Salt and cardiovascular disease

Development of a screening method for determining sodium intake based on the Dietary Reference Intakes for Japanese, 2020: A cross-sectional analysis of the National Health and Nutrition Survey, Japan

Background

Although assessing nutrient intake through dietary surveys is desirable, it can be effort- and time-intensive. We aimed to develop a brief screening method for determining sodium intake in order to raise public awareness regarding the Dietary Reference Intakes for Japanese (DRI-J) 2020.

Methods

Using data from the 2015 National Health and Nutrition Survey, we compared dietary behaviours obtained from a self-administered questionnaire according to sodium intake, which was assessed from one-day dietary records by a semi-weighed method. Participants were divided into 4 groups based on the reference values of sodium (salt equivalent) shown in the DRI-J. We also randomly divided the participants into development and validation groups, and used logistic regression analysis to identify predictive factors for sex-specific DRI-J (<7.5 g/day in men and <6.5 g/day in women) and above-average intakes (≥10 g/day in men and women).

Results

Among the 6,172 Japanese individuals aged ≥20 years old, participants with lower sodium intake were found to use nutrition labels and had a lower frequency of eating out than those with higher intakes (P for difference < .001). Our final model for predicting sodium intake included adjusted sex, age, dietary behaviours, and consumption of mainly processed foods. In the development group, areas under the receiver operating characteristics curves were 0.747 and 0.741 for adherence to sex-specific DRI-J and above-average intake, respectively. The corresponding values in the validation group were 0.734 and 0.730, respectively.

Conclusions

This method could easily identify sodium intake using dietary behaviours and specific food consumption, and is expected to be widely useful for health and nutrition education in Japan.

Resistant Hypertension in Adults With Type 1 or 2 Diabetes: A Structured Diagnostic Approach

People with diabetes often have difficulty reaching their blood pressure targets and are labelled as having resistant hypertension. Clinicians often move quickly to screen such people for secondary causes of hypertension; however, such causes are rare, and resistant hypertension usually has other explanations that are significantly more common. By using a structured approach to resistant hypertension, clinicians can assist patients to reach their target blood pressure levels. Step 1 is to determine out-of-office blood pressure measurements using home or ambulatory blood pressure monitors. Step 2 is to determine the level of adherence to prescribed medications. Step 3 is to identify interfering substances. Step 4 is to check that the prescribed medications are synergistic and optimally dosed. Finally, if all other steps fail to get patients to their blood pressure targets, we consider possible secondary causes of hypertension. This approach is particularly useful in helping people with diabetes to reach their blood pressure targets.

Systematic review of dietary salt reduction policies: Evidence for an effectiveness hierarchy?

BACKGROUND

Non-communicable disease (NCD) prevention strategies now prioritise four major risk factors: food, tobacco, alcohol and physical activity. Dietary salt intake remains much higher than recommended, increasing blood pressure, cardiovascular disease and stomach cancer. Substantial reductions in salt intake are therefore urgently needed. However, the debate continues about the most effective approaches. To inform future prevention programmes, we systematically reviewed the evidence on the effectiveness of possible salt reduction interventions. We further compared "downstream, agentic" approaches targeting individuals with "upstream, structural" policy-based population strategies.

METHODS

We searched six electronic databases (CDSR, CRD, MEDLINE, SCI, SCOPUS and the Campbell Library) using a pre-piloted search strategy focussing on the effectiveness of population interventions to reduce salt intake. Retrieved papers were independently screened, appraised and graded for quality by two researchers. To facilitate comparisons between the interventions, the extracted data were categorised using nine stages along the agentic/structural continuum, from "downstream": dietary counselling (for individuals, worksites or communities), through media campaigns, nutrition labelling, voluntary and mandatory reformulation, to the most "upstream" regulatory and fiscal interventions, and comprehensive strategies involving multiple components.

RESULTS

After screening 2,526 candidate papers, 70 were included in this systematic review (49 empirical studies and 21 modelling studies). Some papers described several interventions. Quality was variable. Multi-component strategies involving both upstream and downstream interventions, generally achieved the biggest reductions in salt consumption across an entire population, most notably 4g/day in Finland and Japan, 3g/day in Turkey and 1.3g/day recently in the UK. Mandatory reformulation alone could achieve a reduction of approximately 1.45g/day (three separate studies), followed by voluntary reformulation (-0.8g/day), school interventions (-0.7g/day), short term dietary advice (-0.6g/day) and nutrition labelling (-0.4g/day), but each with a wide range. Tax and community based counselling could, each typically reduce salt intake by 0.3g/day, whilst even smaller population benefits were derived from health education media campaigns (-0.1g/day). Worksite interventions achieved an increase in intake (+0.5g/day), however, with a very wide range. Long term dietary advice could achieve a -2g/day reduction under optimal research trial conditions; however, smaller reductions might be anticipated in unselected individuals.

CONCLUSIONS

Comprehensive strategies involving multiple components (reformulation, food labelling and media campaigns) and "upstream" population-wide policies such as mandatory reformulation generally appear to achieve larger reductions in population-wide salt consumption than "downstream", individually focussed interventions. This 'effectiveness hierarchy' might deserve greater emphasis in future NCD prevention strategies.

The blood pressure-salt sensitivity paradigm: pathophysiologically sound yet of no practical value

Sodium plays an important pathophysiological role in blood pressure (BP) values and in the development of hypertension, and epidemiological studies such as the Intersalt Study have shown that the increase in BP occurring with age is determined by salt intake. Recently, a meta-analysis of 13 prospective studies has also shown the close relationship between excess sodium intake and higher risk of stroke and total cardiovascular events. However, the BP response to changing salt intake displayed a marked variability, as first suggested by Kawasaki et al. (The effect of high-sodium and low-sodium intakes on blood pressure and other related variables in human subjects with idiopathic hypertension. Am J Med 1978; 64: 193-198) and later by Weinberger et al. (Definitions and characteristics of sodium sensitivity and blood pressure resistance. Hypertension 1986; 8: II127-II134), who recognized the heterogeneity of the BP response to salt and developed the concept of salt sensitivity. We have a large body of evidence in favour of a major role of metabolic and neuro-hormonal factors in determining BP salt sensitivity in association with the effect of genetic variation. There is evidence that salt sensitivity influences the development of organ damage, even independently-at least in part-of BP levels and the occurrence of hypertension. In addition, several observational studies indicate that salt sensitivity is clearly associated with a higher rate of cardiovascular events and mortality, independently of BP levels and hypertension. A cluster of factors with well-known atherogenic potential such as hyperinsulinaemia, dyslipidaemia and microalbuminuria-all known to be prevalent in salt-sensitive hypertension-might at least partially explain the increased cardiovascular risk observed in salt sensitive individuals. The gold standard for the evaluation of BP salt sensitivity is the BP response to a moderate reduction of salt intake for several weeks; nevertheless, these protocols often suffer of poor patient compliance to dietary instructions. To overcome this problem, short-term tests have been proposed that evaluate either large differences in salt intake for a few days or the response to intravenous administration of saline solution and short-acting diuretics. Recently, the use of ambulatory BP measurement has been proposed for the clinical assessment of BP salt sensitivity. Noteworthy, BP salt sensitivity, in whomever or however assessed, behaves as a continuous variable but salt sensitivity is used as a categorical parameter, with salt-sensitive individuals being defined as those with a difference in BP between low- and high-sodium intake >10%, and salt-resistant subjects those in whom BP does not increase or shows an increase <5% under sodium loading. The general conclusion that can and should be drawn from the above considerations is that the paradigm of salt sensitivity, despite its important pathophysiological meaning, is not helpful, so far, to the practising physician in clinical practice nor is it relevant or useful to the design and implementation of a population-based strategy of salt intake reduction; however, further studies are warranted for an accurate assessment of the salt-sensitivity phenotype in clinical practice. In the absence of a population strategy for salt intake reduction, the aim should be the generation of a 'low sodium environment' allowing for a dietary salt intake tailored on true human requirements and not on deleterious lifestyle habits.

The double challenge of resistant hypertension and chronic kidney disease

Resistant hypertension is defined as blood pressure above goal despite adherence to a combination of at least three optimally dosed antihypertensive medications, one of which is a diuretic. Chronic kidney disease is the most frequent of several patient factors or comorbidities associated with resistant hypertension. The prevalence of resistant hypertension is increased in patients with chronic kidney disease, while chronic kidney disease is associated with an impaired prognosis in patients with resistant hypertension. Recommended low-salt diet and triple antihypertensive drug regimens that include a diuretic, should be complemented by the sequential addition of other antihypertensive drugs. New therapeutic innovations for resistant hypertension, such as renal denervation and carotid barostimulation, are under investigation especially in patients with advanced chronic kidney disease. We discuss resistant hypertension in chronic kidney disease stages 3-5 (ie, patients with an estimated glomerular filtration rate below 60 mL/min per 1·73 m(2) and not on dialysis), in terms of worldwide epidemiology, outcomes, causes and pathophysiology, evidence-based treatment, and a call for action.

Emphasized warning reduces salt intake: a randomized controlled trial

Excessive salt intake is a major cardiovascular risk factor. At variance to the developed countries, the main source of sodium in transitional and developing countries is salt added while cooking and/or at the table. The objective of this trial was to examine the impact of warning labels placed on home salt containers on daily salt intake.A sample of treated hypertensives (n = 150) was randomized in two subgroups, one receiving just a leaflet about the harmful effects of excessive salt intake (control; n = 74), and the other one receiving in addition warning stickers for household salt containers (intervention; n = 76). Arterial blood pressure (BP) and 24-hour urinary sodium excretion (Na24) were measured in all the subjects at the start of the trial, and 1 month and 2 months later. The average starting Na24 was 207 ± 71 mmol in the control group and 211 ± 85 mmol in the intervention group (P = .745). One month and 2 months later, a significant decrease was observed in the intervention group (to 183 ± 63 mmol and 176 ± 55 mmol; P < .0001), as opposed to the control group (203 ± 60 mmol and 200 ± 58 mmol; P = .1466). Initial BP was 143.7/84.1 mm Hg in the control, and 142.9/84.7 mm Hg in the intervention group (P = .667). One month and 2 months later, a significant drop in BP, by 5.3/2.9 mm Hg, was observed in the intervention group as opposed to the control group (0.4/0.9 mm Hg). Decrease in Na24 positively correlated to BP lowering (r(2) = 0.5989; P < .0001). A significant reduction in 24Na and BP is achieved with warning labels on harmful effects of excessive salt intake. Decreasing daily salt input by 35 mmol may result in an extra BP lowering by some 5-6/2-3 mm Hg.

Organ system heterogeneity DB: a database for the visualization of phenotypes at the organ system level

Perturbations of mammalian organisms including diseases, drug treatments and gene perturbations in mice affect organ systems differently. Some perturbations impair relatively few organ systems while others lead to highly heterogeneous or systemic effects. Organ System Heterogeneity DB (http://mips.helmholtz-muenchen.de/Organ_System_Heterogeneity/) provides information on the phenotypic effects of 4865 human diseases, 1667 drugs and 5361 genetically modified mouse models on 26 different organ systems. Disease symptoms, drug side effects and mouse phenotypes are mapped to the System Organ Class (SOC) level of the Medical Dictionary of Regulatory Activities (MedDRA). Then, the organ system heterogeneity value, a measurement of the systemic impact of a perturbation, is calculated from the relative frequency of phenotypic features across all SOCs. For perturbations of interest, the database displays the distribution of phenotypic effects across organ systems along with the heterogeneity value and the distance between organ system distributions. In this way, it allows, in an easy and comprehensible fashion, the comparison of the phenotypic organ system distributions of diseases, drugs and their corresponding genetically modified mouse models of associated disease genes and drug targets. The Organ System Heterogeneity DB is thus a platform for the visualization and comparison of organ system level phenotypic effects of drugs, diseases and genes.

Current salt reduction policies across gradients of inequality-adjusted human development in the WHO European region: minding the gaps

OBJECTIVE

To assess current salt reduction policies in countries of the WHO European Region against the backdrop of varying levels of human development adjusted for income, education and health (longevity) inequalities.

DESIGN

Population-based, cross-sectional study, with data gathered through systematic review of relevant databases and supplementary information provided by WHO Nutrition Counterparts.

SETTING

Member States of the WHO European Region.

SUBJECTS

Inequality-adjusted Human Development Index scores were analysed against assessed levels of development and implementation of national nutrition policies and initiatives targeting population-level salt reduction.

RESULTS

Within the WHO European Region, Inequality-adjusted Human Development Index values among countries with no existing salt reduction initiatives (mean 0·643 (se 0·022)) were significantly lower than among those with either partially implemented/planned salt initiatives (mean 0·766 (se 0·017), P < 0·001) or fully implemented salt initiatives (mean 0·780 (se 0·021), P < 0·001).

CONCLUSIONS

Where salt reduction strategies are implemented as an integral part of national policy, outcomes have been promising. However, low- and middle-income countries may face severe resource constraints that keep them from emulating more comprehensive strategies pursued in high-income countries. Care must be taken to ensure that gaps are not inadvertently widened by monitoring differential policy impacts of salt policies, particularly regarding trade flows.

Salt and public health: contested science and the challenge of evidence-based decision making

For more than four decades, starting in the late 1960s, a sometimes furious battle has raged among scientists over the extent to which elevated salt consumption has adverse implications for population health and contributes to deaths from stroke and cardiovascular disease. Various studies and trials have produced conflicting results. Despite this scientific controversy over the quality of the evidence implicating dietary salt in disease, public health leaders at local, national, and international levels have pressed the case for salt reduction at the population level. This article explores the development of this controversy. It concludes that the concealment of scientific uncertainty in this case has been a mistake that has served neither the ends of science nor good policy. The article poses questions that arise from this debate and frames the challenges of formulating evidence-based public health practice and policy, particularly when the evidence is contested.

Spatial variation of salt intake in Britain and association with socioeconomic status

OBJECTIVES

To evaluate spatial effects of variation and social determinants of salt intake in Britain.

DESIGN

Cross-sectional survey.

SETTING

Great Britain.

PARTICIPANTS

2105 white male and female participants, aged 19-64 years, from the British National Diet and Nutrition Survey 2000-2001.

PRIMARY OUTCOMES

Participants' sodium intake measured both with a 7-day dietary record and a 24-h urine collection. By accounting for important linear and non-linear risk factors and spatial effects, the geographical difference and spatial patterns of both dietary sodium intake and 24-h urinary sodium were investigated using Bayesian geo-additive models via Markov Chain Monte Carlo simulations.

RESULTS

A significant north-south pattern of sodium intake was found from posterior probability maps after controlling for important sociodemographic factors. Participants living in Scotland had a significantly higher dietary sodium intake and 24-h urinary sodium levels. Significantly higher sodium intake was also found in people with the lowest educational attainment (dietary sodium: coeff. 0.157 (90% credible intervals 0.003, 0.319), urinary sodium: 0.149 (0.024, 0.281)) and in manual occupations (urinary sodium: 0.083 (0.004, 0.160)). These coefficients indicate approximately a 5%, 9% and 4% difference in average sodium intake between socioeconomic groups.

CONCLUSIONS

People living in Scotland had higher salt intake than those in England and Wales. Measures of low socioeconomic position were associated with higher levels of sodium intake, after allowing for geographic location.

Predictors of resistant hypertension in an unselected sample of an adult male population in Italy

Prevalence, incidence and predictors of resistant hypertension (RH), (defined as blood pressure persistently above goal in spite of the concurrent use of three antihypertensive agents of different classes) in the general population remain largely unknown. A complete database including anthropometric and biochemical data was collected in 1994-1995 (baseline examination) in 1,019 participants (mean age 51.8, range: 25-79 years) and again in 2002-2004 in 794 male participants of the Olivetti Heart Study (OHS) in southern Italy. The incidence of RH over the average follow-up time of 7.9 years was 4.8% (38/794) in the whole study population and 10.1% (31/307) among hypertensive participants. Basal blood pressure (systolic, diastolic or pulse pressure), cholesterol and urinary albumin/creatinine ratio (ACR) significantly predicted the risk of developing RH using a logistic regression model that also included age as covariates. If in the same model we added basal pharmacological treatment, the fractional excretion of sodium (FENa) also became a statistically significant predictor, and this last model explained nearly 25% of the risk of developing RH. In this unselected sample of an adult male population, ACR (an early marker of organ damage), an elevated FENa (a proxy for dietary sodium intake), cholesterol and a higher basal blood pressure level were independent predictors of RH.

The cardio-protective diet

Globalization has made calorie rich, cheap, convenient marketed foods the main menu for the common man. Indians are particularly susceptible to the adverse outcomes of this dietary change because of ethnic, epigenetic reasons and sarcopenic adiposity (less muscle more fat for the same body weight). Children have smaller body frame making them more susceptible to adverse effects of hyperglycaemia leading to stress on beta cells and their damage. This has resulted in escalation of lifestyle diseases by three-fold, that too at our younger age group at lower body mass indices. Preventive measures are necessary in early life to protect the beta cells, to achieve a metabolically healthy society. This will help in sustaining optimal beta cell function throughout a person's life. Modification in dietary habits by educating the society, proper food labelling and legal regulation, restricting calorie, sugar, saturated fat, trans-fat and salt intake has proved its benefits in the developed world. Changes in the quality of food is as important as restricting calorie intake. This includes facilitation of increased consumption of dietary fiber, complex carbohydrates, nuts, fruits and vegetables. Restrictions are needed to reduce trans-fats, saturated fats and cooking habits such as deep frying which oxidizes cholesterol and lipids. Foods with long shelf-life shorten the life line because of their salt, sugar or trans-fat content. Individual meals need to be targeted in the general dietary guidelines, to minimize the post-prandial metabolic insult. In general, we need healthy start to early life particularly the first twenty years of life so that the habits cultured during childhood are sustained for the rest of productive years.

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.

Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies

OBJECTIVE

To assess the relation between the level of habitual salt intake and stroke or total cardiovascular disease outcome.

DESIGN

Systematic review and meta-analysis of prospective studies published 1966-2008.

DATA SOURCES

Medline (1966-2008), Embase (from 1988), AMED (from 1985), CINAHL (from 1982), Psychinfo (from 1985), and the Cochrane Library. Review methods For each study, relative risks and 95% confidence intervals were extracted and pooled with a random effect model, weighting for the inverse of the variance. Heterogeneity, publication bias, subgroup, and meta-regression analyses were performed. Criteria for inclusion were prospective adult population study, assessment of salt intake as baseline exposure, assessment of either stroke or total cardiovascular disease as outcome, follow-up of at least three years, indication of number of participants exposed and number of events across different salt intake categories.

RESULTS

There were 19 independent cohort samples from 13 studies, with 177 025 participants (follow-up 3.5-19 years) and over 11 000 vascular events. Higher salt intake was associated with greater risk of stroke (pooled relative risk 1.23, 95% confidence interval 1.06 to 1.43; P=0.007) and cardiovascular disease (1.14, 0.99 to 1.32; P=0.07), with no significant evidence of publication bias. For cardiovascular disease, sensitivity analysis showed that the exclusion of a single study led to a pooled estimate of 1.17 (1.02 to 1.34; P=0.02). The associations observed were greater the larger the difference in sodium intake and the longer the follow-up.

CONCLUSIONS

High salt intake is associated with significantly increased risk of stroke and total cardiovascular disease. Because of imprecision in measurement of salt intake, these effect sizes are likely to be underestimated. These results support the role of a substantial population reduction in salt intake for the prevention of cardiovascular disease.

Community-based Randomized Controlled Trial of Non-pharmacological Interventions in Prevention and Control of Hypertension among Young Adults

CONTEXT

Hypertension is a major chronic lifestyle disease. Several non-pharmacological interventions are effective in bringing down the blood pressure (BP). This study focuses on the effectiveness of such interventions among young adults.

AIMS

To measure the efficacy of physical exercise, reduction in salt intake, and yoga, in lowering BP among young (20-25) pre-hypertensives and hypertensives, and to compare their relative efficacies.

SETTINGS AND DESIGN

The study was done in the urban service area of JIPMER. Pre-hypertensives and hypertensives, identified from previous studies, constituted the universe. The participants were randomized into one control and three interventional groups.

MATERIALS AND METHODS

A total of 113 subjects: 30, 28, 28 and 27 in four groups respectively participated for eight weeks: control (I), physical exercise (II) - brisk walking for 50-60 minutes, four days/week, salt intake reduction (III) - to at least half of their previous intake, and practice of yoga (IV) - for 30-45 minutes/day on at least five days/week.

STATISTICAL ANALYSIS USED

Efficacy was assessed using paired t test and ANOVA with Games Howell post hoc test. An intention to treat analysis was also performed.

RESULTS

A total of 102 participants (29, 27, 25 and 21 in groups I, II, III and IV) completed the study. All three intervention groups showed a significant reduction in BP (SBP/DBP: 5.3/6.0 in group II, 2.6/3.7 in III, and 2.0/2.6 mm Hg in IV respectively). There was no significant change (SBP/DBP: 0.2/0.5 mmHg) of BP in control group (I). Physical exercise was most effective (considered individually); salt intake reduction and yoga were also effective.

CONCLUSIONS

Physical exercise, salt intake reduction, and yoga are effective non-pharmacological interventions in significantly reducing BP among young hypertensives and pre-hypertensives. These can therefore be positively recommended for hypertensives. There is also a case to deploy these interventions in the general population.

A translational framework for public health research

BACKGROUND

The paradigm of translational medicine that underpins frameworks such as the Cooksey report on the funding of health research does not adequately reflect the complex reality of the public health environment. We therefore outline a translational framework for public health research.

DISCUSSION

Our framework redefines the objective of translation from that of institutionalising effective interventions to that of improving population health by influencing both individual and collective determinants of health. It incorporates epidemiological perspectives with those of the social sciences, recognising that many types of research may contribute to the shaping of policy, practice and future research. It also identifies a pivotal role for evidence synthesis and the importance of non-linear and intersectoral interfaces with the public realm.

SUMMARY

We propose a research agenda to advance the field and argue that resources for 'applied' or 'translational' public health research should be deployed across the framework, not reserved for 'dissemination' or 'implementation'.

What's law got to do with it Part 2: Legal strategies for healthier nutrition and obesity prevention

This article is the second in a two-part review of law's possible role in a regulatory approach to healthier nutrition and obesity prevention in Australia. As discussed in Part 1, law can intervene in support of obesity prevention at a variety of levels: by engaging with the health care system, by targeting individual behaviours, and by seeking to influence the broader, socio-economic and environmental factors that influence patterns of behaviour across the population. Part 1 argued that the most important opportunities for law lie in seeking to enhance the effectiveness of a population health approach.

Part 2 of this article aims to provide a systematic review of the legal strategies that are most likely to emerge, or are worth considering, as part of a suite of policies designed to prevent population weight gain and, more generally, healthier nutrition. While the impact of any one intervention may be modest, their cumulative impact could be significant and could also create the conditions for more effective public education campaigns. This article addresses the key contenders, with particular reference to Australia and the United States.