Double-blind, placebo-controlled trial of potassium chloride in the treatment of mild hypertension

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).

Introductory Chapter: Potassium in Human Health

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Using Predicted Atherosclerotic Cardiovascular Disease Risk for Discrimination of Awake or Nocturnal Hypertension

BACKGROUND

Several atherosclerotic cardiovascular disease (ASCVD) risk factors are associated with awake and nocturnal hypertension.

METHODS

We assessed the association between a composite ASCVD risk score and awake or nocturnal hypertension using data from participants aged 40-79 years who completed ambulatory blood pressure monitoring at the Year 30 Coronary Artery Risk Development in Young Adults study exam in 2015-2016 (n = 716) and the baseline Jackson Heart Study exam in 2000-2004 (n = 770). Ten-year predicted ASCVD risk was calculated using the Pooled Cohort risk equations. Awake hypertension was defined as mean awake systolic blood pressure (SBP) ≥135 mm Hg or diastolic blood pressure (DBP) ≥85 mm Hg and nocturnal hypertension was defined as mean asleep SBP ≥120 mm Hg or DBP ≥70 mm Hg.

RESULTS

Among participants with a 10-year predicted ASCVD risk <5%, 5% to <7.5%, 7.5% to <10%, and ≥10%, the prevalence of awake or nocturnal hypertension as a composite outcome was 29.5%, 47.8%, 62.2%, and 69.7%, respectively. After multivariable adjustment, higher ASCVD risk was associated with higher prevalence ratios for awake or nocturnal hypertension among participants with clinic-measured SBP/DBP <130/85 mm Hg but not ≥130/85 mm Hg. The C-statistic for discriminating between participants with vs. without awake or nocturnal hypertension was 0.012 (95% confidence interval 0.003, 0.016) higher when comparing a model with ASCVD risk and clinic-measured blood pressure (BP) together vs. clinic-measured BP without ASCVD risk.

CONCLUSIONS

Using 10-year predicted ASCVD risk in conjunction with clinic BP improves discrimination between individuals with and without awake or nocturnal hypertension.

What Is the Evidence Base for a Potassium Requirement?

Increased intake of potassium should be promoted to reduce the risk of cardiovascular disease and stroke and to protect against bone loss, but confidence in recommended intakes depends on the strength of the evidence. All public health recommendations are considerably higher than current average intakes. Evidence on which current potassium intake recommendations for the United States, Europe, and globally have limitations. More recent evidence reviewed by the Agency for Healthcare Research and Quality affirms that more evidence is needed to define specific values for optimal potassium intakes. Potassium requirements undoubtedly vary with a number of factors including energy needs, race, and intake of sodium.

Effects of potassium supplements on glucose metabolism in African Americans with prediabetes: a pilot trial

Background: Low potassium has been identified both as a risk factor for type 2 diabetes and as a mediator of the racial disparity in diabetes risk. Low potassium could be a potentially modifiable risk factor, particularly for African Americans.Objective: We sought to determine the effects of potassium chloride (KCl) supplements, at a commonly prescribed dose, on measures of potassium and glucose metabolism.Design: Among African-American adults with prediabetes, we conducted a double-blinded pilot randomized controlled trial that compared the effects of 40 mEq K/d as KCl supplements with a matching placebo, taken for 3 mo, on measures of potassium and glucose metabolism, with measures collected from frequently sampled oral-glucose-tolerance tests (OGTTs).Results: Twenty-seven of 29 recruited participants completed the trial. Participants had high adherence to the study medication (92% by pill count). Participants in both groups gained weight, with an overall mean ± SD weight gain of 1.24 ± 2.03 kg. In comparison with participants who received placebo, urine potassium but not serum potassium increased significantly among participants randomly assigned to receive KCl (P = 0.005 and 0.258, respectively). At the end of the study, participants taking KCl had stable or improved fasting glucose, with a mean ± SD change in fasting glucose of -1.1 ± 8.4 mg/dL compared with an increase of 6.1 ± 7.6 mg/dL in those who received placebo (P = 0.03 for comparison between arms). There were no significant differences in glucose or insulin measures during the OGTT between the 2 groups, but there was a trend for improved insulin sensitivity in potassium-treated participants.Conclusions: In this pilot trial, KCl at a dose of 40 mEq/d did not increase serum potassium significantly. However, despite weight gain, KCl prevented worsening of fasting glucose. Further studies in larger sample sizes, as well as with interventions to increase serum potassium more than was achieved with our intervention, are indicated to definitively test this potentially safe and inexpensive approach to reducing diabetes risk. This trial was registered at clinicaltrials.gov as NCT02236598.

Oral potassium supplementation for management of essential hypertension: A meta-analysis of randomized controlled trials

IMPORTANCE

Increased dietary potassium intake is thought to be associated with low blood pressure (BP). Whether potassium supplementation may be used as an antihypertensive agent is a question that should be answered.

OBJECTIVE

To assess the effect of oral potassium supplementation on blood pressure in patients with primary hypertension.

SEARCH METHODS

We searched Medline, Web of Science, Scopus, Cochrane Central Register of Controlled Trials until October 2016. We also screened reference lists of articles and previous reviews. We applied no language restrictions.

SELECTION CRITERIA

We included randomized placebo-controlled clinical trials addressing the effect of potassium supplementation on primary hypertension for a minimum of 4 weeks.

DATA COLLECTION AND ANALYSIS

We extracted data on systolic and diastolic BP (SBP and DBP) at the final follow-up. We explored the heterogeneity across studies using Cochran's test and I2 statistic and assessed the probability of publication bias using Begg's and Egger's tests. We reported the mean difference (MD) of SBP and DBP in a random-effects model.

RESULTS

We found a total of 9059 articles and included 23 trials with 1213 participants. Compared to placebo, potassium supplementation resulted in modest but significant reductions in both SBP (MD -4.25 mmHg; 95% CI: -5.96 to -2.53; I2 = 41%) and DBP (MD -2.53 mmHg; 95% CI: -4.05 to -1.02; I2 = 65%). According to the change-score analysis, based on 8 out of 23 trials, compared to baseline, the mean changes in SBP (MD -8.89 mmHg; 95% CI: -13.67 to -4.11) and DBP (MD -6.42 mmHg; 95% CI: -10.99 to -1.84) was significantly higher in the intervention group than the control group.

CONCLUSIONS

Our findings indicated that potassium supplementation is a safe medication with no important adverse effects that has a modest but significant impact BP and may be recommended as an adjuvant antihypertensive agent for patients with essential hypertension.

The flavor and acceptability of six different potassium-enriched (sodium reduced) iodized salts: a single-blind, randomized, crossover design

Background

Hypertension is a serious public health problem. Potassium-enriched salt is suggested as a tool for lowering blood pressure. However, its flavor and taste acceptability is essential for population-based salt reduction strategy and needs to be well-understood. This trial assessed the flavor and taste acceptability of six different potassium-enriched iodized salts in the general population.

Methods

We conducted this crossover trial from May to June 2016, enrolling 100 normal volunteer subjects aged 11 to 64 years. We compared regular sodium chloride salt (placebo) with six different potassium-enriched (sodium reduced) iodized salt (experiment), including 0 %, 5 %, 10 %, 15 %, 20 %, 25 %, and 30 %. The participants served as their own control and received a placebo and a sequence of the experiments. They tasted the two salts sequentially and stated their preference and acceptance. Each subject received all salts.

Results

More than 80 % of participants who either did not distinguish between the two salts even in high potassium-enriched salts or preferred potassium-enriched salt (P < 0.001). The number of participants who preferred the flavor of potassium-enriched salt was greater than the number of subjects who preferred the flavor of regular sodium chloride.

Conclusion

Our findings indicated that the six different potassium-enriched salts had a public acceptability of at least 80 % among normal subjects from the general population. Although the acceptability of the potassium-enriched salts by a more general population group would require to be confirmed, universal use of this salt may help us achieve the target of 30 % relative reduction in mean population intake of sodium by 2025.

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.

Dietary potassium and the renal control of salt balance and blood pressure

Dietary potassium (K(+)) intake has antihypertensive effects, prevents strokes, and improves cardiovascular outcomes. The underlying mechanism for these beneficial effects of high K(+) diets may include vasodilation, enhanced urine flow, reduced renal renin release, and negative sodium (Na(+)) balance. Indeed, several studies demonstrate that dietary K(+) intake induces renal Na(+) loss despite elevated plasma aldosterone. This review briefly highlights the epidemiological and experimental evidences for the effects of dietary K(+) on arterial blood pressure. It discusses the pivotal role of the renal distal tubule for the regulation of urinary K(+) and Na(+) excretion and blood pressure and highlights that it depends on the coordinated interaction of different nephron portions, epithelial cell types, and various ion channels, transporters, and ATPases. Moreover, we discuss the relevance of aldosterone and aldosterone-independent factors in mediating the effects of an altered K(+) intake on renal K(+) and Na(+) handling. Particular focus is given to findings suggesting that an aldosterone-independent downregulation of the thiazide-sensitive NaCl cotransporter significantly contributes to the natriuretic and antihypertensive effect of a K(+)-rich diet. Last but not least, we refer to the complex signaling pathways enabling the kidney to adapt its function to the homeostatic needs in response to an altered K(+) intake. Future work will have to further address the underlying cellular and molecular mechanism and to elucidate, among others, how an altered dietary K(+) intake is sensed and how this signal is transmitted to the different epithelial cells lining the distal tubule.

Serum potassium predicts time to blood pressure response among African Americans with hypertensive nephrosclerosis

It is not known whether serum potassium levels affect blood pressure response to anti-hypertensive medication. The African American trial of Kidney disease and Hypertension (AASK) Genomics Study (N=828) is a subset of the AASK trial that randomized 1,094 African American men and women with hypertensive nephrosclerosis to ramipril, amlodipine or metoprolol. Participants were also randomized to a usual (102–107 mmHg) or low (≤92 mmHg) mean arterial pressure (MAP) treatment goal. Time-to-event analyses were used to determine the relationship between serum potassium prior to randomization and time (days) to reach an MAP of 107 mmHg. Mean baseline serum potassium was 4.22 (standard deviation +/− 0.56 and range 2.8–6.0) mmol/L and the median days to reach target MAP was 32 (interquartile range 8–95) days. The adjusted hazard ratio (HR) for each 1mmol/L increase in serum potassium was 1.31 (95%CI: 1.08–1.59) in the usual MAP group, and 1.21 (95%CI: 1.02–1.44) in the low MAP group. Secondary findings suggested that women in the usual MAP group on amlodipine were more likely to reach target MAP compared to women randomized to ramipril (HR: 2.05, 95%CI: 1.30–3.21). Older subjects in the low MAP group (≥55 years) were also more likely to reach target MAP on amlodipine compared to ramipril (HR: 1.57, 95%CI: 1.03–2.38). Serum potassium appears to be a significant predictor of time to blood pressure response, independent of drug class. Results also suggest a benefit of using amlodipine when more rapid blood pressure control is clinically indicated among women and more aggressively managed older subjects.

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.

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.

Lifestyle interventions to reduce raised blood pressure: a systematic review of randomized controlled trials

PURPOSE

To quantify effectiveness of lifestyle interventions for hypertension.

DATA SOURCES

Electronic bibliographic databases from 1998 onwards, existing guidelines, systematic reviews.

STUDY SELECTION AND DATA ABSTRACTION

We included randomized, controlled trials with at least 8 weeks' follow-up, comparing lifestyle with control interventions, enrolling adults with blood pressure at least 140/85 mmHg. Primary outcome measures were systolic and diastolic blood pressure. Two independent reviewers selected trials and abstracted data; differences were resolved by discussion.

RESULTS

We categorized trials by type of intervention and used random effects meta-analysis to combine mean differences between endpoint blood pressure in treatment and control groups in 105 trials randomizing 6805 participants. Robust statistically significant effects were found for improved diet, aerobic exercise, alcohol and sodium restriction, and fish oil supplements: mean reductions in systolic blood pressure of 5.0 mmHg [95% confidence interval (CI): 3.1-7.0], 4.6 mmHg (95% CI: 2.0-7.1), 3.8 mmHg (95% CI: 1.4-6.1), 3.6 mmHg (95% CI: 2.5-4.6) and 2.3 mmHg (95% CI: 0.2-4.3), respectively, with corresponding reductions in diastolic blood pressure. Relaxation significantly reduced blood pressure only when compared with non-intervention controls. We found no robust evidence of any important effect on blood pressure of potassium, magnesium or calcium supplements.

CONCLUSIONS

Patients with elevated blood pressure should follow a weight-reducing diet, take regular exercise, and restrict alcohol and salt intake. Available evidence does not support relaxation therapies, calcium, magnesium or potassium supplements to reduce blood pressure.

Antihypertensive effect of oral potassium aspartate supplementation in mild to moderate arterial hypertension

BACKGROUND

Previous studies showed that potassium chloride (48-120 mmol/day) supplementation reduced arterial blood pressure (BP) in hypertensive patients.

OBJECTIVES

Our aim was to evaluate the effect of a lower dose of potassium aspartate salt on BP in individuals with essential arterial hypertension.

METHODS

One hundred and four patients (65 males, age 53 +/- 12 years) with mild to moderate essential hypertension (systolic/diastolic BP 154.2/96.2 +/- 10.8/5.4 mmHg) were allocated in two comparable groups of 52 to receive or not 30 mmol/day per os of potassium aspartate supplementation for four weeks. Office and 24-h BP, as well as serum and urinary electrolytes, were measured at baseline and at the follow-up visit after four weeks.

RESULTS

Office and 24-h BP did not change in the control group, while these values were significantly reduced in the potassium supplementation group. Changes in office (systolic BP: 154.4 +/- 8.2 vs. 142.2 +/- 7.6 mmHg; diastolic BP: 95.0 +/- 5.6 vs. 87.2 +/- 4.3 mmHg, P < 0.001 for both) and 24-h BP (systolic BP: 142.7 +/- 8.2 vs. 134.8 +/- 6.3 mmHg; diastolic BP: 90.8 +/- 4.4 vs. 84.6 +/- 3.8 mmHg, P < 0.001 for both) following potassium supplementation were highly significant. The changes in day time and night time BP were similar. The treated group showed significantly increased potassium serum level and 24-h urinary excretion of potassium (P < 0.01 in both cases) after four weeks, while the untreated group showed no significant changes of the same parameters. Urinary Na/K ratio decreased significantly with potassium supplementation (P < 0.001). In the treated group changes in office (r = 0.58, P < 0.001) and 24-h SBP (r = 0.51, P < 0.001), but not in DBP (r = 0.29 and r = 0.25, n.s.), correlated positively with the urinary Na/K ratio at baseline.

CONCLUSIONS

A relatively low supplementation of 30 mmol/day of potassium as aspartate lowered office and 24-h ambulatory BP in subjects with mild to moderate essential hypertension. The antihypertensive effect was sustained throughout the day, and was greater in the patients with high basal urinary Na/K ratio.

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.

The role of growth factors and ammonia in the genesis of hypokalemic nephropathy

Hypokalemia is a common electrolyte abnormality encountered in clinical practice. It can be identified in an asymptomatic patient undergoing routine electrolyte screening or can manifest itself as part of a number of functional abnormalities in a variety of organs and systems. Among the most commonly recognized complications are profound effects on the cardiovascular and neuromuscular systems, together with abnormalities in acid-base regulation. In humans, hypokalemia contributes to the development of hypertension and predisposes patients to a variety of ventricular arrhythmias, including ventricular fibrillation. Commonly recognized neuromuscular complications include weakness, cramping, and myalgia. Hypokalemia also affects systemic acid-base homeostasis by interfering with multiple components of the renal acid-base regulation and is a frequent cause of metabolic alkalosis. Less known, however, is the role of potassium deficiency in causing progressive renal failure. In animals, potassium deficiency stimulates renal enlargement because of cellular hypertrophy and hyperplasia. If potassium deficiency persists, interstitial infiltrates appear in the renal interstitial compartment, and eventually tubulointerstitial fibrosis develops. In humans, longstanding hypokalemia is associated with the development of renal cysts, chronic interstitial nephritis, and progressive loss of renal function, the so-called hypokalemic nephropathy. This review focuses on the potential mechanisms involved in the development of the hypokalemic nephropathy with emphasis on the role of ammonia and growth factors in its pathogenesis.

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.

Involvement of the renal kallikrein-kinin system in K(+)-induced diuresis and natriuresis in anesthetized rats

Intravenous infusion of a high-K(+) solution (67.5 mM KCl, 67.5 mM NaCl) to anesthetized rats increased urine volume by 47.6% after 60 min, compared with infusion of a Na(+) solution (135 mM NaCl). This treatment also increased urinary excretion of Na(+) by 32.2%, in parallel with an increase in excretion of K(+) or Cl(-). Urinary excretion of kallikrein increased within 60 min after the start of K(+) infusion. A bradykinin B(2) receptor antagonist, 8-[3-[N-[(E)-3-(6-acetamidopyridin-3-yl)acryloylglycyl]-N-me thylamino ]-2,6-dichlorobenzyloxy]-2-methylquinoline (FR173657; 1.0 mg/kg, i.v. ), inhibited the K(+)-induced diuresis and natriuresis by 41.0% and 26.7%, respectively. These results indicate that K(+) load induces diuresis and natriuresis through the renal kallikrein-kinin system in rats.

A design for testing interventions to improve adherence within a hypertension clinical trial

The Potassium Adherence Clinical Trial (PACT) incorporates one randomized clinical trial within another. A randomized trial of interventions to increase adherence to medication is nested within a second randomized clinical trial testing hypotensive effect of supplemental oral potassium. The trial aims principally to compare the effects of three intervention strategies: two sessions of individual patient counseling, two telephone contacts, or standard care. The trial aims secondarily to evaluate the effect of 60 mEq supplemental oral potassium daily on sitting systolic and diastolic blood pressure in hypertensive patients on established drug therapy. Therefore, it organizes the patients given potassium into three study groups for adherence interventions, and the patients assigned to placebo into a further three. We evaluate adherence primarily by means of the Medication Event Monitoring System (MEMS), an electronic system that records the date and time that the container of study medication is opened. Additional measurements, such as assessments of change in levels of urinary potassium, pill counts, appointment records, self-reporting by patients, and estimates by physician of adherence, are used and correlated with MEMS data. At a single center, the trial enrolled 107 participants between the ages of 26 and 80. This paper describes the background to this trial within a trial, details its design, documents the baseline characteristics of participants enrolled, and describes issues experienced during implementation of the trial.

Early increases in renal kallikrein secretion on administration of potassium or ATP-sensitive potassium channel blockers in rats

1 This study aimed to examine whether administration of potassium or ATP-sensitive potassium channel (KATP channel) blockers caused early increases in renal kallikrein (KK) secretion. To clarify this mechanism, the effect on renal KK secretion of a KATP channel blocker was compared with the effect resulting from use of an osmotic diuretic or volume load. Furthermore, the effect on potassium-induced increases in renal KK secretion by an additional treatment using a KATP channel blocker was examined. Lastly, the effect of a KATP channel blocker on renal KK secretion was also examined in superfused slices of kidney cortex. 2 Intravenous infusion of potassium augmented renal KK secretion within 30 min while urine volume increased gradually in both the potassium loading and control groups. 3 Administration of the KATP channel blocker, 4-morpholinecarboximidine-N-1-adamantyl-N'-cyclohexylhydr ochloride (PNU-37883A) or glibenclamide, caused a dose-dependent increase in renal KK secretion. 4 The concentration of KK in urine was higher in the PNU-37883A group as compared to the osmotic-diuretic or volume-load group. 5 PNU-37883A had no additive effect on the potassium-induced increase in renal KK secretion. 6 Renal KK secretion increased in slices of kidney cortex incubated with PNU-37883A within 10 min of superfusion. 7 In conclusion, administration of both potassium and KATP channel blockers induced early increases in renal KK secretion in the absence of the washout phenomenon. Potassium loading may have increased renal KK secretion through the same mechanism as the KATP channel blocker.

Effects of potassium on blood pressure in salt-sensitive and salt-resistant black adolescents

This study examined the effects of increasing dietary potassium on ambulatory blood pressure nondipping status (<10% decrease in blood pressure from awake to asleep) and cardiovascular reactivity in salt-sensitive and salt-resistant black adolescents. A sample of 58 normotensive (blood pressure, 101/57+/-9/4 mm Hg) black adolescents (aged 13 to 16 years) participated in a 5-day low sodium diet (50 mmol/24 h) followed by a 10-day high sodium diet (150 mmol/24 h NaCl supplement) to determine salt-sensitivity status. Participants showed a significant increase in urinary sodium excretion (24+/-19 to 224+/-65 mmol/24 h) and were identified as salt-sensitive if their mean blood pressure increase was >/=5 mm Hg from the low to high sodium diet. Sixteen salt-sensitive and 42 salt-resistant subjects were then randomly assigned to either a 3-week high potassium diet (80 mmol/24 h) or usual diet control group. Urinary potassium excretion significantly increased in the treatment group (35+/-7 to 57+/-21 mmol/24 h). At baseline, a significantly greater percentage of salt-sensitive (44%) compared with salt-resistant (7%) subjects were nondippers on the basis of diastolic blood pressure classifications (P<0.04). After the dietary intervention, all of the salt-sensitive subjects in the high potassium group achieved dipper status as a result of a drop in nocturnal diastolic blood pressure (daytime, 69 versus 67 mm Hg; nighttime, 69 versus 57 mm Hg). No significant group differences in cardiovascular reactivity were observed. These results suggest that a positive relationship between dietary potassium intake and blood pressure modulation can still exist even when daytime blood pressure is unchanged by a high potassium diet.

The Linear Index Model for establishing nutrient goals in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group

Establishing target levels of nutrients in feeding studies presents a challenge to dietitians. Although researchers studying energy-containing nutrients, such as protein and fat, commonly establish target levels according to body weight or as a percentage of energy, it is less clear how to establish levels of micronutrients. Typically, a constant target level is used regardless of energy requirements. Alternatively, nutrients could be provided at a fixed level per 1,000 kcal. Such an approach, however, could result in absolute levels of nutrient intakes that are difficult to achieve through foods alone, particularly for persons with high energy requirements. This report describes the Linear Index Model, a new approach for establishing target levels of selected micronutrients in the Dietary Approaches to Stop Hypertension trial. This model indexes micronutrient levels to energy levels to achieve a linear range of targeted intake in proportion to the energy intake. The Linear Index Model has several benefits: it takes advantage of indexing nutrients according to energy requirements, thus providing levels of nutrient intakes that can be readily achieved by foods; it is based on population consumption data, thus providing a realistic range of intakes for the experimental conditions; and it ensures distinct contrasts in experimental conditions. The Linear Index Model is a feasible and practical approach for establishing target levels of nutrients in feeding studies.

Potassium supplement upregulates the expression of renal kallikrein and bradykinin B2 receptor in SHR

High potassium intake is known to attenuate hypertension, glomerular lesion, ischemic damage, and stroke-associated death. Our recent studies showed that expression of recombinant kallikrein by somatic gene delivery reduced high blood pressure, cardiac hypertrophy, and renal injury in hypertensive animal models. The aim of this study is to explore the potential role of the tissue kallikrein-kinin system in blood pressure reduction and renal protection in spontaneously hypertensive rats (SHR) on a high-potassium diet. Young SHR were given drinking water with or without 1% potassium chloride for 6 wk. Systolic blood pressure was significantly reduced beginning at 1 wk, and the effect lasted for 6 wk in the potassium-supplemented group compared with that in the control group. Potassium supplement induced 70 and 40% increases in urinary kallikrein levels and renal bradykinin B2 receptor density, respectively (P < 0.05), but did not change serum kininogen levels. Similarly, Northern blot analysis showed that renal kallikrein mRNA levels increased 2.7-fold, whereas hepatic kininogen mRNA levels remained unchanged in rats with high potassium intake. No difference was observed in beta-actin mRNA levels in the kidney or liver of either group. Competitive RT-PCR showed a 1.7-fold increase in renal bradykinin B2 receptor mRNA levels in rats with high potassium intake. Potassium supplement significantly increased water intake, urine excretion, urinary kinin, cAMP, and cGMP levels. This study suggests that upregulation of the tissue kallikrein-kinin system may be attributed, in part, to blood pressure-lowering and diuretic effects of high potassium intake.

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.

Effect of administered potassium on the renin-aldosterone axis in young blacks compared with whites

BACKGROUND

We had observed previously that the aldosterone excretion rate and plasma aldosterone concentration were lower for black children than they were for white children. We did not know whether this was secondary to a lower intake of potassium or to suppression of the renin-angiotensin system in blacks.

OBJECTIVE

To test the hypothesis that the secretion of aldosterone in response to potassium would be different in blacks than in a control group of whites.

DESIGN

Black and white subjects were selected on the basis of their having aldosterone excretion rates that were in the lowest quartile for the entire original cohort. Since the blacks typically had lower aldosterone excretion rates than did the whites, the black participants were represented primarily by those with average rates of aldosterone production among blacks, whereas the whites were represented by those with the lowest aldosterone production rates among whites. The protocol consisted of a placebo-controlled, randomized cross-over study design.

METHODS

Twelve blacks and 12 whites, aged 14.1 +/- 1.6 (mean +/- SD) and 15.4 +/- 2.1 years, respectively, were allocated randomly to double-blind treatment either with placebo or with 40 mmol/day potassium chloride for 7 days and then the alternate treatment Measurements of the plasma renin activity (PRA), plasma aldosterone concentration, and urinary aldosterone excretion were performed in an inpatient research unit at the end of the treatment. The blood pressure was monitored for 24 h.

RESULTS

Treatment with potassium increased the plasma aldosterone concentration (P = 0.0006) and the urinary excretion of aldosterone (P = 0.0002) significantly both for blacks and for whites. There was no significant racial difference in the response to potassium. The PRA was overall 1.605-fold lower in the blacks than it was in the whites (P = 0.0124). The lowest PRA levels, such as those in the blacks when they were supine, tended to be increased with the potassium treatment. The blood pressure did not change significantly with the potassium supplement for either racial group.

CONCLUSIONS

After we had supplemented the intake of potassium, aldosterone production increased in the blacks and in the control group of whites to the same extent The potassium treatment appeared to increase lower PRA levels. A lower intake of potassium could at least partially account for the suppression of the renin-aldosterone system in blacks.

The effects of potassium depletion and supplementation on blood pressure: a clinical review

Nonpharmacologic treatment currently is recognized as an important part in the treatment of hypertension, and the role of dietary potassium intake in blood pressure (BP) control is becoming quite evident. Clinical studies have examined the mechanism by which hypokalemia can increase BP and the benefit of a large potassium intake on BP control. Epidemiologic data suggest that potassium intake and BP are correlated inversely. In normotensive subjects, those who are salt sensitive or who have a family history of hypertension appear to benefit most from the hypotensive effects of potassium supplementation. The greatest hypotensive effect of potassium supplementation occurs in patients with severe hypertension. This effect is pronounced with prolonged potassium supplementation. The antihypertensive effect of increased potassium intake appears to be mediated by several factors, which include enhancing natriuresis, modulating baroreflex sensitivity, direct vasodilation, or lowering cardiovascular reactivity to norepinephrine or angiotensin II. Potassium repletion in patients with diuretic-induced hypokalemia improves BP control. An increase in potassium intake should be included in the nonpharmacologic management of patients with uncomplicated hypertension.

Potassium intake and cardiovascular reactivity in children with risk factors for essential hypertension

OBJECTIVES

Our study objectives were as follows: (1) to determine whether urinary excretion of potassium is lower in black than in white children, (2) to determine whether cardiovascular reactivity (CVR) varies inversely with dietary intake of potassium, and (3) to confirm that CVR is greater in black than in white children, and in children with a family history of hypertension than in those without such a history.

STUDY DESIGN

Baseline measurements included 24-hour urinary sodium, potassium, and creatinine levels and food intake (by questionnaire). Resting and stress blood pressure were measured during blood sampling, cold water foot immersion, and a video game before and after 1 week each of supplementation with potassium citrate, 1.5 mmol/kg per day, and placebo administered in random order.

RESULTS

Thirty-nine children aged 7 to 15 years were studied. White subjects had higher baseline excretion of potassium than black subjects (p < 0.001) and higher vegetable intake (p < 0.01), which were positively correlated (r = 0.53, p < 0.001). At baseline, the 24-hour urinary potassium/creatinine ratio varied inversely with diastolic CVR to the video game stressor in white children (r = -0.55, p = 0.02). Cardiovascular reactivity was not attenuated measurably by potassium supplementation compared with placebo. The CVR was greater in children with a family history of hypertension than in those without, but was not greater in black children than in white children.

CONCLUSIONS

The urinary potassium/creatinine ratio is higher in white than black children because their intake of vegetables is greater; dietary potassium intake may modulate CVR, particularly in white children with a family history of hypertension, but may need to be supplemented for more than 1 week to demonstrate attenuation of CVR; and a family history of hypertension may be a stronger predictor of enhanced CVR than is race.

Reduced dietary potassium reversibly enhances vasopressor response to stress in African Americans

Acute vasopressor responses to stress are adrenergically mediated and hence potentially subject to differential modulation by dietary potassium and sodium. The greater vasopressor responsiveness in blacks compared with whites might then be consequent not only to a high dietary salt intake but also to a marginally reduced dietary potassium intake. Under controlled metabolic conditions, we compared acute vasopressor responses to cold and mental stress in black and white normotensive men during three successive dietary periods: (1) while dietary potassium was reduced (30 mmol K+/70 kg per day) and salt was restricted (10 to 14 days); (2) while salt was loaded (15 to 250 mmol Na+/70 kg per day) (7 days); and (3) while salt loading was continued and potassium was either supplemented (70 mmol K+/70 kg per day) (7 to 21 days) in 9 blacks and 6 whites or continued reduced (30 mmol K+/70 kg per day) (28 days) in 4 blacks (time controls). At the lower potassium intake, cold-induced increase in forearm vascular resistance in blacks was twice that in whites during both salt restriction and salt loading. Normalization of dietary potassium attenuated cold-induced increases in both forearm vascular resistance and systolic and diastolic blood pressures in blacks but only in systolic pressure in whites. In blacks but not in whites, normalization of dietary potassium attenuated mental stress-induced increases in systolic and diastolic pressures. In normotensive blacks but not whites, a marginally reduced dietary intake of potassium reversibly enhances adrenergically mediated vasopressor responsiveness to stress. That responsiveness so enhanced over time might contribute to the pathogenesis of hypertension in blacks.

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

We conducted a randomized, double-blind, placebo-controlled trial of oral potassium chloride supplementation (60 mmol/d) in 353 men and women with an initial average diastolic blood pressure between 80 and 89 mm Hg. In the active (n = 178) compared to the placebo (n = 175) treatment group, the urinary potassium level was significantly (p < 0.001) increased by an average of 44.0 and 42.3 mmol/24 h following 3 and 6 months of therapy, respectively. Compared to placebo, active treatment was associated with a small (mean = 1.8 mm Hg) but significant (p = 0.04) reduction in diastolic blood pressure following 3 months of therapy. Following 6 months, however, this apparent treatment effect had virtually disappeared (mean reduction in diastolic blood pressure = 0.3 mm Hg). There was no significant effect of potassium supplementation on systolic blood pressure at either follow-up visit. There was a significant, independent, dose-response relationship between change in both 24-hour urinary potassium excretion and urinary sodium-potassium ratio and the corresponding change in diastolic blood pressure (-1.49 mm Hg for the highest versus the lowest quartile of change in urinary potassium excretion.

Micronutrient effects on blood pressure regulation

Five micronutrients have been shown to directly influence blood pressure: sodium, calcium, potassium, magnesium, and chloride. The data presented here are based on accumulated findings from epidemiologic, laboratory, and clinical investigations, many of which focused primarily on a single nutrient. However, as also discussed here, nutrients are not consumed in isolation, and their physiologic interactions and combined effects on blood pressure are the subjects of much of the current research in the area of diet and hypertension.

Potassium preserves endothelial function and enhances aortic compliance in Dahl rats

It has recently been proposed that in rat models of genetic hypertension, supplemental dietary potassium preserves release of endothelium-derived relaxing factor independently of its capacity to either attenuate hypertension or increase plasma potassium. To test this hypothesis in Dahl salt-sensitive rats given sodium chloride (4%) for 3 weeks, we supplemented dietary potassium (2.1%) with either KCl (n = 16) or KHCO3 (n = 16). Compared with unsupplemented rats (n = 16), rats supplemented with either potassium salt had a lower mean arterial pressure and a greater release of endothelium-derived relaxing factor, as assessed from acetylcholine-induced relaxation of precontracted aortic rings. However, the maximum relaxation response to acetylcholine correlated inversely with blood pressure (r = -.82, P < .001), not only in the KCl (r = -.68, P < .002) and KHCO3 (r = -.77, P < .001) groups but also in unsupplemented rats (r = -.86, P < .001). With potassium supplementation, plasma potassium concentrations measured between 4 and 6 PM did not increase, but those measured between 4 and 6 AM did increase (P < .05). In isolated ring segments, aortic compliance was greater in both the KCl and KHCO3 groups than in unsupplemented rats (0.015 and 0.017 vs 0.009 mm2/mm Hg) (P < .01). This greater compliance could not be related to differences in blood pressure, plasma potassium, or collagen or elastin content of the aortic wall.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of diet in the genesis and treatment of hypertension

In this brief review, we have not been able to address all of the various dietary factors which have been implicated as causal in hypertension. Because of the heterogeneity of hypertension, it is quite difficult to find a simple answer to the question of how important dietary factors are in causing hypertension and even more difficult to answer the question of how diet should be therapeutically altered in treating a hypertensive patient. Given the difficulties in achieving good compliance to almost any dietary prescription and the lifestyle changes these therapies often require, significant benefit must be demonstrated to justify the efforts. It is worth emphasizing that many of the dietary alterations which have been proposed for treating hypertension have even better established preventative health rationales which justify their use. Although salt intake is a factor in the genesis of hypertension, the effectiveness of salt restriction varies between patients. Despite the absence of good predictors of response, moderate sodium reduction is a reasonable first step when dealing with a hypertensive patient. In obese hypertensive patients, weight loss provides a modest but significant BP reduction. Added benefit may be obtained by lowering total fat content and increasing the ratio of polyunsaturated to saturated fats. The reduction in cardiovascular risk with these changes in dietary fat, over and above the lowering of BP, make this approach appropriate in all hypertensive patients. Potassium supplementation, while sometimes effective, is more difficult to recommend broadly. Calcium supplementation is certainly reasonable in women, for whom such therapy should be seen as good dietary advice for the prevention of osteoporosis. Moderate alcohol intake probably has little deleterious effect, whereas heavy alcoholism does contribute to increased BP. Again, reduction of alcohol intake is important for reasons other than the modest BP reduction attained.

Potassium accelerates urinary sodium excretion during salt loading without stimulating atrial natriuretic polypeptide secretion

1. Effects of potassium (K) supplementation (100 mEq/day) on urinary sodium (Na) excretion and on the secretion of atrial natriuretic polypeptide (ANP) during salt loading (350 mEq/day) were studied in 12 healthy salt-resistant normotensives under strictly controlled metabolic ward conditions. 2. Urinary volume and Na excretion on the first day of the high salt period (HSP) were significantly greater in the K-supplemented group (KG) than in the control group (CG). 3. There was a significant gain in bodyweight after salt loading in both groups, with a significantly greater gain in CG on the second day of HSP. Haematocrit decreased significantly during salt loading in both groups, the degree of which was significantly greater in CG. 4. Plasma norepinephrine decreased significantly during salt loading in both groups, the degree of which was significantly less in KG than in CG. A significant increase in plasma ANP was observed in CG on and after the second day of HSP, while a significant increase in plasma ANP was observed on the fifth day of HSP in KG. 5. These findings indicate that K supplementation accelerates diuresis and natriuresis, resulting in moderate suppression of volume expansion induced by salt loading and that this accelerated diuresis and natriuresis is not a result of the action of ANP.

Sodium excretion and racial differences in ambulatory blood pressure patterns

The influence of Na+ excretion and race on casual blood pressure and ambulatory blood pressure patterns was examined in a biracial sample of healthy, normotensive children and adolescents (10-18 years; n = 140). The slopes relating 24-hour urinary Na+ excretion to systolic blood pressure were different for both black and white subjects for casual blood pressure (p less than 0.001) and blood pressure during sleep (p less than 0.03). For casual blood pressure, the slope was significant for black subjects (beta = 0.17; p less than 0.001) but not for white subjects. For blood pressure during sleep, the slope was again significant for black subjects (beta = 0.08; p less than 0.01) but not for white subjects. Na+ excretion was also related to awake levels of systolic blood pressure for black subjects (beta = 0.08, r = 0.36; p less than 0.01), although the slopes for both black and white subjects were not significantly different. Further analyses indicated the results were not due to racial differences in 24-hour urinary K+ excretion. However, plasma renin activity was marginally related to Na+ excretion in white subjects (r = 0.22; p less than 0.06) but not black subjects, a finding that is consistent with previous studies. Na+ excretion was not associated with diastolic blood pressure or heart rate in either group under any condition. The results of this study support research that has demonstrated a stronger relation between Na+ handling and casual blood pressure in black subjects and extend these findings to blood pressure while the subject is both awake and asleep.

Efficacy of potassium and magnesium in essential hypertension: a double-blind, placebo controlled, crossover study

OBJECTIVE

To evaluate the antihypertensive activity of potassium given alone or in combination with magnesium in patients with mild hypertension.

DESIGN

A double blind, randomised, placebo controlled, crossover trial of 32 weeks' duration.

SETTINGS

Cardiology outpatient department, Sassoon General Hospitals, Pune, India.

PATIENTS

37 Adults with mild hypertension (diastolic blood pressure less than 110 mm Hg).

INTERVENTION

Patients received either placebo or potassium 60 mmol/day alone or in combination with magnesium 20 mmol/day in a crossover design. No other drug treatment was allowed.

MEASUREMENTS

Blood pressure and heart rate assessed at weekly intervals and biochemical parameters at monthly intervals.

RESULTS

Potassium alone or in combination with magnesium produced a significant reduction in systolic and diastolic blood pressures (p less than 0.001) and a significant reduction in serum cholesterol concentration (p less than 0.05); other biochemical variables did not change. Magnesium did not have an additional effect. Urinary potassium excretion increased significantly in the groups who received potassium alone or in combination with magnesium. The drug was well tolerated and compliance was satisfactory.

CONCLUSION

Potassium 60 mmol/day lowers arterial blood pressure in patients with mild hypertension. Giving magnesium as well has no added advantage.

The influence of oral potassium chloride on blood pressure in hypertensive men on a low-sodium diet

Clinical and epidemiologic studies suggest that the intake of potassium chloride lowers blood pressure. To investigate whether supplemental potassium chloride (96 mmol of microcrystalline potassium chloride a day) reduced the need for antihypertensive medication in hypertensive men on a restricted-sodium diet, we conducted a randomized, placebo-controlled, double-blind clinical trial. A total of 287 men 45 to 68 years of age, 142 given potassium chloride and 145 given placebo, were followed for an average of 2.2 years after the withdrawal of their antihypertensive medication. Men in both groups received instructions on following a low-sodium diet. Overnight urinary sodium excretion fell from 63 mmol per eight hours at base line to an average of 45 mmol per eight hours during follow-up. Participants given supplemental potassium chloride had significantly higher (P less than 0.001) serum potassium levels and urinary potassium excretion (averaging 4.5 mmol per liter and 42.5 mmol per eight hours, respectively) during follow-up than participants given placebo (4.2 mmol per liter and 20.0 mmol per eight hours). Seventy-nine participants in each group required reinstitution of antihypertensive medication according to strict indications defined by the protocol. No significant differences in systolic or diastolic blood pressure were observed between the two groups. During follow-up, systolic and diastolic blood pressure averaged 130.6 and 82.5 mm Hg, respectively, for participants given supplemental potassium, and 132.5 and 83.1 mm Hg for participants given placebo. We conclude that supplemental potassium chloride does not reduce the need for antihypertensive medication in hypertensive men on a restricted-sodium diet.

Effects of non-pharmacologic therapy

Whereas there is no doubt that non-drug treatment of hypertension, and modifications in life-style to prevent an age-associated rise in arterial pressure are attractive concepts, opinions vary as to what advice should be offered to hypertensive patients and to populations at large. No modification in diet or life style has been demonstrated to reduce the complications of hypertension. Review of recent reports suggests that moderate exercise, weight reduction in the obese, and moderation of alcohol intake are usually effective in reducing arterial pressure and are unaccompanied by adverse effects. On the contrary, restriction of dietary sodium, or supplementation with potassium, calcium or magnesium have little or variable antihypertensive effects, are not readily accepted by a high percentage of the population, and could have adverse consequences. Other dietary modifications may reduce blood pressure, but additional research is needed to define the relevant component in the diet.