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

Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride

BACKGROUND

In spite of more than 100 years of investigations the question of reduced sodium intake as a health prophylaxis initiative is still unsolved.

OBJECTIVES

To estimate the effects of low sodium versus high sodium intake on systolic and diastolic blood pressure (SBP and DBP), plasma or serum levels of renin, aldosterone, catecholamines, cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triglycerides.

SEARCH METHODS

PUBMED, EMBASE and Cochrane Central and reference lists of relevant articles were searched from 1950 to July 2011.

SELECTION CRITERIA

Studies randomizing persons to low sodium and high sodium diets were included if they evaluated at least one of the above outcome parameters.

DATA COLLECTION AND ANALYSIS

Two authors independently collected data, which were analysed with Review Manager 5.1.

MAIN RESULTS

A total of 167 studies were included in this 2011 update.The effect of sodium reduction in normotensive Caucasians was SBP -1.27 mmHg (95% CI: -1.88, -0.66; p=0.0001), DBP -0.05 mmHg (95% CI: -0.51, 0.42; p=0.85). The effect of sodium reduction in normotensive Blacks was SBP -4.02 mmHg (95% CI:-7.37, -0.68; p=0.002), DBP -2.01 mmHg (95% CI:-4.37, 0.35; p=0.09). The effect of sodium reduction in normotensive Asians was SBP -1.27 mmHg (95% CI: -3.07, 0.54; p=0.17), DBP -1.68 mmHg (95% CI:-3.29, -0.06; p=0.04). The effect of sodium reduction in hypertensive Caucasians was SBP -5.48 mmHg (95% CI: -6.53, -4.43; p<0.00001), DBP -2.75 mmHg (95% CI: -3.34, -2.17; p<0.00001). The effect of sodium reduction in hypertensive Blacks was SBP -6.44 mmHg (95% CI:-8.85, -4.03; p=0.00001), DBP -2.40 mmHg (95% CI:-4.68, -0.12; p=0.04). The effect of sodium reduction in hypertensive Asians was SBP -10.21 mmHg (95% CI:-16.98, -3.44; p=0.003), DBP -2.60 mmHg (95% CI: -4.03, -1.16; p=0.0004).In plasma or serum there was a significant increase 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) with low sodium intake as compared with high sodium intake. In general the results were similar in studies with a duration of at least 2 weeks.

AUTHORS' CONCLUSIONS

Sodium reduction resulted in a 1% decrease in blood pressure in normotensives, a 3.5% decrease in hypertensives, 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. In general, these effects were stable in studies lasting for 2 weeks or more.

The central mechanism underlying hypertension: a review of the roles of sodium ions, epithelial sodium channels, the renin-angiotensin-aldosterone system, oxidative stress and endogenous digitalis in the brain

The central nervous system has a key role in regulating the circulatory system by modulating the sympathetic and parasympathetic nervous systems, pituitary hormone release, and the baroreceptor reflex. Digoxin- and ouabain-like immunoreactive materials were found >20 years ago in the hypothalamic nuclei. These factors appeared to localize to the paraventricular and supraoptic nuclei and the nerve fibers at the circumventricular organs and supposed to affect electrolyte balance and blood pressure. The turnover rate of these materials increases with increasing sodium intake. As intracerebroventricular injection of ouabain increases blood pressure via sympathetic activation, an endogenous digitalis-like factor (EDLF) was thought to regulate cardiovascular system-related functions in the brain, particularly after sodium loading. Experiments conducted mainly in rats revealed that the mechanism of action of ouabain in the brain involves sodium ions, epithelial sodium channels (ENaCs) and the renin-angiotensin-aldosterone system (RAAS), all of which are affected by sodium loading. Rats fed a high-sodium diet develop elevated sodium levels in their cerebrospinal fluid, which activates ENaCs. Activated ENaCs and/or increased intracellular sodium in neurons activate the RAAS; this releases EDLF in the brain, activating the sympathetic nervous system. The RAAS promotes oxidative stress in the brain, further activating the RAAS and augmenting sympathetic outflow. Angiotensin II and aldosterone of peripheral origin act in the brain to activate this cascade, increasing sympathetic outflow and leading to hypertension. Thus, the brain Na(+)-ENaC-RAAS-EDLF axis activates sympathetic outflow and has a crucial role in essential and secondary hypertension. This report provides an overview of the central mechanism underlying hypertension and discusses the use of antihypertensive agents.

The role of obesity, salt and exercise on blood pressure in children and adolescents

The increasing trends of blood pressure (BP) in children and adolescents pose great concern for the burden of hypertension-related cardiovascular disease. Although primary hypertension in childhood is commonly associated with obesity, it seems that other factors, such as dietary sodium and exercise, also influence BP levels in children and adolescents. Several studies support that sympathetic nervous system imbalance, impairment of the physiological mechanism of pressure natriuresis, hyperinsulinemia and early vascular changes are involved in the mechanisms causing elevated BP in obese children and adolescents. Under the current evidence on the association of salt intake and BP, dietary sodium restriction appears to be a rational step in the prevention of hypertension in genetically predisposed children and adolescents. Finally, interventional studies show that regular aerobic exercise can significantly reduce BP and restore vascular changes in obese with hypertensive pediatric patients. This article aims to summarize previous studies on the role of obesity, salt intake and exercise on BP in children and adolescents.

National and subnational mortality effects of metabolic risk factors and smoking in Iran: a comparative risk assessment

Background

Mortality from cardiovascular and other chronic diseases has increased in Iran. Our aim was to estimate the effects of smoking and high systolic blood pressure (SBP), fasting plasma glucose (FPG), total cholesterol (TC), and high body mass index (BMI) on mortality and life expectancy, nationally and subnationally, using representative data and comparable methods.

Methods

We used data from the Non-Communicable Disease Surveillance Survey to estimate means and standard deviations for the metabolic risk factors, nationally and by region. Lung cancer mortality was used to measure cumulative exposure to smoking. We used data from the death registration system to estimate age-, sex-, and disease-specific numbers of deaths in 2005, adjusted for incompleteness using demographic methods. We used systematic reviews and meta-analyses of epidemiologic studies to obtain the effect of risk factors on disease-specific mortality. We estimated deaths and life expectancy loss attributable to risk factors using the comparative risk assessment framework.

Results

In 2005, high SBP was responsible for 41,000 (95% uncertainty interval: 38,000, 44,000) deaths in men and 39,000 (36,000, 42,000) deaths in women in Iran. High FPG, BMI, and TC were responsible for about one-third to one-half of deaths attributable to SBP in men and/or women. Smoking was responsible for 9,000 deaths among men and 2,000 among women. If SBP were reduced to optimal levels, life expectancy at birth would increase by 3.2 years (2.6, 3.9) and 4.1 years (3.2, 4.9) in men and women, respectively; the life expectancy gains ranged from 1.1 to 1.8 years for TC, BMI, and FPG. SBP was also responsible for the largest number of deaths in every region, with age-standardized attributable mortality ranging from 257 to 333 deaths per 100,000 adults in different regions.

Discussion

Management of blood pressure through diet, lifestyle, and pharmacological interventions should be a priority in Iran. Interventions for other metabolic risk factors and smoking can also improve population health.

Food sources and correlates of sodium and potassium intakes in Flemish pre-school children

Objective

The aim of the present study was to investigate dietary sources of Na and K intakes among Flemish pre-school children using multiple linear regression analyses.

Design

Three-day estimated diet records were used to assess dietary intakes. The contribution to Na and K intakes of fifty-seven food groups was computed by summing the amount provided by the food group for all individuals divided by the total intake for all individuals.

Setting

A random cluster sampling design at the level of schools, stratified by province and age, was used.

Subjects

A representative sample of 696 Flemish pre-school children aged 2·5–6·5 years was recruited.

Results

Mean Na intake was above and mean K intake was largely below the recommendation for children. Bread (22 %) and soup (13 %) were main contributors to Na intake followed by cold meat cuts and other meat products (12 % and 11 %, respectively). Sugared milk drinks, fried potatoes, milk and fruit juices were the main K sources (13 %, 12 %, 11 % and 11 %, respectively). Although Na and K intakes were positively correlated, several food categories showed Na:K intake ratio well above one (water, cheeses, soup, butter/margarine, fast foods and light beverages) whereas others presented a ratio well below one (oil & fat, fruits & juices, potatoes, vegetables and hot beverages).

Conclusions

Flemish pre-school children had too high Na and too low K intakes. The finding that main dietary sources of Na and K are clearly different indicates the feasibility of simultaneously decreasing Na and increasing K intake among children.

Indoor air pollution and blood pressure in adult women living in rural China

BACKGROUND

Almost half of the world's population uses coal and biomass fuels for domestic energy. Limited evidence suggests that exposure to air pollutants from indoor biomass combustion may be associated with elevated blood pressure (BP).

OBJECTIVE

Our aim was to assess the relationship between air pollution exposure from indoor biomass combustion and BP in women in rural China.

METHODS

We measured 24-hr personal integrated gravimetric exposure to fine particles < 2.5 µm in aerodynamic diameter (PM2.5) and systolic BP (SBP) and diastolic BP (DBP) in the winter and summer among 280 women ≥ 25 years of age living in rural households using biomass fuels in Yunnan, China. We investigated the association between PM2.5 exposure and SBP and DBP using mixed-effects models with random intercepts to account for correlation among repeated measures.

RESULTS

Personal average 24-hr exposure to PM2.5 ranged from 22 to 634 µg/m3 in winter and from 9 to 492 µg/m3 in summer. A 1-log-µg/m3 increase in PM2.5 exposure was associated with 2.2 mm Hg higher SBP [95% confidence interval (CI), 0.8 to 3.7; p = 0.003] and 0.5 mm Hg higher DBP (95% CI, -0.4 to 1.3; p = 0.31) among all women; estimated effects varied by age group. Among women > 50 years of age, a 1-log-µg/m3 increase in PM2.5 exposure was associated with 4.1 mm Hg higher SBP (95% CI, 1.5 to 6.6; p = 0.002) and 1.8 mm Hg higher DBP (95% CI, 0.4 to 3.2; p = 0.01). PM2.5 exposure was positively associated with SBP among younger women, but the association was not statistically significant.

CONCLUSION

PM2.5 exposure from biomass combustion may be a risk factor for elevated BP and hence for cardiovascular events. Our findings should be corroborated in longitudinal studies.

Feasibility and antihypertensive effect of replacing regular salt with mineral salt -rich in magnesium and potassium- in subjects with mildly elevated blood pressure

Background

High salt intake is linked to hypertension whereas a restriction of dietary salt lowers blood pressure (BP). Substituting potassium and/or magnesium salts for sodium chloride (NaCl) may enhance the feasibility of salt restriction and lower blood pressure beyond the sodium reduction alone. The aim of this study was to determine the feasibility and effect on blood pressure of replacing NaCl (Regular salt) with a novel mineral salt [50% sodium chloride and rich in potassium chloride (25%), magnesium ammonium potassium chloride, hydrate (25%)] (Smart Salt).

Methods

A randomized, double-blind, placebo-controlled study was conducted with an intervention period of 8-weeks in subjects (n = 45) with systolic (S)BP 130-159 mmHg and/or diastolic (D)BP 85-99 mmHg. During the intervention period, subjects consumed processed foods salted with either NaCl or Smart Salt. The primary endpoint was the change in SBP. Secondary endpoints were changes in DBP, daily urine excretion of sodium (24-h dU-Na), potassium (dU-K) and magnesium (dU-Mg).

Results

24-h dU-Na decreased significantly in the Smart Salt group (-29.8 mmol; p = 0.012) and remained unchanged in the control group: resulting in a 3.3 g difference in NaCl intake between the groups. Replacement of NaCl with Smart Salt resulted in a significant reduction in SBP over 8 weeks (-7.5 mmHg; p = 0.016). SBP increased (+3.8 mmHg, p = 0.072) slightly in the Regular salt group. The difference in the change of SBP between study groups was significant (p < 0.002).

Conclusions

The substitution of Smart Salt for Regular salt in subjects with high normal or mildly elevated BP resulted in a significant reduction in their daily sodium intake as well as a reduction in SBP.

Trial Registration

ISRCTN: ISRCTN01739816

Does reducing salt intake increase cardiovascular mortality?

Overwhelming evidence shows that reducing salt intake from 9-12 to 5-6  g/d lowers blood pressure, thereby preventing cardiovascular disease. A recent paper claims that lower salt intake is associated with higher cardiovascular mortality despite lower blood pressure. The study is flawed and cannot refute the evidence for the benefits of salt reduction. The WHO recommends salt reduction as crucial in tackling the global non-communicable-disease crisis. A reduction in population salt intake remains a public-health priority.

Reducing salt intake in the Americas: Pan American Health Organization actions

This article outlines the rationale for reducing dietary salt and some of the Pan American Health Organization actions to facilitate reductions in dietary salt in the Americas. Excessive dietary salt (sodium chloride and other sodium salts) is a major cause of increased blood pressure, which increases risk for stroke, heart disease, and kidney disease. Reduction in salt intake is beneficial for people with hypertension and those with normal blood pressure. The World Health Organization recommends a population salt intake of less than 5 grams/person/day with a Pan American Health Organization expert group recommendation that this be achieved by 2020 in the Americas. In general, the consumption of salt is more than 6 grams/day by age 5 years, with consumption of salt averaging between 9 and 12 grams per day in many countries. Recent salt intake estimates from Brazil (11 grams of salt/day), Argentina (12 grams of salt/day), Chile (9 grams of salt/day) and the United States (8.7 grams of salt/day) confirm that high salt intakes are prevalent in Americas. Sources of dietary salt vary, from 75% of it coming from processed food in developed countries, to 70% coming from discretionary salt added in cooking or at the table in parts of Brazil. The Pan American Health Organization has launched a regionwide initiative called the ?Cardiovascular Disease Prevention Through Dietary Salt Reduction,? led by an expert working group. Working closely with countries, the expert group developed resources to aid policy development through five subgroups: (a) addressing industry engagement and product reformulation; (b) advocacy and communication; (c) surveillance of salt intake, sources of salt in the diet, and knowledge and opinions on salt and health; (d) salt fortification with iodine; and (e) national-level health economic studies on salt reduction.

Nuts, hypertension and endothelial function

BACKGROUND AND AIMS

High blood pressure (BP) is considered a major risk factor for cardiovascular disease. Among lifestyle factors, diet plays a key role in the prevention and control of high BP. Therefore, it is important to elucidate which dietary components can exert beneficial effects on BP through modulation of endothelial function (EF) or by other mechanisms. In this paper we review the role of nutrients, foods, particularly nuts, and dietary patterns on BP control.

DATA SYNTHESIS

Because nuts are low in sodium and contain significant amounts of mono- and polyunsaturated fatty acids, fiber, minerals such as magnesium, potassium and calcium, and antioxidants, they have been suggested as potentially protective foods against hypertension. Limited evidence from prospective studies and clinical trials suggests that nut consumption has a beneficial effect on both BP and EF. However, BP changes were a secondary outcome in nut feeding trials and no study used ambulatory BP monitoring as the standard for BP measurements.

CONCLUSIONS

Further clinical trials, ideally using ambulatory BP monitoring, are needed to establish the potential protective effect of nut consumption on hypertension and vascular reactivity.

Dietary patterns among British adults: compatibility with dietary guidelines for salt/sodium, fat, saturated fat and sugars

OBJECTIVE

To examine dietary patterns among British adults, associations with Na and macronutrient intakes, and implications for dietary advice.

DESIGN

Principal component analysis of 7 d weighed dietary records.

SUBJECTS

Adults aged 19-64 years (n 1724).

SETTING

National Diet and Nutrition Survey (2000/2001).

RESULTS

High Na intake was associated with more energy-dense diets, higher in fat and SFA (percentage of energy) but lower in non-milk extrinsic sugars (NMES). Eight patterns (PC1 to PC8) explained 40 % of the total variance in food intakes. Three patterns - PC3 (high loadings on bread, fats and cheese), PC2 (meat products, eggs and chips) and PC7 (red meat, sauces and alcohol) - were associated with high Na intake. Of these, PC3 correlated with high Na density and Na:K ratio, while PC2 correlated with fat. By contrast, three patterns - 'health-conscious' (PC1; vegetables, fruit, fruit juice, fish), 'breakfast cereals and milk' (PC6) and 'chicken and rice' (PC8) - were associated with modest Na intake, lower Na density and lower fat and SFA. PC2 was positively correlated, and PC1 was negatively correlated, with adding salt to food. Other patterns were 'tea/coffee and cakes' (PC4; associated with high SFA and NMES) and 'soft drinks and snacks' (PC5; associated with high NMES but not fat or SFA). The dietary patterns of males and females differed slightly.

CONCLUSIONS

Dietary patterns PC1, PC6, PC8 (vegetables, fruit, fish, milk, breakfast cereals, poultry) were broadly compatible with guidelines for salt, fat, SFA and NMES. However, other patterns tended to be high in either salt or NMES.

Endothelial function is impaired after a high-salt meal in healthy subjects

BACKGROUND

Dietary salt is related to blood pressure (BP), and cardiovascular disease and increased sodium intakes have been shown to impair vascular function. The effect of salt on endothelial function postprandially is unknown.

OBJECTIVE

The aim was to investigate the postprandial effect of dietary salt on endothelial function as measured by flow-mediated dilatation (FMD) and peripheral arterial tonometry in healthy subjects.

DESIGN

Sixteen healthy, normotensive subjects received a meal with added salt (HSM; 65 mmol Na) and a control low-salt meal (LSM; 5 mmol Na) on 2 separate occasions in a randomized order. Endothelial function was measured while fasting and postprandially at 30, 60, 90, and 120 min by using FMD and reactive hyperemia peripheral arterial tonometry. BP was also measured.

RESULTS

Baseline FMD, reactive hyperemia index (RHI), and BP values were similar across interventions. Overall FMD was reduced 2 h postprandially. FMD was significantly more impaired after the HSM than after the LSM at 30 min [HSM (mean ± SD): 3.39 ± 2.44%; LSM: 6.05 ± 3.21%; P < 0.01] and at 60 min (HSM: 2.20 ± 2.77%; LSM: 4.64 ± 2.48%; P < 0.01). No significant differences in BP or RHI were observed between meals.

CONCLUSIONS

An HSM, which reflects the typical amount of salt consumed in a commonly eaten meal, can significantly suppress brachial artery FMD within 30 min. These results suggest that high salt intakes have acute adverse effects on vascular dilatation in the postprandial state. This trial was registered at www.anzctr.org.au/trial_view.aspx?ID=335115 as ACTRN12610000124033.

Resistant hypertension, secondary hypertension, and hypertensive crises: diagnostic evaluation and treatment

Hypertension is a very common modifiable risk factor for cardiovascular morbidity and mortality. Patients with hypertension represent a diverse group. In addition to those with primary hypertension, there are patients whose hypertension is attributable to secondary causes, those with resistant hypertension, and patients who present with a hypertensive crisis. Secondary causes of hypertension account for less than 10% of cases of elevated blood pressure (BP), and screening for these causes is warranted if clinically indicated. Patients with resistant hypertension, whose BP remains uncontrolled in spite of use of 3 or more antihypertensive agents, are at increased cardiovascular risk compared with the general hypertensive population. After potentially correctible causes of uncontrolled BP (pseudoresistance, secondary causes, and intake of interfering substances) are eliminated, patients with true resistant hypertension are managed by encouraging therapeutic lifestyle changes and optimizing the antihypertensive regimen, whereby the clinician ensures that the medications are prescribed at optimal doses using drugs with complementary mechanisms of action, while adding an appropriate diuretic if there are no contraindications. Mineralocorticoid receptor antagonists are formidable add-on agents to the antihypertensive regimen, usually as a fourth drug, and are effective in reducing BP even in patients without biochemical evidence of aldosterone excess. In the setting of a hypertensive crisis, the BP has to be reduced within hours in the case of a hypertensive emergency (elevated BP with evidence of target organ damage) using parenteral agents, and within a few days if there is hypertensive urgency, using oral antihypertensive agents.

The effects of dietary and nutrient interventions on arterial stiffness: a systematic review

BACKGROUND

Although dietary and nutrient interventions have been extensively studied as a means of improving arterial stiffness, to our knowledge no systematic analysis of the data has been conducted.

OBJECTIVE

The aim of the current study was to systematically review the human clinical trial data and qualitatively examine the efficacy of dietary and nutrient interventions in the treatment of arterial stiffness.

DESIGN

We systematically searched multiple databases until July 2010 for relevant randomized controlled human clinical trials of common dietary and nutrient interventions in the treatment of arterial stiffness. Located studies were subject to strict inclusion criteria and objectively assessed for scientific quality.

RESULTS

Of the 75 relevant studies located, we considered 38 studies to be appropriate for review. Results revealed support for intakes of omega-3 (n-3) fish oils (Cohen's d = 0.21-0.81) and soy isoflavones (Cohen's d = 0.35-0.39) in the treatment of arterial stiffness. There was limited but consistent evidence to suggest that salt restriction (Cohen's d = 0.28-0.37) as well as consumption of fermented-milk products (Cohen's d = 0.15-0.33) that contain bioactive peptides improved arterial stiffness. The evidentiary support for intakes of vitamins, micronutrients, and herbal medicines was insufficient. Limited but consistent evidence suggested that caffeine intake acutely increased arterial stiffness (Cohen's d = 0.34-0.51).

CONCLUSIONS

Current evidence from several small studies suggests that omega-3 and soy isoflavone supplementation provides an effective means of reducing arterial stiffness. There was little research that explored intakes of herbal medicines or micronutrients in the treatment of arterial stiffness, and this remains an area of potential research.

The association between salt intake and adult systolic blood pressure is modified by birth weight

BACKGROUND

Epidemiologic evidence suggests that prenatal growth influences adult blood pressure. Nutritional factors, including salt intake, also influence blood pressure. However, it is unknown whether prenatal growth modifies the association between salt intake and blood pressure in later life.

OBJECTIVE

Our aim was to examine whether the relation between salt intake and adult blood pressure is modified by birth weight.

DESIGN

We studied 1512 participants of the Helsinki Birth Cohort Study who were born between 1934 and 1944. Information on birth weight was abstracted from birth records, and preterm births were excluded. During a clinical study, at the mean age of 62 y, blood pressure, weight, and height were measured. Diet was assessed with a validated food-frequency questionnaire. The relation between salt intake and blood pressure was tested by a piecewise multivariate regression analysis with the best fitting breakpoints to birth weight and salt intake.

RESULTS

An inverse association was observed between birth weight and systolic blood pressure (SBP) (P = 0.02). No significant association between salt intake and SBP was observed in the whole study population. Of those whose birth weight was ≤3050 g, a 1-g higher daily salt intake was associated with a 2.48-mm Hg (95% CI: 0.40, 4.52 mm Hg) higher SBP (P = 0.017) until the saturation point of 10 g. Of those whose birth weight exceeded 3050 g, SBP was not significantly associated with salt intake. For diastolic blood pressure, no significant relations were observed.

CONCLUSION

Adult individuals with low birth weight may be particularly sensitive to the blood pressure-raising effect of salt.

Lifestyle Intervention Strategies for the Prevention and Treatment of Hypertension: A Review

Hypertension (HTN) is an extraordinarily common progressive cardiovascular syndrome in the United States, afflicting approximately one third of the adult population. HTN is a powerful and unequivocal independent risk factor for cardiovascular and renal diseases, including coronary heart disease, stroke, and renal failure. Despite major advances in the understanding and treatment of HTN over the past several decades, the disease remains the most common primary diagnosis in the United States and is a major public health concern. Adoption of healthy lifestyle modifications has proven to be highly effective in both the prevention of new-onset HTN and in the treatment of those diagnosed with HTN. In view of the continuing epidemic of HTN and blood pressure (BP)—related diseases and the invaluable role of applying nonpharmacological therapy in the prevention and management of HTN, a review of current therapeutic lifestyle strategies appears warranted. This review will define 6 well-established nonpharmacological lifestyle modifications for preventing and managing HTN in addition to 3 novel lifestyle interventions that show promise as effective adjunct strategies for lowering BP. A healthy lifestyle prescription ideally comprising a number of these BP-lowering lifestyle intervention strategies should be dispensed by all primary care physicians for both the prevention and treatment of elevated BP, an action that would have major, positive public health ramifications.

The relationship between hypertension and salt intake in Turkish population: SALTURK study

This population-based epidemiological study was aimed to evaluate the daily salt intake and its relation to blood pressure in a representative group of Turkish population. The enrolled normotensive and hypertensive individuals (n = 1970) completed a questionnaire including demographics, dietary habits, hypertension awareness and drug usage. Blood pressure was measured and to estimate salt consumption, 24-h urine samples were collected. The daily urinary sodium excretion was 308.3 ± 143.1 mmol/day, equal to a salt intake of 18.01 g/day. Salt intake was higher in obese participants, rural residents, participants with lower education levels and elderly. A positive linear correlation between salt intake and systolic and diastolic blood pressures was demonstrated (r = 0.450, p = 0.020; r = 0.406, p = 0.041; respectively), and each 100 mmol/day of salt intake resulted in 5.8 and 3.8 mmHg increase in systolic and diastolic blood pressures, respectively. Salt intake and systolic blood pressure was significantly correlated in normal weight individuals (r = 0.257, p < 0.01). The Turkish population consumes a great amount of salt; salt intake and blood pressure was positively correlated. Efforts in sodium restriction are therefore crucial in the management of hypertension as part of national and global health policies.

From good intentions to proven interventions: effectiveness of actions to reduce the health impacts of air pollution

BACKGROUND

Associations between air pollution and a multitude of health effects are now well established. Given ubiquitous exposure to some level of air pollution, the attributable health burden can be high, particularly for susceptible populations.

OBJECTIVES

An international multidisciplinary workshop was convened to discuss evidence of the effectiveness of actions to reduce health impacts of air pollution at both the community and individual level. The overall aim was to summarize current knowledge regarding air pollution exposure and health impacts leading to public health recommendations.

DISCUSSION

During the workshop, experts reviewed the biological mechanisms of action of air pollution in the initiation and progression of disease, as well as the state of the science regarding community and individual-level interventions. The workshop highlighted strategies to reduce individual baseline risk of conditions associated with increased susceptibility to the effects of air pollution and the need to better understand the role of exposure duration in disease progression, reversal, and adaptation.

CONCLUSION

We have identified two promising and largely unexplored strategies to address and mitigate air pollution-related health impacts: reducing individual baseline risk of cardiovascular disease and incorporating air pollution-related health impacts into land-use decisions.

Altered dietary salt intake for preventing and treating diabetic kidney disease

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor for increased blood pressure (BP) and a modest reduction in salt intake lowers BP whether BP levels are normal or raised. Tight control of BP in diabetics lowers the risk of strokes, heart attacks and heart failure and slows the progression of diabetic kidney disease (DKD). Currently there is no consensus in restricting salt intake in diabetic patients.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and DKD.

SEARCH STRATEGY

In January 2010, we searched the Cochrane Renal Group's Specialised Register, CENTRAL (in The Cochrane Library), MEDLINE (from 1966) and EMBASE (from 1980) to identify appropriate articles.

SELECTION CRITERIA

We included all randomised controlled trials of salt reduction in individuals with type 1 and type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion with a third independent author. We calculated mean effect sizes using both the fixed-effect and random-effects models.

MAIN RESULTS

Thirteen studies (254 individuals) met our inclusion criteria. These included 75 individuals with type 1 diabetes and 158 individuals with type 2 diabetes. The median reduction in urinary sodium was 203 mmol/24 h (11.9 g/day) in type 1 diabetes and 125 mmol/24 h (7.3 g/day) in type 2 diabetes. The median duration of salt restriction was one week in both type 1 and type 2 diabetes. BP was reduced in both type 1 and type 2 diabetes. In type 1 diabetes (56 individuals), salt restriction reduced BP by -7.11/-3.13 mm Hg (systolic/diastolic); 95% CI: systolic BP (SBP) -9.13 to -5.10; diastolic BP (DBP) -4.28 to -1.98). In type 2 diabetes (56 individuals), salt restriction reduced BP by -6.90/-2.87 mm Hg (95% CI: SBP -9.84 to -3.95; DBP -4.39 to -1.35). There was a greater reduction in BP in normotensive patients, possibly due to a larger decrease in salt intake in this group.

AUTHORS' CONCLUSIONS

Although the studies are not extensive, this meta-analysis shows a large fall in BP with salt restriction, similar to that of single drug therapy. All diabetics should consider reducing salt intake at least to less than 5-6 g/day in keeping with current recommendations for the general population and may consider lowering salt intake to lower levels, although further studies are needed.

The effect of nutrition on blood pressure

The incidence and severity of hypertension are affected by nutritional status and intake of many nutrients. Excessive energy intake and obesity are major causes of hypertension. Obesity is associated with increased activity of the renin-angiotensin-aldosterone and sympathetic nervous systems, possibly other mineralcorticoid activity, insulin resistance, salt-sensitive hypertension and excess salt intake, and reduced kidney function. High sodium chloride intake strongly predisposes to hypertension. Increased alcohol consumption may acutely elevate blood pressure. High intakes of potassium, polyunsaturated fatty acids, and protein, along with exercise and possibly vitamin D, may reduce blood pressure. Less-conclusive studies suggest that amino acids, tea, green coffee bean extract, dark chocolate, and foods high in nitrates may reduce blood pressure. Short-term studies indicate that specialized diets may prevent or ameliorate mild hypertension; most notable are the Dietary Approaches to Stop Hypertension (DASH) diet, which is high in fruits, vegetables, and low-fat dairy products, and the DASH low-sodium diet. Long-term compliance to these diets remains a major concern.

Effects of soy isoflavone extract supplements on blood pressure in adult humans: systematic review and meta-analysis of randomized placebo-controlled trials

OBJECTIVE

Reported effects of different soy products on blood pressure vary. This systematic review and meta-analysis was performed to clarify the effects of soy isoflavone extract supplements on systolic and diastolic blood pressure (SBP and DBP) in adult humans.

METHODS

PubMed, CENTRAL, ICHUSHI, and CNKI were searched in June 2009 for relevant randomized placebo-controlled trials. Study data and indicators of methodological validity were independently extracted by two authors using predefined data fields. Meta-analysis was carried out in Review Manager 5.0.22.

RESULTS

Searches identified 3740 articles, of which 14 randomized controlled trials (789 participants) were included. Daily ingestion of 25-375 mg soy isoflavones (aglycone equivalents) for 2-24 weeks significantly decreased SBP by 1.92 mmHg (95% confidence interval -3.45 to -0.39; P = 0.01) compared with placebo (heterogeneity P = 0.39, fixed effect model) in adults with normal blood pressure and prehypertension. The effect was not lost on sensitivity analysis. Subgroup analyses suggest greater effects in studies longer than 3 months, in Western populations, at lower doses, and in studies at lower risk of bias. Soy isoflavones did not affect DBP [-0.13 (95% confidence interval -1.03 to 0.78) mmHg, P = 0.78; heterogeneity P = 0.20, fixed effect model].

CONCLUSION

Soy isoflavone extracts significantly decreased SBP but not DBP in adult humans, and no dose-response relationship was observed. Further studies are needed to address factors related to the observed effects of soy isoflavones on SBP and to verify the effect in hypertensive patients.

Sources of sodium in Australian children's diets and the effect of the application of sodium targets to food products to reduce sodium intake

The average reported dietary Na intake of children in Australia is high: 2694 mg/d (9-13 years). No data exist describing food sources of Na in Australian children's diets and potential impact of Na reduction targets for processed foods. The aim of the present study was to determine sources of dietary Na in a nationally representative sample of Australian children aged 2-16 years and to assess the impact of application of the UK Food Standards Agency (FSA) Na reduction targets on Na intake. Na intake and use of discretionary salt (note: conversion of salt to Na, 1 g of NaCl (salt) = 390 mg Na) were assessed from 24-h dietary recall in 4487 children participating in the Australian 2007 Children's Nutrition and Physical Activity Survey. Greatest contributors to Na intake across all ages were cereals and cereal-based products/dishes (43%), including bread (13%) and breakfast cereals (4%). Other moderate sources were meat, poultry products (16%), including processed meats (8%) and sausages (3%); milk products/dishes (11%) and savoury sauces and condiments (7%). Between 37 and 42% reported that the person who prepares their meal adds salt when cooking and between 11 and 39% added salt at the table. Those over the age of 9 years were more likely to report adding salt at the table (χ2 199·5, df 6, P < 0·001). Attainment of the UK FSA Na reduction targets, within the present food supply, would result in a 20% reduction in daily Na intake in children aged 2-16 years. Incremental reductions of this magnitude over a period of years could significantly reduce the Na intake of this group and further reductions could be achieved by reducing discretionary salt use.

Cost-effectiveness analysis of interventions to prevent cardiovascular disease in Vietnam

BACKGROUND

Vietnam is in the process of an epidemiological transition, with cardiovascular disease (CVD) now ranked as the leading cause of death. The burden of CVD will continue to rise unless effective interventions for addressing its underlying risk factors are put in place.

OBJECTIVES

To assess the costs, health effects and cost-effectiveness of a set of personal and non-personal prevention strategies to reduce CVD in Vietnam, including mass media campaigns for reducing consumption of salt and tobacco, drugs for lowering blood pressure or cholesterol, and combined pharmacotherapy for people at varying levels of absolute risk of a cardiovascular event.

METHODS

WHO-CHOICE methods and analytical models were employed, using local data to estimate the costs, effects and cost-effectiveness of 12 population and individual interventions implemented singly or in combination. Costs were measured in Vietnamese Dong for the year 2007 (discounted at a rate of 3% per year), while health effects were expressed in age-weighted and discounted disability-adjusted life years (DALYs) averted.

RESULTS

A health education programme to reduce salt intake (VND 1 945 002 or US$118 per DALY averted) and individual treatment of systolic blood pressure above 160 mmHg (VND 1 281 596 or US$78 per DALY averted) were found to be the most cost-effective measures for population- and individual-based approaches, respectively. Where budget is very limited, a mass media education programme on salt intake and a combination mass media programme addressing salt intake, cholesterol and tobacco should be selected first. If more resources become available, greatest population health gains can be achieved via individual treatment of systolic blood pressure and the absolute risk approach to CVD prevention.

CONCLUSIONS

Contextualization of WHO-CHOICE using local data provides health decision-makers with more sound economic evidence for policy debates on prioritizing health interventions to reduce cardiovascular diseases in Vietnam. When used, cost-effectiveness analysis could increase efficiency in allocating scare resources.

WASH-world action on salt and health

There is overwhelming evidence that our current high-salt intake is the major factor increasing blood pressure (BP) and, thereby, a major cause of cardiovascular disease and kidney disease worldwide. A reduction in salt intake to the recommended level of <5-6 g/day is very beneficial, and could prevent millions of deaths each year and make major savings for healthcare services. Several countries, e.g., Finland and the UK, have already reduced the amount of salt being consumed by a combined policy of getting the food industry to decrease the amount of salt added to foods, clear labelling on food products, and increasing public awareness of the harmful effects of salt on health. Many other developed countries, e.g., Australia, Canada, and the US, are also stepping up their activities. The major challenge now is to spread this out worldwide, particularly to developing countries where ≈80% of global BP-related disease burden occurs. In many developing countries, most of the salt consumed comes from salt added during cooking or from sauces; therefore, public health campaigns are needed to encourage consumers to use less salt. A modest reduction in salt intake across the whole population will result in major improvements in public health and have huge economic benefits in all countries around the world. World Action on Salt and Health (WASH) is a coalition of health professionals from different countries who know very well the harm of high BP and has a major role in implementing changes in their own countries. We welcome nephrologists to join (http://www.worldactiononsalt.com).

ASH position paper: dietary approaches to lower blood pressure

A substantial body of evidence has implicated several aspects of diet in the pathogenesis of elevated blood pressure (BP). Well-established risk factors for elevated BP include excess salt intake, low potassium intake, excess weight, high alcohol consumption, and suboptimal dietary pattern. African Americans are especially sensitive to the BP-raising effects of excess salt intake, insufficient potassium intake, and suboptimal diet. In this setting, dietary changes have the potential to substantially reduce racial disparities in BP and its consequences. In view of the age-related rise in BP in both children and adults, the direct, progressive relationship of BP with cardiovascular-renal diseases throughout the usual range of BP, and the worldwide epidemic of BP-related disease, efforts to reduce BP in nonhypertensive as well as hypertensive individuals are warranted. In nonhypertensives, dietary changes can lower BP and delay, if not prevent, hypertension. In uncomplicated stage I hypertension, dietary changes serve as initial treatment before drug therapy. In hypertensive individuals already on drug therapy, lifestyle modifications can further lower BP. The current challenge is designing and implementing effective clinical and public health interventions that lead to sustained dietary changes among individuals and more broadly in the general population.

Reduction of salt: will iodine intake remain adequate in The Netherlands?

Salt is the main vehicle for iodine fortification in The Netherlands. A reduction in salt intake may reduce the supply of iodine. Our aim was to quantify the effect of salt reduction on the habitual iodine intake of the Dutch population and the risk of inadequate iodine intake. We used data of the Dutch National Food Consumption Survey (1997–8) and an update of the food composition database to estimate habitual salt and iodine intake. To take into account uncertainty about the use of iodised salt (industrial and discretionary) and food supplements, a simulation model was used. Habitual iodine and salt intakes were simulated for scenarios of salt reduction and compared with no salt reduction. With 12, 25 and 50 % salt reduction in industrially processed foods, the iodine intake remained adequate for a large part of the Dutch population. For the extreme scenario of a 50 % reduction in both industrially and discretionary added salt, iodine intake might become inadequate for part of the Dutch population (up to 10 %). An increment of the proportion of industrially processed foods using iodised salt or a small increase in iodine salt content will solve this. Nevertheless, 8–35 % of 1- to 3-year-old children might have iodine intakes below the corresponding estimated average requirement (EAR), depending on the salt intake scenario. This points out the need to review the EAR value for this age group or to suggest the addition of iodine to industrially manufactured complementary foods.

Practical management of diet and lifestyle interventions for people with diabetes or cardiovascular disease

Increased collaboration between the vascular specialities is clearly leading to increased understanding of the interrelationships between the different disease states and how each impacts and influences the other. This advantage will be reflected in improved patient care if the practical outputs of this growing knowledge are carefully implemented at service level. This article outlines how the aspects of diet and lifestyle associated with vascular-related disease complement, contrast and in some cases contradict each other. It gives information and guidelines as to how the expertise of dietitians working in the different specialist areas might usefully be shared to be of maximum advantage to all patients.

Prehypertension: detection, evaluation, and management

Prehypertension was defined as a discrete category in 1993. There is evidence to support active management of this entity given the increased risk of hypertension, cardiovascular disease, heart failure, and stroke. There have been few comprehensive summaries on the management of this population. Therefore, this article summarizes the latest guidelines and studies on the detection, evaluation, and management of prehypertension.

BELFAST nonagenarians: nature or nurture? Immunological, cardiovascular and genetic factors

Nonagenarians are the fastest growing sector of populations across Western European and the developed world. They are some of the oldest members of our societies and survivors of their generation and may help us understand how to age not only longer, but better.

The Belfast Longevity Group enlisted the help of 500 community-living, mobile, mentally competent, 'elite' nonagenarians, as part of an ongoing study of ageing. We assessed some immunological, cardiovascular, nutritional and genetic factors and some aspects of their interaction in this group of 'oldest old'.

Here we present some of the evidence related to genetic and nutritional factors which seem to be important for good quality ageing in nonagenarians from the Belfast Elderly Longitudinal Free-living Ageing STudy (BELFAST).

A comparison of British school meals and packed lunches from 1990 to 2007: meta-analysis by lunch type

Primary school children in the UK have the choice of a school meal provided by the school or a packed lunch provided from home. Currently, more than half of primary school children have a packed lunch. New food-based standards for school meals were introduced in English primary schools in 2006, followed by nutrient-based standards in 2008. No formal comparisons of primary school lunches by lunch type have been undertaken to date. The present review identified seven studies from 1990 to 2007 measuring lunchtime nutrient intake in children aged 5–11 years having a school meal and children having a packed lunch. Pooled estimates for each nutrient were as follows: energy intake was 543 (95 % CI 233, 854) kJ higher in packed lunches; total sugar intake was 14·0 (95 % CI 10·3, 17·7) g higher in packed lunches; non-milk extrinsic sugar intake was 11·7 (95 % CI 7·3, 16·2) g higher in packed lunches; saturated fat intake was 4·7 (95 % CI 2·4, 7·1) g higher in packed lunches and Na intake was 357 (95 % CI 174, 539) mg higher in packed lunches. Differences between school meals and packed lunches were larger for all nutrients after the introduction of food-based standards compared with the period of no standards. However, differences between before and after standards did not reach statistical significance. The nutritional quality of packed lunches is poor compared with school meals. The introduction of food-based standards for school meals in 2006 has moderately improved the nutrient content of school meals, slightly widening the nutritional gap between school meals and packed lunches.

Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

Meat consumption is inconsistently associated with development of coronary heart disease (CHD), stroke, and diabetes mellitus, limiting quantitative recommendations for consumption levels. Effects of meat intake on these different outcomes, as well as of red versus processed meat, may also vary.

METHODS AND RESULTS

We performed a systematic review and meta-analysis of evidence for relationships of red (unprocessed), processed, and total meat consumption with incident CHD, stroke, and diabetes mellitus. We searched for any cohort study, case-control study, or randomized trial that assessed these exposures and outcomes in generally healthy adults. Of 1598 identified abstracts, 20 studies met inclusion criteria, including 17 prospective cohorts and 3 case-control studies. All data were abstracted independently in duplicate. Random-effects generalized least squares models for trend estimation were used to derive pooled dose-response estimates. The 20 studies included 1 218 380 individuals and 23 889 CHD, 2280 stroke, and 10 797 diabetes mellitus cases. Red meat intake was not associated with CHD (n=4 studies; relative risk per 100-g serving per day=1.00; 95% confidence interval, 0.81 to 1.23; P for heterogeneity=0.36) or diabetes mellitus (n=5; relative risk=1.16; 95% confidence interval, 0.92 to 1.46; P=0.25). Conversely, processed meat intake was associated with 42% higher risk of CHD (n=5; relative risk per 50-g serving per day=1.42; 95% confidence interval, 1.07 to 1.89; P=0.04) and 19% higher risk of diabetes mellitus (n=7; relative risk=1.19; 95% confidence interval, 1.11 to 1.27; P<0.001). Associations were intermediate for total meat intake. Consumption of red and processed meat were not associated with stroke, but only 3 studies evaluated these relationships.

CONCLUSIONS

Consumption of processed meats, but not red meats, is associated with higher incidence of CHD and diabetes mellitus. These results highlight the need for better understanding of potential mechanisms of effects and for particular focus on processed meats for dietary and policy recommendations.

Reducing population salt intake worldwide: from evidence to implementation

Raised blood pressure is a major cause of cardiovascular disease, responsible for 62% of stroke and 49% of coronary heart disease. There is overwhelming evidence that dietary salt is the major cause of raised blood pressure and that a reduction in salt intake lowers blood pressure, thereby, reducing blood pressure-related diseases. Several lines of evidence including ecological, population, and prospective cohort studies, as well as outcome trials, demonstrate that a reduction in salt intake is related to a lower risk of cardiovascular disease. Increasing evidence also suggests that a high salt intake may directly increase the risk of stroke, left ventricular hypertrophy, and renal disease; is associated with obesity through soft drink consumption; is related to renal stones and osteoporosis; is linked to the severity of asthma; and is probably a major cause of stomach cancer. In most developed countries, a reduction in salt intake can be achieved by a gradual and sustained reduction in the amount of salt added to foods by the food industry. In other countries where most of the salt consumed comes from salt added during cooking or from sauces, a public health campaign is needed to encourage consumers to use less salt. Several countries have already reduced salt intake. The challenge now is to spread this out to all other countries. A modest reduction in population salt intake worldwide will result in a major improvement in public health.

Dietary sodium intake in a sample of adult male population in southern Italy: results of the Olivetti Heart Study

BACKGROUND/OBJECTIVES

To assess dietary habitual sodium intake and the association between daily sodium intake and anthropometric indices, food habits and hypertension in the sample of adult male population participating in the Olivetti Heart Study.

SUBJECTS/METHODS

The study population was composed of 940 men participating in the 2002-2004 follow-up examination of the Olivetti Heart Study. Blood pressure, anthropometric indices, biochemical parameters and sodium excretion in a 24-h urine collection were measured. The frequency of consumption of selected foods was estimated by a food frequency questionnaire (FFQ) capturing the previous year data. In a subgroup of the study population (n=138), the fractional excretion of sodium was estimated by endogenous lithium clearance.

RESULTS

Dietary sodium intake estimated by 24 h urinary excretion was 203+/-70 mmol/day. Sodium excretion was significantly lower in treated hypertensive patients and higher in overweight/obese participants when compared with normotensive and normal-weight individuals, respectively. In addition, the inverse correlation detected in normal-weight individuals (r=-0.321; P<0.05) between fractional proximal tubular sodium reabsorption and dietary sodium intake was disrupted in overweight/obese individuals (r=0.058; P=NS). The independent determinants of 24 h urinary sodium excretion were body mass index (BMI), the occurrence of antihypertensive treatment, and frequency of consumption of pasta and cold cuts.

CONCLUSIONS

Habitual salt intake in this sample of male adult population in southern Italy was well above the recommended amounts. A higher salt intake and an altered renal sodium handling were observed in overweight and obese participants. Sodium intake was only slightly reduced in hypertensive participants on pharmacological therapy.

Projected effect of dietary salt reductions on future cardiovascular disease

BACKGROUND

The U.S. diet is high in salt, with the majority coming from processed foods. Reducing dietary salt is a potentially important target for the improvement of public health.

METHODS

We used the Coronary Heart Disease (CHD) Policy Model to quantify the benefits of potentially achievable, population-wide reductions in dietary salt of up to 3 g per day (1200 mg of sodium per day). We estimated the rates and costs of cardiovascular disease in subgroups defined by age, sex, and race; compared the effects of salt reduction with those of other interventions intended to reduce the risk of cardiovascular disease; and determined the cost-effectiveness of salt reduction as compared with the treatment of hypertension with medications.

RESULTS

Reducing dietary salt by 3 g per day is projected to reduce the annual number of new cases of CHD by 60,000 to 120,000, stroke by 32,000 to 66,000, and myocardial infarction by 54,000 to 99,000 and to reduce the annual number of deaths from any cause by 44,000 to 92,000. All segments of the population would benefit, with blacks benefiting proportionately more, women benefiting particularly from stroke reduction, older adults from reductions in CHD events, and younger adults from lower mortality rates. The cardiovascular benefits of reduced salt intake are on par with the benefits of population-wide reductions in tobacco use, obesity, and cholesterol levels. A regulatory intervention designed to achieve a reduction in salt intake of 3 g per day would save 194,000 to 392,000 quality-adjusted life-years and $10 billion to $24 billion in health care costs annually. Such an intervention would be cost-saving even if only a modest reduction of 1 g per day were achieved gradually between 2010 and 2019 and would be more cost-effective than using medications to lower blood pressure in all persons with hypertension.

CONCLUSIONS

Modest reductions in dietary salt could substantially reduce cardiovascular events and medical costs and should be a public health target.