Effect of modest salt reduction on blood pressure: a meta-analysis of randomized trials. Implications for public health

Salt and hypertension: is salt dietary reduction worth the effort?

In numerous epidemiologic, clinical, and experimental studies, dietary sodium intake has been linked to blood pressure, and a reduction in dietary salt intake has been documented to lower blood pressure. In young subjects, salt intake has a programming effect in that blood pressure remains elevated even after a high salt intake has been reduced. Elderly subjects, African Americans, and obese patients are more sensitive to the blood pressure-lowering effects of a decreased salt intake. Depending on the baseline blood pressure and degree of salt intake reduction, systolic blood pressure can be lowered by 4 to 8 mm Hg. A greater decrease in blood pressure is achieved when a reduced salt intake is combined with other lifestyle interventions, such as adherence to Dietary Approaches to Stop Hypertension. A high salt intake has been shown to increase not only blood pressure but also the risk of stroke, left ventricular hypertrophy, and proteinuria. Adverse effects associated with salt intake reduction, unless excessive, seem to be minimal. However, data linking a decreased salt intake to a decrease in morbidity and mortality in hypertensive patients are not unanimous. Dietary salt intake reduction can delay or prevent the incidence of antihypertensive therapy, can facilitate blood pressure reduction in hypertensive patients receiving medical therapy, and may represent a simple cost-saving mediator to reduce cardiovascular morbidity and mortality.

Benefit of Monascus-fermented products for hypertension prevention: a review

γ-Aminobutyric acid (GABA) has been reported to play a neurotransmitter in the central nervous system thereby exerting an inhibition in nerve impulse, in turn ameliorating depression; in addition, recent study also reveals the anti-hypertensive effect of GABA in vivo. Edible fungi of the Monascus species have been used as traditional Chinese medicine in eastern Asia for several centuries. Monascus-fermented products possess a number of functional secondary metabolites, including anti-inflammatory pigments (such as monascin and ankaflavin), monacolins, dimerumic acid, and GABA. Several scientific studies have shown that these secondary metabolites have anti-inflammatory, anti-oxidative, and anti-tumor activities. Moreover, many published reports have shown the efficacy of Monascus-fermented products in the prevention or amelioration of some diseases, including hypercholesterolemia, hyperlipidemia, hypertension, diabetes, obesity, Alzheimer's disease, and numerous types of cancer in recent studies. The current article discusses and provides evidence to elucidate the anti-hypertensive benefit of Monascus-fermented metabolites, including anti-inflammatory pigments and GABA.

[Should we consume less salt?]

There is overwhelming evidence that dietary salt is a major cause of increased blood pressure. There is also a link between a high salt intake and risk of stroke, left ventricular hypertrophy, renal disease, obesity, renal stones and stomach cancer. Reduction of salt intake is efficacious and cost-effective. In developed countries, reduction in salt intake requires the participation of food industry.

High salt intake causes adverse fetal programming--vascular effects beyond blood pressure

BACKGROUND

High salt intake causes hypertension, adverse cardiovascular outcomes and potentially also blood pressure (BP)-independent target organ damage. Excess salt intake in pregnancy is known to affect BP in the offspring. The present study was designed to assess whether high salt intake in pregnancy affects BP and vascular morphology in the offspring.

METHODS

Sprague-Dawley rats were fed a standard rodent diet with low-normal (0.15%) or high (8.0%) salt content during pregnancy and lactation. After weaning at 4 weeks of age, offspring were maintained on the same diet or switched to a high- or low-salt diet, respectively. Vascular geometry was assessed in male offspring at 7 and 12 weeks postnatally.

RESULTS

Up to 12 weeks of age, there was no significant difference in telemetrically measured BP between the groups of offspring. At 12 weeks of age, wall thickness of central (aorta, carotid), muscular (mesenteric) and intrapulmonary arteries was significantly higher in offspring of mothers on a high-salt diet irrespective of the post-weaning diet. This correlated with increased fibrosis of the aortic wall, more intense nitrotyrosine staining as well as elevated levels of marinobufagenin (MBG) and asymmetric dimethyl arginine (ADMA).

CONCLUSIONS

High salt intake in pregnant rats has long-lasting effects on the modeling of central and muscular arteries in the offspring independent of postnatal salt intake and BP. Circulating MBG and ADMA and local oxidative stress correlate with the adverse vascular modeling.

Sodium Consumption: An Individual's Choice?

Excess intake of dietary salt is estimated to be one of the leading risks to health worldwide. Major national and international health organizations, along with many governments around the world, have called for reductions in the consumption of dietary salt. This paper discusses behavioural and population interventions as mechanisms to reduce dietary salt. In developed countries, salt added during food processing is the dominant source of salt and largely outside of the direct control of individuals. Population-based interventions have the potential to improve health and to be cost saving for these countries. In developing economies, where salt added in cooking and at the table is the dominant source, interventions based on education and behaviour change have been estimated to be highly cost effective. Regardless, countries with either developed or developing economies can benefit from the integration of both population and behavioural change interventions.

Effects of low-sodium diet vs. high-sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride (Cochrane Review)

BACKGROUND

The question of whether reduced sodium intake is effective as a health prophylaxis initiative is unsolved. The purpose was to estimate the effects of low-sodium vs. high-sodium intake on blood pressure (BP), renin, aldosterone, catecholamines, and lipids.

METHODS

Studies randomizing persons to low-sodium and high-sodium diets evaluating at least one of the above outcome parameters were included. Data were analyzed with Review Manager 5.1.

RESULTS

A total of 167 studies were included. The effect of sodium reduction in: (i) Normotensives: Caucasians: systolic BP (SBP) -1.27 mm Hg (95% confidence interval (CI): -1.88, -0.66; P = 0.0001), diastolic BP (DBP) -0.05 mm Hg (95% CI: -0.51, 0.42; P = 0.85). Blacks: SBP -4.02 mm Hg (95% CI: -7.37, -0.68; P = 0.002), DBP -2.01 mm Hg (95% CI: -4.37, 0.35; P = 0.09). Asians: SBP -1.27 mm Hg (95% CI: -3.07, 0.54; P = 0.17), DBP -1.68 mm Hg (95% CI: -3.29, -0.06; P = 0.04). (ii) Hypertensives: Caucasians: SBP -5.48 mm Hg (95% CI: -6.53, -4.43; P < 0.00001), DBP -2.75 mm Hg (95% CI: -3.34, -2.17; P < 0.00001). Blacks: SBP -6.44 mm Hg (95% CI: -8.85, -4.03; P = 0.00001), DBP -2.40 mm Hg (95% CI: -4.68, -0.12; P = 0.04). Asians: SBP -10.21 mm Hg (95% CI: -16.98, -3.44; P = 0.003), DBP -2.60 mm Hg (95% CI: -4.03, -1.16; P = 0.0004). Sodium reduction resulted in significant increases in renin (P < 0.00001), aldosterone (P < 0.00001), noradrenaline (P < 0.00001), adrenaline (P < 0.0002), cholesterol (P < 0.001), and triglyceride (P < 0.0008).

CONCLUSIONS

Sodium reduction resulted in a significant decrease in BP of 1% (normotensives), 3.5% (hypertensives), and a significant increase in plasma renin, plasma aldosterone, plasma adrenaline, and plasma noradrenaline, a 2.5% increase in cholesterol, and a 7% increase in triglyceride.

Discovery of salt taste enhancing arginyl dipeptides in protein digests and fermented fish sauces by means of a sensomics approach

As enzymatic digests of fish proteins were recently reported to enhance salt taste, the fish protein protamine was digested by chymotrypsin and trypsin and subsequently screened for candidate salt taste modulating (STM) peptides. To achieve this, first, a two-step sensory assay was developed and demonstrated to be a rather suitable tool for the detection of salt taste enhancers and the "quantitation" of their salt taste enhancing activity on the basis of isointensities with reference solutions. By means of activity-guided fractionation using ultrafiltration, gel permeation chromatography, and hydrophilic liquid interaction chromatography in combination with the sensory assay for STM activity assessment, a series of arginyl dipeptides, with RP, RA, AR, RG, RS, RV, VR, and RM being the most active, as well as l-arginine were found as salt taste enhancing molecules in fish protamine digests. For the first time, HPLC-MS/MS analysis on a PFP and a HILIC stationary phase, respectively, enabled the quantitative analysis of the arginyl peptides in a series of commercial and laboratory-made protein hydrolysates as well as fermented fish sauces.

Effect of potassium supplementation on renal tubular function, ambulatory blood pressure and pulse wave velocity in healthy humans

BACKGROUND

Potassium is the main intracellular cation, which contributes to keeping the intracellular membrane potential slightly negative and elicits contraction of smooth, skeletal and cardiac muscle. A change in potassium intake modifies both cardiovascular and renal tubular function. The purpose of the trial was to investigate the effect of dietary potassium supplementation, 100 mmol daily in a randomized, placebo-controlled, crossover trial of healthy participants during two periods of 28 days duration. The participants (N = 21) received a diet that was standardized regarding energy requirement, and sodium and water intake.

METHODS

24-hour ambulatory blood pressure (ABP) and applanation tonometry were used to assess blood pressure, pulse wave velocity (PWV), augmentation index (AIx) and central blood pressure (CBP). Immunoassays were used for measurements of plasma concentrations of vasoactive hormones: renin (PRC), angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP), vasopressin (AVP), pro-brain natriuretic peptide (pro-BNP),endothelin (Endo), urinary excretions of aquaporin 2 (AQP2), cyclic AMP (cAMP), and the β-fraction of the epithelial sodium channel (ENaC(ß)).

RESULTS

AQP2 excretion increased during potassium supplementation, and free water clearance fell. The changes in urinary potassium excretion and urinary AQP2 excretion were significantly and positively correlated. Aldo increased. GFR, u-ENaC- β, PRC, Ang II, ANP, BNP, Endo, blood pressure and AI were not significantly changed by potassium supplementation, whereas PWV increased slightly.

CONCLUSIONS

Potassium supplementation changed renal tubular function and increased water absorption in the distal part of the nephron. In spite of an increase in aldosterone in plasma, blood pressure remained unchanged after potassium supplementation.

The cost-effectiveness of interventions designed to reduce sodium intake

BACKGROUND

To guide resource allocation, policy makers need evidence of the cost-effectiveness of interventions. We summarized such evidence on selected interventions to reduce sodium intake that would be intended as population-wide approaches to control hypertension.

METHODS

We conducted a comprehensive literature review of journal articles published in English from January 2000 to May 2010 by searching the databases of PubMed, EMBASE, MEDLINE, and EconLit. We selected original research articles for abstracting the evidence on cost-effectiveness of interventions, cost savings and the costs of intervention implementation.

RESULTS

From the 53 references obtained from the literature search, we identified 11 original research articles that provided relevant information on the medical cost savings, implementation costs, or cost-effectiveness of interventions to reduce sodium intake. The interventions were low in cost, e. g., one study showed that the cost ranged from US$ 0.03 to 0.32 per person per year for awareness campaign through mass media outlets and government regulations on food products in low and middle-income countries. Population-wide interventions for salt reduction are very cost-effective such as only ARS$ 151 per disability-adjusted life-year (DALY) saved in Argentina, whereas statin therapy to lower high cholesterol was $ 70,994 per DALY saved. Another study showed that sodium reduction could save US$ 18 billion in annual US healthcare costs by reducing sodium intake to 2300 mg/day.

CONCLUSION

The literature provided economic evidence that was in favor of population-wide interventions designed to reduce sodium intake. Reducing the intake of sodium through such initiatives might be one of the best buys in public health. However, the small body of literature and hypothetical scenarios in most studies might limit policy implications of the findings.

Effect of salt reduction intervention program using an electronic salt sensor and cellular phone on blood pressure among hypertensive workers

We investigated the effectiveness of a workplace intervention program that utilized self-monitoring of daily salt excretion by an electronic salt sensor and sent personalized e-mail advice via cellular phone. Forty-one hypertensive male workers were assigned to intervention and control groups, then counseled together. Intervention group members were asked to measure daily salt excretion and received e-mail advice. After 4 weeks, a greater decrease of blood pressure (BP) was observed in the intervention group, with significant reductions to daily salt excretion and home BP. The new intervention program is considered useful for BP control among hypertensive workers.