .05), and direct associations with total fat and monounsaturated fat (both P < .05); for diastolic pressure, inverse associations with calcium (P < .01); magnesium and potassium (both P < .05), protein (P < .01); and carbohydrates and fiber (both P < .05), and direct associations with polyunsaturated fat (P < .01) and monounsaturated fat (P < .05). Analyzing all nutrients simultaneously, for systolic pressure, direct association with total fat (P < .01); for diastolic pressure, inverse associations with calcium (P < .01) and fiber (P < .05), and direct association with total and monounsaturated fats (both P < .05). Results from this sample of children with elevated low-density lipoprotein cholesterol indicate that dietary calcium, fiber, and fat may be important determinants of blood pressure level in children.